Please see the [Transcriber’s Notes] at the end of this text.

INVENTORS AT WORK

Copyright by Park & Co., Brantford, Ontario.

PROFESSOR ALEXANDER GRAHAM BELL.

Inventors at Work
With Chapters on Discovery

By George Iles
Author of “Flame, Electricity and the Camera”

Copiously Illustrated

New York
Doubleday, Page & Company
1907

Copyright, 1906, by
George Iles
Published October, 1906

All rights reserved, including that of translation into foreign languages, including the Scandinavian

TO MY FRIEND
JOSEPHUS NELSON LARNED
OF BUFFALO, NEW YORK

CONTENTS

LIST OF ILLUSTRATIONS

ACKNOWLEDGMENTS

Aid in writing this volume is acknowledged in the course of its chapters. The author’s grateful thanks are rendered also to Dr. L. A. Fischer, of the Bureau of Standards at Washington, who has revised the paragraphs describing the work of the Bureau; to Mr. C. R. Mann of the Ryerson Physical Laboratory, University of Chicago, who corrected the paragraphs on the interferometer; to Mr. Walter A. Mitchell, formerly of Columbia University, New York, who revised most of the chapters on measurement. Mr. Thomas E. Fant, Head of the Department of Construction and Repair at the Navy Yard, Washington, D. C., gave the picture of the model basin here reproduced. Mr. Walter Hough of the National Museum, Washington, D. C., contributed a photograph of the Pomo basket also reproduced here. Mr. John Van Vleck and Mr. Henry G. Stott of New York, Mr. George R. Prowse and Mr. Edson L. Pease of Montreal, have furnished drawings and photographs for illustrations of unusual interest. Mr. George F. C. Smillie, of the Bureau of Engraving, Washington, D. C., Mr. Percival E. Fansler, Mr. Ernest Ingersoll, and Mr. Ashley P. Peck, of New York, have read in proof parts of the chapters which follow. Their corrections and suggestions have been indispensable.

Professor Bradley Stoughton, of the School of Mines, Columbia University, New York, has been good enough to contribute a brief list of books on steel, supplementing the chapter on that theme written with his revision. Had it been feasible, other chapters would have been supplemented in like manner by other teachers of mark. In 1902 the American Library Association published an annotated guide to the literature of American history, engaging forty critics and scholars of distinction, with Mr. J. N. Larned as editor. It is hoped that at no distant day guides on the same helpful plan will be issued in the field of science, duly supplemented and revised from time to time.

In the present volume the author has endeavored to include in his survey the main facts to the close of May, 1906.

New York, September, 1906.

INVENTORS AT WORK

CHAPTER I
INTRODUCTORY

Inventors and discoverers are justly among the most honored of men. It is they who add to knowledge, who bring matter under subjection both in form and substance, who teach us how to perform an old task, as lighting, with new economy, or hand us gifts wholly new, as the spectroscope and the wireless telegraph. It is they who tell us how to shape an oar into a rudder, and direct a task with our brains instead of tugging at it with our muscles. They enable us to replace loss with gain, waste with thrift, weariness with comfort, hazard with safety. And, chief service of all, they bring us to understand more and more of that involved drama of which this planet is by turns the stage and the spectator’s gallery. The main difference between humanity to-day and its lowly ancestry of the tree-top and the cave has been worked out by the inventors and discoverers who have steadily lifted the plane of life, made it broader and better with every passing year.

On a theme so vast as the labors of these men a threshold book can offer but a few glances at principles of moment, to which the reader may add as he pleases from observations and experiments of his own. At the outset Form will engage our regard: first, as bestowed so as to be retained by girders, trusses and bridges; next, as embodied in structures which minimize friction, such as well designed ships; or as conducing to the efficiency of tools and machines; or deciding how best heat may be radiated or light diffused. A word will follow as to modes of conferring form, the influence on form of the materials employed, and the undue vitality of old forms that should long ago have bidden us good-by. Structures alike in shape may differ in size. Bigness has its economies, and so has smallness. Both will have brief attention, with a rapid survey of new materials which enable a builder to rear towers or engines bolder in dimensions than were hitherto possible.

Substance, as important as form, will next receive a glance. First a word will be said about the properties of food, raiment, shelter, weapons and tools. Then, the properties of fuels and light-givers will be considered, as steadily improved in their effectiveness. How properties are modified by heat and electricity will be remarked, with illustrations from steels of new and astonishing qualities, and from notable varieties of glass produced at Jena. A few pages will recount some of the striking phenomena of radio-activity displayed by radium, thorium and kindred substances, phenomena which are remolding the fundamental conceptions of physics and chemistry.

A survey of form and properties, however cursory, must involve measurement, otherwise an inventor cannot with accuracy embody a plan in a working machine, or know exactly how strong, elastic, or conducting a rod, a wire, or a frame is. Measuring instruments will be sketched, their use delineated, and the results of precise measurement noted as an aid to the construction of modern mechanism, the interchangeability of its parts, the economy of materials and of energy in every branch of industry. Next will follow a chapter noting tasks which Nature has long accomplished, and which Art has still to perform, as in converting at ordinary temperatures within the human body fuel energy into work. Plainly, a broad field opens to future invention as it copies the function of plants and animals; functions to be first carefully observed, then explained and at last imitated with the least possible waste of effort.

The equipment and the talents for invention and discovery are now touched upon. First, knowledge, especially as the fruit of disinterested inquiry; Observation, as exercised by trained intelligence calling to its aid the best modern instruments; Experiment, as an educated passion for building on original lines. Then, in the mechanical field, we bestow a few glances at self-acting machines, at the simplicity of design which makes for economy not only in building, but in operation and maintenance. Either in designing a new machine, or in reaching a great truth, such as Universal Development, there is scope for Imagination upon which we next pause for a moment. A succeeding chapter outlines how theories may be launched and tested, how analogy may yield a golden hint, the profit in rules that work both ways, or even in doing just the opposite of what has been done without question for ages past.

Copyright, 1906, by Park & Co., Brantford, Ontario, Canada

BELL HOMESTEAD, BRANTFORD, ONTARIO, CANADA.
Alexander Graham Bell and his Daughter in the Foreground.
Here the Telephone was Perfected in 1874.
Now the Home of the Bell Telephone Memorial Association.

From this brief consideration of method we now pass to a few men who have exemplified method on the loftiest plane; we come into the presence of Newton, the supreme generalizer, and observe his patience and conscientiousness, as remarkable as his resourcefulness in experiment, in mathematical analysis. Even greater in experiment, while lacking mathematical power, is Faraday, who next enlists our regard. This great man, more than any other investigator, laid the foundations of modern electrical science and art. Moreover he distinctly saw how matter might reveal itself in the ‘radiant’ condition now engaging the study of the foremost inquirers in physics.

Electricity has no instrument more useful in daily life, or in pure research, than the telephone. Now follows a narration by its creator, Professor Bell, of his photophone which transmits speech by a beam of light. This recital shows us how an inventor of the first rank proceeds from one attempt to another, until his toil is crowned with success. Next we hear the story of the Bessemer process from the lips of Sir Henry Bessemer himself, affording us an insight into the methods and characteristics of a mind ingenious, versatile and bold in the highest degree. An inventor of quite other type is next introduced,—Nobel, who gave dynamite to the quarryman and miner, smokeless powder to the gunner and sportsman. His unfaltering heart, beset as he was by constant peril, marks him a hero as brave as ever fought hazardous and dreary campaigns to a victorious close.

Many advances in mechanical and structural art have been won rather through a succession of attacks by one leader after another, than by a single decisive blow from a Watt or an Edison. A great band of inventors, improvers, adapters, have accomplished notable tasks with no record of such a feat as Bessemer with his converter, or Abbe with Jena glass. A brief chapter deals with some of the principal uses of compressed air, an agent of steadily increasing range. As useful, in a totally different sphere—that of building material—is concrete, especially as reinforced with steel. A sketch of its applications is offered. Then follows the theme of using fuels with economy, of obtaining from them motive powers with the least possible loss. This field is to-day attracting inventors of eminent ability, with the prospect that soon motive powers will be much cheapened, with incidental abridgment of drudgery, a new expansion of cities into the country, and the production of light at perhaps as little as one-third its present cost. A page or two are next given to a few social aspects of invention, its new aid and comfort to craftsmen, farmers, householders comparatively poor. It will appear that forces working against the undue centralization of industry grow stronger every day.

A closing word gives the reader, especially the young reader, a hint or two in case he wishes to pursue paths of study the first steps of which are taken in this book.

In 1900 was published the author’s “Flame, Electricity and the Camera,” in which are treated some of the principal applications of heat, electricity and photography as exemplified at the time of writing. That volume may supplement the book now in the reader’s hands.

CHAPTER II
FORM

Form as important as substance . . . Why a joist is stiffer than a plank . . . The girder is developed from a joist . . . Railroad rails are girders of great efficiency as designed and tested by Mr. P. H. Dudley.

A lens of ice focussing a sunbeam.

One January morning in Canada I saw a striking experiment. The sun was shining from an unclouded sky, while in the shade a Fahrenheit thermometer stood at about twenty degrees below zero. A skilful friend of mine had moulded a cake of ice into a lens as large as a reading glass; tightly fastened in a wooden hoop it focussed in the open air a sunbeam so as to set fire to a sheet of paper, and char on a cedar shingle a series of zigzag lines. There, indeed, was proof of the importance of form. To have kept our hands in contact with the ice would have frozen them in a few minutes, but by virtue of its curved surfaces the ice so concentrated the solar beam as readily to kindle flame. Clearly enough, however important properties may be, not less so are the forms into which matter may be fashioned and disposed. Let us consider a few leading principles by which designers have created forms that have economized their material, time and labor, and made their work both secure and lasting. We will begin with a glance at the rearing of shelter, an art which commenced with the putting together of boughs and loose stones, and to-day requires the utmost skill both of architects and engineers.

Strength and Rigidity.

Building in its modern development owes as much to improvement in form as to the use of stronger materials, brick instead of clay, iron and steel instead of wood. A stick as cut from a tree makes a capital tent-pole, and will serve just as well to sustain the roof of a cabin. For structures so low and light it is not worth while to change the shape of a stick. By way of contrast let us glance at an office building of twenty-five stories, or the main piers of the new Quebec Bridge rising 330 feet above their copings. To compass such heights stout steel is necessary, and it must be disposed in shapes more efficient than that of a cylinder, as we shall presently see.

In most cases strength depends upon form, in some cases strength has nothing whatever to do with form; if we cut an iron bar in two its cross-section of say one square inch may be round, oblong, or of other contour, while the effort required to work the dividing shears will in any case be the same. But shearing stresses, such as those here in play, are not so common or important as the tension which tugs the wires of Brooklyn Bridge, or the compression which comes upon a pillar beneath the dome of the national capitol. When we place a lintel over a door or a window, we are concerned that it shall not sag and let down the wall above it in ruin: we ensure safety from disaster by giving the lintel a suitable shape. When we build a bridge we wish its roadway to remain as level as possible while a load passes, so that no hills and hollows may waste tractive power: levelness is secured by a design which is rigid as well as strong. If a railroad has weak, yielding rails, a great deal of energy is uselessly exerted in bending the metal as the wheels pass by. A stiff rail, giving way but little, avoids this waste. To create forms which in use will firmly keep their shape is accordingly one of the chief tasks of the engineer and the architect.

Rubber strip suspended plank-wise, and joist-wise.

Board doubled breadthwise through small semi-circle AB, then edgewise through large semi-circle CD.

Plank and Joist.

Forms of this kind, well exemplified in the steel columns and girders of to-day, have been arrived at by pursuing a path opened long ago by some shrewd observer. This man noticed that a plank laid flatwise bent much beneath a load, but that when the plank rested on its narrow edge, joist fashion, it curved much less, or hardly at all. Thus simply by changing the position of his plank he in effect altered its form with reference to the strain to be borne, securing a decided gain in rigidity. Let us repeat his experiment, using material much more yielding than wood. We take a piece of rubber eight inches long, one inch wide and one quarter of an inch thick. Placing it flatwise on supports close to its ends we find that its own weight causes a decided sag. We next place it edgewise, taking care to keep it perpendicular throughout its length, when it sags very little. Why? Because now the rubber has to bend through an arc four times greater in radius than in the first experiment. Suppose we had a large board yielding enough to be bent double, we can see that there would be much more work in doubling it edgewise than flatwise. The rule for joists is that breadth for breadth their stiffness varies as the square of their depth, because the circle through which the bending takes place varies in area as the square of its radius. In our experiment with the rubber strip by increasing depth four-fold, we accordingly increased stiffness sixteen-fold; but the breadth of our rubber when laid as a joist is only one-fourth of its breadth taken flatwise, so we must divide four into sixteen and find that our net gain in stiffness is in this case four-fold.

Telegraph poles under compression. Wires under tension.

Girders.

Here let us for a moment dwell upon the two opposite ways in which strength may be brought into play, as either compression or tension is resisted. An example presenting both is a telegraph pole, with well-balanced burdens of wires. Its own weight and its load of wires, compress it, as we can prove by measuring the pole as stretched upon the ground before being set in place, and then after it is erected and duly laden. Should this downward thrust be excessive, the pole would be crushed and broken down. The strung wires are not in compression, but in the contrary case of tension, and are therefore somewhat lengthened as they pass from one pole to the next. Now observe a mass first subjected to compression, and next to tension. In bearing a pound weight a rubber cylinder is compressed and protrudes; when the weight is suspended from this cylinder, the rubber is lengthened by tension. In each case the effect is vastly greater than with wood or steel, because rubber has so much less stiffness than they have.

Rubber
cylinder.

Flattened by
compression.

Lengthened
by tension.

Rubber
cylinder.

Flattened by
compression.

Lengthened
by tension.

Both tension and compression are exhibited in our little rubber joist, which illustrates the familiar wooden support beneath the floors of our houses. This form in giving rise to the girder has been changed for the better. Let us see how. As the rubber joist sags between its ends, we observe that its upper half is compressed, and its lower half extended, the two effects though small being quite measurable. As we approach the central line, A B, this compression and tension gradually fall to zero; it is clear that only the uppermost and undermost layers fully call forth the strength of the material, the inner layers doing so little that they may be removed with hardly any loss. Hence if we take a common joist and cut away all but an upper and lower flange, leaving just web enough between to hold them firmly together, we will have the I-beam which among rectangular supports is strongest and stiffest, weight for weight. In producing it the engineer has bared within the joist the skeleton which confers rigidity, stripping off all useless and burdensome clothing. An I-beam made of rubber when laid flatwise over supports at its ends will sag much; when laid edgewise it will sag but little, clearly showing how due form and disposal confer stiffness on a structure.

Rubber joist in section, compressed along the top, extended along the bottom.

Girder cut from joist.

Rubber I-beam suspended flatwise, and edgewise.

Simple girder contours.

Girder contours simple and built up.

Girder forms in locomotive draw-bars.

Girders of steel are rolled and riveted together at the mills in a variety of contours, each best for a specific duty, as the skeleton of a floor, a column, or a part of a bridge. Their lengths, if desired, may far exceed those possible to wood. Their principal simple forms are the I-beam; T, the tee; L, the angle; C, the channel; and the Z-bar. Of these the I-beam is oftenest used; its two parallel flanges are at the distance apart which practice approves, they are united by a web just stout enough not to be twisted or bent in sustaining its burdens. Crank shafts of engines, to withstand severe strains, are built in girder fashion; so are the side-bars of locomotives and the braces of steel cars. Plates riveted together may serve as compound girders or columns of great strength and rigidity. In the New York subway the riveted steel columns which support the roof have a contour which enlarges at the extremities.

100,000 pound steel ore car built by the Standard Steel Car Co., Pittsburg, for the Duluth, Missabe & Northern R. R. Of structural steel throughout. Weight unloaded, 32,200 pounds.

Section of standard bulb angle column, New York Subway.

The Rail.

By all odds the most important girder is the rail in railroad service. Let us glance at phases of its development in America, as illustrating the importance of a right form to efficient service. At the outset of its operations, in 1830, the Mohawk & Hudson Railroad, now part of the New York Central & Hudson River Railroad, employed a rail which was a mere strap of iron two and one half inches wide, nine sixteenths of an inch thick, with upper corners rounded to a breadth of one and seven eighths inches; it was laid upon a pine stringer, or light joist, six inches square, and weighed about 14 pounds per yard. Thin as this rail was, its proportions were adequate to bearing a wheel-flange which protruded but half an inch or even less. Where the builders of that day sought rigidity and permanence was in the foundations laid beneath their stringers. Except upon embankments there were for each track two pits each two feet square, three feet from centre to centre, filled with broken stone upon which were placed stone blocks each of two cubic feet. On the heavy embankments cross-ties were laid; these were found to combine flexibility of superstructure with elasticity of roadbed, so that they were adopted throughout the remainder of the track construction and continue to this hour to be a standard feature of railroad building.

Cross Section

Top View

Strap rail and stringer, Mohawk & Hudson R. R., 1830.

It was soon observed that the surface of a track as it left the track-maker’s hands, underwent a depression more or less marked when a train passed over it. With a strap-iron rail this depression was so great that engines were limited to a weight of from three to six tons. Before long the strap form was succeeded by a rail somewhat resembling in section the rail of to-day. Year by year the details of rolling rails were improved, so that sections weighing thirty-five to forty pounds to the yard came into service. These at length united a hard bearing surface for the wheel-treads, a guide for the wheel-flanges, and a girder to carry the wheel-loads and distribute them to the cross-ties. Thereupon the weights of engines and cars were increased, leading, in turn, to a constant demand for heavier rails. In 1865 a bearing surface was reached adequate for wheel-loads of 10,000 to 12,000 pounds, the rail weighing fifty-six to sixty pounds to the yard. But the metal was still only iron, and wore rapidly under its augmented burdens. Then was introduced the epoch-making Bessemer process and steel was rolled into rails four and one-half inches high, of fifty-six to sixty-five pounds to the yard, of ten to fifteen-fold the durability of iron. In design the early steel rails were limber so that they rapidly cut the cross-ties under their seats, pushing away the ballast beneath them. Because they lacked height they had but little stiffness, one result being that the spikes under the rails were constantly loosened, exaggerating the deflection due to passing trains. Throughout the lines every joint became low, and the rails took on permanent irregularities under the pounding of traffic, dealing harmful shocks to the rolling stock.

Dudley’s Track Indicator.

This was the state of affairs in 1880, when Mr. Plimmon H. Dudley invented his track-indicator. This apparatus, placed in a moving car, records by ever-flowing pens on paper every irregularity, however slight, in the track over which it passes. When railroad engineers first saw its records, they believed that the thing to do was to restore their roads to straightness by the labor of track-men. It was abundantly proved that the real remedy lay in using a rail of increased stiffness, that is, a rail higher and heavier. Mr. Dudley, in the light of records covering thousands of miles of running, added fifteen pounds to a rail which had weighed sixty-five pounds, and gave it a height of five inches instead of four and one half, while he broadened its upper surface. At a bound these changes increased the stiffness of the section sixty per cent., the gain being chiefly due to added height. Proof of this came when his improved rail was found to be much stiffer than that of the Metropolitan Railway, of London, which weighed eighty-four pounds to the yard and had a base of six and three eighths inches, but a height of only four and one half inches. In July, 1884, the Dudley rail was laid in the Fourth Avenue viaduct, New York; so satisfactory did it prove that in less than two years five-inch rails were in service on three trunk lines. Then followed their introduction throughout America, their smoothness and stability as a track giving them acceptance far and wide.

Photograph by F. M. Somers, Cincinnati, O.

PLIMMON H. DUDLEY

of New York.

The performance of the Dudley rail so impressed Mr. William Buchanan, Superintendent of Motive Power for the New York Central Railroad that in 1889 he planned his famous passenger engine, No. 870, which entered upon active duty in April, 1890. It carried 40,000 pounds upon each of its two pairs of driving wheels, instead of 31,250, as did its heaviest predecessor; its truck bore a burden of 40,000 pounds more; its loaded tender weighed 80,000 pounds, making a total of 100 tons, an advance of forty per cent. beyond the weight of the heaviest preceding engine and tender. Mr. Buchanan’s forward stride has been worthily followed up. Since 1890, passenger locomotives have nearly doubled in the weight borne upon their axles, while tractive power has increased in the same degree. Through express and mail trains have more than doubled in weight, and their speeds have increased thirty to forty per cent. The tonnage of an average freight train has been augmented four to six-fold, with reduction of the crews necessary to keep a given amount of tonnage in motion. This economy is reflected in a reduction of rates which are now in America the lowest in the world, and which steadily fall. In capacity for business united with stability of roadbed, mainly due to stronger and stiffer rails and to adapted improvement in rolling stock, railroad progress in the past fifteen years is equal to that of the sixty years preceding. With rails increased to a weight of 100 pounds to the yard there is shown, even in passing over the joints, an astonishing degree of smoothness as contrasted with the jolting action of rails comparatively low and light. Stiffness of rail reduces the destructive action of service, originally enormous, upon both equipment and track, lowering in a marked degree the cost of maintenance. Size of rail as well as form plays a part in this economy. A passenger train weighing 378 tons has required 820 horse power on 65-pound rails, and but 720 horse power on 80-pound rails, the speed in both cases being 55 miles an hour; it is estimated that with 105-pound rails 620 horse power would have sufficed. In freight service Dudley rails have reduced the resistances per ton from between 7 and 8 pounds to one half as much; a further reduction, to 3 pounds, is in prospect. In passenger service, with rails of unimproved type the resistance at 52 miles an hour is 12 pounds per ton; with Dudley rails this resistance for heavy trains is not augmented when the speed rises to 65 or 70 miles an hour. Dudley rails, and rails derived from their designs, are now in use on three fourths of all the trackage of American railroads, effecting a vast economy. Seventy-five years ago the DeWitt Clinton locomotive and tender weighed only five sixths as much as the main pair of driving wheels, boxes, axle, and connecting rods of the present Atlantic type of engine. That such an engine can haul a heavy train at seventy miles an hour largely depends upon the production of that simple and important element in railroading, its rail.[1]

[1] Mr. Dudley’s rails, and those of other designers, are fully illustrated and discussed in “Railway Track and Track Work,” by E. E. Russell Tratman. Second edition. New York, Engineering News Publishing Co.

Dudley rails.

Steel cross-ties and rails.—Carnegie Steel Co., Pittsburg.

In Ninth Street, Pittsburg, the rails of the traction line are for some distance carried on steel ties similar in form, as here shown.

CHAPTER III
FORM—Continued. BRIDGES

Roofs and small bridges may be built much alike . . . The queen-post truss, adapted for bridges in the sixteenth century, was neglected for two hundred years and more . . . A truss bridge replaces the Victoria Tubular Bridge . . . Cantilever spans at Niagara and Quebec . . . Suspension bridges at New York . . . The bowstring design is an arch disguised . . . Why bridges are built with a slight upward curve . . . How bridges are fastened together in America and England.

King-post truss. AK, king-post.

Roofs and Bridges Much Alike.

Rails are girders used by themselves: girders are often combined in trusses; of these much the largest and most important are employed for bridges. There is now under construction near Quebec a cantilever bridge whose channel span of 1,800 feet will be the longest in the world. See [page 29]. It will take us a little while to understand how so bold a flight as this was ever dared. We will begin with a glance at a truss of the simplest sort, such as we may find beneath the roof of an old-fashioned barn. A pair of rafters, AB and AC, are inclined to each other at an obtuse angle, and are fastened to the horizontal beam, BC, at B and C. Their apex, A, is joined to BC by the king-post, AK, which binds the three strongly and firmly. This whole structure makes up a triangle, and so does each of its halves, ABK and AKC. No other shape built of straight pieces will keep its form under strain. Take in proof say four pieces of lath and unite them with a freely turning pin at each corner to make the frame, ABCD; it is easily distorted by a slight pull or push; but insert cross-pieces, AC and BD so as to divide the square into triangles, and at once the frame resists any strain not severe enough to break the wood or crush its fastenings. As the roof presses down the frame ABC, its sides, AB and AC, tend to slide away at their lower ends, B and C, but this is prevented by the horizontal beam, BC, which while it holds them in place is itself so stretched as to be held level and straight. This calling into play of tension constitutes the chief merit of the truss, and enables it in roofs and bridges to span breadths impossible to simple beams bending downward under compressive strains. Not only in houses, but in ships, the truss has great value; it was introduced in this field by Robert Seppings of Chatham, in England, about 1810. To resist the pressure of grinding ice, the “Roosevelt” is built with trusses of great strength. She sailed in 1905, under Commander Peary, for a voyage of Arctic discovery.

Frames of four sides. For rigidity diagonals are needed, AC, BD.

Were our barn roof flat instead of sloping to form a truss, its supporting timbers, under compression, would have a decided sag from which BC is free. When we fashion a small model of a king-post truss, its sides, AB and AC, must be of metal or wood because they will be in compression; the king-post, AK, and the base, BC, which will be under tension, may be of rubber or cord. Always as in this case the parts of a truss exposed to compression must be of rigid material. When a part may be of cord, rope or wire, we know that it is resisting tension.[2]

[2] A model easily put together illustrates the truss in its simplest form. Take a pair of wooden compasses, each half of which is 15 inches long, such as are sold for blackboard use by the Milton Bradley Co., Springfield, Mass., at 50 cents. At each tip fasten, by the ring provided with the compasses, a chair castor such as may be had at any hardware store. Join the tips of the castors by a rubber strip. Holding the compasses upright, and applying pressure from the hand, they will extend until the rubber will be so stretched as to become almost perfectly horizontal. Various weights may in succession be suspended from the compass-joint, replacing manual pressure, and serving to measure the exerted tensions.

Cross-section of the “Roosevelt,” Commodore Peary’s new Arctic ship. Reproduced by permission from the Scientific American, New York.

Pair of compasses stretch a rubber strip.

Wrought iron exerts about as much resistance to compression as to tension; so does steel. For this reason, and on account of their great strength, they have immense value in building. Cast iron can bear only about one sixth as much tension as compression, so that it is useful as foundations, for the bed-plates of engines and machinery and the like, but is unsuitable for girders. Wood is much stronger under tension than compression; in white pine this proportion is as eight to one. In designing timber bridges the strains are, therefore, as far as possible, arranged for tension.

Queen-post truss.
DE, HO, queen-posts.

Upper part of a roof truss.
Interborough Power House, New York.

Let us now enter another barn, about one half wider than the first, and look upward at its rafters. We see its roof sustained by timbers disposed as DCMH, to avoid the undue weight necessary for a design resembling that of our first roof, ABC. Instead of one upright post, AK, as in that case, we have now two, DE and HO, called queen-posts, sustaining the horizontal beam, CM. In large modern roofs the simple queen-post is modified and multiplied, as in the main power house of the Interborough Rapid Transit Company, West 59th St., New York. Returning to our simple queen-post design, let us imagine a creek flowing between walls spanned by DCMH; that truss and a mate to it, parallel at a distance of say ten feet, would easily carry a roadway and give us a bridge. A truss for a bridge must be much stronger than for a roof of equal span, because a bridge has to bear moving loads which may come upon it suddenly, giving rise not only to serious strains but to severe vibrations, all varying from moment to moment.

Two queen-post trusses form a bridge.

Palladio trusses.

Palladio’s Long Neglected Truss.

The queen-post truss was remarkably developed by Palladio, a famous Italian architect of the sixteenth century. Two of his designs, here given in outline, are from his work on architecture published in 1570; their contours, little changed, are in vogue to-day. Strangely enough the trusses of Palladio, for all their merit, passed out of notice until their principles were revived and improved by Theodore Burr, in 1804, in a wooden bridge over the Hudson at Waterford, New York. This bridge had spans respectively of 154, 160 and 180 feet, stretches impossible to single wooden beams. Professor J. B. Johnson, an eminent engineer, says that this is the most scientific design ever invented for an all-wooden bridge; during fifty years it stood unrivaled as a model for highway purposes in this country. The Burr bridges were usually covered in, so as to resemble the roofs we began by inspecting. In a truss bridge each part bounded by two adjacent uprights, as DOEH in the [queen-post] figure on page 21, is a panel; every part under compression, as DO, HE, is a strut, post, or column; every part subject to tension as DE, HO, is a tie.

Burr Bridge, Waterford, N. Y.
DO, HE, struts. DE, HO, ties. DHEO, panel.

In 1830 as the first American railroad train sped on its way, a new era dawned for the bridge builder as well as for his neighbors. At once sprang up a demand for bridges longer and stronger than those which in the past had served well enough. A score of wagons laden with wheat or potatoes were a good deal lighter than a locomotive followed by a train of loaded freight cars. A market-wagon, too, could easily be taken aboard a ferry-boat, but for an engine and its cars a bridge was imperative, if the stream were not so wide as to forbid all opportunity to the bridge builder. His response to the demands of the railroad was two-fold. First in the use of metal instead of wood, beginning with iron rods to bind together frames of timber. As iron became cheaper and its value more and more evident, he employed it for additional parts of his structure until at last he built the whole bridge of iron.

To-day good steel is so cheap that railroad bridges are seldom reared of anything else. Besides using stronger materials, the designer has gradually improved the form of his structure, not only in its parts but as a whole, so that to-day, strength for strength, a bridge may be only one tenth as heavy as a bridge of fifty years ago. Advances in form have been due to experience as one type has been compared with another; meanwhile the mathematicians have carried their analysis of strains as far as the extreme complexity of their problems will allow, greatly to the betterment of designs.

In building a bridge, as in rearing many other structures, girders of various contours are used. In bridge building the I-beam is most employed. When the roadway proceeds on the top chord, as DH, in the [queen-post] figure, page 21, we have a deck bridge; when it is built on the bottom chord, as CM, we have a through bridge.

HOWE TRUSS

PRATT TRUSS

The Burr Bridge Simplified by Howe and Pratt.

The Burr bridge of 1804, already mentioned, included an arch and was in part sustained by struts projecting from abutments. These features were omitted by William Howe in the bridge which he patented in 1840, and which was, as far as is known, the first successor to a design of Palladio in employing a simple truss for long spans. The Howe truss was built of wood, except its terminal tie-rods, which were of iron; it has been repeated thousands of times throughout the world. In 1844 Thomas W. and Caleb Pratt patented a bridge which in design was the converse of Howe’s. Its diagonals of iron were used in tension, while its vertical struts of timber were in compression; in the Howe pattern the diagonals were in compression, the verticals in tension. This plan, by shortening the struts, diminished the cross-section necessary in a truss. When wrought iron took the place of wood for bridges, the Pratt design became the most popular of all, combining as it did more desirable features than any of its rivals. To-day for long spans the Baltimore truss is much in favor. Its stresses, that is, its resistances to change of form under strain, are readily ascertained; the shortness of its panels means strength; and its diagonals have the inclination which wide and varied experience has shown most desirable. The roadway, it will be observed, is upheld by sub-verticals, that is, by verticals which reach the floor from half the height of a panel.

Diagram of Baltimore truss.

Whipple Bridge.

An important study concerns itself with the intensity and distribution of strains, first in girders, next in trusses, and lastly, in bridges as units, all with intent to ensure the best possible designs throughout. In this field of inquiry the pioneer was Squire Whipple, a maker of mathematical instruments in Utica, N. Y., who published in 1847 his analysis of the strains in a truss bridge due to its own weight and to its moving loads. With the laws of these strains in mind he devised several bridges of great merit, the most noteworthy being reared in 1852 on the Rensselaer & Saratoga Railroad, seven miles north of Troy, which did service until 1883; its sides or web system had ties extended across two panels in double intersection.

In a long truss bridge, which in its entirety may be regarded as a girder of the utmost size, the cross pieces between the main beams of the structure are much less heavy than if continuous plates, of no more strength. The original form of the Victoria Bridge at Montreal was that of a continuous tube of iron, square in section; it has given place to a truss bridge of five times greater capacity which weighs only twice as much. ([Illustrations] of both on pages 27 and 28.)

Thus to lessen weight in comparison with strength is a matter of great importance in a suspended structure, which must not only bear its own weight, but carry heavy moving loads.

Simple cantilevers.
FG, HI, are first separate; then in contact; last are joined by a plank laid above them.

VICTORIA BRIDGE, MONTREAL.
Original tubular form designed by Robert Stephenson.

VICTORIA BRIDGE, MONTREAL,
Rebuilt with trusses.

CANTILEVER BRIDGE ACROSS THE ST. LAWRENCE, NEAR QUEBEC.
Total length, CF, 3300 feet. Channel span, DE, 1800 feet. Central truss, AB, 675 feet.

Advantages of the Cantilever, Arch, and Bowstring Designs.

In most cases a bridge crosses a valley or a river in a place which permits the engineer to erect scaffolding to support his trusses until they can be united and become self-sustaining. In some places this course is denied; a river such as the Ohio or the Mississippi may have to be spanned at a point where the waters in a single day may rise forty feet, bearing along trees and timbers with destructive violence. As a rule the difficulty is met by employing cantilever spans which require no scaffolding for their construction. To understand their principle let us suppose that on opposite banks of a creek we roll out to meet each other the joists FG and HI, taking care that the parts over the water shall always be lighter than the parts on land. When the joists at last touch they are secured to each other as a continuous roadway. Or, while they are at a moderate distance apart they may be joined by a third timber laid across the gap from one to the other. In practice the simple principle thus illustrated is developed and varied in many ways, but in every application the one rule is that the trusses as they stretch out from the two sides of a pier shall balance each other, the shore ends being duly weighted down or safely anchored to solid rock. And thus, at length, we come to the wonderful bridge, six miles west of Quebec, whose channel span of 1,800 feet will be the longest ever reared. See [illustration], page 29. From the cantilever arms, DA and BE, will be suspended the central truss, AB, of 675 feet. A cantilever span may be much longer than a simple truss because on a pier, as D of this bridge, a part, DA, of the whole span, DE, is balanced either, as in this case, by a shore span, CD, or by a corresponding part of the next span should that span not extend to the shore but pass from one pier to another.

Kentucky river cantilever bridge

The first cantilever bridge in America was designed by C. Shaler Smith for the Cincinnati Southern Railroad, to cross the Kentucky River; it was built in 1876-7.

Arch bridge, Niagara Falls

Spanning the gorge of Niagara, close to the Falls, is an arch bridge of 840 feet in its central span, which, in its construction during 1898, followed the plan originated by James B. Eads in building the St. Louis bridge nearly thirty years before. As scaffolding was out of the question in both cases, each bridge was built out from its piers on the cantilever principle. An arch is sometimes disguised as a modified bowstring, as in the Burr design of 1804, a horizontal tie connecting the extremities of the arched rib and taking its thrust, dispensing with the abutments demanded by an arch. In the chords of such a pattern the strength comes as near to uniformity throughout as practical considerations permit, avoiding the losses of early days when one part of a bridge might be twice as strong as another. The bowstring was adopted for the great span of 542¹⁄₂ feet over the Ohio at Cincinnati built in 1888, and for the span of 546¹⁄₂ feet erected at Louisville in 1893. A bowstring 533 feet long, forming part of the Delaware river bridge of the Pennsylvania Railroad, built in 1896, in Philadelphia, is outlined on [page 32]. At Bonn, on the Rhine, there was completed in 1904 a bridge whose central span is a bowstring 616¹⁄₄ feet long.

Bowstring Bridge, Pennsylvania R. R., Philadelphia.

Suspension Bridges and Continuous Girders.

If we take the design of an arch bridge and turn it upside down we have a contour such as that of the Williamsburg Suspension Bridge, opened in 1903 between Brooklyn and Manhattan, [depicted] on page 33. For the utmost length this is the only available span; it brings into play the tensile strength of wire, the strongest form that steel can take. A steel cable of suitable diameter, if it had to support only itself, might safely be three miles long. A suspension bridge has another advantage in employing an anchorage to bear strains which would break down a simple truss resting on piers. As first erected suspension bridges were liable to extreme and harmful vibration, in many cases being shaken to pieces by storms of no great violence. It was found that this vibration was checked and that safety was ensured by introducing stiffening trusses which, at the same time, benefited the bridge by distributing the load uniformly throughout the sustaining cables.

WILLIAMSBURG BRIDGE, NEW YORK CITY.

At Lachine, about eight miles west of Montreal, on the line of the Canadian Pacific Railroad, a remarkable bridge crosses the St. Lawrence river. Its design is that of a continuous girder of four spans, the two side spans being 269 feet each in length, and the two others each 408 feet. This type is discussed by Mr. Mansfield Merriman and Mr. Henry S. Jacoby in Part IV, page 30, of their work on Roofs and Bridges. One of the advantages presented is that deflection under live load is less, and stiffness greater than for simple, discontinuous girders, the harmful effect of oscillation being thus diminished. Furthermore, less material is required than for simple, discontinuous spans. Both these elements of gain are brought out in placing a strip of rubber, AD, upon four equidistant points of support, when we find that BC, the central third of the strip sags less than either AB or CD, the first or last third. Cutting off one-third of the whole strip we deprive the removed piece, at its surface of separation, of the cohesion which did much to keep the whole strip, before cutting, almost horizontal at that point. We take AB, our short removed piece of rubber, and lay it at its ends on two points of support; it now serves in a rough-and-ready way as a model of a simple truss, all by itself; its decided sag shows it much less rigid than when it formed a part of an unbroken and longer structure. Continuous girders despite their advantages are seldom employed; they are liable to serious difficulties; among these may be mentioned that changes, often unavoidable, of level in piers and abutments cause them to suffer great reversals of stress, always a source of danger; furthermore, variations of length due to changes of temperature are, of course, much greater and more troublesome to provide against than in the case of discontinuous girders.

Continuous girder bridge, Canadian Pacific R. R., Lachine, near Montreal.

Rubber strip supported at 4 points, and at 2 points.

Plate girder bridge.

Best Proportions for Spans: A Slight Upward Curve is Gainful. Pins or Rivets in Fastening.

Whether spans are long or short, engineers are fairly well agreed as to the best proportions for girders and panels. They consider that a girder should have about one-twelfth to one-tenth as much depth as span; and that the weight of a web should be about equal to that of its flanges. They usually give panels twice as much depth as length, with a tendency to increase the proportion of depth to length, in order to minimize the deflections and oscillations which shorten the life of a structure. For definite lengths of span, particular types of construction are preferred; usually for lengths of from 20 to 125 feet, plate girders are chosen; for spans of 125 to 150 feet riveted lattice trusses are built; for spans of 150 to 600 feet pin-connected trusses are employed. Here we reach the economical limit of a length for simple trusses; beyond 600 feet the engineer is obliged to have recourse either to a cantilever or a suspension bridge.

Part of lattice girder bridge, showing rivets.

Whatever the breadth of the stream or the chasm over which he is to build a roadway, each case must be studied in the light of its special circumstances. There must be due regard to business as well as to engineering considerations; the designer will bear in mind that types of parts customarily turned out at great steel works are procurable in less time, and at less cost, than novel types requiring to be manufactured to order. Then, in speed of construction, he will remember that a pin-connected bridge can be built much faster than a riveted structure. Furthermore, every part must be vastly stronger than ordinary duty requires. Tempests and floods may suddenly arise; at any instant a derailment or a collision may create a strain of the utmost severity; and even under ordinary circumstances it must not be forgotten that train loads grow constantly heavier because economy lies that way.

Upper shelf, unladen, has upward curve or camber.
Lower similar shelf is straightened by its load.

One detail of bridge design is worth a moment’s attention. When a book-shelf is a thin board, quite straight as manufactured, it sags in the middle when fully burdened. This downward dip may be avoided by making the shelf at first with a slight curve which brings the middle a little higher than the ends. In bridge building a like curve, or camber, is given to each span so that when fully loaded it will be level or nearly so. In a span of 500 feet it is found that a rise of half a foot at the centre is sufficient. In suspension bridges, for the sake of strengthening the structure, the camber far exceeds this ratio.

Pin connecting parts of a bridge.

In fastening together the parts of a bridge the usual American practice, already mentioned, is to employ pins which pass through eye bars. In England riveting is preferred, as shown in the [figure] of the lattice truss, page 36. This difference in methods arose through the use of materials which differed. In the construction of bridges the English engineer started with the flanged girder of cast or rolled iron, or some other form of stiff beam, and as bridges increased in size so as to require the framing of a truss, his whole effort was directed toward making that truss as much like the original flanged or box girder as possible. The American engineer, on the other hand, had at first little or no iron or steel to work with, and of necessity used wood. As the necessary bridges were of considerable span, the only feasible method was to pin together small pieces of wood so as to form a connected series of triangles. To make rigid joints in wood was impracticable, and indeed rigid joints were not desired, because the strength of wood is slight when strains are applied in any direction other than that of the fibres of the piece, and the pin joint insures just this line of action. As a rule a riveted bridge requires more metal than a pin-connected design, takes more time to build, but demands somewhat less skill. To provide for changes in length as a bridge is subjected to variations of temperature, friction rollers are used to support its extremities. In the first suspension bridge at Niagara Falls, built by Roebling, a little cement accidentally covered the friction rollers and prevented them from turning; fortunately the structure escaped the destruction to which it was thus exposed.

Bridge rollers in section and plan.
New York, Pennsylvania & Ohio R. R.

We have now taken a rapid survey of some of the methods by which the designer of bridges plans a structure which is at once safe and to the utmost extent economical of material. Step by step he has discovered how little steel he may use for designs all the bolder because his hand is so sparing of weight. His success began in adopting the girder, which we have seen to be in effect the working skeleton long concealed within the common joist; the cantilever span near Quebec, which compasses 1,800 feet in its flight, has been dissected out of preceding burden bearers in the same way. Its metal stands forth as so much sheer muscle kept to the most telling lines, unencumbered by a single pound of idle substance. A designer of such a fabric is an artist skilled in disengaging from masses of material every ounce that can be wisely removed. In some cases, as when Roebling linked together New York and Brooklyn, a bridge is created as much a thing of beauty as of use, as graceful as it is strong.[3]

[3] Mr. David A. Molitor has a chapter, copiously illustrated, on the esthetic design of bridges, beginning page 11 in the “Theory and Practice of Modern Framed Structures,” by Mr. J. B. Johnson and other authors, New York, John Wiley & Sons. Eighth edition, revised and enlarged. $10.00.

CHAPTER IV
FORM—Continued. WEIGHT AND FRICTION DIMINISHED.

Why supports are made hollow . . . Advantages of the arch in buildings, bridges and dams . . . Tubes in manifold new services . . . Wheels more important than ever . . . Angles give way to curves.

Having glanced at methods by which forms, judiciously chosen, economize the materials of buildings and rails, of bridges diverse in type, we pass to further consideration of these and like shapes, to find that they effect a saving in material while they make feasible a new boldness of plan, and introduce new elements of beauty. We will also remark that judicious forms prevent waste of energy as structures are either set in motion, or serve to convey moving bodies. Incidentally we shall see that well chosen shapes insure a structure against undue hurt and harm.

Square

Octagonal

16-Sided

Round

Girder sections.

Hollow Columns and Tubes.

In lofty structures, the box girder is frequently employed as a column or a beam because it has even greater rigidity than the I-beam; usually it has four sides, but it may have eight, sixteen, or more, and thus step by step we come to a hollow cylindrical column which has, indeed, the best form that can be bestowed on supporting material. Chinese builders learned its economy on the distant day when they adopted the bamboo for their walls and roofs. Comparison with a solid stick of timber of like weight and substance will show that an equal length of bamboo is decidedly preferable. The inner half of a round solid stick does comparatively little in holding up a burden; to remove that half is therefore as gainful as to strip from a joist the timber surrounding its working skeleton. At first the journals or axles of engines and large machines, as well as the axles of railroad cars and the shafts of steamships were solid; to-day, in a proportion which steadily increases, they are hollow. The advantage of this form comes out when we take two cylinders of rubber, alike in length and weight, one solid, the other hollow. Supporting both at their ends, the hollow form sags less than the solid form, proving itself to be the more rigid of the two.

Solid rubber cylinder sags much.
Hollow rubber cylinder sags less.

Handle-bar of bicycle in steel-tubing.

A sulky in steel tubing.

A pneumatic hammer, steel tubing.

Fishing-rod in steel tubing.

Bridge of steel pipe.

With like advantage seamless tubing is adopted for a broad variety of purposes. It builds bicycles and sulkies which far out-speed vehicles of solid frames; it is worked up into elevator cages, mangle rolls, pneumatic tools, fishing-rods, magazine-rifle tubes, inking rollers, farm machinery, poles, masts and much else where strength and lightness are to be united. Steel tubing is readily bent into any needed contour, even when of considerable diameter. Mr. Egbert P. Watson has pointed out its availability for highway bridges of about forty feet span, no professional bridge-builders being needed for their construction. Near Saxonville, Massachusetts, a pipe-arch bridge, eighty feet long, provides a roadway across the Sudbury River, while carrying within its pipe a stream which forms part of the Boston water system. A bridge of similar form, 200 feet long, spans Rock Creek in the City of Washington. The Eads bridge crossing the Mississippi, at St. Louis, employs for each span eight steel tubes of nine inches exterior diameter. Tubes large and small have been strengthened by adopting the model of an old-fashioned fire-lighter, or spill, a bit of paper rolled spirally as a hollow tube. Blow sharply into it and you but tighten its joints. In like manner tubes and pipes of metal are all the tighter when their seams are spiral instead of longitudinal. An eager quest for combined strength and lightness in the bicycle has ended in the choice of tubes spirally welded.

Arch bridge of steel pipe,
Sudbury River, near Saxondale, Mass.

Spiral fire-lighter.

Spiral weld steel tube.

Arches.

When builders of old began to rear masonry they repeated in stone or brick the forms they had constructed in wood. Accordingly the lintels of their doors and windows were flat. It was a remarkable step in advance when the arch was invented, probably by a bricklayer, spanning widths impossible to horizontal structures. A flat course of stone or brick presses downward only; an arch presses sidewise as well as downward. It is this sidewise thrust, calling into play a new resource, that gives the arch its structural advantage. In modern masonry the boldest arch is that of the bridge at Plauen, Germany, with its span of 295¹⁄₄ feet. Of pointed arches the chief sustain the walls of Gothic cathedrals; it was to counteract the outward thrust of these arches that external buttresses were reared, either solid, as at St. Remy in Rheims, or flying, as at Notre Dame in Paris. The Saracenic arch, offering more than half of a circle, is not so strong as the Roman arch, but it has a grace of its own, fully revealed in the Alhambra, and in the incomparable mosque at Cordova. A chain of small links, a watch-chain, for example, freely hanging between two points of support strikes out a catenary curve; this Galileo suggested as the outline for an arch in equilibrium; it is adopted for suspension bridges.

Longest stone arch in the world, Plauen, Germany.

Church of St. Remy, Rheims, France.
Section across buttressed choir.

Curve of suspended chain.

Dam across Bear Valley, San Bernardino County, California.

“The arch,” says Mr. William P. P. Longfellow in “The Column and the Arch,” “was the great constructive factor in the architecture of the Roman Empire; it added enormously to the builder’s resources in planning, and to his means of architectural effect. It gave him the means of spanning wide openings, and when expanded into the vault, of covering great spaces; it habituated him to curved lines and surfaces. Helped by it, and spurred by the new wants of the complex Roman civilization, he enlarged the scale of his buildings and greatly increased the intricacy of their plans. He used his new combinations with a boldness and fertility of invention that have been the wonder of the world from that age to ours, constructing on a scale that dwarfed everything that had gone before except the colossal buildings of Egypt. Under a new stimulus, and with new means of effect, Roman building greatly outstripped that of the Greeks in extent, in variety, and magnificence.”

An arch built on its side, with its convexity upstream, and its ends braced against rocky banks, serves admirably as a dam. It has in many cases withstood floods much higher than those expected by its designers. Such dams must not be too long, or what is saved in thickness is more than lost in length. Arches inverted are used in many places as gulleys for drainage. Near Bristol, in England, they anchor the cables of the Clifton Suspension Bridge, at a depth of eighty-two feet below the surface of the ground. Many tunnels finished in masonry have outlines which are two arches united, the lower arch being inverted. The Cloaca Maxima, the famous sewer at Rome, is of this pattern; it is twenty-six feet high, sixteen feet broad, and is now in its twenty-fifth century of service.

Ferguson locking-bar pipe. East Jersey Pipe Co,. Paterson, N. J.

Circles and Other Curves.

From arches, built of parts of circles, let us pass to the circle itself, and glance at the use of tubes of circular section as we begin to consider how resistances to motion may be minimized. The use of the bamboo not only for building, but for the carriage of water, began in the remote past. As structural material it was light and strong as we have noticed; laid upon the ground it was a ready-made water pipe of excellent form. When trees were hollowed out to convey water, when clay was modeled into tubes, the hollow cylindrical shape of the bamboo was in the mind of the Asiatic artisan, to be faithfully copied. That form has descended to all modern piping for water, steam, and gas, because the best that a pipe can take. No other shape has, proportionately to capacity, so little surface for friction inside or rust outside. A locking-bar water pipe, devised by Mephan Ferguson, of Perth, Australia, is made of two plates of equal width, curved into semi-circles which are pressed at their ends into channel bars of soft steel. As the locking-bars and joints are opposite each other, their joints can be tightly closed by a simple machine which exerts pressure in a straight line. This construction may be used not only for pipes, but for hydraulic cylinders, air receivers, mud and steam drums, tubular boilers and boiler shells where high pressures are to be withstood.

A steam boiler or other vessel under severe internal strains had best be spherical if equality to resistance is particularly desired. Usually a cylindrical shape is much more convenient, and no other is given to simple steam boilers or to the tubes of water-tube or fire-tube boilers. Tubes comparatively narrow, are readily manufactured without seam, so that they may be quite safe though thin; large boilers of plates riveted together, must be built of thick metal. It was estimated by Mr. F. Reuleaux, the eminent engineer, that if such boilers could be made in one continuous piece of metal by the Mannesmann process, so successful in tube-making, an economy in weight of at least one third would be feasible.

Hand-hole plates.
Erie City water-tube boiler.

In water-tube boilers a gainful departure from the circular form in a detail of their design is worthy of notice. In order that their tubes may be kept sound and clean they are rendered accessible by hand-holes which pierce the front and back of the boiler. Usually these hand-holes and their covers are round, a form which makes it necessary to put the cover outside the boiler where even a good joint, well stayed, may leak or give way under a pressure which tends to force apart the cover and its seat. In the Erie City boiler the covers are elliptical; they are readily passed through the hand-holes so as to rest not on the outside, but on the inside, of the boiler, where the steam pressure makes their joints all the tighter. A further advantage is that each elliptical plate is large enough to give access to two tubes instead of one, lessening the lines of juncture along which leakage may occur.

Wheels.

It was a memorable day when first a round log or stick was thrust under a burden, easing its motion and leading to the wheel by piecemeal improvements. A section cut off from the end of a round log is to-day the wheel for ox-carts in China and India. In its crudest form a roller enables a man to drag a load instead of carrying it, and he can readily drag much more than he can carry. Wheelwrights of old soon found that a wheel need not be solid, that strong spokes, a sound rim, and a metal tire embody the utmost strength and lightness. Roller and ball bearings much extend the benefits of simple wheels; they lessen friction in the best typewriters, bicycles, and elevators; in wagons, carriages, and automobiles roller bearings are so helpful that their use should be universal. Of notable efficiency is the Hyatt bearing, formed by winding a steel strip into a spiral roller. This device has a flexibility which enables it to conform to irregularities of motion much better than can a solid cylinder.

Bullock cart with solid wheels.

For machinery the wheel is indispensable. The hand does its work chiefly in moving to and fro, as in sawing and whittling. Machines outdo manual toil by moving swiftly and continuously in a circle: instead of the smoothing iron we have the mangle, boards are planed by rotary knives, timber is divided by circular saws, and the steam turbine is displacing the steam engine which every moment has to check the momentum of huge reciprocating masses. Noteworthy in this regard is the perfecting press which prints a newspaper from a continuous roll, as contrasted with the old machine which demanded for each impression a distinct series of to and fro movements. The Harris Rotary Press for job printing is of like model. It feeds itself with 6,500 sheets an hour, printing from a stereotype or an electrotype curved upon its cylinder. The lathe, simple enough a century ago, has been developed into machines of great complexity, power, and variety, all with the original rotary mandrel as their essential feature. Milling machines, steadily gaining more and more importance, employ rotary cutters which dispense with the manual chipping and filing of former days.

Section—A B
Ball thrust collar bearing.
Ball Bearing Co., Philadelphia.

Rigid bearings for driving axles of automobiles.
Ball Bearing Co., Philadelphia.

Hyatt helical roller bearing.

Hyatt rollers supporting an axle.

Treads and risers joined by curves.

Angles Replaced by Curves.

Wood as commonly hewn, sawn, and planed; bricks as usually molded; stone as it leaves an ordinary hammer, all have flat sides and square edges. Hence it has been easiest to build walls and floors which meet at right angles, and to leave sharp corners on outer walls, windows, doorways, and chimneys. This is being changed for the better; in staircases the boards on which we tread and those which join them together now meet in smooth curves; so do the walls of rooms as they reach ceilings and floors, conducing to ease and thoroughness in sweeping and cleansing. In outer walls, in doorways and windows, similar curves reduce liability to hurt and harm. A wagon wheel easily knocks pieces from an angle of brickwork; it makes little impression on bricks retiring from the street line in a sweeping curve, as in the Madison Square Garden, New York. Factory chimneys have long been built round instead of square; to-day in the best designs the ducts to a chimney are also freely curved. In blast furnaces this is the rule for every part of the structure, ensuring gain in strength, lessening resistance to the flow of gases, and thus saving much fuel. When waterpipes varying in diameter are joined, the junction should be a gradual curve, otherwise retarding eddies will arise, wasting a good deal of energy; the same precaution is advisable in laying pipes for steam or gas. The elbows of pipes for gas, steam or water exert the least possible friction when given the utmost feasible radius. All the various parts of heavy guns are curved, since any sharpness of angle at a joint brings in a hazard of rupture under the tremendous strains of explosion.

Corner Madison Square Garden,
Madison Avenue and 26th Street,
New York.

Two pipes with funnel-shaped junction.

Embossing and stamping machines may either decorate a sheet of note paper or make a tub from a plate of steel. Whatever their size these machines have the edges of their dies nicely rounded, so as to avoid tearing the material they fashion. To ensure the utmost strength in the machines themselves they are contoured in ample curves. In hydraulic presses, subjected to strains vastly greater, the same shaping is imperative, otherwise a cylinder may part abruptly with disastrous effect. So, too, in the manufacture of magnets and electro-magnets, their terminals are well rounded to ensure the closest possible approach to uniformity of field and of working effect.

A glance at a warship discovers her varied use of curves in defence; to deflect assailing shot and shell, her plates are given bulging lines, her turrets are built in spherical contours, and her casemates are convex throughout. On much the same principle fortifications are rendered bomb-proof, or rather bomb-shedding; while outworks are so inclined that bombs fall to distances at which they do little or no harm. As in war so in peace; there is gain in building breakwaters with an easy curve; to give their masonry and timbers a perpendicular face would be to invite damage, whereas a flowing contour like that of a shelving beach, slows down an advancing breaker and checks its shock. In rearing lighthouses to bear the brunt of ocean storms the outline of a breakwater is repeated to the utmost degree feasible. Often, however, the base supporting a lighthouse is too small in area for such an outline to be possible.

CHAPTER V
FORM—Continued. SHIPS

Ships have their resistances separately studied . . . This leads to improvements of form either for speed or for carrying capacity . . . Experiments with models in basins . . . The Viking ship, a thousand years old, of admirable design . . . Clipper ships and modern steamers. Judgment in design.

Forms of Ships Adapted to Special Resistances.

In giving form to a ship a designer has a three-fold aim,—strength, carrying capacity and speed. Strength is a matter of interior build as much as of external walls; it is conferred by girders, stays and stiffeners which we have already considered, so that we may here pass to the general form of the hull, which decides how much freight a ship may carry, and, to a certain extent, how fast she may run. A ship is the supreme example of form adapted to minimize resistance to motion; its lesson in that regard will be the chief theme of this chapter. Until the close of the eighteenth century the resistance to the progress of a ship was regarded as a single, uncompounded element, plainly enough varying with the vessel’s speed and size. It was Marc Beaufoy, who first in 1793 in London, pointed out that a ship’s resistance has two distinct components; first, friction of the shell or skin with the water through which the vessel moves, dependent upon the area of that skin; second, resistance due to the formation of waves as the ship advances, dependent upon the speed of the vessel and the shape of her hull. Other resistances have since been detected, but these two are much the most important of all; each varies independently of the other as one ship differs from another in form, or as in the same ship one speed is compared with another. To take a simple case: a ship’s model of a certain form, of perfectly clean skin, is towed at various speeds and the pull of the tow-line is noted; then the same model with its skin roughened and covered with marine growths is towed at the same speeds, and much greater pulls are observed in the tow-line. The wetted surface is the same in the two series of experiments, the speeds correspond throughout, and the increase of resistance due to a roughening of surface can only mean that the friction between the water and the submerged skin has increased. Next we take a model of certain form and definite size, and a second model having the same area of wetted surface but a different form; we tow both models at the same speed to find that one requires a decidedly stronger pull than the other. This difference cannot be due to frictional resistance of surface, for this is the same in both models, therefore it must be due to the increased resistance offered by the water as it is pushed aside, a resistance measurable in the created waves. Mr. Edmund Froude, an eminent English authority, says:

“For a ship A, of the ocean mail steamer type, 300 feet long and 31¹⁄₂ feet beam and 2,634 tons displacement, going at 13 knots an hour, the skin resistance is 5.8 tons, and the wave resistance 3.2 tons, making a total of 9 tons. At 14 knots the skin resistance is but little increased, namely 6.6 tons; while the wave resistance is nearly double, namely, 6.15 tons. Mark how great, relatively to the skin resistance, is the wave resistance at the moderate speed of 14 knots for a ship of this size and of 2,634 tons weight or displacement. In the case of another ship B, 300 feet long, 46.3 feet beam, and 3,626 tons displacement—a broader and larger ship with no parallel middle body, but with fine lines swelling out gradually—the wave resistance is much more favorable.[4] At 13 knots the skin resistance is rather more than in the case of the other ship, being 6.95 tons as against 5.8 tons; while the wave resistance is only 2.45 tons as against 3.2 tons. At 14 knots there is a very remarkable result in this broader ship with its fine lines, all entrance and run and no parallel middle body:—at 14 knots the skin resistance is 8 tons as against 6.6 tons in ship A, while the wave resistance is only 3.15 tons as compared with 6.15 tons. The two resistances added together are for B only 11.15 tons, while for A, a smaller ship, they amount to 12.75 tons.”

[4] The entrance is that part of the ship forward where it enters the water and swells out to the full breadth of the ship; the run is the after part from where the ship begins to narrow and extending to the stern. A ship may consist of only entrance and run; it may have a middle body of parallel sides between the entrance and run. Such a middle body is discussed by Lord Kelvin in “Popular Lectures and Addresses,” Vol. III, Navigation, p. 492.

Experimental Basins.

These figures show that a designer must bear in mind the speed at which this ship is to run; they prove that he may choose one form to minimize friction, or another form if he particularly wishes to bring wave-making resistance to the lowest possible point. Forms of these two kinds are readily studied when represented in models 12 to 20 feet in length towed through tanks built for the purpose. Experiments of this kind were undertaken as long ago as 1770, in the Paris Military School; the methods then inaugurated and copied in London at the Greenland Docks were greatly improved by Mr. William Froude in a tank which he constructed at Torquay in England, in 1870. His modes of investigation, duly adopted by the British Admiralty, and after his death continued by his son, Mr. Edmund Froude, have created a new era in ship design. To-day in Europe and America there are eleven such tanks as Mr. Froude’s, all larger than his and more elaborate in their appliances. In addition to learning the behavior of models diverse in type, Mr. Froude worked out the rules which subsist between the performance of a model and that of a ship of like form; these he brought to proof in 1871 when he towed Her Majesty’s Ship Greyhound, and verified his estimates in towing its model. The rules concerned, known as those of mechanical similitude, are given in detail by Professor Cecil H. Peabody in his “Naval Architecture,” page 410. While experiments become more and more valuable as one refinement succeeds another, there is always much well worth knowing to be learned from the actual behavior of a vessel as she takes her way through a canal, a shallow river, or the storm-beaten stretches of the sea.

The experimental tank of the United States Navy at Washington, is 470 feet long, 44 broad, and 14¹⁄₂ deep; it is arranged for models 20 feet in length. See the page opposite. The towing carriage is a bridge spanning the tank just above the water; it is a riveted steel girder. The towing mechanism, of massive proportions, is driven by four electric motors of abundant power. A double set of brakes brings the carriage gradually and quietly to rest from a high speed. A self-acting recorder measures both speed and resistance. Ship builders may have models built by the Bureau in charge, that of Construction and Repair of the United States Navy Department, and have these models towed at any desired speeds, paying simple cost.

MODEL BASIN, U. S. NAVY YARD, WASHINGTON, D. C.

It was in 1880 that the lessons of towing experiments with models began to be adopted in practice. As a result the forms of steamers have been greatly improved. Originally their lines were taken from those of sailing vessels but, as dimensions grew bolder and speeds were increased, it became clear that steamers demanded wholly different lines of their own. These lines, fortunately, may be plainly disclosed in experiments with a model, because a steamer usually runs on an even keel, in which position a model is easily driven through a tank. A sailing vessel, on the contrary, is nearly always heeled over by the wind so that it seldom runs on an even keel; tank experiments, therefore, avail but little for the improvement of its lines. Even were the model inclined at various angles in one test after another, sails must be omitted, with their influence on steering, their lifting and burying effects, often extreme.

1. Starboard Side. 2. Horizontal Sections. 3. Vertical Sections. 4. Central Longitudinal Section. 5. Part of the Gunwhale inside, with its Skirting in Front and in Section. 6. Section through AB. 7. Bird’s Eye View.

THE VIKING SHIP.

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A Viking Ship a Thousand Years Old.

A thousand years ago the Vikings of Norway roved the seas in boats of a form which is admired to-day. To those hardy adventurers swiftness and seaworthiness meant nothing less than life and victory, their eyes perforce were keen to note what craft sped fastest through the water, what new curves kept waves from coming aboard. Perchance as they refined upon keel and rib they took golden hints from the shapes of gulls and fish. To be sure, long before science was dreamt of, they had to work by rule-of-thumb, but the thumb was joined to brains that did honor to human nature. On page 56 is illustrated the [Viking Ship] unearthed early in 1880 at Godstad, near Sandefjord in Norway, in a mound where, according to tradition, a king and his treasure had been buried. It is the most complete and the best preserved vessel of ancient date in existence. It is fully described and pictured in “The Viking Ship,” by Mr. N. Nicolaysen, a work published in 1882 by Mr. Albert Cammermeyer, Christiania. Mr. Nicolaysen regards the vessel as having been built about A. D. 900, for use in war by the great chieftain whose tomb it became. The ship was 65 feet, 10 inches long, on the keel; with an extreme length over all of 78 feet, 1 inch; amidships it was 16 feet, 9 inches; its depth amidships from the top of the bulwarks to the keel was 3 feet, 11¹⁄₄ inches. The material throughout was pine. The helm, a plank shaped like a broad oar, was fastened to the side of the vessel. In accordance with the number of its oars and shields this ship must have had a crew of sixty-four, besides these came the steersman, the chieftain and probably a few more of his companions, making a total, in all likelihood, of seventy to be carried by her. Says Mr. Nicolaysen: “In the opinion of experts this must be deemed a masterpiece of its kind, not to be surpassed by aught which the shipbuilding craft of the present age could produce. Doubtless, in the ratio of our present ideas, this is rather a boat than a ship; nevertheless in its symmetrical proportions, and the eminent beauty of its lines, is exhibited a perfection never attained until after a long and dreary period of clumsy unshapeliness, when it was once more revived in the clipper-built craft of the nineteenth century.”[5]

[5] A detailed description of the Viking Ship is given in the “Transactions of the Institute of Naval Architects”. (London), Vol. XII, p. 298.

CLIPPER SHIP “YOUNG AMERICA.”
Length of deck, 235 feet. Beam molded, 40 feet, 2 inches. Depth of hold, 25 feet, 9 inches. Tonnage, 2900.

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Clipper Ships and Modern Steamers.

Thirty to sixty years ago much of the world’s commerce was borne by clipper ships. In all likelihood as good lines as ever went into a vessel of this kind were displayed in the [Young America], outlined on page 58, built in 1853 for California and East India trade. She once ran from New York to San Francisco in 103 days, and from San Francisco to New York in 63 days, records which have never been excelled. Her deck length was 235 feet; her depth of hold 25 feet, 9 inches; her moulded beam was 40 feet, 2 inches; her displacement was 2,713 tons. The lines worthiest of remark in her design are the diagonals and buttocks, together with her easy entrance and run. Most clipper ships were fuller forward than aft; this had two advantages: first, when forward burdens, anchors and the like, tended to an undue settling down at the head, it was well to increase the buoyancy forward; second, towing experiments prove that a form slightly fuller forward than aft offers less resistance than the reverse. This shape was hit upon by the old-time designers, doubtless as a result of many a shrewd experiment.

In the early days of steamships, hollow or somewhat concave water lines forward were in favor. Experiments with models have demonstrated that for boats so full in section as to be nearly square, it is best to have forward lines which are straight or nearly so. Recently it has been shown that at high speeds, with a midship section nearly semicircular, resistance is a little lessened by very slightly hollowing the water lines forward.

If a steamer is to have the utmost speed, as the [Kaiser Wilhelm II], outlined on page 60, her design will be very unlike that of a vessel required to carry as much cargo as possible at a moderate or low speed, as in the case of the [steamship] sketched on page 61. The dimensions of the Kaiser Wilhelm II are:—length over all, 706¹⁄₂ feet; beam, 72 feet; depth, 29 feet, 6¹⁄₄ inches; displacement, 29,000 tons; speed, 23¹⁄₂ knots; indicated horse power, 38,000. As we compare with her details of form the general features of our cargo carrier, page 61, we observe in this freighter the full form of its water lines, its almost straight and blunt entrance forward; we also notice that the lower part of the bow has been cut away to avoid a reversal of curves which would create an eddy with its consequent increase of resistance. Further we may remark the squareness of the midship section, which means carrying capacity at its maximum, together with the long parallel middle body, little resisted by the water, ending aft in buttocks and water-lines quickly turned. This is a twin-screw ship: of length 358 feet, 2 inches; beam, 46 feet; draft, 23 feet; depth from shelter deck, 34 feet, 8 inches; displacement, 8,270 tons; speed, 9 to 10 knots.

STEAMSHIP KAISER WILHELM II.
Length over all, 706 feet, 8 inches. Beam, 72 feet. Draft, 29 feet, 6.3 inches.
Displacement, 29,000 tons. Indicated horse-power, 38,000. Speed, 23.5 knots.

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TWIN-SCREW CARGO STEAMER.
Length, 358 feet. Beam, 46 feet. Draft, 23 feet. Displacement, 8270 tons.

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U. S. TORPEDO-BOAT DESTROYER.
Length over all, 246 feet. Beam, 22 feet, 3 inches. Displacement, 489 tons.
Speed, 30 knots.

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A good designer has an easy task in drawing lines for a freighter in which the weight of hull, machinery and coals may be only 40 per cent. of the displacement, leaving 60 per cent. for earning space. Contrast this with an Atlantic flyer, where but 5 per cent. may remain for cargo. Here the designer’s problems are difficult indeed, and the chief way out of them is to enlarge his ship as much as he dares, for the bigger his vessel, its form and speed unchanged, the less will be its resistance as compared with displacement. But to an increase of size there are hard and fast bounds; first, those imposed by the shallowness of channels and harbors; while the depth of a ship is thus restricted, its length may be somewhat extended with safety and gain; to increase of beam there are distinct and moderate limits, to overpass them means that the ship will follow the wave contour of a heavy sea so closely as to have a quick, jerky and dangerous motion.

Cross-sections of ships

Judgment in Ship Design.

To design a ship in this case and every other is plainly a matter of compromise, a quest of the optimum by a balancing of demands for safety, strength, speed, capacity, handiness, good behavior in a sea-way, so that each invested dollar may in the long run earn the largest return possible. Excellent examples of judicious design are the best passenger steamers plying between Europe and New York. Usually their section amidships is like that of a cargo vessel, but for a special reason. Within the freighter’s walls the greatest feasible cross-section must be created; so that the shape is box-like; in a high-speed passenger ship the form is also square, because harbors are shallow; were they less shallow the designer would choose a midship section somewhat semicircular in contour. Were our harbors deepened, the easy sections of the first transatlantic steamers could be repeated in their gigantic successors of to-day, with increased speed for each horse power employed.

What a designer can do when his aim is swiftness at the expense of all other considerations, is shown in the lines of the torpedo-boat destroyer, page 62. Its length over all is 246 feet; length at water level, 240 feet, 10 inches; beam, 22 feet, 3 inches; mean draft, 6 feet, 1¹⁄₂ inches; displacement, 489 tons; speed, 30 knots. It is interesting to contrast, on page 63, the [cross-section] amidships of this vessel, with similar lines of three other typical vessels described in this chapter.[6]

[6] In writing these pages on the forms of ships I have been much indebted to Mr. Harold A. Everett, Instructor in Naval Architecture, Massachusetts Institute of Technology, Boston.

G. I.

CHAPTER VI
FORM—Continued. SHAPES TO LESSEN RESISTANCE TO MOTION

Shot formed to move swiftly through the air . . . Railroad trains and automobiles of somewhat similar shape . . . Toothed wheels, conveyors, propellers and turbines all so curved as to move with utmost freedom.

Projectiles and Vehicles of Like Pattern.

While ships are much the largest structures built for motion, and therefore meet resistances which the designer must lessen as best he may, other moving bodies, small as compared with ships, encounter resistances so extreme that their reduction enlists the utmost skill and the most careful study. Speeds vastly higher than those of ships are given to projectiles. A ball leaving a gun muzzle with a velocity of 3,410 feet a second, as at Sandy Hook in January, 1906, suffers great atmospheric resistance, overcome in part by the shot having a tapering or conoidal form. Indians long ago stuck feathers obliquely into arrows so as to keep flight true to its aim by giving shafts a spiral motion; an attendant advantage being to lengthen flight. The same principle appears in rifling, that is, in cutting spiral grooves in the barrels of firearms large and small, a missile receiving a spinning motion through its base, a thin protruding disk of soft metal, forced into the grooves by the explosive. At first the grooves in firearms were straight with intent to preclude fouling; spiral grooves were introduced by Koster of Birmingham about 1620. Delvigne, a Frenchman, devised a lengthened bullet narrower than the bore so as to enter freely, under the pressure of firing it completely filled the bore, rotating with great velocity as it sped forth.

Racing automobile. Wedge front and spokeless wheels.

Now that railroad speeds are approaching those of projectiles, the outlines of trains are resembling those of shot and shell. In the experiments with very fast trains at Zossen, in Germany, October, 1903, each car had a paraboloidal front, much diminishing the resistance of the air. Racing automobiles are usually encased in a pointed shell which parts the air like a wedge; their wheels, too, are supported not by spokes, but by disks having no projections. As electric traction becomes more and more rapid in its interurban services, the cars will undoubtedly be shaped to lessen atmospheric resistance. Especially is this desirable in a tunnel service, such as that of the New York Subway, where the resistances are extreme for the same reason that a boat in a canal is harder to draw than if in water both broad and deep. Just as in ship-design, it is in sharpening the front and rear of a car or a train that most economy is feasible; the friction at the sides cannot be much lessened except, in the case of a train, by joining each car to the next by a vestibule such as that of the Pullman Company.

Electric traction finds gain in a track having in places a decided inclination. In the monorail line between Liverpool and Manchester a downward dip in the line at each terminal quickens departure, and in arrival aids the brakes by checking speed on the up-grade. In the swift motion of ordinary machinery the resistance of the air is a source of considerable loss. By encasing a heavy flywheel in sheet iron so as to present a smooth surface to the atmosphere, M. Ingliss has saved 4.8 per cent. of the energy of a 630 horse power engine.

Bilgram skew gearing.

Gearing: Conveyors.

In the simplest machines motion may be transmitted by wheels in contact, faced with adhesive leather, rubber, or cloth. Teeth, however, are usually employed; as wear takes place they permit a little play, a slight looseness, which contact wheels altogether refuse. Toothed wheels have the further advantage that they do not slip, their motion is positive. How teeth may best be contoured involves nice questions in geometry. They should always push and never grind each other, and should move with the least possible friction. In some ingenious designs the teeth of any one particular wheel of a series will enmesh with the teeth of any other wheel, no matter how much larger or smaller. Bevel gears cut by Mr. Hugo Bilgram, of Philadelphia, turn with hardly any friction whatever, although in some wheels the teeth run askew, or are sections of cones which do not meet at their apices. The Bilgram gear cutter, and the Fellows’ gear shaper which turns out plain gear, exert a to and fro planing action. Ordinary gears are cut on milling machines by rotary cutters, or may be manufactured on a Bliss press without cutting the original lines of fibre. The importance of accurate and easy-running gears increases steadily; they are, for example, applied to steam turbines whose velocity must be reduced in the actuation of ordinary machines. Automobiles and bicycles also demand reducing gear running with the utmost freedom.

Grain elevator.

Robins conveying belt of rubber moved on rollers.

The grain elevator, invented many years ago, is the parent of manifold conveyors of coal, lime, ore or aught else. Their receivers have links shaped so as to extend for hundreds of feet as continuous belts. Link belting may be had in detachable sections, fitting each other at secure hinges which allow free motion.

The Augustin B. Wolvin, a typical ore-carrier on the great lakes, is 56 feet in depth; its hold is curved to allow a clam-shaped bucket to seize ten tons of ore at each dip. It is probable that at no distant day rapid transit in cities will employ continuous moving platforms, just as conveyors and telpherage systems are taking the place of the discontinuous transport of grain, coal, cotton, ore, and heavy merchandise.

Ewart detachable link belting.

Propellers.

The screw, an inclined plane wound about an axis, forms the propeller for steamships and many steamboats. There is a good deal of debate as to the principles which should decide its best lines. Here evidently is a field which will handsomely repay thorough investigation. The power expended in steamships, whether fast or slow, is prodigious; any marked improvement in the contour of screws will mean either a saving of fuel or an increase of speed. Of equal importance with water-propulsion is the setting in motion of air. In blast furnaces enormous volumes of air are forced at high pressure into the fuel and ore: the fans are carefully molded in screw form, any departure from the best curves entailing serious loss. Fans for less important services are seldom shaped with care and usually waste much energy.

Turbines.

Allied to screws are turbine wheels, much the most efficient of water motors. The shaping of their vanes as volutes minimizes the loss of energy in shock as the water comes in, and lessens to the utmost the velocity of the stream as it leaves the wheel. Now that steam turbines are scoring a success both on land and sea the contouring of their vanes with extreme nicety is an important problem of the engineer. A perfected form means the highest economy.

Curves of turbines.
Niagara Power Co.

It is interesting to note how the screw propeller, the fan, and the turbine wheel have each led to a converse invention. Mr. Edwin Reynolds, of Milwaukee, has devised a pump in screw form of capital efficiency under low heads. The fan has long had its converse in the windmill, now more popular throughout America than ever before, mainly because shaped with new excellence. In the best models, built of steel, the sails are each a section of a volute carefully designed to discharge the wind evenly, just as in the parallel case of emission from a water mover, such as the Worthington pump. This capital pump is simply a turbine wheel reversed. Its impeller and diffusion vanes take up water from rest, lift it to a height which may be as much as 2,000 feet, and then deliver it at rest, with little loss from internal eddies or slippage.

Steel vanes of wind-mill.
Fairbanks, Morse & Co., Chicago.

The Pelton wheel, pre-eminent among water-motors of the impulse type, owes its economy chiefly to each bucket being divided in halves and curved with the utmost nicety.

Pelton water wheel.

Jet for Pelton wheel.

CHAPTER VII
FORM—Continued. LIGHT ECONOMIZED BY RIGHTLY SHAPED GLASS. HEAT SAVED BY WELL DESIGNED CONVEYORS AND RADIATORS

Why rough glass may be better than smooth . . . Light is directed in useful paths by prisms . . . The magic of total reflection is turned to account . . . Holophane globes . . . Prisms in binocular glasses . . . Lens grinding . . . Radiation of heat promoted or prevented at will.

A Shrewd Observer Improves Windows.

These are times when an inheritance, such as the window pane, venerable though it be, is freely criticized and shown to be far from perfect. We find, indeed, that surfaces and forms long given to the glass through which light passes, or from which light is reflected, are faulty and wasteful. This means that sunshine can be turned to better account than ever before, that artificial light can be employed with an economy wholly new. A few years ago when we provided a window with plate glass, smooth enough for a mirror, nothing better seemed possible. Thanks to the late Edward Atkinson, of Boston, we know to-day that in many cases glass may be too smooth to give us the best service, that often we may get much more light from panes of rough, cheap make than from costly plate glass. He tells us: “In 1883, when I inspected a large number of English cotton mills, I found them glazed with rough glass of rather poor quality, the common glass of England being inferior to our own from the general lack of good sand. On asking why rough glass was used instead of smooth I was told that rough glass gave a uniform and better light. To my astonishment I found this true. The interior of a mill so lighted had the aspect of diffused illumination. This led me to reason on the subject. I looked into the construction of the Fresnel lens, in which a combination of lenses and curved surfaces concentrates rays of light into a single far reaching beam. I reasoned that if one set of angles or curves could thus concentrate light, then by reversal of such angles or surfaces, light could be diffused.”

Mr. Atkinson proceeded to gather specimens of glass not only of common rough surface, but also in ribbed and prismatic forms. These he handed for examination and comparison to Professor Charles L. Norton of the Massachusetts Institute of Technology, Boston. His report says: “The hopelessness of trying to get something for nothing, that is, to get a sheet of window glass to throw into a room more light than fell upon it, appeared so plain to me that I made all my preparations to measure not a gain but a loss of light in using Mr. Atkinson’s samples. The results of the tests may be briefly stated: In a room thirty feet or more deep we may increase the light to from three to fifteen times its present effect by using ‘Factory Ribbed’ glass instead of plane glass in the upper sash. By using prisms we may, under certain conditions, increase the effective light to fifty times its present strength. The gain in effective light on substituting ribbed glass or prisms for plane glass is much greater when the sky-angle is small, as in the case of windows opening upon light shafts or narrow alleys. With the use of prisms a desk fifty feet from a window has been better lighted than when but twenty feet from the same window fitted with plane glass. . . . ‘Ribbed’ and ‘Maze’ glass are of very great value in softening the light, especially when windows are directly exposed to the sun, aside from their effectiveness in strengthening the light at distant points. With the ‘Maze’ glass the artist may have, in all weathers and in all directions, what is in effect a much-desired north light. The same glass provides the photographer with light as well diffused as when cloth screens or shades are employed and of much greater intensity.”

Plate prism glass is now manufactured with its outer or street surface ground and polished like plate glass, with its prisms accurate and smooth. In dimensions which may reach fifty-four by sixty inches it affords surfaces easily kept clean, and transmitting much more light than glass held in frames of small divisions.

Whence the gain in thus exchanging plane glass for glass rough, ribbed, or prismatic? Rays streaming through an ordinary window strike nearby surfaces of wall, ceiling, and floor; from these they are reflected in large measure and return through the glass to outer space. Rough, ribbed, or prismatic glass throws the rays much further into the room, hence they strike so much larger an area of wall, ceiling, and floor that in being reflected again and again the light is well diffused, and but little is sent forth again into outside space. The form of the glass gives the entering light its most useful direction, so that the new panes serve better than the old. This effect is most striking when prisms are carefully adapted to a particular case in both their angles and their placing. In traversing glass, light is absorbed and wasted, so that the shorter its path the better. In the compound lens devised in 1822 for lighthouses by Augustin Jean Fresnel, light is as effectively bent by the part of the glass shown in dark lines as if the whole lens were employed.

Luxfer prism.

Fresnel lens.

This brings us to means for the best use of artificial light. Within the past thirty years the standard of illumination, thanks to electricity, has steadily risen. More important than ever, therefore, is it that light should be employed pleasantly and effectively. This in the main is a question of placing the sources of light judiciously, and of so reflecting and refracting their rays that they will be of agreeable quality, and arrive where they are wanted with the least possible loss. Reflectors rightly shaped and kept clean economize much light. For lack of them in streets and squares we may sometimes observe half the rays from a lamp taking their way to the sky where they do no good. In shop windows ribbed reflectors throw full illumination on the wares displayed, while the sources of light are out of view. The same method is employed in art galleries and in museums. A parabolic reflector sends forth as parallel rays the powerful beam of a lighthouse, a locomotive, or a searchlight. An incandescent lamp of ingenious design is silvered on its upper half so that none of its light is wasted. Because the arc lamp is the cheapest of all illuminants it is adopted for out-of-door lighting where its unpleasant glare is tempered by distance. In factory lighting its brightness is excessive and harmful unless moderated. A capital plan is to employ an ordinary continuous current and place the positive carbon, with its brilliant centre, below the negative carbon; beneath these two carbons a good reflector throws the rays to the ceiling, whence they descend with agreeable diffusion and much less loss than when globes of ground glass surround the arc. A common white ceiling when quite flat is an excellent reflector; indeed, a sheet of white blotting paper returns light nearly as well as a polished mirror, and for many purposes it serves better; the mirror sends back its beam in a sharply defined area which may be dazzling, the paper scatters light with thorough and agreeable effect.

Lamp and reflector a unit.

Inverted arc-light.

Usually a mirror is a sheet of highly polished metal, or a plate of glass with a quicksilver backing; preferable to either is clear glass, all by itself, so formed as totally to reflect an impinging beam of light. To understand the principle involved in its use we will for a little while bid good-by to lamps of all kinds.

Delight and Gain as We Watch a Fish in Water.

A hall of delights is the New York Aquarium, in the historic Castle Garden at the Battery. Its tanks display a varied and superb collection of fish, whose beauty of form and color heightened by swift and graceful motion, fascinates the eye as no museum of dead things, however splendid, ever does. When a tank is still, or nearly still, and a gold-fish or a perch is quietly resting near the surface of the water, one may see its form reflected from that surface as perfectly as if by a mirror. The point of view must be close to the tank, with the eye somewhat lower than the fish. So perfect, at times, is this mirroring that young folks are apt to suppose the reflection to be a second fish, and they are puzzled to remark how strangely it resembles its mate just below. What explains this reflection? A ray of light can always pass from a rare medium, such as air, into a dense medium, such as water, because it is bent toward their common perpendicular. But a ray cannot always pass from a dense into a rare medium, from, let us say, water into air, for if the ray were to be bent away from the common perpendicular more than 90° it would altogether fail to emerge from the water. No luminous ray can pass from water into air if it makes a greater angle with the perpendicular than 48° 35´. Suppose AB ([page 78]) to be the water level of a tank. A ray leaving F will be bent so as to reach C, a ray from G will reach D, a ray from H will reach E; but a ray from L will be bent so much as to pass along the surface of the water as OB, and a ray from I will be bent so as to return beneath the surface of the water to I. Rays such as I, undergoing total reflection, afford us our second image of a fish at rest near the surface of water: to observe this kind of image we need not journey to the New York Aquarium; with patience we may behold it in a small home aquarium with flat sides of clear glass, waiting until the water is quiet and a fish comes close to the surface.

Sacramento perch totally reflected in aquarium.
A, surface of water.

Every dense transparent substance has this ability to yield images by total reflection, each substance having a critical angle of its own; we have just seen that for water this angle is 48° 35´. Glass is made in many varieties, each with a special critical angle, never much different from that of water. A right-angled prism of glass, which any optician can supply, serves as a capital mirror for rays striking its surface at ninety degrees. Such prisms are employed in opera glasses, in hand telescopes, in reflectors for light-houses, and in the Holophane globes we are about to examine. The efficiency of these prisms may be as much as 92 per cent., whereas that of the best silvered mirrors never exceeds 90 per cent. The loss in a prism is due to a slight reflection by the surface on which the rays first fall, and by the absorption of light in the glass itself; this second loss, of course, increases with the thickness of the prism.

AB water level. F, G, H, L are refracted to C, D, E, B.
I is totally reflected to I.

Holophane globe, vertical section.

Section of Holophane globe.
Ray A is refracted as A´, C as C´. B, totally reflected, then refracted, emerges as B´. D takes a similar course, emerging as D´.

Total Reflection in Artificial Lighting: Holophane Globes.

Now that we understand the principle of total reflection, let us see how it is applied to increasing the effectiveness of a Welsbach mantle or an electric lamp. And first let us say that we may wish light upon a small area, mainly in a single direction, as downward upon a desk or reading-chair. Or, in a quite different manner, if we are to illuminate a wide space such as that of a large parlor. These requirements are fulfilled by the Holophane globes, devised by M. Blondel and M. Psaroudaki, which are made in many shapes, each adapted to a specific duty. The upper half of each globe is formed into prisms of such angles that, zone by zone, the glass totally reflects impinging rays in just the directions desired. The contouring is accurate to the thousandth part of an inch. With this thorough reflection is combined diffusion as thorough, the interior of the globe being shaped as ribs. Thus, with the least possible waste, the upper half of the source of light is utilized. What of the lower half? Its rays pass through prisms formed so as to refract impinging light into desired paths with but little loss. As a whole, therefore, these globes furnish a beautiful means of illumination with all but perfect economy, special forms of them sending light in any direction desired.

Diffusing curves.
Holophane globe. Rays are split into b, e, reflected, then as e, f, g, refracted; and into b, c, d, refracted.

Class A,
Holophane globe, throwing rays mainly downward.

Class B,
rays mainly directed at an angle of 60°.

Class C,
casting rays chiefly in a
lateral direction.

Class A,
Holophane globe, throwing rays mainly downward.

Class B,
rays mainly directed at an angle of 60°.

Section of Holophane globe and Welsbach mantle, showing distribution of light.
Each typical ray as refracted is marked by a letter of its own.

Total Reflection in Binocular Glasses.

In the Zeiss Works at Jena, in Germany, optical instruments of the highest excellence are manufactured; many of these take advantage of the principle of total reflection we have been considering. When the task was assumed of producing a new and improved telescope, it was observed that an ordinary telescope, built up of lenses, is inconveniently long and heavy in comparison with its magnifying power. The question arose whether it was possible to construct short instruments of a magnifying power of four to twelve diameters. Porro, an Italian, about the middle of the nineteenth century suggested totally reflecting prisms so placed that while the total travel of a ray would be the same as in an ordinary telescope, the two ends of the luminous path would be near together, while the whole would be more effective than if four mirrors were employed. His idea may be represented by a wire one meter long so bent that its ends are much less than one meter apart. In an illustration of a field-glass as manufactured at the Zeiss Works, on the Porro principle, it will be remarked that the entering ray passes through lenses which are farther apart than the lenses which form the eye-pieces. Thus a much wider field is viewed than that of an ordinary glass, while as the two images received from the two eye-pieces differ more than those observed in direct vision, the perception of depth is increased in a notable degree. This construction is adapted to sporting, marine, and opera-glasses, as well as to field-glasses.

How a wire may be shortened while its original direction is resumed.

Four mirrors, 1, 2, 3, 4, reflect a ray in a line parallel to its original path.

Prisms for Zeiss binocular glasses.

Lenses Still Much Used.

Lenses nevertheless continue to be much more important than prisms, and the proper shaping of their surfaces involves high reaches of both science and art. The properties of the glass, of course, count for most in producing combinations free from color for telescopes, microscopes, and cameras. [Jena glass], described in another chapter of this book, with its extraordinary range of refractive and dispersive qualities has brought optical instruments to virtual perfection. Meanwhile the arts of lens-grinding leave little to be expected in the way of future improvement. It is astonishing that a lens forty-two inches wide can be so truly curved as to focus the image of a star as an immeasurable dot.

Zeiss binocular glasses: longitudinal and cross-sections.

The Production of Optical Surfaces.

Let us look at some of the instruments designed by a master for shaping glass discs into lenses. Some of the best telescopes in existence are from the hands of Mr. John A. Brashear, of Allegheny, Pennsylvania. The grinding tools he employs he has contoured in such wise as to produce desired curves free from error. The first polishers are of the ordinary form with square or circular facets equally distributed over the surface of the tool, as in [Figs.] H and 8. When the polish is brought to its best, the glass is allowed to cool slowly to a normal temperature, and is then carefully studied as to its defects. These are removed and the surfaces finished with iron tools, of the same diameter as the surface to be worked, each tool being laid off into six sections, as in Figs. 3, 4, 5, 6, 7. The tool being warmed, pitch is spread over its leaf-like spaces, which are given the proper curve by being pressed down on the previously wetted concave surface; the pitch and tool are next quickly cooled with water. In the shaping of these spaces rests success. The zone, a, a, in the first figure, needing the greatest amount of abrasion, meets the widest part of the leaflet, but in order that no zonal error may be introduced, as in b, c, c, b, of the second figure, it is gently tapered in each direction, the amount of taper being governed by the lateral stroke given to the polisher, as well as by the amount of departure of the zone from the normal curve.

Tools for producing optical surfaces.
John A. Brashear, Allegheny, Pa.

But after all the astronomers aided by lenses thus carefully shaped are few, while millions of people suffer from defects of sight which are overcome by suitably formed spectacles.

Bi-focal Spectacles.

In this field a recent minor improvement is worthy of mention. Benjamin Franklin many years ago made a pair of spectacles in which the upper half of each glass was ground for far seeing, the lower half for near seeing. To-day such bi-focal spectacles are not made in halves, with an unpleasant broken line across them. In each of the new eyeglasses toward the base a small lens of dense quality is enclosed; through this lens a wearer looks at objects nearby; through the upper part of the eyeglass he looks at distant objects. The joining of the three parts is effected so skilfully as not to be discernible.

Bi-focal lens for spectacles.

Economy of Heat.

From light we pass to its twin phase of energy, heat, for a glance at the forms of devices which enable us to use heat with economy. When we wish a furnace, crucible, or cooking vessel to maintain the highest possible temperature, we give it as little surface as possible. On the contrary when a warming apparatus is devised, its surface is freely extended. The traditional fireplace, for all its cheerfulness, yields but little heat. Benjamin Franklin copied its form in the stove which bears his name; as it stands out from a wall it warms the air all around itself, instead of on one side only. This model is familiar in gas stoves, whose heat thoroughly radiated and convected far exceeds that derived from fireplaces. In Canada forty years ago it was usual, especially in the country, to set up gallows-pipes and dumb-stoves, or drums, bulky, hollow structures of sheet iron, which obliged the heated products of combustion to take a roundabout course as they passed to the chimney. To be sure as thus cooled the gases were less effective as draft makers, but we must remember that one of the most wasteful uses of fire is in warming air or other gases for the sake of putting them in motion. In modern factories, central lighting stations, and the like huge installations, mechanical draft sends a quick current through a short chimney, saving much fuel. Excellent in design are the tile stoves of Germany and Holland. Their gentle heat does not parch the air; in moderately cold weather they render it unnecessary to light furnaces which develop, at such times, unduly high temperatures.

Canadian box stove with gallows-pipe.

In factories the heating coils filled with steam or hot water were at first fastened to the floor. Then came attaching them to the ceiling whence their heat is gently radiated; on the floor the coils may gather dust and dirt with risk of fire; with the other plan there is a saving of floor space, and accidental leaks are at once in evidence.

Canadian dumb-stove.

Tubes for warming are specially effective when dented or buckled in directions at right angles to each other and to the axis of the tube. This form gives the heating water or steam a swirling motion which causes it to part more rapidly with its heat than does a cylindrical tube of the same surface. Gold’s electric heater for street-cars, bath-rooms, and the like, is a spiral of resistant alloy, hung in a light metallic frame, the whole presenting a large surface to the air. Automobiles driven by heat engines require coils of the utmost possible surface whereat cooling can take place; in many cases this cooling is furthered by the action of a quick fan. In like manner the condensers of steam-engines, especially aboard ship, are made up of slender tubes presenting to the steam a chilling area of vast extent.

Tubing for radiator.
Dalham Works, Manchester, England.

Gold’s electric heater.

Stolp wired tube for automobiles.

Inventors have long addressed themselves to the difficulty caused by the expansion and contraction of structures as temperatures change. For years the cylindrical fire-boxes of marine boilers have been corrugated, so as to allow them a certain play without breaking from their fastenings, or tearing their seams, when heated or cooled. This form is adopted with success for the Morison fire-boxes of the Vanderbilt locomotives. In quite different situations metal piping, in a length of let us say 100 feet, is provided against trouble from shrinkage or expansion by a U bend. When the diameter of the pipe is twelve inches, this bend is usually about ten feet in extent; for a six inch pipe, a bend six feet long suffices. Another difficulty due to heat is the limitation of speed imposed by the heat which friction creates. A new type of circular saw has a hollow arbor through which flows cold water, so that motion may be faster than ever before. The same arbor appears in various other machines with like advantage.

Corrugated boiler.

Pipe so bent as to permit contraction or expansion.

CHAPTER VIII
FORM—Continued. TOOLS AND IMPLEMENTS SHAPED FOR EFFICIENCY

Edge tools old and new . . . Cutting a ring is easier than cutting away a whole circle . . . Lathes, planers, shapers, and milling machines far outspeed the hand . . . Abrasive wheels and presses supersede old appliances . . . Use creates beauty . . . Convenience in use . . . Ingenuity may be spurred by poverty in resources.

Tools and Implements.

We have just reviewed, all too briefly, how light and heat are economized by structures of judicious form. At this point we will bestow a rapid glance at the economy of work as promoted by sound design in tools and implements, in the machines which embody these for tasks far beyond the personal skill or power of the strongest and deftest mechanic.

When of old a savage took up a stone to serve as a rude knife or chisel, we may be sure that he chose the sharpest flint he could find. If he could better its shape by knocking it into something like a wedge, what task was easier? Our museums display an immense variety of stone hammers, axes, knives, and arrowheads, showing how art long ago improved the forms of simple tools and weapons offered by nature. Modern tools and weapons, for all their immense diversity, were every one prefigured in the rude armory of primitive man.

Descended from his flint knife is the abounding variety of steel cutting tools all the way from the razor, concave on both sides, to the axe, doubly convex. As the arts have become more specialized, as artificial power has been introduced, the contrasts of the form of one tool with another have grown more and more striking. The bar which slices metal is stout of build, and rectangular in section, while a lancet is little wider or thicker than a blade of grass. The knives which divide leather, rubber, and rope, differ much from one another; the knife which separates the leaves of a book serves best when dull. Gouges for carving are nicely adapted to the profiles they are to cut; while the exigencies of the power-lathe require its tools to be designed of particular strength and rigidity. Among revolving hand-tools the brace is the most important, enabling the workman to exert great leverage. A minor tool, the gimlet, was formerly more in use than to-day. Now that screws are made with gimlet points they break their own paths.

Carving chisels and gouges.

Lathe cutters.

Ratchet bit brace.

From the beginning tool-makers have shown skill in fitting a tool to the hand, as in the Eskimo skin-scraper; this simple adaptation may have arrived in copying the effect of wear. Other good hints have come from observing an implement after its work is done. At the places where mud clung to a plowshare the plow-maker was long ago told at what points to raise his metal; conversely, when a cutter of any kind is unduly worn at any part of its side, there the metal asks to be somewhat narrowed down.

Eskimo skin scraper.

Double tool drill cutting boiler plate.

A common drill removes a whole circle of stone.

A ring drill removes much less stone with the same effect.

Annular Drills.

A circle of say two feet in diameter, may be readily cut from a boiler plate by two cutters, one at each end of a horizontal bar, the bar being supported by a central upright axis receiving the motive power. Because the cut is narrow, but little metal is wasted as chips. A cut of this ring-shape effects a desirable saving even when the circle to be swept is but an inch or so in width instead of several feet. When an auger takes its way through a plank it removes as chips all the wood within the circle of its range; a drill, of common form, as it pierces stone or metal acts in a similar manner. Motive power is greatly economized when a drill is tubular, with the further advantage that within the ring cut a solid cylinder remains to be broken off at intervals and lifted out, its core informing to the engineer in quest of bed-rock, to the prospector of mines or oil-fields, or to the geologist who reads at a glance the composition of a mineral, the forces which have impressed it age after age. Such drills, set with bortz diamonds, have accomplished remarkable feats. In boring out 260 columns surrounding the dome of the capitol at Springfield, Illinois, cores 22³⁄₄ inches in diameter were removed from holes 24 inches wide; without sacrifice of strength there was a saving in weight of three-fifths. At the Ellenwood coal mine, Kingston, Pennsylvania, a core 17 feet, 5 inches in breadth was taken from a bore only five inches wider. When the engineers in 1896 were planning the foundations for the Williamsburg Bridge, New York, the deepest of their 22 borings was 112 feet below high water. Steel drills had indicated bed-rock 12 to 20 feet higher than was the actual case; the diamond drill showed the supposed bed-rock to be merely a deposit of boulders. No other known means could have accomplished these results. In the same way steel guns of large calibre have been drilled so as to leave a core of much value, while in this as in all other such tasks, the boring demanded less energy and proved less straining than if all the metal within the sweep of the drill had been reduced to fragments. All these tools were prefigured in a simple ring drill used two thousand years ago on the banks of the Nile; hollow reeds were employed, with sand as a cutter.

Twist drill.

Twist Drills.

Twist drills are superseding flat drills as stronger and better in every way. A twist drill is made with a slight taper toward the shank end. Its cross-section is not quite round, the diameter being reduced from a short distance behind the cutting edge, so as to diminish friction and give the sides of the drill as much clearance as possible. The advanced edges of the flutes are all full circle, so as to maintain the diameter of the drill and keep the tool steady. The advantage of the twist drill is that its cuttings find free egress, while it always runs true, without reforging or retempering. The cutting edges are usually ground to an angle of sixty degrees to the center line of the drill; for brass work the angle should be fifty degrees.

Lathe and Planer Tools.

The manner in which a lathe tool cuts metal is shown in an [outline] which represents a tool feeding a cut along a piece of wrought iron. The removed metal, in its diameter and openness, tells the expert operator both the quality of his cutter and how it is being affected by wear. The principal consideration, says Mr. Joshua Rose, in determining the proper shape of a cutting tool, for use in a lathe or a planer, is where it shall have the rake, or inclination, to make it keen enough to cut well, and yet be as strong as possible; this is governed, in a large degree, by the nature of the work.

How a tool cuts metal.
Beginning a second cut.

Dacotah fire-drill.

Machine Tools: Lathes.

In giving form to wood and metal cheaply and rapidly, machine-tools have within recent years risen to great importance. Of these the lathe is one of the chief. It seems to be descended from the bow drill, the tool which was whirled by a cord wrapped round it, or it may be, that under another sky, the lathe was derived from the potter’s wheel whose axle was changed from a vertical to a horizontal plane. For centuries all lathes had their cutting tools simply laid on a bar, or rest, just as in the hand cutting lathe of to-day. While this afforded opportunity to skill it did not lend itself to large or uniform production. Henry Maudslay, about a century ago, immensely broadened the machine in scope by devising the slide rest which firmly grasps the cutting tool, and automatically moves it toward or away from the axis of the work, as well as along the work in any desired line. This device is equally applicable whether in turning a pencil case, the granite columns for a cathedral, or the propeller-shaft of an ocean steamer.

Lathe: a, work; b, tail-stock; c, hand-tool rest; d, dead-centre; e, live-centre; f, face-plate; g, live-spindle; h, dead-spindle; k, head-stock; m, cone-pulley; n, driving-pulley; o, belt; p, treadle; r, treadle-hook; s, shears; t, treadle-crank.

Compound slide rest.
C, shears; E, tool carriage; H, cross slide; K, cross slide handle; L, cross feed handle; P, tool post; T, tool; D, driver; W, work.

Blanchard Lathe.
A, frame; B, carriage; C, gun stock; D, former; E, cutter-head; F, guide wheel; G, swinging frame; H, feed motion; K, shaft for revolving stock and former.

The lathe has been developed in many ways until it has become one of the most complex of all machines, adapted to tasks which even twenty years ago seemed impossible. Only two of its varieties can here be noticed, the Blanchard lathe for cutting irregular forms, and the turret lathe. An illustration, taken from an old engraving shows the Blanchard lathe as originally built for shoe-lasts. A pattern-last and the block to be carved are fixed on the same axis and are revolved by a pulley. On a sliding carriage are fastened pivots from which are freely suspended the axles of a cutting wheel, and a friction wheel, equal in diameter. The cutting wheel turns on a horizontal axle, and bears on its periphery a series of cutters. The friction wheel is in contact with the pattern-last and presses against it while in motion. During revolution, the pattern, irregular in its surface, causes the axis to approach or recede from this friction wheel; the cutting wheel in its corresponding motion removes wood from the block until a duplicate of the pattern appears. This lathe much improved and modified now turns not only gun-stocks, axe-handles and the like, but repeats elaborate carvings with precision. Ornaments for Pullman cars are produced by this machine.

Turret lathe: an early Brown & Sharpe model.
C, carriage; T, turret; L, hand lever; F, face plate; D, jaw chuck; E, tool.

Turret of turret lathe.
Side view. Top view.

The turret lathe, equally ingenious, has a turret or capstan, which carries let us say eight different tools, one on each of its eight faces. In its turn each tool operates on the work in its forward traverse; it then retires while the turret automatically moves through one-eighth of a circle, when the next tool emerges for its task, and so on.[7]

[7] The turret principle is embodied in drills and a variety of other machines. It was adopted in remarkable fashion by John Ericsson in his Monitor, launched in 1862 for service in the Civil War. Because this vessel had to navigate shallow streams, its draft was limited to eleven feet. As it was thus impossible to carry the burden of armor necessary to protect a high-sided vessel, he was obliged to design a sunken hull. Guns and gunner were protected within a covered cylindrical turret which as it turned on its vertical axis, delivered an all-round fire while the Monitor stood still. Ericsson’s original turret, and its later modifications in the leading navies of the world, are described in the Life of John Ericsson, by William Conant Church, New York, Scribner, 1890.

Ericsson’s Monitor.

Lathes have given rise to planers, now built of great strength and in highly complicated designs. In a lathe the object turns upon centers against a tool; a planer carries its tool in a revolving cylinder, the work being fed in a straight line. A shaper, with much the same essential construction, moves along its work, the wood or metal operated on remaining stationary. With a planer or a shaper the size and uniformity of the work depend upon the skill of the operator. The planer has led to the invention of a machine which dispenses with this skill. Bramah, in 1811, employed a revolving cutter to plane iron, adapting to metal the familiar mechanism for planing wood. This was the beginning of the milling machine, now so remarkably developed and improved. A skilled mechanic sets the machine and the chucks which hold the work; an unskilled hand can continue the operations, his products being uniformly of the dimensions and forms desired. Intricate shapes are easily executed, quite impracticable on any other machine. At first the revolving mechanism and its cutters were a single piece of metal; to-day cutters of costly quality are inserted in cheap metal; these inserted cutters when worn out are easily replaced.

Iron planer; a, b, c, d, fixed cutting tools; M, moving bed.
Niles-Bement-Pond Co., New York.

Iron shaper: a, b, fixed cutting tools. K, M, traveling bars.
Niles-Bement-Pond Co., New York.

Milling machine, R. K. Le Blond Machine Tool Co., Cincinnati.
A, table; B, overhanging arm; C, cutters; D, spindle; E, feed box.

In many cases the milling machine ousts the planer as much more economical. At the shops of the Taylor Signal Company, Buffalo, a miller of the Cincinnati Milling Machine Company does nine-fold as much work as a planer. It takes a first cut ¹⁄₈ inch deep across a full width of 12 inches, makes 60 revolutions per minute, feeds .075 inch per turn, giving a table travel of 4¹⁄₂ inches per minute, with an accuracy limit of .001 inch.

Milling cutters with inserted teeth.
Cincinnati Milling Machine Co.

Now for a glimpse of what a great inventor had to suffer because he lived prior to the era of machine tools, before the days, indeed, of that indispensable organ of the lathe, its slide rest. The first steam engines of James Watt built at the Soho Works, near Birmingham, are thus described:—“A cast iron cylinder, over 18 inches in diameter, an inch thick and weighing half a ton, not perfect, but without any gross error was procured, and the piston, to diminish friction and the consequent wear of metal, was girt with a brass hoop two inches broad. When first tried the engine goes marvelously bad; it made eight strokes per minute; but upon Joseph’s endeavoring to mend it, it stood still; and that, too, though the piston was helped with all the appliances of hat, papier maché, grease, blacklead powder, a bottle of oil to drain through the hat and lubricate the sides, and an iron weight above all to prevent the piston leaving the paper behind in its stroke—after some imperfections of the valves were remedied, the engine makes 500 strokes with about two hundred weight of coals.” In another month or two, with better condensation, it “makes 2,000 strokes with one hundred weight of coals.”

Milling cutters executing complex curves.
Brown & Sharpe, Providence, R. I.

Emery and Carborundum Wheels.

Emery, carborundum and alundum wheels are developed from the grindstone of the distant past. That stone gives a straight-line finish or edge to the surfaces submitted to it; and as the work is shifted in front of the stone these surfaces may take a curved or other contour. But a grindstone, let it be as hard as can be found, is not hard enough to take and keep any other than a cylindrical form. Its successors of to-day, the carborundum wheel especially, can be of varied shapes, and transfer these to metal with celerity and economy.

Carborundum, a compound of silicon and carbon, is produced at Niagara Falls, New York, by a process devised by Mr. E. G. Acheson. In an electrical furnace are placed granulated coke, sand, a little salt, and some sawdust to keep the mixture porous and allow generated gases to escape freely. The crystals of carborundum thus produced require seven horse-power hours for each pound; in hardness they are excelled by the diamond only. United under severe hydraulic pressure by a vitrified bond they are eight times as efficient as emery in abrasion. Carborundum wheels are replacing lathes as a means of finishing axles, piston-rods and rolls; their accuracy is unsurpassed, while they demand but one third the time needed by a steel tool.

Emery wheels.

Carborundum Co., Niagara Falls, N. Y.
Carborundum wheel edges.

Form in Plastic Arts.

At the very dawn of art moist clay was molded into useful plates and bowls. This foreran not only all that the potter has since accomplished, but all that has been achieved in the foundry and the mint. In making bricks, tiles, and terra cotta, the first task is to make the clay plastic, then advantage is taken of its plasticity. In like manner we heat a metal to fluidity, and then pour it into a mold to make a fence rail, a stove plate, or a car wheel. An electric bath refines upon this process. Copper, let us say, dissolves in a tank, and concurrently its particles are deposited on a mold from which the metal can be readily stripped, avoiding the distortion inevitable when heat has come into play.

Within the past ten years concrete has grown into much importance as a building material, especially as reinforced with steel. It is a great deal easier and cheaper to pour a wall into molds than to lay courses of brick, or cut and dispose stone-work. Elsewhere in this book a few pages are given to [reinforced concrete], and its applications.

Pressing and Stamping.

Pressing, like molding, has of late years much extended its range of forms. In germ it goes back to the distant day when seals were impressed upon clay tablets, and coins or medals were struck from hard matrices. In glass manufacture the press has been used for centuries. Cheap pressed tumblers and bowls have long been accompanied by cheap metal pots and pans, plates and basins, stamped by machinery. To-day much enlarged and improved, such machinery, as a Bliss press, makes a kitchen sink from a sheet of steel, forms gears and pinions from round bars of metal, and executes the intricate curves of a mandolin in a plate of aluminum. For a good while the spinning lathe gave us from thin metallic sheets a variety of cups, saucers, dishes, parts of kettles, lamps, and the like. To-day each of these articles is produced by a single blow of a die, proving that metals are plastic in a degree unsuspected in former days. Thus it comes about that the seams necessary to the tinman and the coppersmith, with all their liability to leaks and uncleanliness, have been largely dismissed and may soon be wholly banished. Pressing is illustrated on [pages 184 to 186] of this book.

Old and New Means of Conferring Form.

To-day we are rich in old and new facilities for the bestowal of form. To confer shape by division we have an immense variety of knives, scissors, saws, axes, hatchets and shears. These, together with hammers, chisels and gouges enable us to disengage from a mass not merely a simple rail, panel, or table-top, but a carving or a statue. Surfaces are smoothed with a rasp, a file, a plane; sand is rubbed on abrasively, or falls from a height, or is forcibly blown with a blast of steam or air. Emery either spread on paper, or glued upon a wheel, grinds with an accuracy and speed new to art; and all that emery can do is outdone by carborundum and alundum, which slice away metal as if chalk, be its hardness what it may. Perforation is accomplished with rotary drills, or by a sandblast, or on occasion by corrosive acids—a final resource in treating refractory stone. Rolls of tremendous power reduce iron and steel in thickness, and, when suitably shaped, confer form on railroad rails, girders and the like. Every tool and implement, old or new, is now embodied in machines of gigantic force, or multiple effect, so that the skill of an earlier generation is either not in demand at all or passes to tasks of a delicacy never attempted before. It is by virtue of presses, enormous in power, that to-day shapes are bestowed on metals in successful rivalry with the ancient art of the founder himself. Indeed the art of conferring form by pouring a liquid into molds is at this hour largely exercised in work where heat plays no part whatever,—as in the tasks of the builder in concrete, the labors of the electrician as he employs a bath to separate a metal from its ore, or to plate a surface with silver or gold.

Diagram of rolls to reduce steel in thickness.

Use Creates Beauty.

In strong contrast with the varied resources of modern toil are the simple tools and implements of prehistoric skill which, modified much or little, are at this hour still indispensable to the mechanic, the builder, the engineer. These simple aids early became admirable in form so as to be all the more useful. Says Mr. George Bourne:—

“The beauty of tools is not accidental but inherent and essential. The contours of a ship’s sail bellying in the wind are not more inevitable, nor more graceful, than the curves of an adze-head or of a plowshare. Cast in iron or steel, the gracefulness of a plowshare is less destructible than the metal, yet pliant, within the limits of its type. It changes for different soils; it is widened out or narrowed; it is deep-grooved or shallow; not because of caprice at the foundry or to satisfy an artistic fad, but to meet the technical demands of the expert plowman. The most familiar example of beauty indicating subtle technique is supplied by the admired shape of boats, which is so variable, says an old coastguardsman, that the boat best adapted for one stretch of shore may be dangerous if not entirely useless at another stretch ten miles away. And as technique determines the design of a boat, or of a wagon, or of a plowshare, so it controls absolutely the fashioning of tools, and is responsible for any beauty or form they possess. Of all tools, none, of course, is more exquisite than a fiddle-bow. But the fiddle-bow never could have been perfected, because there would have been no call for its tapering delicacy, its calculated balance of lightness and strength, had not the violinist’s technique reached such marvelous fineness of power. For it is the accomplished artist who is fastidious as to his tools; the bungling beginner can bungle with anything. The fiddle-bow, however, affords only one example of a rule which is equally well exemplified by many humbler tools. Quarryman’s pick, coachman’s whip, cricket-bat, fishing-rod, trowel, all have their intimate relation to the skill of those who use them; and like animals and plants adapting themselves each to its own place in the universal order, they attain to beauty by force of being fit. That law of adaptation which shapes the wings of a swallow and prescribes the poise and elegance of the branches of trees, is the same that demands symmetry in the corn-rick and convexity in the barrel; and that, exerting itself with matchless precision through the trained senses of haymakers and woodmen, gives the final curve to the handles of their scythes and the shafts of their axes. Hence the beauty of a tool is an unfailing sign that in the proper handling of it technique is present.”[8]

[8] Cornhill Magazine, London, September, 1903.

In the course of a judicious review of the mechanical engineering of machine tools, Mr. Charles Griffin has this to say regarding convenience:—[9]

[9] Engineering Magazine, New York, May, 1901.

Convenience in the Use of Machines.

“A tool is an investment, the interest which it earns depending on the amount of work it turns out in a given time. This depends largely on its convenience of manipulation, involving a study of levers, handles, wheels, knobs and other auxiliary devices, their shape and place with reference to the best adaptation to the average human frame, the ease and extent of their motions, and the rapidity with which these motions may be accomplished. The position of the operator, his natural tendencies, the motions he will go through, all have to be imagined in view of the attainment of his maximum convenience. This study, in the absence of any counterpart of the proposed machine, often forces a resort to rough models, or in lieu of this, a full-size blackboard sketch, extending to the floor, upon which the location of parts may be tried for convenience.”

Resources Rich or Meagre as Affecting Invention.

In the National Museum, at Washington, the visitor as he inspects examples of American aboriginal art is astonished at its union of utility and beauty. Boat and paddle, spear and hook, basket and vase, are as admirable in form as useful in traveling, fishing, or carrying corn or water. How far an aboriginal designer may go largely turns upon what variety of resources Nature offers him. No few score families on a lonely islet of the Pacific can possibly rival the cloths and carvings displayed by tribes ranging a Pennsylvania, or a California, abounding with diverse minerals, plants and animals. When skill and invention occupy so rich a land they flower into the highest creations of aboriginal art. And yet it may be that the very fewness of a designer’s resources but spurs him to all the more ingenuity. It depends upon who the man is. As we look upon a collection of Eskimo harpoons and knives, coats and kayaks, we marvel that all these should be produced with so much excellence and variety from a scanty store of bones and teeth, sinews and hides, with but little iron or none at all.[10]

[10] Two unrivalled books on aboriginal invention have been written by Mr. Otis T. Mason, Curator of the Department of Ethnology at the National Museum, Washington:—“Woman’s Share in Primitive Culture,” New York, D. Appleton & Co., 1894; and “The Origin of Inventions,” London, Walter Scott Publishing Co., and New York, C. Scribner’s Sons, 1905. Both volumes are fully illustrated.

The annual reports of the Bureau of Ethnology, Smithsonian Institution, Washington, describe and illustrate American aboriginal art so fully and admirably as to be indispensable to the student.

CHAPTER IX
FORM—Continued. FORM IN ABORIGINAL ART, AS AFFECTED BY MATERIALS. OLD FORMS PERSIST IN NEW MATERIALS

Nature’s gifts first used as given, then modified and copied . . . Rigid materials mean stiff patterns . . . New materials have not yet had their full effect on modern design.

Aboriginal Art.

So multiplied are the resources of modern industry that desired forms are created at will, almost without regard to the material employed. It is not so in primitive art, to which for a brief space we will now turn so that our survey of form, though all too cursory, may be refreshed by a contrast of old with new. Let us begin with a glance at some of the aids with which man first provided himself, taking the gifts of nature just as they were offered. In large areas of the Southern States, and of Central America, the gourd for ages has been a common plant, and has long served many Indian tribes as a water pitcher. On sea-shores, where the gourd did not grow, conch-shells were used instead, their users breaking away the outer spines and the inner whorls, leaving within a space clean and clear. Both gourds and shells gave their forms to the clay vessels which succeeded them.

Gourd-shaped vessel from Arkansas.
“Pottery of the Ancient Pueblos.”
W. H. Holmes.

Gourd and derived forms. “Pottery of the Ancient Pueblos.”
W. H. Holmes.

Pomo basket. National Museum, Washington.

In Zuni land, says Mr. F. H. Cushing, the first vessels for water were sections of cane or tubes of wood. We may infer that the wooden tubes were copied from the cane stems. What at first was passively accepted as nature gave it, was afterward changed a little, and then was step by step changed much, so that at length there grew up processes of manufacture. There was, for example, in California a wealth of osiers, reeds, and roots well suited for making baskets; these at last were perfected as water-tight receptacles neither brittle like a shell nor liable to a gourd’s swift decay. Beginning probably in mere wattling, in the rude plaiting of mats and roofs, the weaver came gradually upon finer and stronger materials than at first, with equal pace rising to new delicacy of finish and beauty of design. At the National Museum in Washington, the Hudson collection of Indian baskets from California includes the finest specimen in the world, a Pomo basket. Its sixty stitches to the running inch were possible only through using the carex root, easily divided into threads at once slender and strong.[11]

[11] Many of the handsomest baskets at the National Museum, as well as baskets from other great collections, are illustrated, partly in color, in “Indian Basketry,” by Otis T. Mason, curator of the ethnological department of the National Museum. The publishers are Doubleday, Page & Co., New York.

Bilhoola basket of woven cedar bast. “Basket work of North American Aborigines.” Otis T. Mason.

It is interesting to observe the limitation imposed upon a primitive designer by the qualities of the leaf, shell, or cane in his hands, the way in which these qualities point him to the forms in which he may excel. Of this we have capital examples in the basket-work of the North American aborigines as described by Mr. Otis T. Mason, in the report of the Smithsonian Institution, 1883-84. He says: “Along the coast of British Columbia the great cedar (Thuja gigantea) grows in the greatest abundance, and its bast furnishes a textile material of the greatest value. Here in the use of this pliable material the savages seem for the first time to have thought of checker-weaving. Mats, wallets, and rectangular baskets are produced by the plainest crossing of alternate strands varying in width from a millimeter to an inch. Ornamentation is effected both by introducing different-colored strands and by varying the width of the warp or the woof threads. . . . It is not astonishing that a material so easily worked should have found its way so extensively in the industries of this stock of Indians. Neither should we wonder that the checker pattern in weaving should first appear on the west coast among the only peoples possessing a material adapted to this form of ornamentation.”

A square inch of the Bilhoola basket.

Referring to the water-bottles of the Pai Utes, Mr. Mason says: “This style can be made coarse or fine, according to the material and size of the coil and outer threads. If two twigs of uniform thickness are carried around, the stitch will be hatchy and open; but if one of the twigs is larger than the other, or if yucca or other fibre replace one of them and narrower sewing material be used, the texture will be much finer.” Baskets and rain-hats, as woven by Haidas and many other tribes, are waterproof when wet, owing to the closeness of their texture.

A free-hand scroll.

The same developed in a woven fabric.

“Form and Ornament in Ceramic Art.” W. H. Holmes.

Idiom of Material.

When reeds or somewhat rigid fibres are woven, they compel a straightness of edge in patterns and designs. A wave has to be suggested by stepped or broken lines, and so we have a rectilinear meander or fret, in contrast with its free-hand form as developed in a woven fabric. Under the constraint of her material a squaw as she weaves a design into a basket, must give squareness to a contour which would be somewhat rounded were it executed in delicate threads. This is clear in the human figures of the [Pomo basket] shown on page 109; and in those of a [Yokut basket bowl], also in the National Museum in Washington, illustrated on the next page.

Yokut basket bowl.
“Basket Work of North American Aborigines.” Otis T. Mason.

Stone and brick-work, in their rectilinear shapes, impose a rigidity in architectural design from which modern bricks, in their rich variety of flat and curved surfaces, have wrought emancipation. In the new residential streets of St. Louis, for example, the architecture owes much of its freedom and beauty to the new shapes in which brick is now manufactured. Even wider liberty than now falls to the lot of the brick-maker has always been enjoyed by the potter. In his hands clay lends itself to any desired imitation, to any fresh design however fanciful; what is more it invites those modifications of old forms in which art takes its chief forward strides. All but infinite are the variations which Japanese potters have played on the shapes of vases, jars, kettles, and basins, each clearly true to its type, while at the same time original in a pleasing way. How the Japanese artist in clay has rejoiced in his freedom is exemplified in the collection of Japanese pottery at the Museum of Fine Arts, in Boston. Says Mr. Edward S. Morse, who brought this collection together: “Utensils for every day life, terra cotta funeral urns, large terra cotta bowls, weights for fishing nets, brush handles, and even clothes-hooks are in Japan made of pottery. Where we use silver and other metals, or glass, in making articles for daily use, the Japanese use pottery.” He adds: “The prehistoric pottery of Japan was modeled by hand, and to-day in various parts of the empire, this ancient art is continued in its prehistoric form. There are many potters in Japan who are still at work using only the hand in making bowls, delicate tea-pots, and dishes of various kinds. The pottery vessels offered at Shinto shrines are usually made without the use of the wheel and are unglazed. The potter’s wheel was brought to Japan from Korea. The first was probably the kick-wheel used in Satsuma and other southern provinces.”

The Japanese employ not only clay but wood in methods that richly repay study. Says Mr. Ralph Adams Cram:—“In one respect Japanese architecture is unique: it is a style developed from the exigencies of wooden construction, and here it stands alone as the most perfect mode in wood the world has known. As such it must be judged, and not from the narrow canons of the West that presuppose masonry as the only building material. . . . Perhaps the greatest lesson one learns in Japan is that of the beauty of natural wood, and the right method of treating it. The universal custom of the West has been to look on wood as a convenient medium for the obtaining of ornamental form through carving and joinery, the quality of the material itself being seldom considered. In Japan the reverse is the case. In domestic work a Japanese builder shrinks from anything that would draw attention from the beauty of his varied woods. He treats them as we do precious marbles, and one is forced to confess that under his hand wood is found to be quite as wonderful a material as our expensive and hardly worked marbles. In Japan one comes to the final conclusion that stains, paints, and varnish, so far as interior work is concerned, are nothing short of artistic crimes.”[12]

[12] “Impressions of Japanese Architecture and the Allied Arts,” by Ralph Adams Cram. New York, Baker & Taylor Co., 1905.

In strong contrast with the art of Japan is that of Egypt; on the banks of the Nile the first buildings were of limestone, succeeded by huge structures reared from Syene granite, with no little loss in delicacy of ornamentation. It was only when marble, all but plastic under the chisel, was adopted by the Greek sculptor, that the frieze of the Parthenon could spring into life.

Here William Morris should be heard. In “Hopes and Fears for Art,” he says: “All material offers certain difficulties to be overcome and certain facilities to be made the most of. Up to a certain point you must be master of your material, but you must never be so much the master as to turn it surly, so to say. You must not make it your slave, or presently you will be its slave also. You must master it so far as to make it express a meaning, and to serve your aim at beauty. You may go beyond that necessary point for your own pleasure and amusement, and still be in the right way; but if you go on after that merely to make people stare at your dexterity in dealing with a difficult thing, you have forgotten art along with the rights of your material, and you will make not a work of art, but a mere toy; you are no longer an artist, but a juggler. The history of art gives us abundant examples and warning in this matter. First clear, steady principle, then playing with the danger, and lastly falling into the snare, mark with the utmost distinctness the times of the health, the decline, and the last sickness of art.” He illustrates this in detail from the history of mosaic in architecture.

While the modern artist duly respects the idiom of his new materials, their diversity and refinement, in granting him the utmost freedom, enable him to attain a truth of execution unknown before to-day. For writing on papyrus a brush had to be used; on vellum or paper, a pen or pencil may also be employed, tracing lines no wider than a hair. Our grandmothers were fond of sewing on a perforated card a motto or a flower in silk thread; such a sampler always had an unpleasant straightness in its outlines. When in weaving silk or linen there may be two hundred threads to the running inch instead of ten, the designer can introduce curves almost as flowing as if he were a painter. So too in architecture: the log hut was perforce straight in its every line; stone and brick made possible the arch; iron and steel are bringing in a free choice of the best lines, whether straight or curved, all with a new sprightliness, as witness the best of our office-buildings in New York, such as the Whitehall, Trinity, and Empire Buildings.

Sampler on cardboard, executed in silk thread.

Bark vessel, and derived form in clay.
“Form and Ornament in Ceramic Art.” W. H. Holmes.

Old Forms Repeated in New Materials.

Art in its early stages seldom displays any outright invention; with all the force of habit the savage artist clings to old familiar shapes, and it is interesting to remark how dealing with a new material may lead or even oblige him to modify a traditional form. The Algonquins inhabit a country in which the birch is common. They cut and fold its bark into vessels which, when imitated in pottery, have an unusual rectangularity. In many Indian tribes it was customary to use as a water-holder the paunch of a deer or a buffalo; many ancient urns of Central America have an aperture at an upper extremity, copied from the paunch, in every case with a simplification of outline. Winged troughs of wood were undoubtedly in the mind of the man who made the [earthen vessel] illustrated on the next page, found in an ancient grave in Arkansas. As usual the borrower put something of himself into his work, reminding us that the law of evolution is descent with modification. An [earthen vessel], illustrated on the next page, was plainly copied from a shell vessel such as the specimen found not far off, in Indiana. When the Clallam Indians, of the State of Washington, began to weave baskets, they imitated the forms of their rude wicker fish-traps. The like persistence was shown by the Haida squaws when taught by the missionaries to make mats from rags; they repeated their ancient twined model, long employed for mats and hats of vegetable fibres. As in America, so also in Europe; when the makers of celts passed from stone to copper or bronze, they reproduced the old forms, and only gradually learned to economize metal, so much stronger than stone, and so much harder to get, by narrowing and flattening their new weapons and tools.

Vase from tumulus. St. George, Utah.
“Pottery of the Ancient Pueblos.” W. H. Holmes.

Wooden tray.

Clay derivative.

“Form and Ornament in Ceramic Art.” W. H. Holmes.

Shell vessel made from a Busycon perversum, found at Ritchersville, Indiana.

Earthen vessel, imitation of shell,
Missouri.

From W. H. Holmes’ “Art in Shell of the Ancient Americans.”

Electric lamps in candle shapes.

Modern manufacture in its designs gives us a kindred persistence of old forms in new things. For electric illumination we have bulbs which recall the shape of a candle-blaze, or surmount an old-fashioned candlestick; a gas-burner, popular for fifty years, repeats in milky porcelain the whole length of a candle. Gas-grates, in uncounted thousands throughout our cities every winter, offer us flames which flicker and leap over asbestos and clay molded into the semblance of maple or charcoal. Nor is the engineer himself, for all his sternness of discipline, quite free from prolonging the reign of the past, even at unwarrantable cost. When steel was first used for steam boilers there was a period of hesitation during which the metal was used unduly thick, as if to maintain the long familiar massiveness of iron structures. When automobiles were invented, they at first closely resembled common carriages. To-day, designers have departed from tradition, and provide us with horseless vehicles which respond to their new needs in ways wholly untrammeled by inherited ideas. In an automobile, driven by steam or gasoline, there must be due disposition of fuel, of machinery, of cooling apparatus, all so combined as to bring the center of gravity as low as may be best, affording ready access to any part needing lubrication, repair, or renewal; throughout there must be the minimum of dead weight, of friction, and of liability to derangement; all with means of easy, quick, and certain control. Why should these requirements be deferred to repeating the model of a carriage drawn by a horse? In Europe, to this hour, the railroad carriages are an imitation of the old road-coaches, horse carriages slightly modified. America, fortunately, from the first has had cars directly adapted to railroad exigencies, with a thoroughfare extending the whole length of a train, avoiding the box-like compartments which may give the lunatic or the murderer an opportunity to work his will.

Notre Dame de Bonsecours, Montreal. Before restoration.

NEW AMSTERDAM THEATRE, NEW YORK.
No pillars obstruct a full view of the stage.

Sometimes an inherited form taken to a new home proves to be faulty there, and is discarded. When Normandy sent forth its children to Canada, they built on the shores of the St. Lawrence just such high-pitched roofs as had sheltered them in Caen and Rouen. An example remains at Montreal in the roof of Notre Dame de Bonsecours. But in Montreal and Quebec the snowfall is much heavier than in Northern France, and the Norman roofs at intervals from December to March were wont to let loose their avalanches with an effect at times deadly. To-day, therefore, in French Canada many of the roofs, especially in towns and cities, are flat or nearly flat, while the best models quite reverse the old design. In breadths somewhat concave they catch the snow as in a basin, and allow it to melt slowly so as to run down a pipe through the center of the building.

Under our eyes, day by day, iron and steel are taking the place of stone and wood in architecture and engineering; yet the force of habit leads us to continue in metal many troublesome details which were imperative in the weak building materials of generations past. It was as recently as the autumn of 1903 that the first large American theater was opened having no columns to obstruct views of its stage. The architects of the [New Amsterdam Theater], New York, simply by availing themselves of the strength of steel cantilevers have shown that henceforth all large auditoriums may be free from obstructions to a view of the stage, pulpit or platform. See facing page 118.

Modern architecture, in the judgment of an eminent critic, has not yet fully responded to its new materials and methods. Says Mr. Russell Sturgis, of New York, in “How to Judge Architecture”:—“Every important change in building, in the past, has been accomplished by a change in the method of design, so that even in the times of avowed revival there was seen no attempt to stick to the old way of designing while the new method of construction was adopted; now in the nineteenth century, and in what we have seen of the twentieth century, our great new systems of building have flourished and developed themselves without effect as yet upon our methods of design. We still put a simulacrum of a stone wall with stone window casings and pediments and cornices and great springing arches outside of thin, light, scientifically combined, carefully calculated metal—the appearance of a solid tower supported by a reality of slender props and bars.”

CHAPTER X
SIZE

Heavenly bodies large and small . . . The earth as sculptured a little at a time . . . The farmer as a divider . . . Dust and its dangers . . . Models may mislead . . . Big structures economical . . . Smallness of atoms . . . Advantages thereof . . . A comet may be more repelled by the sun’s light than attracted by his mass.

Buildings, carriages, structures of all kinds, whether reared by art or nature, often resemble one another in form while varying much in size. Differences of dimensions are of importance to the inventor and discoverer, and will be here briefly considered, beginning with a few of their obvious and elementary aspects.

Cinders large and small on hearth.

A cube as subdivided into 8 cubes of 4 times more surface.

Cinders Big and Little.

One frosty evening I sat with three young pupils in a room warmed by a grate-fire. Shaking out some small live coals, I bade the boys observe which of them turned black soonest. They were quick to see that the smallest did, but they were unable to tell why, until I broke a large glowing coal into a score of fragments, which almost at once turned black. Then one of them cried, “Why, smashing that coal gave it more surface!” This young scholar was studying the elements of astronomy that year, so I had him give us some account of how the planets differ from one another in size, how the moon compares with the earth in volume, and how vastly larger than any of its worlds is the sun. Explaining to him the fiery origin of the solar system, I shall not soon forget his delight—in which the others presently shared—when it burst upon him that because the moon is much smaller than the earth it must be much cooler; that indeed, it is like a small cinder compared with a large one. It was easy to advance from this to understanding why Jupiter, with eleven times the diameter of the earth, still glows faintly in the sky by its own light, and then to comprehending that the sun pours out its wealth of heat and light because the immensity of its bulk means a comparatively small surface to radiate from.

Cube built of 27 cubes of 9 times more surface.

To make the law concerned in these examples definite and clear, I took eight blocks, each an inch cube, and had the boys tell me how much surface each had—six square inches. Building the eight blocks into one cube, they then counted the square inches of its surface—twenty-four: four times as many as those of each separate cube. With twenty-seven blocks built into a cube, that structure was found to have a surface of fifty-four square inches—nine times that of each component block. As the blocks underwent the building process, a portion of their surfaces came into contact, and thus hidden could not count in the outer surfaces of the large cubes. The outer surfaces of these large cubes I then painted white; when each was separated into its eight or twenty-seven blocks, we saw in unpainted wood how surfaces were increased by this separation into the original small cubes. Observation and comparison brought the boys to the rule involved in these simple experiments. They wrote: Solids of the same form vary in surface as the square, and in contents as the cube, of their like dimensions.

This elementary law I traced that year in a variety of illustrations presented in “A Class in Geometry,” published by A. S. Barnes & Co., New York. Our excursions, since extended, are here given as an example of the knitting value of a pervasive rule kept constantly in mind.

Earth Sculpture.

Our planet in diverse ways illustrates the law, just stated, of surfaces and volumes. Forces of unresting activity quietly transform the hills and plains, the sea coasts and lake shores of the world, and so gradually that in many cases detection proceeds only by noting the changes wrought in a century. For the most part these forces break up large masses into fragments, or slowly wear away the surfaces of rocks into dust. A lichen takes root on a granite ledge, and in a few years reduces the rock to powder. Rain always contains a little acid, so that in time flint itself is consumed, for all its hardness. Water soaking through soils to form underground streams has hollowed out vast caves, as notably in Virginia and Kentucky. Limestones and sandstones are of open texture, and take up much moisture into their pores; in cold weather this freezes, and in expansion wedges off thin flakes of stone. In the North one sees the ground strewn with such splinters when the warm April sun has melted the snow from beside a limestone fence. Watch the rills as they descend a hillside during a rainstorm and just afterward. They are dark with mud, and on steep declivities they carry down pebbles and bits of broken stone, building up valleys at the expense of high ground. Fed on a huge scale by such mud, the Mississippi River bears in suspension to the Gulf of Mexico a little more than a pound of solid matter in every cubic yard, a prime example of how the waters of the globe gain upon the land. The Falls of Niagara have retreated several miles from their original plunge; the carving of their channel has been wrought much less by the rushing waters than by their burden of abrading earth and sand. The ceaseless churning of water at the foot of the Falls cuts back into the rock, undermining its upper layers, so that ever and anon they break off from the brink of the cataract, with the effect that the stream steadily retires.

Throughout the ocean are strong currents to be constantly surveyed and charted on the mariner’s behalf. These currents transport fine mud, and organisms living and dead. Corals flourish best where such currents fetch an abundant supply of food, just as plants thrive best in rich, loose soil. Life in the sea just like life on land is thus dependent on forces which divide large masses into small, and distribute these small masses over wide areas, chiefly by water carriage.

Breaking Earth for Removal or Tilth.

Inventors have taken a hint from nature as she carries a burden of mud and pebbles in a rapid stream of water. A modern method of deepening a water course is to reduce to fine silt the surface of its bed, and then remove this silt with a powerful stream. Water in swift eddies both lifts and bears away not only clay, but stone and gravel when these are small enough. In placer-mining streams of water much more powerful are directed against hill-slopes of earth and stone, which disappear a great deal faster than by means of spades and shovels. One of our Northwestern railroads runs for some miles along the base of a steep ridge, from which at times heavy rains wash down masses of earth, sand and gravel to the track. A powerful steam pump forcing a stream through hose removes the obstructions from the line with amazing rapidity. Work a good deal commoner and vastly more important consists in taking a process begun by nature and carrying it many steps further, so as to break up masses of earth again and again. The plow, the harrow, the sharp-toothed cultivator, divide and subdivide the soil of farm and garden so as to offer rootlets new surfaces at which rain may be drunk in with its nourishing food. When a garden patch is to be fertilized by bones, these serve best when reduced to meal, so as to be quickly and widely absorbed.

Work of the Winds.

In earth-sculpture one of the busiest agents is the wind, especially as it seizes ocean waves and dashes them upon beach and cliff, grinding large stones to pieces, and reducing these at last to mere pebbles and sand. On land the gales take hold of sand and dust with effects even more telling: sand flung against the hardest quartz or granite will bring it to powder at last. Sand dunes, shifting under the stress of high winds, have spread desolation around Provincetown, Massachusetts, and in many another region once fertile enough. This process of nature immemorially old has been copied in modern invention, by the sandblast devised by the late General Tilghman of Philadelphia. In its simplest form, sand from a hopper falls in a narrow stream upon window panes, glassware and the like, to be roughened except where protected by a paper pattern. Had sandstone in lumps, as large as playing marbles, been dropped on the glass, there would have been harmful fracture; as each particle of sand weighs too little in proportion to its striking surface to do more than detach a tiny chip, we have a bombardment wholly useful.

Dimensions in Ignition.

Primitive man achieved an incomparable triumph when first he kindled fire by swiftly twirling one dry stick upon another, dropping the tiny sparks on finely divided tinder, quick to catch fire because it presented much surface to the air. Peat, a fuel common in many parts of the world, easily dug from bogs and marshes, can be readily dried if chopped into fragments and exposed to the wind in open sheds. Charcoal easily produced from wood of any kind, is often used to absorb harmful gases in boxes of preserved meats and in household refrigerators. Its effectiveness is due to its minute pores, presenting as they do a vast area of capillary attraction. Charcoal, of course, burns faster when powdered than when unbroken; and gunpowder, into which charcoal largely enters, is molded into cakes either big, if it is to burn somewhat slowly, or is pressed into fine grains, when an explosion all but instantaneous is desired.

Dust Common and Uncommon.

Common dust surrounds us always, entering the tiniest chink of wall and ceiling to show its path by a defacing mark. In dry seasons it abounds to a distressing degree, and accumulates rapidly at considerable heights from the ground. Observe a roof of the kind that slopes gradually toward the street, with a trough running along the cornice to carry off the rain or melted snow. When such a gutter is undisturbed for a few months it is clogged with mud due to the dust which has been lifted by winds to the roof, and swept by successive showers into the gutter. Dust particles, because they have so much surface for their mass, are readily caught up and borne to heights far exceeding those of the highest roofs. The terrific explosion of the volcano at Krakatoa, in the Sunda Strait of Java in 1883, shot more than four cubic miles of dust into the upper levels of the atmosphere, encircling the globe with particles which fell so slowly as for months to color the sunsets of New York and Canada, ten thousand miles away.

Inflammable Dust.

Wheat like other grain is combustible, hence as food it sustains bodily warmth. Under stress of necessity wheat, corn, and barley have been burned as fuel when coal and wood have been lacking. In the process of flour-making wheat is ground to a powder so fine that when its particles are diffused through the air of a mill, there is a liability to explosion because the inflammable dust comes so near to contact with the atmospheric oxygen that at any moment they may unite. At Minneapolis, frightful disasters were brought about in this way until specially devised machines removed the dust. In coal mines, too, coal may fill the air with a dust so fine that explosions take place, with serious loss of life. In Austria it has been found that the fineness of the dust has more to do with the violence of such explosions than has the chemical composition of the particles.

In mining, let us observe, the whole round of work consists in separations which bring masses from bigness to smallness, again and again. First of all the solid walls and floors are broken up by pick, or drill, or powder, or all together. Iron ores as hoisted to the surface of the earth are taken to breakers which crush them into pieces suitable for the blast furnace. When the ores carry gold, copper, lead, or tin, this crushing is followed by stamping to facilitate the final process by which metal is separated from worthless rock.

Dimensions in Woven Fabrics.

Spinning and weaving, remote as they are from mining, are equally subject to the law of surfaces and volumes. It is in furthering adhesion by giving their thread a multiplied surface that the spinner and weaver manufacture cloth at once strong and durable. The best linens and silks are spun in exceedingly fine threads; canvases and tweeds have threads comparatively coarse. From the cut edge of a piece of fine silk fabric it is hard to pull out a lengthwise thread; the task is easy with sailcloth.

The Dimensions of Models.

From observation let us turn to experiment as we further consider the law of size. Inventors, especially young inventors, are apt to underrate the difficulty of supplying an old want in a new and successful way. In their enthusiasm they may lose sight of principles which oppose their designs, as for instance, the rules which govern the plain facts of dimensions. Mr. James B. Eads, in planning his great bridge at St. Louis, chose three spans instead of one span. Why? For the simple reason that if built in one span the weight of the bridge would have been twenty-seven times that of a span one-third as long, while only nine times as strong, assuming that both structures had the same form. Two pieces of rubber will clearly exhibit the contrast in question. One piece is three feet long, one inch wide, one inch thick; the other piece is one foot long, and measures in width and thickness one-third of an inch. Placing each on supports at its ends we see how much more the longer strip sags than the shorter. The longer has twenty-seven times the mass of the other, but only nine times its strength. Many an inventor has ignored this elementary fact and built a model of a bridge, or roof, which has seemed excellent in the dimensions of a model, only to prove weak and worthless when executed in full working size.

The upper strip of rubber is thrice as long, wide and deep as the lower, which sags less.

Why Big Ships are Best.

We have glanced at a few cases of invention where it has been remembered that the larger a mass of given shape the less its surface as compared with its bulk. Let us note how this rule enters into the tasks of the shipbuilder. We take a narrow vial of clear glass, nearly fill it with white oil or glycerine, cork it, and shake it smartly. Holding the vial upright we observe that the largest bubbles of imprisoned air come first to the top of the liquid, because in comparison with bulk they have least surface to be resisted as they rise. For a parallel case we visit the docks of New York, and note a wide diversity of steamers. Here is the “Baltic,” of the White Star Line, with a length of 726 feet, and a displacement of 28,000 tons. Less than a mile away is a small steamer trading to Nova Scotia, having a length of but 260 feet, and a displacement of only 1,000 tons or so. We recognize at once why the quickest ships are always among the biggest. It is simply the case of bubbles small and great over again; the biggest vessels in proportion to size have least surface whereat to resist air and sea, so that they can run fastest between port and port. As with ships, so with their engines; economy rests with bigness; the largest engines have proportionately least surface at which to lose heat by radiation or by contact, or for resistance by friction as they move. Indeed in designing ocean steamers of the greyhound type it is imperative that the utmost possible dimensions be adopted. The “Mauretania” and the “Lusitania” just built for the Cunard Company, to be driven by steam turbines at 25 knots an hour, will each demand 70,000 horse-power. They are 790 feet in length over all, 88 feet in beam, 60¹⁄₂ feet in depth, with a displacement of 45,000 tons. Mr. William F. Durand, in his work on the resistance and propulsion of ships, considers three vessels less huge and swift than these Cunarders and able to cross the Atlantic in say seven days. The 5,000-ton ship could barely make the trip with no cargo at all, a 16,000-ton ship would be able to carry 3,000 tons of freight, while a 20,000-ton ship could carry 4,200 tons of cargo. Burdens of hull, machinery, and coal do not increase as rapidly as gross tonnage when the dimensions of a ship are enlarged.

Air bubbles rising in oil.

Bigness Needs Strong Materials.

Now we begin to realize how great is the boon of cheap steel, much stronger than iron, of which ships and engines may be built bigger than at any earlier period. Steel of great strength has made feasible, too, the Eiffel Tower in Paris, nearly a thousand feet tall, the office-buildings of New York thirty stories in height, and steel will soon cross the St. Lawrence near Quebec with a single span of 1,800 feet. In 1904, at Schenectady, N. Y., the New York Central & Hudson River Railroad Company began comparisons between an [electric locomotive] of 201,000 pounds, shown opposite page 476, and a steam locomotive so huge that with its tender it weighed no less than 342,000 pounds. Steel, as the material of engines and tools of all sorts enables us to build in dimensions bolder than ever before; or, if old dimensions are not surpassed, we are free to employ velocities quite out of the question with iron.

It is a long time since adventurers first entrusted themselves to floating logs, afterward tied together as rafts, and slowly improved until they became boats moved by paddles or oars. Thus far little else than failure has attended the inventors who have sought to navigate the air as easily as river, lake or sea. A stride toward success was however distinctly taken when the strongest known alloys, those of steel and nickel, gave the aeronaut a stronger boiler, pound for pound, than he ever had before, with wings lighter in proportion to their power than those of earlier experiments. Let the burden of his apparatus be further reduced, and by one-half; then we may expect him to reign in the air as securely as the sea-gull. The original resource of the aeronaut, his balloon, suffers from a permanent disability. Air has but ¹⁄₇₇₀ the specific gravity of water, so that a balloon must be enormous to have any carrying capacity worth while. And what would become of a balloon, its rudder and ropes, if caught in a hurricane of eighty miles an hour?

A Store Continues the Lesson.

Let the aeronaut continue his wistful and envious gaze at the birds in the sky while we turn our attention to mother earth, there to note how every day trade surrounds us with further illustrations of the law of size, of the gains which may attend bigness. We enter a department store, displaying a varied stock of foods, clothing, shoes, furniture, and so on. As we cast our eyes about its counters, shelves, and floor we see cans of vegetables, fruit, and fish; jars of olives and vinegar; boxes of rice, soap and crackers; paper sacks of flour and meal. Outside the door are piled kegs, barrels, and packing cases. Plainly the cost of paper, glass, tin, and lumber for packages must levy a large tax on retailing. Once more is recalled our old lesson with the inch-cubes; the bigger a jar, box, or sack, the less material it needs in proportion to its capacity. Wholesale packers of merchandise save money as they form packages of the largest size. The contents of each box, crate, and sack tell the familiar story once again. The coffee is ground from the bean that it may be readily infused in the coffee-pot; wheat is reduced to flour, oats to fine meal, that they may be quickly cooked; sugar is crushed that it may rapidly dissolve in the tea cup. This very task began long ago with the mastication of food by the teeth, diminishing the size of morsels while moistening them for digestion before they reached the stomach.

Summer Holiday Notes.

During a visit to the country one summer, we observed new examples of our familiar rule. When we compared the dimensions of a small sectional cabin with those of a large house, we saw the principal reason why the cabin was hard to keep cool in July, and hard to keep warm in December. We noticed tasks which depended upon giving wood, cloth or other material as much surface as possible, whether new forms were like old ones or not. A neighboring sawmill was busy cutting up logs into thin boards; these were piled in open tiers, so that the drying winds might speedily finish their work. In the same way we noted a laundress spreading out by itself each table-cloth and apron fully to catch the wind, instead of leaving the linen as a solid heap in her basket, where only the edges would be dried. When the farm-hands went haymaking they followed the same rule; they tedded out their gavels to give them the utmost supply of sun and air; when all was as dry as a bone they reared a haycock of compact form so as to expose the least possible surface to rain and snow.

Dimensions Molecular.

So much for things to be observed in a country ramble, in a city store, or at the docks of a busy port. Apart from all such things is a world unseen, standing beneath the visible world, and equally worthy of study. Here knowledge is based upon inferences, upon what lawyers call circumstantial evidence. The chemist by means purely indirect studies the molecule and the atom, objects that far elude his microscope. A molecule is a part of a compound so small that it cannot be divided without becoming something simpler. Thus a sugar molecule is made up of carbon, hydrogen, and oxygen atoms; were these disjoined, the sugar, as such, would cease to be, just as a brick wall no longer exists when its bricks and their several slices of mortar are parted from one another as separate units. Small as molecules are they have not escaped the measuring rod of the physicist. Some years ago Lord Kelvin experimentally arrived at the estimate that the average molecule has a diameter of ¹⁄_760,000,000 inch. Such molecules when compared with masses of like form, and of a diameter of one inch; have 760,000,000 times as much surface. In the transmission of motion, with adhesion in play, surfaces count for much, as when a wheel in motion is brought into contact with a wheel at rest. Here may be an explanation of why electricity is conducted through a wire with a velocity far exceeding any speed we can mechanically impress upon the metal, because the molecules concerned have incomparably more surface than the wire as a mass.

Reservoirs of Energy.

By virtue, also, of its minuteness the molecule as a reservoir of energy can far excel a mass of visible dimensions. Let us compare two rotating spheres, one of them of seven times the radius of the other. We spin both at the same peripheral rate, and gradually increase this speed: which will be the first to break apart under centrifugal strain? The larger, and why? Because the cohesion of a sphere is in proportion to the area of its great circle, which varies as the square of its diameter, while centrifugal strain under swift rotation varies as the cube of that diameter, or as the volume of the sphere. From this it follows that we may safely spin our small sphere with a circumferential velocity seven times that given the large sphere; therefore as containers of energy small spheres are more effective than large, and this inversely as their diameters. Spheres, or bodies of any other form, if reduced in dimensions to ¹⁄_760,000,000th, would as reservoirs of energy gain 760,000,000-fold. Thus we open a door of explanation regarding the stupendous contrast between chemical energy and mechanical work. Chemical processes are exerted by molecules and atoms, mechanical work takes place among masses comparatively enormous in bulk. It may require a hundred blows from a ponderous steam hammer to raise the temperature of an iron bar ten degrees; that bar melts in ten seconds when plunged into a flame produced by a few ounces of hydrogen and oxygen gases.

Recent experiments by Professor Joseph J. Thomson point to the probability that the atom of the chemist while a unit, is in part built of electrons each but one-thousandth part the size of a hydrogen atom. An electron, by virtue of its infinitesimal minuteness, becomes able to hold proportionately much more energy than is possible to an atom moving as a whole. This brings us to some comprehension of the astonishing powers of radium, an element which maintains itself at a temperature 3° to 5° Centigrade higher than that of its surroundings, probably through the collision within each atom of its component parts.

Dvorak Sound-mill.

Repulsion by Sound and Light.

Water-waves as they strike a shore or the sides of a basin exert a thrust, or a repelling action, which may easily be observed. That sound-waves act in similar fashion is proved by a little sound-mill devised in 1883 by Professor V. Dvorak, of the University of Agram in Austria. It consists of four vanes, each a small card slightly curved, mounted on a spindle. In a sounding-box nearby is a tuning-fork which may be struck through its stem F. A Helmholtz resonator has its wide opening turned toward this box, its narrow opening toward the mill. A stroke on the tuning-fork emits vibrations which send tiny jets of air against the sails of the mill, which accordingly rotate at a pace proportionate to the loudness of the sound.

A beam of light deflects dust.

Professor Ernest F. Nichols of Columbia University, New York, and Professor Gordon F. Hull of Dartmouth College, in the Journal of Astrophysics, Chicago, June, 1903, describe their apparatus for measuring the radiation pressure of light, a phenomenon analogous to that studied by Professor Dvorak in the field of sound. In the same number of that Journal they detail an experiment to show light exerting a driving action on very tenuous particles. They burned a puff ball of lycoperdon to charcoal spherules of about one-sixth the specific gravity of water. These spherules, with some fine emery sand, they placed in a glass tube shaped like an hour-glass; this tube was then exhausted of its gases until a mere fraction remained which could not be removed. With the sand and charcoal in its upper half the tube was held upright, while a beam of light twenty to forty times as strong as sunshine was thrown on the tube just below its neck. By tapping the glass a stream of sand and charcoal descended; the sand fell through the beam without deflection; the charcoal particles were driven away from the stream as they fell through the light. Part of this effect was due to the slight remnant of gas left in the tube which, warmed by the light, produced a motion resembling that of a Crookes’ radiometer; the remainder of the effect was caused by the drive or repulsion of the luminous beam. It is argued that this repulsion by light is probably one of the causes why the sun seems to drive away the tail of a comet, whose particles being extremely minute have much surface and little bulk, so that they are more repelled by the light of the sun than they are attracted by his mass. To approach cometary conditions in an experiment it would be necessary to intensify sunlight no less than 1,600-fold, because on the surface of the earth its own gravitation is 1,600 times greater than that which is there exerted by the sun.

A Law as a Binding Thread.

The law that a given shape when enlarged increases much more rapidly in volume than in surface has, in our brief survey, bound together a wide diversity of facts in astronomy, geology, geography, navigation, engineering, mechanics, physics, and chemistry. A good many times I have brought it before young folks as a means of linking together everyday observations and principles of sweeping comprehensiveness. Boys and girls are apt to think that there is a formidable barrier between science and common knowledge. No such barrier exists. The sun, his planets and their moons; the forces which carve mountains and valleys; the arts of shipbuilders, of designers of bridges, office-buildings, and lighthouses; the plans of the inventors of machinery; the rules discovered by investigators who pass from appearances to the underlying reality of molecule and atom, are all within the sway of the elementary law we have been studying. There is a gain in thus pursuing a connecting thread of classification, conferring order as it does on what might else be an assemblage of things collected at random. A law such as that of size links into unity, and fastens in the memory a vast array of observations and experiments which otherwise would have no associating tie, no common illumination.

CHAPTER XI
PROPERTIES

Food nourishes . . . Weapons and tools are strong and lasting . . . Clothing adorns and protects . . . Shelter must be durable . . . Properties modified by art . . . High utility of the bamboo . . . Basketry finds much to use . . . Aluminium, how produced and utilized . . . Unwelcome qualities turned to profit . . . Properties long worthless are now gainful . . . Properties may be created at need.

Materials are valued for their properties as well as their forms. We now pass to a rapid survey of properties as observed in gifts of nature, as modified by art, as turned to account in many ingenious ways, as studied by the investigators who would fain know in what particulars of ultimate form, size and motion, properties may really consist.

We go to market with a few different coins: one of them is worth a hundred times as much as another of about the same size, because gold is more beautiful than nickel, does not tarnish, may be hammered into leaves of extreme thinness, or unites with copper as an alloy which withstands abrasion for years after it leaves the mint. When we build a house we wish strength in its foundation and walls, so we pay a higher price for granite than for limestone; and choose for joists, floors and rafters well seasoned wood in preference to newly sawn lumber liable to warp and crack with heat in summer, with cold in winter. So with raiment: silk is preferred to cotton or wool because handsomer, stronger, more lasting. But food comes before shelter, raiment or any other need of mankind, and qualities of nourishment and palatability mark off nuts, fruits, grain and roots as suitable for food. In this regard all living creatures exercise discrimination under penalty of death.

Food.

A score of sparrows are flitting about a door-yard; strew a handful of crumbs on the gravel before them; at once the birds begin picking up the bread, leaving the gravel alone. They know crumbs, good to eat, from stone, not good to eat. The earliest races of men, immeasurably higher than birds in the scale of life, have eaten every herb, root, grass, and fruit they could find. Experiment here was as wide as the world, and bold enough in all conscience. In many cases new and delicious foods, thoroughly wholesome, were discovered. At other times, as when the juice of the poppy was swallowed, sleep was induced, with a hint for the escape from pain in artificial slumber. In less happy cases the new food was poisonous; yet even this quality was pressed into service. In Mendocino County, California, to this day, the Indians throw soap root and turkey mullein, both deadly, into the streams; the fish thus killed are eaten without harm. These same Indians make acorns and buckeye horse chestnuts into porridge and bread, pounding the seeds into a fine flour and washing out its astringent part with water. These and other aborigines use for food and industry many plants neglected by the white man, taking at times guidance from the lower animals. One of the early explorers of South Africa, Le Vaillant, says that the Hottentots and Bushmen would eat nothing that the baboons had left alone. Following their example he would submit to a tame baboon new plants for acceptance or rejection as food.

Weapons and Tools.

As with food so with other resources almost as vital. Long ago the savage learned that hickory makes good bows and arrows, that as a club it forms a stout and lasting weapon. He discovered, too, that in these qualities soft woods are inferior and the sumach altogether wanting. Thus, too, with the whole round of stones from which as a warrior or a craftsman he fashioned knives, chisels, arrowheads, axes; it was important that only tough and durable kinds should be employed. No lump of dry clay ever yet served as a hammer or an adze; happy were the tribes, such as those of ancient Britain, who had at hand goodly beds of flint from which a few well directed blows could furnish forth a whole armory of tools and weapons.

Properties Modified.

In the eating of foods simply as found, in the use of materials for clothing or building just as proffered by the hand of nature, much was learned as to their qualities; some were found good, others indifferent, still others bad. Then followed the art of modifying these qualities, so as to bring, let us say, a fibre or a thong from stiffness to pliability and so make it useful instead of almost worthless. The progress of man from downright savagery may be fairly reckoned by his advances in the power to change the qualities of foods, raiment, materials for shelter, tools, and weapons. These arts of modification go back very far. At first they may have consisted simply in taking advantage of the effects of time. In the very childhood of mankind it must have been noticed that fruit harsh and sour became mellow with keeping, just as now we know that a Baldwin apple harvested in October will be all the better for cellarage until Christmas, the ripening process continuing long after the apple has left its bough. Grains and seeds when newly gathered are usually soft and, at times, somewhat damp; exposed to the sun and dry air for a few days they become hard and remain sound for months or even years of careful storage. In warm weather among many Indian tribes such food was almost the only kind that remained eatable; all else went to swift decay, except in parched districts such as those of Arizona, so that roots, fruits, the flesh of birds, beasts, and fish had to be consumed speedily, a fact that goes far to account for the gluttony of the red man. His stomach was at first his sole warehouse; that filled, any surplus viands went to waste. In frosty weather this havoc ceased; as long as cold lasted there was no loss in his larder. A few communities, as at Luray, Virginia, or at Mammoth Cave, Kentucky, in their huge caverns had storehouses which would preserve food all the months of the twelve. In New Mexico and other arid regions the air is so dry that meat does not fall into decay. How it was discovered that smoke had equal virtue we know not. Probably the fact came out in observing the accidental exposure of a haunch of venison as the reek from a camp-fire sank into its fibres. Salt, too, was early ascertained to have great value in preserving food. Suppose a side of buffalo, or horse, to have fallen accidentally into brine in a pool or kettle, and stayed there long enough for saturation, its keeping sweet afterward would give a hint seizable by an intelligent housewife. Preservation by burial in silos began in times far remote, and was fully described by Pliny in the first century of the Christian era.

Properties in Clothing.

The skin just taken from a sheep, the hide when removed from an ox, are both as flexible as in life. But they soon stiffen so as to be uncomfortable when worn as garments. Wetting the pelt is but a transient resource; satisfactory, because lasting, is the effect of rubbing grease, fat, or oil into the texture of the hide. Peary in Greenland found that pelts in small pieces, and bird-skins, were softened by the Eskimo women chewing them for hours together.

Wetting was as notable an aid to handicraft of old as today. Boughs, roots, withes, osiers, or the stems of fibrous plants, when thoroughly saturated with water became so soft as to be easily worked, yielding strands, as in the case of hemp, separated from worthless pulp. Hence the basketmaker, the wattler, the builder, the potter, the weaver of rude nets and traps, long ago learned to wet their materials to make them plastic. Take now the reverse process of drying, which toughens wood, and the sinews used as primitive thread. Leaves when dried become hard and brittle of texture, hence the necessity that when woven and interlaced as roofs the work shall promptly follow upon gathering the material. In plaiting coarse mats and sails may have begun the textile art which to-day gives us the linens of Belfast, the silks of Lyons and Milan.

Cotton Strengthened and Beautified.

A good and serviceable imitation of silk is due to a simple and ingenious treatment of cotton. In 1845 John Mercer, a Lancashire calico printer, one day filtered a solution of caustic soda through a piece of cotton cloth. He noticed that the cloth, as it dried, was strangely altered; it had shrunk considerably both in length and breadth, had become stronger, with an increased attraction for dyes. This was the beginning of the mercerization which to-day produces cotton fabrics almost as strong and handsome as if silk. The cloth, preferably woven of long Sea Island staple, is immersed in a solution of caustic soda, and afterward washed in dilute sulphuric acid and in pure water. As it enters the caustic bath the cotton is pure cellulose, as it leaves the bath the fabric is hydrated cellulose, with new and valuable properties. The structural change in the fibre is decided. The original filament of cotton is a flattened tube, the sides of which are close together, leaving a central cavity which is enlarged at each edge of the surrounding tube. It is opaque and the surface is not smooth. The fibre has also a slight twist. The tube after treatment becomes rounded into cylindrical form; its cavity is lessened and the walls of its tube thicken; the surface becomes smooth and each fibre assumes a spiral form. Effects like these of mercerization are produced in paper as well as in cotton cloth, yielding vegetable parchment, a familiar covering for preserve jars and the like.

Properties in Building Materials.

Some sandstones, such as are common in Ohio and Indiana, soft when hewn in the quarry, soon harden on exposure to wind and weather; materials of this kind in early times afforded shelter more lasting than tents of boughs or hides. But the building art was to know a gift vastly more important when an artificial mud was blended of clay and water, with a steady improvement both in the strength and durability of the product. It was a golden day in the history of man when first a clayey paste was patted into a pot, a bowl, a kettle: then was laid the foundation of all that the potter, the brick maker, the tile molder have since accomplished. Another remarkable discovery, needing prolonged and faithful experiment, was reached when pottery was found to keep its form better when broken potsherds and bits of flint were mingled with its clay. A discovery of equal moment was that of mortar, probably approached in the daubing of mud or clay into chinks of stones, with the admixture first of one substance and then another until the right one was found, and the binder and the bound became of one and the same hardness. The Romans, a deliberate race, took two years in making a batch of mortar; that bond to-day protrudes from their walls as more resistant to the tooth of time than stone itself.

Flame and Electricity as Modifiers.

But if water did much to modify properties, flame did infinitely more. A block of blue limestone thrust into a fire was burned to whiteness, and became lime, which, mixed with water, proved a biting compound of slippery feel,—an alkali indeed. This same wonderful flame caused water wholly to disappear from a heated kettle; or could dissipate almost the whole of an ignited brand or lump of fat. By cooking a food, it gave a new relish to the poorest dish, banished from such a root as tapioca its poison, and when a yam was baked it remained eatable for a twelvemonth. Fire enabled man to melt metals as if they were wax, to soften iron or copper which a deftly swung hammer shaped as he willed. Here, too, opened the whole world of chemistry, one of its first gifts the power to take an ore worthless when unchanged, and gain from it a battle-axe, a knife, an arrowhead. Even in this day of electricity it is fire which the engineer must evoke to create acids, alkalis, sugars, alcohols, from substances as different from these as iron is from iron ore.

Electricity as a modifier of properties in turn throws flame into eclipse. Take an example: a strip of ferro-nickel is fast dissolving in an alkaline bath; attach one end of the metal to the negative pole of a battery or a dynamo, the other end to the positive pole; at once solution ceases and the metal begins to pick out kindred particles from the bath, adding them to itself. Electricity has completely reversed the wasting process; what was eaten away is now growing, what was a compound is now shaken into its elements, one of which rapidly increases in mass. Nothing in the empire of heat is as striking as this process—familiar in renewing the energy of a storage battery. Many a union or a parting impossible to fire is wrought instantly by the electric wave.

The Bamboo Rich in Utilities.

When Mr. Edison devised his electric lamp, his first successful filaments were fibres of bamboo; they glowed more brilliantly than anything else he could find, they were tenacious enough to withstand intense heat for weeks together. A single gift of nature, such as the bamboo, may be so many-sided that its applications greatly enrich human life. A task of interest would be to trace the vast indebtedness of modern science and art to carbon, iron, or silver, in their various forms. But the bamboo is cheaper and more abundant than any of these, so that it will be worth while to glance at the many wants it has satisfied, at the creations it has suggested to ingenuity. In Ceylon, India, China, Japan, the Malay archipelago, it is the chief item of natural wealth, the main resource for the principal arts of life. First of all it provides food. More than one case is recorded where its abundant seeds have staved off the horrors of famine; these seeds, too, are commonly fermented to produce a drink resembling beer. Many species of bamboo have shoots which when young and tender are a palatable and nourishing food. As a building material it is strong, durable and easily divided. Its sizes are various enough to provide a fishing-rod for a boy, or a column for a palace.

“To the Chinaman, as to the Japanese,” says Mr. Freeman-Mitford, in “The Bamboo Garden,” “the bamboo is of supreme value; indeed it may be said that there is not a necessity, a luxury, or a pleasure of his daily life to which it does not minister. It furnishes the framework of his house and thatches the roof over his head, while it supplies paper for his windows, awnings for his sheds, and blinds for his verandah. His beds, tables, chairs, cupboards, his thousand and one small articles of furniture are made of it. Shavings and shreds of bamboo stuff his pillows and mattresses. The retail dealer’s measure, the carpenter’s rule, the farmer’s waterwheel and irrigating pipes, cages for birds, crickets, and other pets, vessels of all kinds, from the richly lacquered flower-stands of the well-to-do gentleman down to the humblest utensils of the very poor, all come from the same source. The boatman’s raft, and the pole with which he punts it along; his ropes, his mat sails, and the ribs to which they are fastened; the palanquin in which the stately mandarin is borne to his office, the bride to her wedding, the coffin to the grave; the cruel instruments of the executioner, the beauty’s fan and parasol, the soldier’s spear, quiver, and arrows, the scribe’s pen, the student’s book, the artist’s brush and the favorite study for his sketch; the musician’s flute, the mouth-organ, plectrum, and a dozen various instruments of strange shapes and still stranger sounds—in the making of all these the bamboo is a first necessity. Plaiting and wickerwork of all kinds, from the coarsest baskets and matting down to the delicate filigree which encases porcelain, are all of bamboo fibre. The same material made into great hats like inverted baskets protects the coolie from the sun, while the laborers in the rice fields go about looking like animated haycocks in waterproof coats made of the dried leaves of the bamboo sewn together.”

Materials for Basketry.

In North America the Indians have had no such resource as the bamboo, but with tireless sagacity they have laid under contribution either for food or for the arts every gift of the soil. In seeking materials for basketry, for example, they have surveyed the length and breadth of the continent, testing in every plant the qualities of root, stem, bark, leaf, fruit, seed and gum, so far as these promised the fibres or the dyes for a basket, a wallet, a carrier. With all the instinct of scientific research they have sought materials strong, pliant, lasting and easily divided lengthwise for refined fabrics. In his work on “Indian Basketry” Mr. Otis T. Mason has a picture of a bam-shi-bu coiled basket, having a foundation of three shoots of Hind’s willow, sewn in the lighter portions with carefully prepared roots of kahum, a sedge; while its ornamental designs are executed in roots of a bulrush, the tsuwish. Often a basket, as in this case, is built of materials found miles apart, each requiring patient and skilful treatment at the artist’s hands.

A few trees, the cedar in particular, lend themselves to the needs of the basketmaker with a generous array of resources. Mats of large size made from its inner bark are common among the Indians of the Northern Pacific Coast. From the roots of the same tree hats are woven as well as vessels so close in texture as to be watertight. When the roots are boiled so as to be readily torn into fibres, these are formed into thread, either woven with whale-sinews or with kelp-thread as warp. Among the handsomest of all Indian [baskets] are those of the Pomo tribe, one of which is shown on page 109. The splints for their creamy groundwork are made from the rootstock of the Carex barbarae, which are dug from the earth with clam shells and sticks, a woman securing fifteen to twenty strands in a day. These she places in water over night to keep them flexible, and to soften the scaly bark which is afterward removed. To make a basket watertight the Indians of Oregon weave the inner bark of their maple with the utmost closeness. In other regions a simpler method is to apply as water-proofing the gum of the piñon, the resins of pines, or mineral asphalt. Equal diligence and sagacity mark the Indians as users of stone. The Shastas heat a stone of such quality that in cooling it splits into flakes for weapons and tools. They place an obsidian pebble on an anvil, and with an agate chisel divide it as they wish; all three being chosen from a vast diversity of stones which must have been tried and found, inferior.

Aluminium and Its Uses.

From Indian handicrafts, developed by aboriginal skill, patience and good taste to remarkable triumphs, let us turn to an achievement of a modern chemist who, calling electricity to his aid, bestowed a new metal upon industry, making possible new economies in a wide sisterhood of arts. Aluminium was discovered in 1828 by Wohler, a German chemist, who noted its lightness, toughness, and ductility. At the Centennial Exhibition at Philadelphia, in 1876, a surveyor’s transit built of aluminium was shown, but the metal at that time was six-fold the price of silver, so that the instrument for some years remained uncopied. Of course, engineers and mechanics were much interested in a metal only about one-third as heavy as brass or copper, of white lustre, and with as much as five-eighths the electrical conductivity of copper. All that hindered the extensive use of the metal was its high cost. If that cost could be lowered, at once copper, and even silver, would face a rival. After many unsuccessful because expensive processes for obtaining the metal had been devised, a method was found at once simple and inexpensive.

This method of separating aluminium from its compounds was devised by Charles M. Hall, while an undergraduate student at Oberlin College, Ohio. His success turned on his knowledge of the properties of related metallic compounds. He recognized the probable value of aluminium in the arts, could it be produced in large quantity at low cost. He believed that electrolysis would prove the most convenient, thorough and inexpensive method; but there was at that time no process known by which it could be applied to this element. His problem was to find a form of electrolyte rich in aluminium which should be comparatively easy to separate into its elements, and to discover a substance for the solvent which should prove a satisfactory bath. This latter substance must, furthermore, be a good conductor of electricity, must readily dissolve the proposed electrolyte, and must have a higher resistance to electrolytic disruption than the electrolyte. To discover the needed substances for electrolyte and solvent involved the examination of all available compounds of aluminium, the study of the various possible solvents for the compound selected, and the determination of electric conductivities. By virtue of rare familiarity with the chemistry and physics of the subject, with the properties of every substance concerned, the search was, after a time, rewarded with complete success. It was found that bauxite—the oxide of aluminium, alumina, in fact—is dissolved by molten cryolite, the double silicate of aluminium and sodium, and that the latter, while dissolving the bauxite freely and serving as an ideal solvent, also itself breaks up under the action of the electric current at a much higher voltage than alumina. So far as known, these are the only substances in nature which stand to each other in such relation as to permit the commercial production of the metal.

Aluminium as constructive material has disappointed some of its earlier advocates. It is difficult to work, gumming the teeth of files and resisting cutting and drilling tools by virtue of the very toughness which makes it desirable for tubes, columns, and the like. Its excellences, however, are manifold: the German army on investigation found that helmets of aluminium, as light as felt, turned the glancing impact of a bullet. For soldiers’ use it now forms not only helmets, but cooking vessels, cartridge cases, buttons, sword and bayonet scabbards. It gives the photographer as well as the surveyor instruments which unite strength with lightness. It has furthermore the quality which has long given value to the lithographic stone of Hohenlofen in Bavaria. Aluminium takes a sketch as perfectly as does the stone, with the inestimable advantages that the metal may be readily curved for a cylinder press, that it is compact and light in storage, while without the brittleness which has made stone so costly a servant to both artists and printers. To produce a deep color from stone it may be necessary to print one impression over another again and again; from aluminium a single impression is enough, as severe pressure may be safely applied.

Aluminium has so great an affinity for oxygen as to play a conspicuous part in the metallurgy of other metals. In the casting of iron, steel or brass, the addition to each ton of two to five pounds of aluminium greatly improves the product; the aluminium by combining with the occluded gases reduces the blowholes and renders the molten metal more fluid and therefore more homogeneous. A second use for aluminium turns on the same quality; it was devised by Dr. Goldschmidt for producing high temperatures, and is especially useful in welding steel rails and pipes. A mixture of iron oxide and aluminium finely divided is ignited by a magnesium ribbon; a very high temperature results as the aluminium combines with the oxygen derived from the iron oxide.

Aluminium by reason of its lightness occupies a large field in naval and military equipments, in motor-car construction, and the like, where the reduction of weight is of paramount importance. For cooking utensils the use of aluminium is constantly extending; the metal is a capital conductor of heat, is not liable to deteriorate in use, and gives rise, if dissolved, to harmless compounds. The chief objection to aluminium is its low tensile strength, which, for the cast metal is only 10,000 to 16,000 pounds per square inch. An improvement is effected by adding as an alloy a small quantity of some other metal, such as nickel or copper. When one part of aluminium is joined with nine parts of copper we have aluminium bronze, the strongest and handsomest of copper alloys, much resembling gold in its lustre.

Aluminium is finding acceptance as an electrical conductor. An installation of this kind in Canada unites Shawinigan Falls with Montreal, 84.3 miles distant. Three cables are employed, each composed of seven No. 7 wires. The total loss in the transmission of 8,000-horse power, at 50,000 volts at the generating station, is about eighteen per cent. Comparing equal conductors, in round numbers the cross-section of an aluminium cable is one-and-a-half times that of a copper cable, the weight being one-half and the tensile strength three-quarters. Everything considered when aluminium is 2¹⁄₁₀ the price of copper, the investor is equally served by both metals as conductors. This is true only where the conductors are bare. Where insulated cables are needed, the increased diameter of an aluminium conductor entails extra cost for insulating material.

Properties at First Unwelcome are Turned to Account.

At first the lightness and weakness of aluminium were much against it; these, as we have seen, were soon overcome by alloying the metal with copper or nickel. But by giving aluminium forms of utmost stiffness, by reinforcing these forms with steel wires, the metal is quite strong and rigid enough for cups, plates, cameras and other instruments for which lightness is most desirable. In many another case a material or a characteristic at first unwelcome has been turned to excellent account. Smokiness in a fuel is not a quality mentioned in its advertisements, and yet smokiness is just what is sought in the twigs, stubble, or coals set on fire to give plants a cloud protecting them from unseasonable frosts. It is astonishing how little fuel will serve in such cases, especially if the atmosphere is calm, so as not to carry the smoke where it is not needed. Many another instance might be given of a quality objectionable for one service and then turned to satisfying a new want. Sometimes, too, offensive qualities are most useful. Illuminating gas, as at first manufactured, had a distressing odor, which gave prompt and unmistakable notice of a leak. When water gas came into use, most harmful when inhaled, the chemists were puzzled to know how to give it an offensive smell; they found that a quality long complained of was really an advantage in disguise.

So in the electrical field, when an unsought quality has intruded itself, and proved unwelcome, the question has arisen, what service can we enlist it for? Not seldom the answer has been gainful in the extreme. Dr. Oliver J. Lodge tells us that a bad electrical contact was at one time regarded simply as a nuisance, because of the singularly uncertain and capricious character of the current transmitted by it. Professor Hughes observed its sensitiveness to sound-waves, and it became the microphone, which, duly modified, brought the telephone from the whisper of a curious toy to the full tones which ensured commercial success the world over. This same “bad” contact turns out to be sensitive to electric waves also, forming indeed nothing else than the coherer of the wireless telegraph.

Many an electrician has been perplexed and thwarted by the small bubbles of air which place themselves on a metallic surface immersed in an electric bath, interrupting the attack sought to be carried to a finish. Happily there is a task which these very bubbles perform as if they had been created for no other purpose, namely, the re-sharpening of files. First the dull and dirty files are placed for twelve hours in a fifteen to twenty per cent. solution of caustic soda; they are then cleaned with a scratch-brush and a five per cent. soda solution. Next they are placed in a bath of six parts of forty per cent. nitric acid, three parts sulphuric acid, and 100 parts water, each file being connected to a plate of carbon immersed close to it, by means of a copper plate connecting at the top all the carbons and the files. This produces a short-circuited battery generating gas at the surface of the files; the bubbles which adhere to the points of the files protect them from being eaten away, while the rest of the metal is being etched. Every five minutes the files are taken out and washed in water to remove the oxide which collects on their surfaces. When sufficiently etched they are placed in lime-water to remove any adherent acid, dried in sawdust to prevent rusting, and rubbed with a mixture of oil and turpentine. Indispensable in the whole process is the protection afforded by the bubbles of air.

Evil, Be Thou My Good.

For a long time its creation of sparks kept electrical machinery out of mines liable to fire-damp, which might be exploded by these sparks. In many other places they worked evils quite as serious, setting fire to shavings, cotton and such like. To-day these very sparks are applied to touching off the charges of gas and air in gas-engines of all types, whether stationary, or for automobiles and motor-boats. In another respect the automobile should be provided with a means of creating what is usually considered a nuisance, namely, a noise. Moving rapidly as it does on thick rubber tires, it gives no warning to hapless wayfarers. In Canadian cities, where in winter deep snow may muffle the tread of horses, every sleigh, under severe penalty, must be furnished with efficient bells.

Compensating Devices.

Sometimes an important property has unwelcome effects which, in particular cases, cannot be applied to advantage, and must be counterbalanced with as much care as possible. Many pieces of mechanism from the qualities of their materials are subject to deviations which must be compensated by introducing equal and opposite action. Tasks of this kind proceed upon an intimate acquaintance with the properties of substances common and uncommon. From the first making of clocks there was much trouble due to changes of temperature which affected the dimensions of pendulums, and consequently their rate of going. This difficulty is overcome by taking advantage of the fact that heat expands zinc about two-and-a-half times as much as it expands steel. Accordingly the two-second pendulum of the great clock at Westminster is built of a steel rod 179 inches in length, and a zinc tube, less massive, 126 inches long; they are joined at their lower ends only and are parallel. As temperatures vary, the fluctuations in length of the steel compensate those which occur in the zinc. Another mode of effecting the same purpose is to employ a cylinder partly filled with mercury; as this rises when warmed it exactly compensates for the lengthening by expansion of its supporting rod of steel.

Gravity, that universal force at which we have just glanced as it swings a pendulum, cannot be banished, but its downward push may be balanced by an equal upward thrust. In a remarkable feat Plateau poured oil into a blend of water and alcohol, adding alcohol until he produced a mixture having the same specific gravity as the oil—which now became a sphere, taking its place in the middle of the diluted spirits. He then introduced into the oil a vertical disc which he rotated; very soon spherules of oil separated themselves from the parent mass, and as satellites moved in the same direction as the primary sphere, because immersed as they were in the diluted alcohol, they shared the direction of its motion: the whole afforded a remarkable illustration of how nebulae may become planets, moons, and suns.

On somewhat the same principle as Plateau’s model are the liquid compasses for ships. Their needles are disposed within hollow metallic holders of the same specific gravity as the immersing liquid, in which therefore they move with perfect freedom on their sapphire bearings. Sometimes it is desired to use compass needles so poised that they will respond to the slightest magnetic influence. To this end one needle is placed above another, the north pole of the first over the south pole of the second; the astatic needle formed by this union is much more sensitive than a simple needle. The astatic needle, for all its ingenuity, is little used; of incomparably more importance is that other magnetic device, the telephone. No sooner had it entered into business than a serious fault was found with its messages; they arrived blurred and mingled with many sounds and noises, as if the conveying wire had caught every audibility of a neighborhood. The difficulty is remedied by using two conductors instead of one, and so arranging them that the currents induced on one conductor are exactly equal and opposite to those induced in the other.

Properties Long Deemed Useless are Now Gainful.

If properties at first unwelcome have at last been turned to account, so also have properties which were long deemed utterly useless. A big and interesting book might be filled with the story of how by-products, long thrown away as worthless, have rewarded careful study with great profit. Thus for ages was bran discarded in flour-mills: to-day it may afford all the miller’s profit, or even more than that profit. In the Southern States until a generation ago cotton seed was regarded as valueless. At present that product, so long wasted, is the basis of a great industry, a ton of seed yielding about 1089 lbs. of meat to 20 lbs. of lint; out of this meat 800 lbs. are cake and meal; the remainder, 289 lbs., forms an oil which furnishes a substitute for olive oil and lard. Until a few years ago glycerine was thrown away as produced in candle-works and soap factories. It is now so valuable that manufacturers adopt just that method of preparing fatty acids which yields most glycerine from neutral fats. So in paper-making, the soda which formerly was sent into creeks and rivers to the pollution of sources of water-supply, is now used over and over again, largely increasing the net results of manufacture. No industry has shown of late years so large utilization of products formerly wasted as the iron and steel manufacture. Its slags are made into bricks, cement, and glassy non-conductors of heat and electricity. Its gases are used for engines developing immense motive powers, or they are in part condensed for valuable acids or other compounds. In these cases and thousands more the question has been, What are the properties of these by-products? How can they be made useful?

Separation Turns on Diversity of Properties.

Let us note how diverse substances are separated from one another by taking hold of differences in their properties. When a handful of grain which has just passed under a flail is thrown upward in a breeze, its chaff is blown much farther than the grain; the difference in breadth of surface, joined to a difference in density, enables the wind to effect a thorough separation. A common fanning mill, with its quick air current, works much better than the fitful wind, because continuously. That simple machine, like every other which takes a mixture and separates its ingredients, seizes upon a difference in properties. In Edison’s apparatus for removing iron from sand or dust, a series of powerful magnets overhang a stream of sand or powdered material, deflecting the iron particles so that they fall into a bin by themselves, while the trash goes into an adjoining larger bin. The Hungarian process of flour-milling first crushes wheat through rollers; the various products are then separated by processes which lay hold of differences in specific gravity—often but slight.

A feat more difficult than that of the Hungarian mill would seem to be the division of diamonds from other stones. It has been accomplished by Mr. Frederick Kersten of Kimberley, South Africa. He noticed one day at his elbow a rough diamond and a garnet on a board. He raised one end of this board, and while the garnet slipped off, the diamond remained undisturbed. What was the reason? He observed that the wood bore a coating of grease, which possibly had held the diamond while the garnet had slipped away. He took a wider board, greased it, and dropped upon it a handful of small stones, some of which were rough diamonds. He found that by inclining the board a little, and vibrating it carefully, all the stones but the diamonds fell off, while the diamonds stuck to the grease. He forthwith built a machine with a greasy board as its separator, and scored a success.

On quite a different plan is built the coal washer which separates coal from slate. Pulses of water are sent upward through a sieve so as to strike a broken mixture of coal and slate, making a quicksand of the mass. Because the slate is heavier than the coal it is not carried so far, and is therefore caught in a separate stream and thrown away.

Properties Newly Discovered and Produced.

Separations, such as we just considered, turn upon obvious differences in density. Properties not obvious, yet highly useful, come into view year by year as observers grow more alert and keen, as new instruments are devised for their aid, as measurements become more refined, so that matter is constantly found to be vastly richer in properties than was formerly supposed. We have long known that carbon has forms which vary as widely as coal, graphite and the diamond. Many other elements are detected in a similar masquerade. Iron, for instance, takes three forms, alpha, beta, and gamma. Alpha iron is soft, weak, ductile and strongly magnetic; beta iron is hard, brittle and feebly magnetic; gamma iron is also hard and feebly magnetic, yet ductile. Joule, the famous English experimenter, prepared an amalgam of iron with mercury; when he distilled away the mercury, the remaining iron took fire on exposure to the air, proving itself to be different from ordinary iron. Moissan has shown that similar effects follow when chromium, manganese, cobalt and nickel are released from amalgamation with mercury.

At first steel was valued for its strength and elasticity; to-day we also inquire as to its conductivity for heat or electricity, its behavior in powerful magnetic fields, its capacity to absorb or reflect rays luminous or other. As art moves onward we enter upon new powers to change the properties of matter, compassing new intensities of heat and cold, each with new effects upon tenacity, elasticity, conductivity. So also with the extreme pressures, possible only with modern hydraulic apparatus, which prove marble to be plastic, and reduce wood to a density comparable with that of coal, explaining how anthracite has been consolidated from the vegetation of long ago.

And one discovery but breaks the path for another, and so on indefinitely. Coming upon a new property, the sensitiveness of silver compounds to light, meant a new means of further discovery, the photographic plate. That plate, responsive to rays which fall without response upon the retina, reveals much to us otherwise unknown and unsuspected. Of old when an observer saw nothing, he thought there was nothing to see. We know better now. Thanks to the sensitive plate we have reason to believe that properties, once deemed exceptional, are really universal. Phosphorescence, for ages familiar in the firefly, in decaying logs and fish, now declares itself excitable in all substances whatever, although usually in but slight measure. The case is typical: the polariscope, the spectroscope, the fluoroscope, the magnetometer, the electroscope, each employing as its core a substance of extraordinary susceptibility, detects that quality in everything brought within its play. Thus from day to day matter is disclosed in new wealths of properties, and therefore in new and corresponding complexities of structure. In ages past mankind was on nodding terms with many things, and had no intimate knowledge of anything.

With materials before him richer in array than ever before, and better understood than of old, the inventor asks, What properties do I wish in a particular substance? Then, he proceeds to make, if he can, a dye of unfading permanence, an insulator resistant to high temperatures, an alloy which when subjected to heat or cold remains unaltered in dimensions. He finds materials much more under command than a century ago could have been imagined, as the glass manufacture, the alloying industry, the making of artificial dyes, abundantly prove.

Edison’s Warehouse as an Aid.

Mr. Edison, for aid in finding just the substance he needs for a new purpose, has at his laboratory in Orange, New Jersey, a large store-room filled with materials of all kinds. He may wish a particularly high degree of elasticity, hardness, abrasive power, or what not; to provide these he has gathered a wide diversity of woods, ivories, fibres, horn, glass, porcelain, metals pure and alloyed, alkalis, acids, oils, varnishes and so on. Take one example from among many which might be given from his shelves; he finds that a sapphire furnishes the best stylus wherewith to cut a channel on a phonographic cylinder. Hard, flinty particles from the air are apt to enter the wax, so as to blunt a cutting edge. Diamonds would be best as channelers, but their cost obliges him to choose sapphires as next best; they are purchasable at reasonable prices and last ten years under ordinary conditions of wear.

CHAPTER XII
PROPERTIES—Continued

Producing more and better light from both gas and electricity . . . The Drummond light . . . The Welsbach mantle . . . Many rivals of carbon filaments and pencils . . . Flaming arcs and tubes of mercury vapor.

Light Giving Properties.

Mr. Edison has achieved triumphs not only in giving sound its lasting registration, but in producing an electric light of new economy. Both exploits proceeded upon a masterly knowledge of properties. A century ago candles provided illumination both to rich and poor, the sole difference being that wax shone in the palace and tallow in the hut. The oil lamps which gleamed in the lighthouses of England and America, for all their bigness, were plainly of kin to the Eskimo saucer filled with blubber, edged with moss as wick. Yet for ages, from every hearth in Christendom, there had been the promise of better things as bituminous coals, or sticks of wood, had cheered as much by their light as by their warmth. We owe much to James Watt, who improved the steam-engine and gave it essentially the form it retains to the present hour. We owe also a weighty debt to an assistant of his, William Murdock, who, thanks to a suggestion from Lord Dundonald, attentively observed the process by which coals produce light. He saw that under stress of intense heat the solid fuel emitted streams of gas which burned with great brilliancy. Here gas-making and gas-burning went on at the same moment in the same place; might the process be separated, so that gas might be made here, and burned elsewhere at any convenient time? An experiment proved the project to be feasible, and forthwith the Soho Works, near Birmingham, in which Watt’s engines were built, were lighted by gas. Such was the beginning of an industry now important in many ways. To-day gas not only yields light, but heat and power, while, especially in metallurgy, fuels are more and more used after reduction to the gaseous form.

How the Gas Mantle was Invented.

Early in the day of gas-making it was noticed that gases of various kinds differed much in light-giving quality. It was presently shown that their light depended on the carbon brought to incandescence in a flame; in the absence of that carbon, as when a jet of pure hydrogen was consumed, extreme heat was accompanied by no light whatever. Then came a capital discovery, namely, that lime introduced within a burning jet of hydrogen became intensely luminous while itself but slowly consumed. Adopting lime for the core of his apparatus, Captain Thomas Drummond, of the Royal Engineers, in 1835 devised the lime light. Upon a block of pure, compressed quick lime, he directed a jet of burning gas, obtaining a beam of great vividness still employed in stereopticons and in theatres. For modern types of the Drummond lamp a twin jet of hydrogen and oxygen is used. Lime has many sister substances having light-giving quality when highly heated, and among them are many rare earths, oxides of uncommon elements. These strange substances were destined to play a prominent part in the battle between gas and electricity as illuminants. When Edison in 1878 perfected his incandescent bulb, it seemed as if electricity were soon to be the sole illuminator of houses. But the gas engineers were to be rejoiced by the invention of a mantle which quadrupled the brillancy of a gas flame, withstanding the rivalry of electricity in a notable degree. This mantle was invented by Dr. Auer von Welsbach, a chemist of Vienna, who virtually adopted the principle of the Drummond light. His efforts give us an admirable example of an inventor passing from a hint to a test, day after day meeting new difficulties with unfailing courage and resourcefulness.

In 1880 Dr. von Welsbach took up the study of rare earths, mainly with a view to ascertaining their value as illuminants. As he brought one specimen after another to melting heat on bits of platinum wire, he found that the little beads formed were unfavorable in shape to the production of light. Then came into his mind an idea of that golden quality which occurs only to the man who earns it: Why not soak cotton with solutions of salts of rare earths, burn the cotton and leave behind an earthy skeleton of slight thickness and much surface? Experiment proved that the idea had promise, but the skeletons crumbled to dust with the least tremor. For success a fair degree of cohesion was imperative, but to secure that cohesion demanded skill, resource, and patience. After a long series of trials a mantle was made with lanthanum oxide; immersed in flame its beam was particularly bright, now for the first time suggesting that the rare earths might yield light on a large scale. But trouble was at hand, to be overcome only at the end of much toil.

During an absence of several days, the inventor left a mantle of lanthanum oxide locked up in his laboratory. When he returned it had fallen to powder, having attracted from the atmosphere both moisture and carbon dioxide. Evidently this harmful attraction must be avoided by adding an ingredient to keep the mantle dry and preserve it from union with carbon dioxide. For this purpose magnesia was chosen; the resulting compound proved to be durable, and gave an agreeable light of moderate intensity. But, alas, after glowing about seventy hours, the mantle failed in its radiance, becoming of glassy and translucent texture. Thus impeded, the untiring inventor turned to mixtures having zirconium as a basis; these not only gave a steady beam, but extended to hundreds of hours the life of a mantle. Still bent on getting more light if he could, Dr. von Welsbach tested thorium oxide with gratifying results; yet, strange to say, when he had purified this material to the utmost, his light fell off in an unaccountable fashion. What could be the matter? Surely in the purifying process some invaluable element had been cast aside. This element, in the researches of an associate, Mr. Ludwig Haitinger, proved to be cerium in minute quantity. Here was a discovery of the highest moment; at the end of many experiments it was determined that one per cent. of cerium and ninety-nine per cent. of thorium oxide are the best proportions for a mantle such as we use to-day. Why these proportions are best nobody knows, any more than why one per cent. of carbon added to iron gives us a steel incomparably better than iron for many uses. A Welsbach mantle has good points apart from its economy of gas. Its combustion is thorough, so that it throws into the air a much lower percentage of injurious products than does an ordinary gas flame. It never smokes, and its light is so steady as to be available for work with the microscope and other exacting demands. It has one defect which may yet be removed: its light has a somewhat unpleasant tinge of green. In another chapter of this book, producer gas, much cheaper than common illuminating gas, is described. Dowson producer gas, with a Welsbach mantle, yields a light of 8 to 10 candle-power with a consumption of 4.5 to 4.8 cubic feet per hour.

Dr. CARL FREIHERR AUER von WELSBACH
of Vienna.

Boivin burner for alcohol, attachable to any lamp.

Thus far no successful mantle for a petroleum lamp has been devised. With alcohol a mantle yields a brilliant flame. A lamp with a Boivin burner and a Welsbach mantle has given a light of 30.35 candle-power for 57 hours and 5 minutes in consuming one gallon of alcohol, almost twice as much light as given by a Miller lamp with a round wick and a central draft, burning a gallon of kerosene. In the United States on January 1, 1907, there will cease to be an excise tax on alcohol used in the arts, a denaturalizing process rendering the liquid unfit to drink. As this alcohol may be easily produced from grain or potatoes at 20 to 25 cents a gallon, a capital illuminant will be available for the public, as well as an excellent fuel and a substitute for gas or gasoline in motors.

As first manufactured, gas-mantles were woven, they are now knitted,—a change for the better in closeness and firmness of texture. Nearly all the thorium used for mantles is found in the monazite sands of the provinces of Bahia and Espirito Santo, along the coast of Brazil. These sands were for a long time valuable only for the zinc they contained. To-day the thorium they carry is of vastly more account; for chemical treatment this is sent to Germany whence the manufactured product is borne to every quarter of the globe.

Improvements in Electric Lighting: Incandescent Lamps.

While the Welsbach mantles have been constantly improved in quality, and given new and inverted forms of special value, the inventors in the field of electric lighting have not stood still. For interior illumination the Edison incandescent bulb still holds its own despite many a threat of dispossession. Since 1881 its details of manufacture have been steadily bettered and its price much reduced, while its consumption of current has fallen from 5.8 watts per candle to 3.1. This advance, marked as it is, leaves a long path ahead of the inventor whose estimate is that were the whole of an electric current transformed into light, a candle would cost us but .11 of a watt, that is, but one twenty-eighth part as much as when we set a carbon filament aglow. In electrical terms a horse-power yields 748 watts, representing, were there no waste in conversion, no less than 425 lamps each of 16 candle-power.

Alcohol lamp with ventilating hood.

It is this immense margin for improvement that has spurred ingenuity to attack the problem of electric lighting from many new sides. The General Electric Company produces a carbon filament of one fifth greater efficiency than an ordinary untreated filament. Fibers of the usual cellulose kind are enclosed in a carbon box, placed in a carbon-tube resistance furnace heated to between 3,000° and 3,700° C. This converts the filament into a graphite of increased luminosity which, furthermore, blackens its enclosing glass much less than a common filament does.

Welsbach mantle.

In the early days of electric lighting a good many experiments were tried with threads of platinum, but without success. That metal remains unmelted at a very high temperature, but as a light-giver its quality is poor. Of late years investigators have turned to other metals, of high melting points, and with results so remarkable that we may expect some of them to be in general use in the near future. Tantalum, a rare and costly metal, has been found to give a candle-power with as little as two watts and, in specially favorable circumstances, with only 1.85 watts. Osmium, in the hands of Dr. Auer von Welsbach, reduces this figure to 1.5 watts. Dr. Hans Kuzel, of Baden, Austria, has employed filaments of tungsten in lamps which he claims demanded only one watt per candle. From among these new lamps it seems highly probable that as soon as methods of manufacture are settled and standardized the world will be given an electric light, in small units, much cheaper than ever before.

Tantalum lamp.

Tungsten lamp of Dr. Hans Kuzel.

New Arc Lamps.

For large spaces indoors and for out of doors the arc-lamp maintains its popularity in much the form originally devised by Mr. Charles F. Brush of Cleveland. But, as in the case of the incandescent bulb, many a rival is now disputing the field, so that supersedure may be close at hand. In what are known as flaming or luminous arcs the carbon pencils are impregnated with salts of the calcium group of elements, of extreme luminosity. In these lamps the electric arc itself is the chief source of light, instead of the glowing end of the positive carbon as in a common arc lamp. As the calcium salts volatilize into gases they provide a path of less resistance than air for the passage of the current, so that the electrodes may be drawn apart to a distance which may be as much as 2¹⁄₂ inches. These lamps require free ventilation, so that they must be open. Their economy is extraordinary, a candle-power being afforded for .353 watt, as against 1.78 watts for an enclosed arc lamp, a five-fold gain in effectiveness. To renew the carbons, which waste rapidly, a new device provides fresh pencils, cartridge fashion, as required. Without this aid, trimming is often necessary, and this fact joined to the high cost of the carbons lessens the net gain in their use. On another line of experiment noteworthy results have been reached with metallic oxides. Magnetite, an oxide of iron, has developed a candle-power with but one half of one watt. Ferro-titanium, a compound of iron and titanium, has given a candle-power with only one third of a watt, and it is expected that still higher efficiencies will soon be attained with this wonderful compound.

Hewitt mercury-vapor lamp.

Hewitt Mercury-Vapor Lamp.

From quite another side Mr. Peter Cooper Hewitt enters the field of light production, utilizing the glow of a vapor instead of a solid stick. His lamp is a long, slender tube of glass; within each end is sealed a metallic wire; at one end is a little mercury. When a powerful pump has exhausted the tube to a high degree it is sealed, and its wire terminals are placed in an electric circuit. On tilting the tube the mercury flows from end to end, an arc is formed, and the mercury vapor becomes luminous. This vapor remains unconsumed, and the lamp asks no attention whatever. Its rays are greenish, so that where normal colors are desired, it is well to use supplementary lamps of carbon filaments to furnish red rays. For streets, squares, freight-sheds and the like, the Hewitt light is capital just as produced, its rays being widely diffused and casting no heavy shadows. Its high actinic power makes it specially useful to photographers, while in factories, drafting rooms, composing rooms and so on, its color is unobjectionable. Its cost is small, as a candle-power is produced in large tubes with but 0.55 of a watt. A Hewitt lamp of automatic type, recently devised, has a small solenoid or magnet on the suspension bar just above the holder. On closing the circuit the current flows through this solenoid which instantly tilts the tube and starts the light. This lamp is particularly suited to places, such as the lofty ceilings of foundries, where it would be difficult to tilt the tube by hand. Hewitt lamps use either a direct or an alternating current.

In an [earlier chapter] we glanced at reflectors and refractors, newly invented, which give light its most useful paths with as little avoidable loss as possible. These devices, applied to Welsbach burners and the new electric lamps, greatly economize modern illumination in comparison with that of former times.[13]

[13] In February, 1906, the Illuminating Engineering Society was established in New York. Its secretary is A. H. Elliott, 4 Irving Place, New York. The Society publishes its proceedings and discussions.

CHAPTER XIII
PROPERTIES—Continued. STEEL

Its new varieties are virtually new metals, strong, tough, and heat resisting in degrees priceless to the arts . . . Minute admixtures in other alloys are most potent.

From a brief consideration of illuminants let us pass to a rapid survey of a most important group of structural materials, the steels. Here, as always, we shall find how abundant are the harvests reaped in a searching study of properties. Within the past fifty years new steels have been produced in so ample and rich a variety that we have gained what are virtually many new metals of inestimable qualities.

Steels for Strength.

In 1781 Professor Torbern Bergman, of the University of Upsala, in Sweden, showed that steel mainly differs from iron in containing about one fifth of one per cent. of plumbago, or carbon, as we would say now. Steels may contain all the way from one tenth to one and a half per cent. of carbon; the lower this percentage, the more nearly does the steel approach wrought iron in softness; as the proportion of carbon increases up to one per cent. the steel increases in tenacity, beyond one per cent. tenacity diminishes and brittleness is augmented. Hardness depends upon the percentage of carbon a steel contains. Physical conditions are almost as important as chemical composition; a mass of red-hot steel, carefully hammered or pressed is thereby strengthened, an effect due either to minimizing the process of crystallization, or to breaking up crystals as fast as they form. The microscope reveals many details of structure in steel, and has enabled the analysts greatly to economize the manufacture of desired varieties. Under the microscope steels much resemble crystalline rocks in structure, with constituents differing widely. Of these the most important is ferrite, a pure or nearly pure metallic iron, soft, weak, ductile, of high electric conductivity. Next in importance is cementite, an iron carbide (Fe₃C), harder than glass and nearly as brittle, but probably very strong under gradually and axially applied stress. A third constituent, austenite, is a solid solution of carbon, or perhaps of an iron carbide, in gamma allotropic iron (there being also alpha and beta irons). Austenite is hard and brittle when cold, is stable at high temperatures, and is slowly transformed by reaction into compounds of ferrite or cementite. Several other ingredients of importance, as [pearlite], illustrated on the opposite page, have also been studied.[14]

[14] Henry Marion Howe, “Iron, Steel and Other Alloys.” Second edition. Published by Albert Sauveur, Cambridge, Mass., 1906.

While carbon is the most decisive element in admixture, other ingredients have marked influence, silicon and manganese especially. The process invented by Bessemer, described by himself in [another chapter] of this book, as introduced in 1855, revolutionized the steel manufacture by its directness, cheapness and speed. It consists in burning out from pig-iron, by a hot air blast, all or nearly all its carbon. Then spiegeleisen, or other mixture, containing a definite quantity of carbon and manganese, is added to the molten mass, yielding steel of the quality desired. This method produces more rails for railroads than any competing method; in other fields it is being rivalled more and more severely by the open hearth process.

Pearlite, magnified about 750 diameters.

Steel containing more than nine-tenths of one per cent of crystals of pearlite, surrounded by envelopes of cementite (Fe₃C). Magnified 200 diameters.

CLEANING CARS BY THE “VACUUM” METHOD.

The Open Hearth Process.

Steel making by the open hearth process is chiefly due to the late Sir William Siemens. In a gas producer he gave his fuel the gaseous form, in which it is more easily controlled and more efficient than when solid. Of more importance were his regenerators, chambers of brickwork, heated by the products of combustion, and then employed to warm incoming currents of air and gas on their way to the furnace. The Siemens furnace has been modified in many ways and much improved in its details. A good example of an [open hearth furnace], as planned by the late Mr. Bernard Dawson, is shown on page 165. It centers in a large hearth built of refractory materials, upon which the metal is melted as flames play over it. At each end are two regenerators filled with checker firebricks through which air or gas passes on its way to the furnace, and through which, at due intervals, the products of combustion emerge as they pass to the stack. On each side, one of the regenerators is for air, the other for gas; between them is a substantial wall to prevent any mixing before their currents reach the hearth. It is in the regenerator, which utilizes heat which otherwise would be wasted, that the open hearth displays its best feature. Its products vary in composition as its raw materials vary, whether pig-iron of a specific kind, a particular ore, or scrap; and just as in the Bessemer process, a harmful element, as phosphorus, is removed almost wholly by the addition of a suitable ingredient, such as lime. In excellence and uniformity of quality open hearth steels are preferred to those of the Bessemer converter, even for railroad rails which for years were made solely by the Bessemer process.

Open hearth furnace.

The Gayley Dry-Blast Process.

A remarkable improvement in blast-furnace practice, cheapening cast or pig-iron, and therefore lowering the cost of derived steels, is the dry-blast process due to Mr. James Gayley, of Pittsburg. It has long been known that blast-furnaces ask more fuel in warm and damp weather than in cold and dry weather; beginning with this familiar fact Mr. Gayley proceeded to dry the air blown into his furnaces, by passing it around large coils of iron pipes through which a freezing mixture circulated, melting the snow as formed by passing hot brine through the pipes, a few of them at a time. The air thus dried was then heated by being sent through hot blast stoves in the usual mode. This simple drying of the blast saves about 19 per cent. of the fuel, and makes the action of the furnace much more regular than when ordinary air is used. It lowers the temperature of the gases which escape from the top of the furnace, and raises their percentage of carbon dioxide, symptoms of the great increase in fuel efficiency. Atmospheric moisture has a cooling effect on the lower part of a furnace, just where the highest temperature is needed to melt the iron and slag, remove the sulphur and deoxidize the silica. A comparatively small increase of temperature by broadening the margin of effective heat, which margin at best is narrow, has the astonishing effect of economizing fuel to the extent stated, 19 per cent.[15]

[15] Henry Marion Howe, “Iron, Steel and Other Alloys.” Second edition. Cambridge, Mass., Albert Sauveur, 1906.

Steels to Order.

What is chiefly sought in steel is tensile strength, next in value is elasticity; in some cases hardness is indispensable. By varying the proportions of the carbon, silicon and manganese added to his iron, the steel-maker produces an alloy with the tenacity, elasticity or hardness he wishes. Nickel, as a further ingredient, in certain proportions yields an astonishing gain. A steel containing fifteen per cent. of nickel has shown a tensile strength of 244,000 pounds to the square inch, four times as much as before admixture; the elastic limit also was much increased. Hardness and strength tend to exclude ductility, but nickel steel is at once strong, hard and extremely ductile; hence its use for armor plate, great guns, and the barrels of small arms. Nothing but the high price of nickel prevents these alloys from having wide utilization, for they mean lighter and therefore more economical machines and engines than those of ordinary steel. Many turbines actuated by water, steam or gas, are best operated at speeds forbidden to common steel, which would fly to pieces under the centrifugal stress exerted, yet these speeds are quite feasible and safe when nickel steel is employed. This alloy brings nearer the day of mechanical flight, first promising to transportation on land and sea engines increased in power while much diminished in weight. In exceptional cases, where the expense may be borne, we may expect soon to see nickel steel used for higher towers, longer bridge-spans, thinner boilers, than those of to-day. Part of the bridge crossing Blackwell’s Island, New York, is built of nickel steel. Even with costs at their present plane, it is worth while for the designer of machinery to remember that friction is reduced when masses become smaller, power for power. It is found profitable, for instance, to use nickel steel for the cylinders of automobiles of high power.

In many tools and implements two different kinds of steel are united with decided gain. Thus the cutting edge of a cold chisel is hard and brittle, while its shank, much less hard, is tough and able to resist the shocks it receives. So also a projectile is hardened at its point and nowhere else. Plowshares are often made very hard on their surfaces, with a backing which is comparatively soft but elastic enough to suffer no harm in the blows dealt by rough ground and stones. One of the drawbacks in the use of steel is its liability to corrosion. An alloy of 30 per cent. nickel and 70 per cent. steel has proved to be corrodible in but slight measure, affording a material of great value to the arts.

Heat Treatment.

While the chemical composition of a steel is of prime importance, the quality of the steel will next depend upon its heat treatment in manufacture. The temperature to which heating is carried, the period during which it is maintained, the rate at which cooling takes place, and the circumstances of cooling, each has its effect on the character of the product. It is chiefly in this field that the steel-maker within wide limits is able to turn out an alloy either hard or soft, brittle or ductile, tenacious or weak, at pleasure. While much has been learned within the past few years as to the proper treatment of steel by heat, much still remains to be discovered.

To quote typical instances from Professor Henry Marion Howe, of Columbia University, New York:—“In the case of steel with less than 0.33 per cent. of carbon the temperature from which slow cooling occurs appears to have little influence on the tensile strength; but it is the general belief that if that temperature approaches the melting-point, the tensile strength decreases. In the case of higher-carbon steel, the tensile strength at first increases as the temperature from which slow cooling occurs rises to 800°, or even to 900° or 1000° C. Then, after varying somewhat, it falls off very abruptly in the case of steel of 0.50 per cent. of carbon, when that temperature approaches 1400°.”[16]

[16] In his “Iron, Steel and Other Alloys.” Second edition. Published by Albert Sauveur, Cambridge, Mass., 1906.

Tempering and Annealing.

For rock drills, cold chisels, milling and other tools it is necessary to use steel carefully tempered, so that brittleness is greatly reduced while considerable hardness and cutting power remain. Other changes of properties, as remarkable, follow upon subjecting steel to greater heat than that used for tempering. Says Professor Roberts-Austen:—“Three strips of steel identical in quality are taken. By bending one it is shown to be soft; if it is heated to redness and plunged in cold water it will become hard and will break on any attempt to bend it. The second strip, after heating and rapid cooling, if again heated to about the melting point of lead, will at once bend readily, but will spring back to a straight line when the bending force is removed. The third piece may be softened by being cooled slowly from a bright red heat, and this will bend easily and remain distorted. The metal has been singularly altered in its properties by comparatively simple treatment, and all these changes, it must be remembered, have been produced in a solid metal to which nothing has been added, and from which nothing has been taken away.”

It is the comparative slowness of cooling in oil, the greater slowness of cooling in air, that make these by far the best tempering processes, because the molecular re-arrangement, in which tempering consists, requires time. Often the critical temperature, at which a desired re-arrangement takes place, is declared by the metal losing all power of response to a magnet: this fact affords the steel-maker welcome aid; he has only to shut off heat as soon as his steel ceases to attract a magnet and plunge the steel into water in order to obtain the hardness he wishes.

The complex phenomena of heat treatment in steel manufacture are fully discussed by Professor H. M. Howe, in his “Iron, Steel and Other Alloys,” second edition, 1906.

Steel for Railroad Rails.

In another chapter of this book a word is said as to the form of rails at which Mr. P. H. Dudley has arrived as the outcome of years of experiment. He thus describes the properties which the steel should possess by virtue of due chemical composition and proper heat treatment:—

“Ductility to ensure power to resist the shock of the driving wheels, so that the steel may not break; resistance to abrasion, that it may not wear out; and high limit of elasticity, that it may not take a permanent set and be bent into a series of waves between its supporting ties, by the enormous pressures which the wheels of to-day throw upon it. The best composition is carbon 0.55 to 0.60 per cent., silicon 0.10 to 0.15, manganese 1.20, sulphur under 0.06, phosphorus under 0.06; with 50,000 to 60,000 granulations to the square inch. More granulations, or fewer, mean an increase of brittleness in the steel.”[17]

[17] Henry Marion Howe, “Iron, Steel and Other Alloys.” Second edition. Published by Albert Sauveur, Cambridge, Mass., 1906. And a note from Mr. P. H. Dudley to the author, May 2, 1906.

Invar: A Steel Invariable in Dimensions Whether Warmed or Cooled.

While the great strength of steel makes it of pre-eminent value in the arts, steel in the huge dimensions of modern roofs and bridges has the demerit of expanding with heat and contracting with cold in a troublesome degree. A notable case is that of the steel rails on the elevated railroad of New York. If this fault, common to all metals, can be materially reduced or abolished, then steel enters upon a new field of golden harvests. Here, by dint of acumen and skill the goal has been reached by M. Charles Edouard Guillaume, of the International Bureau of Weights and Measures in Paris. A few years ago he began investigating the singular magnetic qualities of nickel-steels. Then in studying expansibility by heat he discovered that when the nickel was increased to 36.2 per cent. the alloy was almost indifferent to changes of temperature, expanding but one part in one million when warmed from zero to 1° Centigrade. Because of this insensibility, the alloy at the suggestion of Professor Thury is named invar. In observations of invar which extended through six years, an elongation of one part in 100,000 was detected; subsequently its changes of length each year seemed less than one-millionth. This slight inconstancy may be overcome by further experiment; in the meantime while invar is not available for standards of length of the first order, such as those of the Bureau of Standards at Washington, there is a vast and useful field for the alloy. It offers itself for secondary standards, to be compared at intervals with primary standards at Washington or other capitals of the world.

A leading application will be in surveying. Already wires of invar have been employed by the Survey of France with the utmost success, dispensing with the burdensome apparatus formerly needed in compensating variations due to temperature. With invar wires ten men have advanced at the rate of five kilometers a day; ten years before, with ordinary steel measures, fifty men advanced one half a kilometer, that is, with but one fiftieth as much efficiency.

In time-keeping invar is likely to be as valuable as in surveying. At the Bureau of Standards and the Naval Observatory at Washington, pendulums of invar have been adopted with gratifying results. In ordinary watches and clocks the alloy will banish the compensating devices now requisite, of brass and steel which expand with heat and shrink with cold. For chronometers of the highest grade it is desirable that invar be improved with respect to its stability, an improvement which appears to be highly probable.

One other discovery by M. Guillaume deserves a word. He has found a nickel-steel which when warmed has the same expansibility as glass, so that it may displace platinum wire in leading an electric current into an incandescent lamp, a Crookes’ tube or similar illuminator. More singular still is another of his nickel-steels which shrinks slightly when warmed, holding out the hope of finding an alloy which will neither shrink nor expand as its temperature rises. With such a substance, of trustworthy stability, the arts would have a working material of inestimable value for theodolites, frames for microscopes and telescopes, and cameras for exact picturing.

Manganese Steel.

The magnetic properties of steel, to-day of supreme importance, have for ages excited curiosity. As long ago as 1774, Rinman observed that steel alloyed with manganese is non-magnetic. Here was a material for time-pieces which would free them from magnetic derangement. In the hands of Mr. R. A. Hadfield, of the Hecla Works, Sheffield, England, manganese steel has been produced in remarkable varieties. As the proportion of manganese is increased, the alloys manifest singular changes in their properties. When the manganese is four to six per cent., and the carbon less than one-half per cent., the alloy is brittle enough to be readily powdered by a hand hammer. When the proportion of manganese is doubled, the alloy displays great strength, which reaches its maximum when the manganese is fourteen per cent. No other material approaches manganese steel in its ability to resist abrasion; it outwears ordinary steel four times, much reducing the need for repairs, renewals, or pauses in work while worn-out parts are being replaced. It gives equally good service as the pins and bushings of dredges of the bucket-ladder type, lifting gold-bearing gravels and sands. It is used for centrifugal pumps in dredging sandy harbors, slips, or ponds, where the grit borne in the water plays havoc with ordinary steel surfaces. In ore-crushing manganese steel is particularly effective; a pair of jaws built of it have crushed 21,000 tons of flinty ore and were still good for 4,000 to 6,000 tons more, while the best chilled iron plates failed to crush as little as 4,000 tons.

This alloy is so hard that it cannot be machined or drilled by ordinary means; it must be treated by emery or carborundum wheels. Yet it is so malleable that it can be used for rivets when headed cold. It is so tough that it may be bent and twisted at will without rupture, so that it forms railroad switches, frogs, and crossings of great durability.

High-Speed Tool Steels.

Until 1868, the steel tools used in lathes and drills, planers and so on, were limited to the moderate pace at which they remained cool enough to keep their temper. Beyond that quiet gait they became worthless, snapped apart, or melted as if wax. In 1868 Robert Forester Mushet, of the Titanic Steel and Iron Company, Coleford, England, discovered an alloy of steel, tungsten and manganese which took rough cuts at a depth and with a speed unknown before. This alloy, because hardened simply in air, was called “air-hardening” or “self-hardening.” Thirty years afterward at the Bethlehem Steel Works, Pennsylvania, a tool of this steel was heated to what was feared to be a ruinously high temperature; experiment proved that the tool could be used at a heat, and therefore at a speed, never attained before in the workshop. From that hour hundreds of investigators have proceeded to combine steel with tungsten in various percentages, adding manganese, molybdenum, chromium, silicon, and vanadium. Of these ingredients much the most important are tungsten and molybdenum. Particular pains must be taken thoroughly to anneal the alloy when worked into bars.

As to the gain introduced by high-speed tool steels let Mr. J. M. Gledhill testify from the experience of the Sir W. G. Armstrong, Whitworth & Company’s works at Manchester:—

“Formerly where forgings were first made and then machined with ordinary self-hardening steel, a production, from bars eighteen and one half by six and five eighth inches, of eight bolts in ten hours was usual. With the new steel forty similar bolts from the rolled bar are now turned out in the same time, further abolishing the cost of first rough forging the bolt to form. The speed is 160 feet a minute, the depth of cut three-quarter inch, of feed ¹⁄₃₂ inch, the weight removed from each bolt sixty-two pounds, or 2,480 pounds per day, the tool being ground only once in that time. This is a fairly typical case. Just as striking is the behavior of this steel in twist drills, which supersede the punching process by passing through stacks of thin steel plates quite as swiftly and economically as a punch, while avoiding the liability to distress which accompanies the action of a punch.”

With the quickening of pace due to these steels, the designer is asked to remodel machine tools so that they may stand up against new pressures and speeds. A lathe thus re-patterned is mentioned by Mr. Gledhill: it absorbs sixty-five horse power as against twelve formerly, and has a belt trebled in width so as to measure twelve inches. Mr. Oberlin Smith expects high-speed steel to have other effects on machine design than the conferring of new strength: he looks for a rivalry keener than ever between rotary and reciprocating tools. In his judgment the milling tool, which can be speeded indefinitely, will encroach more and more on the planer, limited as the planer is by its movement being to and fro.

When work on cast iron must proceed at the utmost pace, a jet of air, delivered to the chips with force enough to clear them off as fast as they are formed, enables the speed to be quickened, while, at the same time, the life of the cutter is lengthened.[18]

[18] The foregoing pages on steel have been revised by Professor Bradley Stoughton, of the School of Mines, Columbia University, New York. He contributes at the end of this chapter a brief [list of books] for the reader who may wish to know something of the literature of iron and steel.

Alloys for Electro-Magnets.

In electrical art the alloy employed for electro-magnets should be permeable by magnetism fully and easily, otherwise dynamos and motors will waste energy as their magnetism is constantly gained, lost, or reversed. Once more the experimenter is Mr. Robert A. Hadfield of Sheffield, who produces an excellent alloy by uniting iron with 2.75 per cent. silicon, .08 per cent. manganese, .03 per cent. sulphur, .03 per cent. phosphorus. This alloy is improved by being heated to between 900° and 1100° C., followed by quick cooling; then being reheated to between 700° to 800° C., and cooled very slowly.

Iron is largely used as an electrical conductor, so that it is well to know how its conductivity is affected by ordinary admixtures. In experiments with sixty-eight specimens, Professor W. F. Barrett alloyed iron separately with carbon, aluminium, silicon, chromium, manganese, nickel, cobalt, and tungsten. In every case there was a loss of conductivity, and usually in a degree proportioned to the atomic weight of the added ingredient. Between one element and another there was often a wide disparity of effect. For example, in admixtures, each of one per cent., tungsten increased the resistance of a conductor by two per cent., while aluminium did seven-fold as much harm.

Magnetic Alloys of Non-Magnetic Ingredients.

We have so long been accustomed to thinking that there must be iron in everything magnetic that we hear with astonishment that metals each insusceptible of magnetism, when united strongly display this property. Such is the discovery of Mr. Fr. Heusler, of Dillenburg, near Wiesbaden. He noticed one day that an alloy of manganese, tin, and copper adhered to a tool which he had accidentally magnetized. In the course of experiments Mr. Heusler found that carbon, silicon, and phosphorus did not confer magnetism; while arsenic, antimony, and bismuth did so, all three metals being diamagnetic, that is, placing themselves at right angles to a common steel magnet above which they are freely suspended. An alloy of remarkable magnetic strength was composed of copper 61.5 per cent., manganese 23.5 per cent., and aluminium 15 per cent. This alloy is brittle and considerable changes of temperature but slightly affect its magnetism. When a little lead is added magnetism disappears between 60° and 70° C. This alloy therefore is magnetic when placed in cold water; when the water is heated the magnetism disappears before the water boils, only to reappear when the water cools. The main interest of these discoveries is that the new alloys bridge the gap betwixt magnetic and diamagnetic bodies, that is, they join the iron, nickel, and cobalt group, which place themselves along the line of a magnetic field, with the diamagnetic elements, bismuth, antimony, zinc, tin, lead, silver, and arsenic, which place themselves at right angles to the lines of a magnetic field. We have been accustomed to suppose that magnetism is a property possessed by only a few elements; these alloys show us that magnetism may arise as a result of grouping atoms, none of which by itself has any magnetism whatever. Indeed it may be possible to make an alloy more magnetic than iron, furnishing the electrician with electro-magnets of new power.

Anti-Friction Alloys.

We have briefly glanced at recent progress in the art of alloying in so far as it has produced steels of new strength, elasticity, or hardness; new ability to resist abrasion or high temperatures, new capacity for magnetism, new indifference to changes of temperature as affecting dimensions. Alloying has of late years conferred other gifts upon industry, of which one example may be cited from among many of equal importance. Friction levies so grievous a tax upon the mechanic and the engineer that they are quick to seize upon any material for bearings which reduces friction. As the result of extensive experiments Dr. C. B. Dudley recommends an alloy of tin, copper, a little phosphorus, with ten to fifteen per cent. of lead. He finds the loss of metal by wear under uniform conditions diminishes as the lead is increased and the tin diminished.

Influence of Minute Admixtures.

We have seen how remarkably the properties of iron are affected by minute additions of carbon which may be assumed to enter into chemical union with the metal. The properties of other metals may be influenced by minute quantities of added elements, although in quantities so small as to preclude the possibility of their forming ordinary chemical compounds. It by no means follows, however, that the atom of an added element does not exert a direct influence. In Professor Roberts-Austen’s laboratory, in London, two ladles were filled with exceptionally pure bismuth; into one ladle a tiny fragment of tellurium was placed. The ladles were poured each into a separate mold, and when the metal became cold it was fractured by a hammer. The bismuth to which the tellurium was added had become minutely crystalline; while that which remained pure had crystallized in broad mirror-like planes. One reflected light as a mirror; the other, containing the tellurium, scattered the light it received. With no guidance but that of mere inspection, one would have said that the two substances were distinct elements, and yet the only difference was that one contained ¹⁄₂₀₀₀ part of tellurium and the other no tellurium at all.

Submarine telegraphy presents us with a case as striking: were its copper wire to contain but one-thousandth part of bismuth, the line would be so much reduced in conductivity as to be commercially worthless: quite as harmful are mixtures of antimony. In coining, the addition to gold of one five-hundredth part by weight of bismuth produces an alloy which crumbles under the die and refuses to take an impression. In the manufacture of such dies it is necessary to employ a steel containing 0.8 to 1 per cent. of carbon and no manganese. It is usual, says Professor Roberts-Austen, to water-harden and temper it to a straw color, and a really good die will strike 40,000 coins without being fractured or deformed, but if the steel contains 0.1 per cent. too much carbon, it would not strike 100 pieces without cracking, and if it contained 0.2 per cent. too little carbon, it would probably be hopelessly distorted and its engraved surface destroyed in the attempt to strike a single coin. As in coining so in steam-engineering. A little arsenic added to copper improves it for the fire-boxes of locomotives. Boilers of old, formed of copper slightly admixed with sulphur, lasted longer than modern boilers built of copper free from sulphur. Antimony behaves like arsenic, and in due proportion strengthens copper; bismuth, on the contrary, weakens copper, and a perceptible effect is wrought by a mere trace. Nickel is made malleable by adding extremely small quantities of phosphorus, magnesium, or zinc.

BOOKS ON IRON AND STEEL

Chosen and annotated by Professor Bradley Stoughton, School of Mines, Columbia University, New York. (Graduated Yale University, 1893, as Ph.B. In 1896 Assistant in Mining and Metallurgy at Massachusetts Institute of Technology, Boston, where he received the degree of B.S. In 1898-99, metallurgist of South Works. Illinois Steel Co., South Chicago. Superintendent in 1900 of steel foundry, Briggs-Seabury Gun and Ammunition Co., Derby, Conn. Manager of Bessemer plant, Benjamin Atha & Co., Newark, N. J., in 1901. Instructor in metallurgy, Columbia University, 1902-03. Next year became Adjunct Professor of Metallurgy, Columbia University and, as consulting metallurgist, entered the firm of Howe & Stoughton, New York.)

Bale, George R. Modern Foundry Practice. Part I, 1902. Part II, 1906. London, Technical Publishing Co. 3s. 6d. each.

An admirable work, the only one covering the whole field. The author thoroughly understands his subject, and writes most intelligibly. The principles underlying every detail of practice are clearly explained.

Part I deals with foundry equipment, materials used, furnaces and processes, describes blowers, ladles, cranes, hoists, cupola, air furnaces, drying ovens, dry and green sand, the manufacture of chilled castings and malleable iron castings.

Part II takes up machine molding, physical properties, the effects produced by various ingredients, the principles of mixing irons, cleaning castings. Costs are considered in conclusion.

Bell, Sir Isaac Lowthian. Principles of the Manufacture of Iron and Steel. London, George Routledge & Sons, 1884. 722 pp. 21s.

A classic. Like “Chemical Phenomena of Iron Smelting,” by the same author, now out of print and rare, it will never be replaced by a new book in the metallurgist’s library, although somewhat out of date. Deals with principles ever important, while our knowledge of them increases constantly. Begins with a brief history, then passes to the direct processes for the production of iron and steel. Then follow sections on the fundamental principles of blast furnace operation, and a study of the refining of pig-iron, or, in other words, the principles of the conversion of pig-iron into wrought iron and steel. For recent metallurgical practice, some later book is to be preferred.

Campbell, Harry Huse. Manufacture and Properties of Iron and Steel. 2d edition. New York, Engineering and Mining Journal, 1903. 839 pp. $5.00.

Mr. Campbell is a careful and deep thinker. He is well known as the successful manager of a large and important steel works. Out of abundant knowledge, gathered in long experience and study, he gives in this book much valuable information. Details of the various furnaces and their operations are frequently lacking, but as a comparative study of leading methods of steel-making, and of the commercial conditions involved, this work has no equal.

Harford, F. W. Metallurgy of Steel. With a section on the Mechanical treatment of Steel, by F. W. Hall. Revised edition. London, Charles Griffin & Co., 1905. 792 pp. 25s.

This exhaustive treatise is the best of its kind. Abounds with valuable information on furnaces and their working, on the effects of different impurities in steel. On the shaping of steel mechanically it is the only complete treatise. This work deals, however, chiefly with English practice, while American practice is larger and more progressive.

Howe, Henry M. Iron, Steel and Other Alloys. 2d edition, slightly revised. Boston, A. Sauveur, 1906. 18+495 pp. $5.00.

The best and most complete work on the modern theory of the constitution of steel by the highest living authority. Can be readily understood by any one having a slight knowledge of chemistry. In addition to the study of iron and steel as metals, brief but satisfactory chapters in manufacture are included.

Howe, Henry M. Metallurgy of Steel. Vol. I. 4th edition. New York, Engineering and Mining Journal, 1890. 385 pp. $10.00.

Still recognized the world over as the standard authority; every book written on its theme since 1890 builds upon this work as the source of highest reference. Devoted chiefly to the effects of different impurities, and of treatment, on steel. The crucible and Bessemer processes are described at some length. Not a work for general readers.

Mellor, J. W. Crystallization of Iron and Steel: an Introduction to the Study of Metallography. London and New York, Longmans, Green & Co., 1905. 154 pp. 5s. $1.60.

Reprinted lectures giving an excellent popular account of the constitution and nature of cast iron and steel. Includes right and wrong methods of annealing, hardening and tempering steel, and their microscopic examination. The information is presented in a terse and attractive style. Any reader of a scientific turn will find profit in this book.

Sexton, A. Humboldt. Outline of the Metallurgy of Iron and Steel. Manchester, Scientific Publishing Co., 1902. 16s.

The best, because most recent of the good elementary text-books on iron and steel. It is behind the times in regard to American practice, but contains a great deal of important information, clearly expressed. Covers iron ores, their physics and chemistry, construction and working of the blast furnace, foundry practice, puddling, forging, the Bessemer, open hearth and crucible processes, special steels, the testing of steel and protection from corrosion. Its sketch of the structure and heat treatment or iron and steel is very incomplete.

Swank, James M. Short History of the Manufacture of Iron in all ages, particularly in the United States from 1585 to 1885. 2d edition. Philadelphia, American Iron and Steel Association, 1894. 428 pp. $5.00.

The best historical account of iron and steel manufacture, written in an interesting manner. So carefully systematized that the history of any branch of the subject may be studied independently.

Swank, James M. Directory of the Iron and Steel Works in the United States and Canada. Embracing a full description of the blast furnaces, rolling mills, steel works, tin plate and terne plate works, forges and bloomaries in the United States; also classified lists of the wire rod mills, structural mills, plate sheet and skelp mills, Bessemer steel works, open hearth steel works, and crucible steel works. 16th edition. Philadelphia, American Iron and Steel Association, 1904. $10.00.

A Supplement to this directory contains a classified list of leading consumers of iron and steel in the United States, corrected to January, 1903. 196 pp. $5.00.

The Penton Publishing Co., Cleveland, Ohio, publish a list of the iron foundries in the United States and Canada, mentioning plants not listed by Mr. Swank, 1906. $10.00.

Turner, Thomas. Metallurgy of Iron and Steel. Edited by Prof. W. C. Roberts-Austen. Vol. I, Metallurgy of Iron. London, Charles Griffin & Co., 1895. 367 pp. 16s.

If but one book is to be chosen, this is the best on ores, construction and working blast furnaces, the properties of cast iron, the manufacture and properties of wrought iron. It also has valuable chapters on foundry practice, the history of iron, blast furnace fuels, forging and rolling, and the corrosion of iron and steel.

Woodworth, Joseph V. Hardening, Tempering, Annealing and Forging of Steel: a treatise on the practical treatment and working of high and low grade steel. New York, Norman W. Henley & Co., 1903. 288 pp. $2.50.

Treats of the selection and identification of steel, the most modern and approved processes of heating, hardening, tempering, annealing and forging, the use of gas blast forges, heating machines and furnaces, the annealing and manufacture of malleable iron, the treatment and use of self-hardening steel, with special reference to case-hardening processes, the hardening and tempering of milling cutters and press tools, the use of machinery steel for cutting tools, forging and welding high grade steel forgings in America, forging hollow shafts, drop-forging, and grinding processes for tools and machine parts.

It is almost impossible to say which is the best book on the practice treated in this book. It has been chosen because it contains much valuable information which has the rare quality of not only being useful in the shop, but of being accompanied by the reasons involved. Copiously illustrated. Many useful tables. For one looking for general knowledge it will be found serviceable. For the seeker who wishes special data no single book will suffice.

Journal of the Iron and Steel Institute. Edited by Bennett H. Brough. London. Published by the Institute. Semiannual. Each number 16 shillings; mailed by Lemcke & Buechner, 11 E. 17th St., New York. $4.50.

Contains many articles of importance, and abstracts of a large part of the current literature of iron and steel. Thus almost every metallurgist who begins the study of a new subject uses this Journal; he finds it a guide to the latest information which has not yet found its way into reference and text books.

Revue de Metallurgie. Edited by Henri Le Chatelier. Paris. Monthly. Per annum, 40 francs; mailed by Lemcke & Buechner, 11 E. 17th St., New York. $10.00.

Most valuable for recent literature on the constitution of iron and steel and their alloys. Contains bibliographies of works on these subjects.

CHAPTER XIV
PROPERTIES—Continued

Glass of new and most useful qualities . . . Metals plastic under pressure . . . Non-conductors of heat . . . Norwegian cooking box . . . Aladdin oven . . . Matter seems to remember . . . Feeble influences become strong in time.

Jena Glass.

As in the case of the aluminium bronzes and nickel steels, alloys of the utmost value have been formed by introducing new ingredients, often in little more than traces, or by modifying but slightly the proportions in which ingredients long familiar have been mingled together. An equal gain has followed upon varying anew the composition of glass. For centuries the only materials added to sand for its melting pot were silicic acid, potash, soda, lead-oxide, and lime. As optical research grew more exacting the question arose, Will new ingredients give us lenses of better qualities? First of all came the demand for glasses which combined in lenses would yield images in the telescope and microscope free from color. In a simple lens, such as that of an ordinary reading glass, we can readily observe the production of color by a common beam of light. The rays of different colors, which make up white light, are refrangible in different degrees, so that while the violet rays come to a focus near the lens, the red rays have their focus farther off; the images, therefore, instead of being sharply defined, are surrounded by faint colored rings. In a telescope or microscope a simple lens would be of no value from the indistinctness of its images. To correct this dispersion of color a second lens of opposite action is placed behind the first, that is, a crown-glass lens is added to a flint-glass lens. (See [cut], p. 255.) This remedy is not quite perfect for the reason that the distribution of the spectrum from violet to red varies with each kind of glass, and in such a way that through failure of correspondence, color to color, in a compound lens, variegated fringes of light, though faint, are perceptible, much to the annoyance of the microscopist, the astronomer, and the photographer.

With a view to producing glasses which united in compound lenses should be color free, Rev. Vernon Harcourt, an English clergyman, in 1834 began experiments which he continued for twenty-five years. By using boron and titanium in addition to ordinary ingredients of glass, he produced lenses less troubled by color than any that had before been made. His labors, only in part successful, were in 1881 followed by those of Professor Ernst Abbe and Dr. Otto Schott at Jena. With resources provided by the Government of Prussia, these investigators were able to do more for the science and art of glass-making than all the workers who stood between them and the first melters of sand and soda. They immensely diversified the ingredients employed, carefully noting the behavior of each new glass, how much light it absorbed, how it behaved in damp air, what strength it had, how it retained its original qualities during months of keeping, and in particular how variously colored rays were distributed throughout its field of dispersion. As in the blending of new alloys it was found that many of these novel combinations were useless. Of the scores of new glasses produced some were extremely brittle, others were easily tarnished by air, or so soft as to refuse to be shaped as prisms or ground as lenses. A more systematic plan of experiment was therefore adopted: for the production of new glasses there were by degrees separately introduced in varied quantities, carefully measured, boron, phosphorus, lithium, magnesium, zinc, cadmium, barium, strontium, aluminium, berylium, iron, manganese, cerium, didymium, erbium, silver, mercury, thallium, bismuth, antimony, arsenic, molybdenum, niobium, tungsten, tin, titanium, fluorine, uranium. An early and cardinal discovery was that the relation between refraction and dispersion may be varied almost at will. For example, boron lengthens the red end of the spectrum relatively to the blue; while fluorine, potassium, and sodium have the opposite effect. With the distribution of the diverse hues of the spectrum thus brought under control, there were produced glasses which, when united as compound lenses, were almost perfectly color-free, rendering images with a new sharpness of definition. Yet more: in their unceasing round of experiments Professor Abbe and Dr. Schott came upon glass so little absorbent of light that combinations of much thickness intercepted only a small fraction of a beam; they were indeed almost perfectly transparent. This achievement is of great importance to the photographer, whose planar combination of six lenses may be four inches in thickness. At Jena the researchers are endeavoring to perfect another gift for the camera: they seek to produce glasses each transmitting but one color, for service in color-photography.

To microscopy they have recently given lenses which completely transmit ultra-violet rays so as to photograph the diffraction discs of objects, such as gold particles in colloidal solutions, otherwise invisible, because below the resolving power of the most powerful microscope. It is estimated that with this new aid an object but ¹⁄_250,000,000 of a millimeter in length may indirectly be brought to view.

One ancient art, that of annealing glass, Professor Abbe and Dr. Schott greatly improved, eliminating from their products the stresses which distort an image. By means of an automatic heat-regulator, the temperature of a batch of glass could be kept steadily for any desired period at any point between 350° and 477° C.; or allowed to fall uniformly at any prescribed rate. The glass was usually contained in a very thick cylindrical copper vessel, on which played a large gas flame. The highest temperature found necessary to banish stress, that is, to cause softening to begin, was 465° C. The lowest temperature required to ensure complete hardening was about 370° C. Thus the temperatures of solidification all lie between 370° and 465°. This fall of 95° was spread over an interval of four weeks, instead of a few days as formerly, with the result that stress was banished utterly.

Photograph by Bräunlich & Tesch.

THE LATE PROFESSOR ERNEST ABBE, OF JENA.

A practical example of the benefits gained in the properties of Jena glass is exhibited by its use in measuring heat. A thermometer of common glass when first manufactured may tell the truth, and in a month or two may vary from truth so much as to be worthless. The reason is that the dimensions of the glass slowly change day by day, as in a less degree do those of many alloys. It was one of the aims of the Jena laboratory to produce a glass which should remain constant in its dimensions while exposed to varying temperatures, so that, made into thermometers, it would be thoroughly trustworthy. Here, too, success was attained, so that thermometers of Jena glass are found to be reliable as are no instruments of ordinary glass. This product is available for astronomical lenses, otherwise liable to serious changes of form as exposed successively to warmth and cold.

Heat was to be staunchly withstood not only in moderate variations, but in extreme degrees. From time immemorial heat suddenly applied to glass has riven it in pieces. Could art dismiss this ancient fault? To-day a beaker from Jena may be filled with ice and placed with safety on a gas flame. In its many varieties this glass furnishes the chemist with clean, transparent and untarnishing vessels for the delicate tasks of the laboratory, all of singular indifference to heat and cold. Yet again. Special kinds of this glass in chemical uses are attacked by cold or hot corrosive liquids only one-twelfth to one-fourth as much as good Bohemian glass, the next best material.

Not only to heat but to light Jena glass renders a service. Glass of ordinary kinds when used for the tubes of a Hewitt mercury-vapor lamp, absorbs a considerable part of the ultra-violet rays upon which photography chiefly depends. A Jena glass free from this fault is formed into Uviol lamps of great value in taking photographs, photo-copying, and photo-engraving. These lamps are also employed in ascertaining the comparative stability of inks and artificial dyes; so intense is their action that brief periods suffice for the tests. Uviol rays severely irritate the eyes and skin; they may prove useful in treating skin diseases. They moreover quickly destroy germs. In all these activities reminding us of radium.

Thus by a bold departure from traditional methods in glass-making, the eye receives aid from lenses more powerful and more nearly true than ever before swept the canopy of heaven, or peered into the structure of minutest life. Meanwhile instruments of measurement take on a new accuracy and retain it as long as they last. All this while a material invaluable for its transparency is redeemed from brittleness and corrodibility, and given a strength all but metallic; at the same time transmitting light with none of the usual subtraction from its beams.

Bliss forming die. A, bed plate. B, blank-holder. C, drawing punch. D, push-out plate. O, P, annular pressure surfaces.

Bliss process of shell making.

Power Presses in Metal Working.

From glass let us now turn to metals. It is their tenacity that chiefly gives them value; this tenacity is usually accompanied by a hardness which disposes us to regard nickel, for example, as of a solidity quite unyielding. But the coins in our pockets prove that under the pressure of minting machinery they are as impressible as wax. In molds and dies, each the counterpart of the other, brass, bronze, iron, steel, and tin-plate take desired forms as readily as if paste. Solid though these metals appear they yield under severe stress with a semi-fluid quality. We have long had stamped kitchen ware, baking pans, and the like; the principle of their manufacture has of late years been extended to ware of more importance. Bliss power presses are to-day turning out hundreds of articles which until recently were either slowly hammered or spun into form, pieced with solder, or shaped by the gear cutter or the milling machine. These presses furnish the United States Navy with sharp-pointed projectiles, some of them so large as to demand a million pounds pressure for their production; they make strong seamless drawn bottles, cylindrical tanks for compressed air and other gases, and cream separators able to withstand the bursting tendency of extremely swift rotation.

Mandolin pressed in aluminium.

Pressed Seamless pitcher.

Barrel of pressed steel.

Presses less powerful produce scores of parts for sewing machines, typewriters, cash registers, bicycles, and so on; or, at a blow, strike out a gong from a disc of bronze. Presses of another kind stamp out cans in great variety, and even a mandolin frame in all its irregular curves. Tubs are quickly pressed from sheets of metal; a pair of such tubs, tightly joined at their rims by a double seam, form a barrel impervious to oil or other liquid, and hence preferable to a wooden barrel. A press operated by a double crank may be arranged to supersede the forging of hammers, axes, and mattocks. Another press at a blow cuts out the front for a steel range. Still another press invades the foundry, producing excellent gear wheels for trolley cars, not weakened by being cut from a casting across the grain of the metal. Sometimes the article manufactured requires a series of operations, as in the case of a kettle cover with its knob. At the Lalance & Grosjean factory, Woodhaven, New York, a Bliss press makes such covers in a single continuous round. Another press treats soft alloys, so that a disc one inch in diameter when hit by a plunger is forced into the shape of a tube suitable to hold paint or oil.

In large manufactures as in small the hydraulic forge has wrought a quiet revolution. If a steel freight car were produced by planing, turning, slotting and similar machines, it would be much heavier and dearer than as turned out to-day from ingeniously fashioned dies under severe pressure. Its girders are molded of the same strength throughout with no waste of material, and without rivets; corner pieces are avoided; stiffeners are built up from the plates themselves through the introduction of ridges and depressions: and in a structure having the fewest possible parts, uniform strength is attained because dimensions everywhere may freely depart from uniformity.

Range front pressed from sheet steel.

Pressed paint tube and cover.

Non-Conductors of Heat.

In a vast manufactory of steel cars, of steel structural forms, steam has to be conveyed long distances from the boilers. Here, as in similar huge establishments, or in the heating of towns and cities from central stations, it is desirable to lose as little heat as possible by the way, for undue waste means enormous inroads upon profits. There are other reasons for wishing to keep heat within a steam pipe; much damage may be done to fruit, flour and other merchandise unduly warmed. Furthermore there is a risk of setting fire to woodwork, paper, cotton and the like; it has been observed that after a month’s exposure to heat from steampipes, wood takes fire at a temperature which at first would not have led to ignition, because then the wood contained a little moisture. To guard against loss and danger it has long been the practice to cover steampipes with jackets of non-conducting material, such as mineral-wool,—furnace-slag blown into short glassy fibres by a sharp blast of air. Felt, loosely folded, also serves well. Many advertised claims for asbestos are not well founded; this mineral is incombustible and is therefore useful in thick curtains to separate a stage from the auditorium of a theatre. But it is a fairly good conductor, and for steampipes should be used as a direct covering of the metal simply to keep an outer and much thicker coat of felt from being charred. Whatever the material chiefly employed, one point is clearly brought out by experiment, namely, that the air detained by the fibres of a covering greatly aids in obstructing the passage of heat. Hence it is well to keep the materials from becoming compacted together, as do ashes when moistened. Asbestos fibres, which are smooth and glassy, do not take hold of air as do cork and wool.

Professor J. M. Ordway, of the Massachusetts Institute of Technology, Boston, tells us that non-conductors should be of materials that are abundant and cheap; clean and inodorous; light and easy to apply; not liable to become compacted by jarring or to change by long keeping; not attractive to insects or mice; not likely to scorch, char or ignite at the long-continued highest temperature to which they may be exposed; not liable to spontaneous combustion when partly soaked in oil; not prone to attract moisture from the air; not capable of exerting chemical action on the surfaces they touch. No material combines all these desirable qualities, but a considerable range of substances fulfil most of the requirements.

Tests of steam-pipe coverings at Sibley College, Cornell University, and at Michigan University, have resulted as follows:—

In general the thickness of the coverings tested was one inch. Some tests were made with coverings of different thicknesses, from which it would appear that the gain in insulating power obtained by increasing the thickness is very slight compared with the increase in cost.[19]

[19] Rolla C. Carpenter, “Heating and Ventilating Buildings,” p. 229. New York, John Wiley & Sons, 1905.

Some properties of matter seem to have family ties. Tenacity and conductivity for heat, as an example, go together; all the tenacious metals as a group are conducting as well. Conversely, the non-conductors,—felt, gypsum, and the rest, are structurally weak. If the inventor could lay hands on a material able to withstand high pressure and, at the same time, carry off wastefully but little heat, he would build with it cylinders for steam engines much more economical than those of to-day He would also give cooking apparatus of all kinds a covering which would conduce to the health and comfort of the cook, while, at the same time, heat would be economized to the utmost. One of the advantages of electric heat is that it can be readily introduced into kettles and chafing dishes surrounded by excellent non-conductors; the result is an efficiency of about ninety-five per cent., quite unapproached in the operations of a common stove or range.

Norwegian Cooking Box.

The costliness of electric heat forbids the housekeeper from using much of it. Her main source of heat must long continue to be the common fuels. These, however, thanks to cheap non-conductors, may be used with much more economy and comfort than of old. Take, for example, the Norwegian cooking box, steadily gaining favor in Europe and well worthy of popularity in America. It consists of a box, preferably cubical, made of closely fitted thick boards, with a lid which fits tightly. Box and lid are thickly lined with felt or woolen cloth, and filled with hay except where pots are placed. These pots, filled with the materials for a soup, a stew, a ragout, are brought to a boil on a fire and then placed within the box, its lid being then fastened down. For two hours or so the cooking process goes on with no further application of heat. To be sure the temperature has fallen a little, but it is still high enough to complete the preparation of a wholesome and palatable dish, with economy of fuel and labor, without unduly heating the kitchen.

Norwegian cooker.

Aladdin oven.

On the same principle is the Aladdin oven, invented by the late Edward Atkinson of Boston, and manufactured by the Aladdin Oven Company, Brookline, Mass. It is built of iron, surrounded with air cell asbestos board, so as to maintain a cooking temperature of 400° Fahr. with little fuel or attention. Its drop door when open forms a shelf, when closed it is fastened by a brass eccentric catch, ensuring tightness; its wooden stand has an iron top to hold the oven firmly in place. This apparatus cooks a wide range of dishes admirably, retaining the natural flavors of meats, fish, vegetables and fruits as ordinary excessive temperatures never do. Mr. Atkinson wrote “The Science of Nutrition,” which sets forth the construction and uses of this oven.[20]

[20] Published by Damrell & Upham, Boston. $1.00.

Aladdin Oven.

Matter Impressed by Its History.

Every property of matter seems universal. The best non-conductor of heat transmits a little heat; the best conductor is by no means perfect: the two classes of substances are joined by materials which gradually approach one end of the scale or the other. Nothing is so hard but that it may be indented or engraved, and where neither a blow nor severe pressure is employed, we may have, as in the photographic plate, an impression which is chemical instead of mechanical, displaying itself to the eye only when treated with a suitable developer. A bar of steel hammered on an anvil is changed in properties; as it becomes closer in texture its tenacity is increased. When that bar takes its place in a structure, the work it has to do, the shocks it bears, equally tell upon its fibres. Stresses and strains leave their effects upon the stoutest machines, engines, bridges; they are never the same afterward as before, and usually their experience does them harm. Says an eminent engineer, Mr. W. Anderson: “The constant recurrence of stresses, even those within the elastic limit, causes changes in the arrangement of the particles which slowly alter their properties. In this way pieces of machinery, which theoretically were abundantly strong for the work they had to do, have after a time failed. The effect is intensified if the stress is suddenly applied, as in the case of armor plate, or in the wheels of a locomotive. . . . When considerable masses of metal have been forged, or severely pressed while heated, the subsequent cooling of the mass imposes restrictions on the free movement of some if not all the particles, hence internal stresses are developed which slowly assert themselves and often cause unexpected failures. In the manufacture of dies for coinage, of chilled rollers, of shot and shell hardened in an unequal manner, spontaneous fractures take place without apparent cause, through constrained molecular motion of the inner particles gradually extending the motion of the outer ones until a break occurs.”

Sir Benjamin Baker says:—“Many engineers ignore the fact that a bar of iron may be broken in two ways—by a single application of a heavy stress, or by the repeated application of a comparatively light stress. An athlete’s muscles have often been likened to a bar of iron, but if ‘fatigue’ be in question, the simile is very wide of the truth. Intermittent action, the alternative pull and thrust of the rower, or of the laborer turning a winch, is what the muscle likes and the bar abhors. A long time ago Braithwaite correctly attributed the failure of girders, carrying a large brewery vat, to the vessel being sometimes full and sometimes empty, the repeated deflection, although imperceptibly slow and free from vibration, deteriorating the metal, until in the course of years it broke. These girders were of cast iron, but it was equally well known that wrought iron was similarly affected, for Nasmyth afterward called attention to the fact that the alternate strain in axles rendered them weak and brittle, and suggested annealing as a remedy, having found that an axle which would snap with one blow when worn, would bear eighteen blows when new or just after annealing. We know that the toughest wire can be broken if bent backward and forward at a sharp angle; perhaps only to locomotive and marine engineers does it appear that the same result will follow in time even when the bending is so slight as to be unseen by the eye. A locomotive crank-axle bends but ¹⁄₃₄ inch, and a straight driving axle but ¹⁄₆₄, under the heaviest bending stresses to which they are exposed, and yet their life is limited. Experience proves that a very moderate stress alternating from tension to compression, if repeated about a hundred million times, will cause fracture as surely as bending to a sharp angle repeated a few hundred times.”

Hence an axle, or other structure, should be tested by just such stresses as it is to withstand in practice. A steel bar may satisfactorily pass a tensile test applied in one direction, only to break down disastrously under alternating stresses each less severe.

Magnetization.

That matter virtually remembers its impressions is plain when we study magnetism. Steel when magnetized for the first time does not behave as when magnetized afterward. It is as if magnetism at its first onset threw aside barriers which never again stood in its way. If the steel is to be brought to its original state it must be melted and recast, or raised to a white heat for a long time. In quite other fields of channeled motion we remark that violins take on a richer sonority with age; their fibres, under the player’s hand, seem to fall into such lines as better lend themselves to musical expression.

In 1878 the late Professor Alfred M. Mayer of the Stevens Institute of Technology, Hoboken, New Jersey, published a series of remarkable experiments in the “American Journal of Science.” He there told and pictured how he had magnetized several small steel needles, thrust through bits of cork set afloat in water, the south pole of each needle being upward. As the needles repelled each other, or had their repulsion somewhat overcome by a large magnet held above them with its north pole downward, the needles disposed themselves symmetrically in outlines of great interest, which varied, of course, with the number of needles afloat at any one time. Three needles formed an equilateral triangle, four made up a square, five disposed themselves either as a pentagon or as a square with one magnet at its centre, and so on in a series of regular combinations, all suggesting that magnetic forces may underlie the structure of crystals.

Mayer’s floating magnets.

The Crystal Foreshadows the Plant.

One of the remarkable attributes of a crystal is its ability to grow and act as a unit, as if it had a life of its own, despite the evident variety and great number of its parts. Take a crystal of alum, break off a corner and then immerse the broken mass in its mother liquor; at once the crystal will repair itself, new molecules building themselves into its structure as if they knew where to go. This unity of effect may be observed during a northern winter on a scale much more striking. In cold weather on a large sheet of plate glass exposed as a window, a frost pattern will extend itself as if a tree, beautiful branches spreading themselves from a main stem which may be seven feet in height. It is altogether probable that polar forces, such as we observe in the magnet, are here at work. Their harmony of effect, in spaces comparatively vast, is astonishing. Forces of allied character rise to a plane yet higher in vegetation, culminating in the magnificent sequoia of California, whose life, measured by thousands of years, goes back almost to the dawn of human civilization. The union of tools, levers, wheels, as an organized machine; the co-ordination in research of the parts to be played by observers, recorders, depicters, generalizers; the regimentation of soldiers, so that all march, advance and fire as one man under the control of a single will, is prefigured in the forces which make a unit of every crystal of saltpetre in a soldier’s cartridge-box. Of all the characteristics of matter none is more pervasive and more marvelous than its ability to form a unit which moves and acts as if no part were separable from any other, while manifesting a highly complicated structure, with functions at once intricate and co-ordinate.

A
Alum crystal.

B
After a part has been
broken off.

C
Restored by immersion
in alum solution.

From photographs by Herr Hugo Schmidt, Hackley School, Tarrytown, N. Y.

During Long Periods Minute Influences Become Telling.

Qualities of matter, much more simple, may now engage our attention. First, then, let us note how minute influences, acting for long stretches of time, may change the qualities of metals and rocks. Forces, too slight for measurement as yet, are known in the course of a year or two to affect steel at times favorably, at other times unfavorably. The highest grades of tool-steel are improved by being kept in stock for a considerable time, the longer the better. It seems that bayonets, swords, and guns are liable to changes which may account for failure under sudden thrust or strain. Gauges of tool steel, which are required to be hard in the extreme, are finished to their standard sizes a year or two after the hardening process. Slow molecular changes register themselves in altered dimensions. In the Bureau of Standards at Washington are a yard in steel and a yard in brass, at first identical in length; after twenty years they were found to vary by the ¹⁄₅₀₀₀ of an inch. Take another case, familiar enough to the railroad engineer: in a mine, or a tunnel, the roof or wall may tumble down a month or more after a blasting. The stone which fell immediately upon the explosion was far from representing all the work done by the dynamite. A stress was set up in large areas of rock and this at last, beginning in slight cracks, overcame the cohesion of masses of huge extent.

Iron tube enclosing marble
before and after deformation.

Marble before deformation
and after.

Properties undergo change during the simple flight of time: a parallel diversity is worthy of remark. A substance exhibits quite diverse qualities according to whether the action upon it is slow or speedy. A paraffine candle protruding horizontally half way out of a box, during a New York summer will at last point directly downward, for all its brittleness. If shoemaker’s wax is struck a sudden blow, it breaks into bits as might a pane of window glass. But place leaden balls on the surface of this same wax and in the course of ten or twelve weeks you will find them sunk to the bottom of the mass. When sharply smitten, the wax is rigid and brittle; to a long continued, moderate pressure the wax proves plastic, semi-fluid almost. All this is repeated when stone is subjected to severe pressure for as long a period as two months. At McGill University, Montreal, a small cylinder of marble thus treated by Professor Frank D. Adams became of bulging form, without fracture, but with a reduction in tensile strength of one-half. When the pressure was applied during but ninety minutes the tensile strength of the resulting mass was but one-third that presented by the original marble; when the experiment occupied but ten minutes the tenacity fell to somewhat less than one-fourth its first degree. These researches shed light on the stratifications of rocks often folded under extreme pressure as if rubber or paste.

Take another and quite different example of how variations in time bring about wide contrasts of result: a rubber ball thrown in play at a wall rebounds; send it forth from a cannon, with a hundred-fold this velocity, and it pierces the wall as might a shot of steel.

CHAPTER XV
PROPERTIES—Continued. RADIO-ACTIVITY

Properties most evident are studied first . . . Then those hidden from cursory view . . . Radio-activity revealed by the electrician . . . A property which may be universal and of the highest import . . . Its study brings us near to ultimate explanations . . . Faraday’s prophetic views.

Properties age after age have become more and more intimately known. At first the savage took account solely of the obvious strength of an oak, the sharpness of a flint, the pliability of a sinew. With the first kindling of fire he discovered a new round of properties in things long familiar. All kinds of wood, especially when dry, were found combustible, so were straw and twigs, as well as the fat of birds, the oil of fish. Then it was noticed that the ground beneath a fire remained unburnt and grew firm and hard, so that its clay or mud might be used for rude furnaces and ovens. Soon come experiments as to the coverings which maintain coals at red heat, ashes proving the readiest and best.

A century ago the mastery of electricity began to unfold a new knowledge of properties, so wide and intimate as to recall the immense expansion of such knowledge that long before had followed upon the kindling of fire. The successors of Volta, as they reproduced his crown of cups, asked, What metals dissolved in what liquids will give us an electric current at least outlay? Then followed the further question, What metals drawn into wire will bear currents afar with least loss? With the invention of the electro-magnet came another query, What kinds of iron are most swiftly and largely magnetized by a current; and when the current ceases, which of them loses its magnetism in the shortest time? Plainly enough the electrician regards copper, zinc, iron, steel, acids, alkalis from a new point of view; he discovers in them properties which until his advent had been utterly ignored.

Among the properties of matter revealed by electricity none are more striking than those displayed in tubes containing highly rarified gases. The study of their phenomena has led to discoveries which bring us within view of an ultimate explanation of properties, an understanding of how matter is atomically built. All this began simply enough as Plucker, in 1859, sent an electric discharge through a tube fairly well exhausted, producing singular bands of color. Geissler, afterward using tubes more exhausted, produced bands of still higher variegation. In 1875 Professor William Crookes devised the all but vacuous tube which bears his name, through which he sent electric pulses from a cathode pole, revealing what he called “radiant matter,” as borne in a beam of cathode rays, as much more tenuous than ordinary gases as these are more rare than liquids. In 1894 Professor Philipp Lenard observed that cathode rays passed through a thin plate of aluminium, much as daylight takes its way through a film of translucent marble. Next year came the epoch-making discovery of Professor Conrad Wilhelm Röntgen that cathode rays consist in part of X-rays which readily pass through human flesh, so as to cast shadows of bones upon a photographic plate. Cathode rays make air a fairly good conductor of electricity, while ordinary air is non-conducting in an extreme degree. This singular power is also possessed by the ultra-violet rays of sunshine, as readily shown by an electroscope. In 1897 Professor Joseph J. Thomson, of Cambridge University, demonstrated that cathode rays are made up of corpuscles, or electrons, about one-thousandth part the size of a hydrogen atom, and bearing a charge of negative electricity. Such electrons form a small part of every chemical atom, the remainder of which is, of course, positively electrified. All electrons are alike, however various the “elements” whence they are derived; as the most minute masses known to science they may be among the primal units of all matter.

France, as well as Germany and England, was to take a leading part in furthering the study of radio-activity. In Paris the famous Becquerel family had for three generations devoted themselves to studying phosphorescence. Henri Becquerel, third of the line, said, “I wonder if a phosphorescent substance, such as zinc sulphide, would be excited by X-rays.” He tried the experiment, causing the sulphide to glow with new vigor. From that moment proofs have accumulated that the rays of common phosphorescence such as are emitted by matches, decaying wood and fish, are of kin to the cathode rays which the electrician evokes from any substance whatever when he employs a high-tension current. One day M. Becquerel came upon a remarkable discovery. He noticed that compounds of uranium, whether phosphorescent or not, affected a photographic plate through an opaque covering of black paper, and rendered the adjacent air an electric conductor. Compounds of thorium, similar to those used for incandescent mantles, were found to have the same properties. And here was detected the cause of an annoyance and loss which had long perplexed photographers. Often they had bestowed sensitive paper or plates within wrappers of stout paper, or card, or thick wood, secluded in dark cupboards or drawers. All in vain. At the end of a few weeks or months these carefully guarded surfaces were as much discolored as if they had been for a few minutes exposed, here and there, to daylight itself. All the while each material relied upon as a safeguard had been sending forth a feeble but constant beam; treachery had lurked in the trusted guardian.

At the suggestion of M. Becquerel, M. and Madame Pierre Curie undertook a thorough quest for these effects in a wide diversity of substances. They found that several minerals containing uranium were more radio-active than that element itself. Pitchblende, for instance, consisting mainly of an oxide of uranium, was especially energetic as it approached an electroscope, suggesting the presence of an uncommonly active constituent, thus far not identified. At the end of a most laborious series of separations they came at last to a minute quantity of radium chloride displaying extraordinary properties. Another compound of radium, a bromide, has since been arrived at: radium by itself has not yet been obtained. In radio-activity radium chloride surpasses uranium about one-million-fold. Provided with an electroscope of exquisite sensibility, Professor Ernest Rutherford of McGill University, Montreal, has discovered seven distinct radiations from radium, each with characteristics of its own. Directed upon plates of aluminium he finds its gamma rays to be 100 times more penetrating than its beta rays, and beta rays 100 times more penetrating than its alpha rays. Each radiation has qualities as distinct as those of an ordinary chemical element. Beta rays behave in all respects like cathode rays, so that here a bridge is discerned betwixt the qualities of radium and the long familiar phenomena of the Crookes tube.

The substance ranking next in radio-activity to radium is thorium. Professor Rutherford has observed it throwing off a substance he calls Thorium X; this radiates strongly for a time, the parent mass not radiating at all. Gradually Thorium X ceases to radiate and the original thorium resumes an emission of Thorium X. From Thorium X emanates what seems a gas, condensible by extreme cold, which attaches itself to adjacent bodies so as to make them radio-active. This emanation in its turn produces successively three new and distinct kinds of radiation. Professor Charles Baskerville, of the College of the City of New York, has separated from thorium two substances probably elementary, carolinium and berzelium.

Other radio-active substances have each several derivatives: actinium has nine, uranium has four. As researchers broaden their range of inquiry they steadily lengthen the list of radio-active substances. Minerals of many kinds, water from springs, especially those of medicinal value, the leaves of plants, newly fallen snow, and even common air, are found to be radio-active, although usually in but a slight degree, so that the doubt may be expressed, Is the observed effect due to a trace of some highly radio-active material diffused in something else which is not radio-active at all? Should it be established that radio-activity is really present in all matter it would be no other than a parallel to what, at another point in the physical scale, presents itself as ordinary evaporation.

Solids are not as Solid as They Seem.

In a northern winter we may observe in air almost still, the wasting away of a large block of ice, so that during a week it loses a considerable part of its bulk. The giving forth of vapor is evidently not restricted to high or to ordinary temperatures, but may occur below the freezing point of water. In 1863, Thomas Graham, the eminent Scottish physicist, from many experiments with metals expressed the opinion that what seems to be a solid may be also in a minute degree both liquid and gaseous as well. Confirmation of this view was afforded in 1886 by Professor W. Spring, of Liege, who formed alloys by strongly compressing their constituents as powders at ordinary temperatures. It is probable that a slight pervasive liquidity gave success to the experiment. Professor Roberts-Austen once observed that an electric-deposit of iron on a clean copper plate adhered so firmly that when they were severed by force, a film was stripped from the copper plate and remained on the iron, signifying that the two metals had penetrated each other at an ordinary temperature. This interpenetration he found to take place through films of electro-deposited nickel. In a remarkable round of experiments he also found that at 100° C., a temperature much below the fusing point of lead, gold as leaf is slightly diffused through a mass of lead; when the lead is fluid at 550° C., the proportion of diffused gold is increased 160,000 times. This volatility of the particles of a heavy metal shows us plainly that virtual evaporation may be always taking place from metallic surfaces at ordinary temperatures,—a phenomenon which may be the same in kind as the pouring out of a perceptible stream of corpuscles under strong electrical excitation. The analogy goes further, at least in the case of liquids, which exhale a vapor usually different in composition from the parent body; take, for example, a solution of sugar in water which sends forth watery vapor only, or observe a mixture of much water and a little alcohol as it emits a vapor largely alcoholic and but slightly aqueous.

Every Property May be Universal.

Here we are reminded of a striking experiment by Faraday: exciting an electro-magnet of gigantic proportions he showed that every substance he brought near to it was affected in a definite degree. He found iron to be pre-eminently magnetic, much as Madame Curie has shown radium to be vastly more radio-active than any other substance. From Faraday’s time to the present hour the whole trend of investigation has built up the probability that every known property in some degree exists in all matter whatever. Copper conducts electricity remarkably well, and gutta percha conducts remarkably ill; but gutta percha has some little conductivity, or thinner sheets of it than those now used would suffice to keep within an ocean cable the throbs which pass between America and Europe. In radio-activity many substances may be as low in the scale as is gutta percha in the list of electric conductors; in that case no existing means of detection would make the property manifest.

Radium Reveals Properties Unknown Till Now.

While radio-activity may be a universal property of matter, to be disclosed more and more as means of detection are refined and improved, radium compounds are to-day in a class quite by themselves. Radium bromide constantly maintains itself at a temperature of 3° to 5° C. higher than that of its surroundings, so that every hour it could boil its own weight of water. Professor Rutherford estimates the life of radium as 1,800 years, its emanations in breaking up through their successive stages emitting about three million times as much energy as is given out by the union of an equal volume of hydrogen and oxygen, mixed in the proportions which form water, a union accompanied by more heat than that evolved in any other chemical change. Whence this amazing stream of energy? It is probable that each radium atom may break into minute parts, or corpuscles, which, moving at a velocity of 120,000 miles a second or so, collide so as to cause the observed heat.

From another side the compounds of radium bid us revise the laws of chemical change as taught up to the close of the nineteenth century. In the pores of many radio-active minerals may be found that remarkable element, helium, first detected in the sun by means of the spectroscope, then afterward discovered in the pores of cleveite, a mineral unearthed in Norway. Sir William Ramsay and Mr. Frederick Soddy have found helium in the gases evolved from radium chloride kept as a solid for some months. The spectrum of helium was at first invisible; it soon appeared and steadily grew more intense with the lapse of time. “It appears not unlikely,” says Professor Rutherford, “that many of the so-called chemical elements may prove to be compounds of helium, or, in other words, that the helium atom is one of the secondary units with which the heavier atoms are built up.”[21]

[21] Ernest Rutherford “Radio-activity.” Second edition. New York: Macmillan Co.; Cambridge, England, University Press, 1905.

Photograph by Rice, Montreal.

PROFESSOR ERNEST RUTHERFORD,
McGill University, Montreal.

Already the phenomena of radio-activity, although of puzzling intricacy, have greatly broadened our conceptions of matter. Where we were wont to deem it of simple structure, it displays a baffling complexity, as indeed has long been suggested in so highly diversified a spectrum as that of iron. We find that radiations from an “element” may consist not only in the undulations of an ether, but also in an emission of matter as real as the projection of steam from a boiling pot. Newton believed sunshine to be a stream of corpuscles: he was wrong with respect to sunlight, his conception is true of many other kinds of radiation. Until quite lately we looked upon atoms as indivisible bodies; to-day we have learned that at least some of them may on occasion divide into many parts, each part moving with a speed approaching that of light, with energy far exceeding that of any chemical action we know. In the field of ray-transmission our knowledge has undergone a like gain in width. Twenty years ago we spoke of the opacity of lead, the transparency of flint glass, as absolute properties. To-day we learn that given its accordant ray any substance whatever affords that ray free passage, as when oak an inch thick transmits pulses from radium. Yet more: ordinary chemical changes require us to bring one substance into contact with another; usually we must also apply heat or electricity to the bodies thus joined; they are always responsive to changes of temperature. Within the past six years we have become acquainted with changes incomparably more energetic than those of the most violent chemical action; many of them proceed with apparent spontaneity from a substance all by itself. In the case of radium neither extreme cold nor extreme heat has any perceptible effect upon the radiant stream.

One of the results of investigation in radio-activity is that it shows the alchemists in their attempts at transmutation to have stood on solid ground. Says Professor Rutherford: “There can be no doubt that in the radio-elements we are witnessing the spontaneous transformation of matter, and that the different products which arise mark the stages or halting places in the process of transformation, where the atoms are able to exist for a short time before breaking up into new systems.”

History of the Universe Rewritten in the Light of Radio-Activity.

Radio-activity has a vivid interest far beyond the laboratories of chemists and physicians. One of the long standing puzzles of geology has been to explain why the temperature of the earth has remained fairly constant ever since organic life made its appearance. A sister problem has been the maintenance by the sun of its vast output of heat and light, age after age, with little or no diminution of intensity. Professor Rutherford and Mr. Soddy believe that the phenomena of radio-activity may solve both these problems: an element like helium may furnish a store of energy vastly greater than that of ordinary chemical action, and much lengthen the cooling process due to radiation from either the sun or the earth.

Radio-activity, furthermore, throws new light upon evolution regarded in its broadest aspects. The corpuscles discovered in 1897 by Professor J. J. Thomson, as he severed atoms in pieces, are all alike whatever chemical element may be the parent body. Hence it is argued that we may have here the primal units of all matter whatever. Sir Norman Lockyer long ago pointed out that helium and hydrogen predominate in the hottest stars, while in stars less hot more complex types of matter appear. He argues that these stars as they successively lose heat show a development of what chemists call elements. His views are parallel with the suggestion that in the radio-active corpuscle we make acquaintance with an ultimate element of all matter, whether observed in a laboratory tube or in the squadrons bright of the midnight heavens.[22]

[22] Radio-activity and other physical phenomena recently discovered are set forth in “The New Knowledge,” by Professor Robert Kennedy Duncan, published by A. S. Barnes & Co., New York, 1905; and “The Recent Development of Physical Science,” by W. C. D. Whetham, published by John Murray, London, and P. Blakiston, Son & Co., Phila., 1906.

The phenomena of radio-activity revive interest in the prophetic views of Michael Faraday. In 1816, when he was but twenty-four years of age, he delivered a lecture at the Royal Institution in London on Radiant Matter. In the course of his remarks there occurs this passage:—

Faraday’s Prophetic Views.

“If we now conceive a change as far beyond vaporization as that is above fluidity, and then take into account the proportional increased extent of alteration as the changes arise, we shall perhaps, if we can form any conception at all, not fall short of radiant matter; and as in the last conversion many qualities were lost, so here also many more would disappear.

“It was the opinion of Newton, and of many other distinguished philosophers, that this conversion was possible, and continually going on in the processes of nature, and they found that the idea would bear without injury the applications of mathematical reasoning—as regards heat, for instance. If assumed, we must also assume the simplicity of matter; for it would follow that all the variety of substances with which we are acquainted could be converted into one of three kinds of radiant matter, which again may differ from each other only in the size of their particles or their form. The properties of known bodies would then be supposed to arise from the varied arrangements of their ultimate atoms, and belong to substances only as long as their compound nature existed; and thus variety of matter and variety of properties would be found co-essential.”[23]

[23] “Life and Letters of Faraday,” by Bence Jones. Vol. I, p. 216.

Three years later he returned to this theme in another lecture:—

“By the power of heat all solid bodies have been fused into fluids, and there are very few the conversion of which into gaseous forms is at all doubtful. In inverting the method, attempts have not been so successful. Many gases refuse to resign their form, and some fluids have not been frozen. If, however, we adopt means which depend on the rearrangement of particles, then these refractory instances disappear, and by combining substances together we can make them take the solid, fluid, or gaseous form at pleasure.