The Project Gutenberg eBook, Rudimentary Treatise on the Construction of Locks, by A. C. Hobbs, Edited by Charles Tomlinson

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

RUDIMENTARY TREATISE
ON THE
CONSTRUCTION OF LOCKS.

LONDON:
PRINTED BY LEVEY, ROBSON, AND FRANKLYN,
Great New Street and Fetter Lane.

RUDIMENTARY TREATISE
ON THE
CONSTRUCTION OF LOCKS.
EDITED BY
CHARLES TOMLINSON.

“Il n’y a point de machines plus communes que les serrures: elles sont assez composées pour mériter le nom de machine; mais je ne sais s’il y en a qui soient aussi peu connues par ceux qui les emploient. Il est rare qu’on sache en quoi consiste la bonté d’une serrure, le degré de sûreté qu’on peut s’en promettre. Leur extérieur est presque la seule chose à quoi l’on s’arrête. Les usages importans auxquels elles sont employées devraient cependant exciter la curiosité à les connaître, si la curiosité était toujours excitée raisonnablement.”—M. de Réaumur, “Des Serrures de toutes les espèces,” forming the fifth chapter of M. Duhamel’s Treatise “Art du Serrurier,” in the “Descriptions des Arts et Metiers faites ou approuvées par Messieurs de l’Académie Royale des Sciences.”

LONDON:
JOHN WEALE, 59 HIGH HOLBORN.
MDCCCLIII.

“There are no machines more common than locks: they are sufficiently complex to merit the name of machine; but I know of no others the structure of which is so little understood by those who use them. It is rare to find any one who knows wherein the goodness of a lock consists, or the degree of security that he can attach to it. The outside of a lock is usually all that attracts attention. Doubtless the important uses to which locks are applied would excite curiosity respecting their structure, if curiosity were always excited for worthy objects.”—M. de Réaumur.

PREFACE.

The reader is entitled to know the origin of the small work which he holds in his hands.

In August 1852, being about to write a short article on Locks for a Cyclopædia of Useful Arts, of which I am the editor, I consulted my esteemed and lamented friend, the late Professor Cowper, of King’s College, as to the desirability of explaining to the general reader the defects of some of our English locks, which, previous to the celebrated “lock controversy” of 1851, had borne a high character for skilful construction, beauty of workmanship, and undoubted security. Professor Cowper expressed his strong conviction that by exposing the defects of our locks, the cause of mechanical science, as well as the public in general, would be benefited; that if our locks were defective, inventors would be stimulated to supply the defects, and the art of the locksmith would be raised accordingly. He considered that Mr. Hobbs had made a considerable step in advance in the constructive details of his art, not only in having detected the weak points of some of our best English locks, but also in having introduced two or three new locks, which appeared to be more secure than any of those previously produced. Professor Cowper gave me an introduction to Mr. Hobbs, who placed at my disposal a variety of literary materials relating to the history and construction of locks, and stated his intention at some future time of bringing out a small book on the subject, if he could meet with a publisher. I recommended him to offer the work to Mr. Weale, for insertion in his series of Rudimentary Works. This was accordingly done, and I was invited to prepare the work; but as my engagements did not leave me sufficient leisure to write the book, I requested my friend Mr. George Dodd to put the materials together, and to search for more. Mr. Dodd acceded to my request; and having completed his part of the work, I subjected it to a careful revision, and added various details which seemed to be necessary to completeness, at least so far as the narrow limits of a small rudimentary work would admit of completeness. The manuscript was then sent to press: each sheet as it was received from the printer was submitted to Mr. Hobbs, who read it with care, and made his annotations and corrections thereon. Mr. Hobbs and I then had a meeting, when the additions and corrections were read and discussed, and admitted or rejected as the case might be. The sheet having been thus corrected was sent to press.

It should also be stated that, during the progress of the work, Mr. Weale, at my request, wrote to Messrs. Bramah, and also to Messrs. Chubb, informing them that a Rudimentary Treatise on the Construction of Locks was being prepared, and requesting them to state in writing what alterations or improvements they had made in their locks since the date of the Great Exhibition. The communications which we have received from these celebrated firms are inserted verbatim, in their proper places, in the present work.

Such is the mode in which this small volume has been prepared. I have endeavoured to perform an editor’s duty conscientiously, without entertaining the feeling of a partisan in the matter. My chief object in superintending the production of this book (an object in which the Publisher fully participates) is to advance the cause of mechanical science, and to supply a deficiency in one of the most interesting portions of its English literature.

C. TOMLINSON.

Bedford Place, Ampthill Square,
July 1853.

ADVERTISEMENT.

The first edition of this volume, though at the date of its appearance co-ordinating with the state of knowledge of the period, and containing matter well arranged and lucidly described—as must have been expected from the reputation of its author—had, through the lapse of the few intervening years, inevitably become somewhat behind the state of the art of which it treats—one which is daily receiving the attentive consideration of many skilful men, and occasional marked improvements. Amongst those of later years none are more noteworthy than the locks patented by Mr. Fenby, of Birmingham; of these an account, with accurate illustrations, for which the drawings are supplied by the inventor, is now added,—together with a brief essay upon the important but popularly ill-understood subject of iron safes.

ROBERT MALLET.

April, 1868.

In reference to Mr. Smyth’s letter, which is given at [pp. 130], [131], that gentleman is desirous to state that it was in consequence of the defects there pointed out that Mr. Hobbs was enabled to pick the Bramah lock operated upon, which had been manufactured forty years previously, when the sliders were made of iron instead of steel as they now are, and yet, notwithstanding that and the other defects pointed out, it took Mr. Hobbs sixteen days to pick it. In proof of the security of the Bramah lock, Mr. Smyth mentions that Mr. Hobbs’s best workman failed in picking an ordinary 3-inch Bramah box lock; and that a person in the employ of Messrs. Johnson and Ravey, of Conduit Street, failed also in his attempt to pick a 6-inch cellar-door lock, though he had the lock in his possession for twelve months, employing his evenings in making instruments and trying to pick it. Mr. Smyth contradicts the statement made at [page 128], that the new lock was removed from the window through any fear of its being opened. On the contrary, it was put up especially to afford an opportunity for Mr. Hobbs to make, if he thought fit, another trial, and it remained in the window four months. The sole cause of its removal was to stop the impertinent applications of men and boys, which interfered too much with the general business of the firm.

CONTENTS.

ON THE
CONSTRUCTION OF LOCKS.

CHAPTER I.
ON LOCKS AND LOCK-LITERATURE.

The manufacture of locks, and a consideration of the mechanical principles involved in their construction and security, have never yet been treated with any degree of fulness in an English work. Lock-making has occupied a large amount of ingenuity, and lock-patents have been obtained in considerable number, though not always, we are satisfied, with a commensurate return for the expense incurred,—but lock-philosophy (if so it may be designated) has not been largely attended to.

And yet it may safely be said that much which is both mechanically and commercially important is comprised in a lock. Every improvement in the manufacture of iron, steel, and brass—that is, in the tool-making and machine-making processes—may be made to reflect its light on the lock-manufacture; the stamping, the casting, the planing, the slotting, the screw-cutting, the polishing of metals,—all, in proportion as they are improved, impart some of their aid to the lock-maker. Then, in the finer kinds of locks, the works are so delicate as to approach to the nicety of clockwork; thereby combining the manipulative skill of a talented artisan with the rougher mechanical work of the smith. The principles of mechanical science are also appreciated by many lock-makers. The lever, the inclined plane, the eccentric, the cam, the screw, the wheel and pinion, the ratchet, the spring,—all are brought to bear on the internal mechanism of locks, frequently in many novel combinations.

The commercial importance of locks—though of course never seriously questioned when once fairly brought before one’s attention—has been recently rendered so apparent as to have risen to the position of a public topic. If a strong room, containing gold and silver, notes and bills, books and papers—if such a room be necessarily shielded from intrusion, it becomes no less necessary that the shield should be really worthy of its name, trusty and reliable: a good lock is here nearly as indispensable as a faithful cashier. And without dwelling on such an auriferous picture as a room fall of gold, we shall find ample proof of the commercial importance of lock-making in the ordinary circumstances by which we are every day surrounded. Until the world becomes an honest world, or until the honest people bear a larger ratio than at present to the dishonest, the whole of our movables are, more or less, at the mercy of our neighbours. Houses, rooms, vaults, cellars, cabinets, cupboards, caskets, desks, chests, boxes, caddies,—all, with the contents of each, ring the changes between meum and tuum pretty much according to the security of the locks by which they are guarded.

A commercial, and in some respects a social, doubt has been started within the last year or two, whether or not it is right to discuss so openly the security or insecurity of locks. Many well-meaning persons suppose that the discussion respecting the means for baffling the supposed safety of locks offers a premium for dishonesty, by shewing others how to be dishonest. This is a fallacy. Rogues are very keen in their profession, and know already much more than we can teach them respecting their several kinds of roguery. Rogues knew a good deal about lock-picking long before locksmiths discussed it among themselves, as they have lately done. If a lock—let it have been made in whatever country, or by whatever maker—is not so inviolable as it has hitherto been deemed to be, surely it is to the interest of honest persons to know this fact, because the dishonest are tolerably certain to be the first to apply the knowledge practically; and the spread of the knowledge is necessary to give fair play to those who might suffer by ignorance. It cannot be too earnestly urged, that an acquaintance with real facts will, in the end, be better for all parties. Some time ago, when the reading public was alarmed at being told how London milk is adulterated, timid persons deprecated the exposure, on the plea that it would give instructions in the art of adulterating milk; a vain fear—milkmen knew all about it before, whether they practised it or not; and the exposure only taught purchasers the necessity of a little scrutiny and caution, leaving them to obey this necessity or not, as they pleased. So likewise in respect to bread, sugar, coffee, tea, wine, beer, spirits, vinegar, cheap silks, cheap woollens—all such articles as are susceptible of debasement by admixture with cheaper substances—much more good than harm is effected by stating candidly and scientifically the various methods by which such debasement has been, or can be produced. The unscrupulous have the command of much of this kind of knowledge without our aid; and there is moral and commercial justice in placing on their guard those who might possibly suffer therefrom. We employ these stray expressions concerning adulteration, debasement, roguery, and so forth, simply as a mode of illustrating a principle—the advantage of publicity. In respect to lock-making, there can scarcely be such a thing as dishonesty of intention: the inventor produces a lock which he honestly thinks will possess such and such qualities; and he declares his belief to the world. If others differ from him in opinion concerning those qualities, it is open to them to say so; and the discussion, truthfully conducted, must lead to public advantage: the discussion stimulates curiosity, and the curiosity stimulates invention. Nothing but a partial and limited view of the question could lead to the opinion that harm can result: if there be harm, it will be much more than counterbalanced by good.

The literature of lock-making is, as we have implied, very scanty, both in England and America. The French and Germans, though far below our level as lock-makers, are very superior to us in their descriptions of the construction and manufacture of locks. Take, for instance, the French treatise published more than eighty years ago by the Académie des Sciences, and forming part of a folio series of manufacturing treatises, illustrated very fully by engravings. It is worth while to examine this work, to see how minutely and faithfully the writers of such treatises performed their task nearly a century ago. The Art du Serrurier, with the distinguished name of M. Duhamel du Monceau as the author or editor, was published in 1767. It occupies 290 folio pages, and is illustrated by 42 folio plates. The first chapter gives us an introduction and general principles, in which the choice and manipulation of materials are touched upon; the different qualities of iron and steel; and the processes of forging, founding, welding, stamping, filing, polishing, &c. In the copper-plates representing these smiths’ operations and the tools employed,[1] there is a smithy, with about a dozen smiths engaged in all these various occupations, with stockings down, and a due amount of workshop slovenliness. The next chapter takes us into what may perhaps be called “smith’s work in general,” or at least it treats of the manufacture of various kinds of ironmongery for doors, windows, and house-fittings generally. Then the third chapter treats of “smith’s work which serves for the security of houses,” consisting of railings, palings, bars, and gates of various kinds—such at least as are made of iron. In chapter four we have a notice of such kinds of smith’s work as relate to the fastenings for doors, windows, closets, chests, &c.; such as hinges, hasps, latches, bolts, and other contrivances less complex than an actual lock. This brings us, by a natural transition, to locks in general, which form the subject of chapter five, to which is attached the illustrious name of M. de Réaumur as the author. Here are given a hundred folio pages of description, illustrated by twenty folio plates relating to locks, lock-making, and locksmiths. The sixth chapter relates to the iron-work of carriages, or the labours of the coachsmiths; while chapter seven, to wind up the work, relates to bell-hanging.

[1] It is worthy of remark, that the tools described are the same as those which are used by the locksmith at the present day; shewing how little improvement has been made in the means of producing locks.

That chapter of the work which has reference to locks is the only one with which we have to do here. It is arranged in a systematic manner, beginning with the simpler locks, without wards or tumblers, and proceeding thence to others of more complex construction. The period at which the work was written was too early to lead us to expect to find a tumbler-lock described and delineated: there are, however, numerous examples of single tumbler-locks, many of them of great ingenuity. The use of multiple bolts, that is, of many bolts shot at once by one action of the key, seems to have been familiar enough to the locksmiths of those days. One lock represented is remarkable; it is attached to a strong and ponderous coffer or chest. The chest is open; and the whole under or inner surface of the cover is seen to be occupied by a lock of intricate construction; there are no less than twelve bolts, three on each long side, one on each short side, and one in each corner; these bolts are so placed as to catch under a projecting rim fixed round the top of the coffer. The collection of keys, exhibited on a separate plate, is remarkable for the great variety of forms given to them. We shall by and by copy some of the drawings of this curious work.

It was to be expected that in the Encyclopédie Méthodique, published in the same country and in the same century, the locksmith’s art would be treated at some such length as in the work just described. Among the two hundred volumes of which the Cyclopédie consists, several are devoted to arts and manufactures; and one of them contains the article in question. It occupies 168 quarto pages, and is illustrated by 35 copper-plate engravings, shewing in detail not only the parts of various locks, but the tools used by the lockmaker. It is proper, however, to remark, that much of the letterpress and many of the plates relate to smith’s work generally, and not exclusively to lock-work; the French name serrurerie being applied not only to lock-making, but to most of the smith’s work required in dwelling-houses. This affords, indeed, a striking illustration of the fact, that until lately a lock-maker has been regarded rather as a smith than as a machinist, rather as a forger and filer of pieces of iron, than as a fabricator of delicate mechanism. One of the most curious features in this treatise is a vocabulary, containing, in alphabetical arrangement, a minute account of all the French technical terms employed in the locksmith’s art. This vocabulary alone occupies 38 quarto pages.

The Germans, like the French, bestow great attention on their treatises relating to the manufacturing arts. Some of these are, indeed, worked up to a degree of minuteness which would seem superfluous, where little distinction is drawn between the importance of fundamental principles and that of mere technical details. Locks have had their due share. The article on locks in Prechtl’s Technological Encyclopædia written by Karmarsch, and published in 1842, occupies about 140 pages. Locks are very minutely classified by the author, according to their purposes and their modes of action, and are illustrated by many plates. One of his classifications is into German, French, and Bastard locks, referring in part to the extent to which the key turns round in the lock; and the last of the three having an intermediate character between the other two. After treating of the ordinary warded locks, he comes to the combination principle; and it is profitable here to notice, how well the works of our machinists are understood on the continent, when they have any thing to recommend them; there are a dozen closely printed pages devoted to a minute description of Bramah’s invention, with all the separate parts illustrated by copper-plate engravings. After this comes a more general account of the details and manufacture of locks, similarly illustrated by engravings.

Whatever may be the merits of the different articles relating to locks in the various English cyclopædias, there are none approaching in length to the article in Prechtl’s work. But when we consider that Prechtl devotes twenty large volumes to technological or manufacturing subjects, he is of course able to devote a larger space to each article than is given in English works. Both in England and in America, men are more disposed to do the work than to describe it when done. In the Encyclopædia Britannica, in Rees’ Cyclopædia, in Hebert’s Engineers’ and Mechanics’ Cyclopædia, in the Encyclopædia Metropolitana, in the Penny Cyclopædia, and in other similar works, locks are described as well as can be expected within the limits assigned to the articles. Mr. Bramah’s essay on locks, and on his own lock in particular, is one of the few English pamphlets devoted expressly to this subject. An excerpt from the proceedings of the Institute of Civil Engineers, in 1851, gives an interesting paper on locks by Mr. Chubb; and shorter reports of papers and lectures have been published in various ways. Perhaps the best account of locks which we have, considering the limited space within which a great deal of information is given in a very clear style, is that contained in Mr. Tomlinson’s Cyclopædia of Useful Arts.

CHAPTER II.
ANCIENT LOCKS: GRECIAN, ROMAN, EGYPTIAN.

Locks and door-fastenings have not, until modern times, been susceptible of any classified arrangement according to their principles of construction. They have been too simple to require it, and too little varied to permit it. That some such fastenings must be employed wherever doors of any kind are used is sufficiently apparent; and there is a little (though only a little) information obtainable, which shews the nature of the fastenings adopted in early times. The bolt, the hasp, the chain, the bar, the latch, the lock, all were known, in one or other of their various forms, in those ages which we are accustomed to consider classical. Travellers, generally speaking, do not descend to locks, or rather they do not think about them; otherwise they might have collected much that would have been novel and applicable to the present work; and, indeed, there is some ground for the assertion, that a notice of the door-fastenings of all nations would reveal to us something of the social and domestic habits of various members of the great human family. Be this as it may, however, we may profitably make a little inquiry into the locks of ancient times.

In the volumes of Lardner’s Cyclopædia relating to the “Manners and Customs of the ancient Greeks and Romans,” we do not find any mention of the kinds of locks used by those nations; but the author, while describing the houses, says:—“Doors turned anciently upon large pivots in the centre, let into sockets in the lintel and threshold, so that one of the sides opened inwards, the other outwards; and Plutarch gives the following curious reason why persons were to knock and alarm the porter, viz. lest the visitor entering unawares should surprise the mistress or daughter of the family busy or undressed, or servants under correction, or the maids quarreling.” As the visitors had thus the power (if permitted so to do) to open the outer door of a house, it would appear that very little in the nature of a lock was employed under ordinary circumstances, unless indeed it were a mere latch. In respect to Roman houses it is stated, that “the doors revolved upon pivots, which worked in a socket below, and were fastened by bolts which hung from chains.” There is no mention of locks here. Mr. St. John, in his work on the same subject, says: “The street-door of a Grecian house, usually, when single, opened outwards; but when there were folding-doors they opened inwards, as with us. In the former case it was customary, when any one happened to be going forth, to knock, or call, or ring a bell, in order to warn passengers to make way.” After describing the various kinds of wood of which the doors were made, he proceeds: “The doors at first were fastened by long bars passing into the wall on both sides; and by degrees smaller bolts, hasps, latches, and locks and keys, succeeded. For example, the outer door of the thalamos in Homer was secured by a silver hasp, and a leathern thong passed round the handle, and tied, perhaps, in a curious knot.”

Mr. Yates, in a learned article on this subject in Smith’s Dictionary of Greek and Roman Antiquities, collects numerous details scattered through various early writers. We will string together a few of these details, so far as they have any relation to the fastenings of doors. The outer door of a Roman house was generally called janua; whereas the inner doors were called ostia. The doorway, when complete, consisted of four indispensable parts—the threshold or sill, the lintel, and the two jambs. The threshold, on which the feet trod, was often regarded with a kind of superstitious reverence; the lintel, which crossed the doorway at the top, having a considerable superincumbent weight to bear, was usually made of one piece of timber or stone of great strength; the jambs, or side uprights, were also made in one piece each. The doorway, in every building of the least importance, contained two doors folding together; even the internal doors had their bivalve construction. But in every case each of the two valves was wide enough to allow persons to pass through without opening the other; in some cases even each valve was double, so as to fold like our window-shutters. These doors, or valves, were not hinged to the side-posts, as with us, but were, as has already been stated, pivoted to the lintel above and the threshold below. The fastening usually consisted of a bolt placed at the base of each valve or half-door, so as to admit of being pushed into a socket made in the sill to receive it. The doorways in some of the houses at Pompeii still shew two holes in the sill, corresponding to the bolts in the two valves. At night, the front door of the house was further secured by means of a wooden and sometimes an iron bar placed across it, and inserted into sockets on each side of the doorway; hence it was necessary to remove the bar in order to open the door. Chamber-doors were often secured in the same manner. In the Odyssey there is mention of a contrivance (adverted to by Mr. St. John) for bolting or unbolting a door from the outside; it consisted of a leather thong inserted through a hole in the door, and by means of a loop, ring, or hook, capable of taking hold of the bolt so as to move it in the manner required. We have here evidently the elements of a more complete mechanism; for the bolt was a rude lock in the same degree that the thong was a rude key. That the Romans afterwards had real locks and keys is clear; for the keys found at Herculaneum and Pompeii, and those attached to rings, prove that a kind of warded lock must have been well known.[2] There are the remains of a tomb at Pompeii, the door of which is made of a single piece of marble, including the pivots, which were encased in bronze, and turned in sockets of the same metal; it is three feet high, two feet nine inches wide, and four and a quarter inches thick; it is cut in front to resemble panels, and thus approaches nearer in appearance to a modern wooden door; and it was fastened by some kind of lock, traces of which still remain.

[2] An examination of the Roman keys in the British Museum sufficiently attests this fact.

The same facts frequently become more clear when described in different words by different writers. We shall make use of this circumstance. Mr. Donaldson, in his Essay on Ancient Doorways, presents us with details which illustrate many of the foregoing remarks. “Homer describes the treasures and other valuable objects (mentioned in the Odyssey) as being kept in the citadel, secured merely by a cord intricately knotted. This, of course, was soon found to be a very insufficient protection, and therefore a wooden bar was adopted inside the doors of houses, to which it was attached by an iron latch, fastened or removed by a key adapted to it; this key was easily applied from within; but in order to get at it from without, a large hole was made in the door, allowing the introduction of the hand, so as to reach the latch and apply the key. The lock called the Lacedæmonian, much celebrated by ancient writers, was invented subsequently; it was especially fitted for the inner chambers of houses, the bar fastenings continuing to be employed for closing the outer doors of dwellings and the entrance-gates to cities. The Lacedæmonian lock did not require a hole to be made in the door, for it consisted of a bolt placed on that side of the entrance-door which opened, and on the inside of a chamber-door. When a person who was outside wished to enter, it was necessary for him to insert the key in a little hole and to raise the bolt; and in time this species of fastening was improved by the insertion of the bolt in an iron frame or rim permanently attached to the door by a chain, and fastening the door by the insertion of the hasp, through the eye of which was forced the bolt inside the lock by applying the key.” After quoting a Latin sentence from Varro in elucidation of his subject, Mr. Donaldson proceeds to observe, that for the most part the locks of the ancients were different in principle from those of modern days, not being inserted or mortised into the doors, nor even attached except by a chain; they were, in fact, padlocks.

One of the passages in the Odyssey alluding to the primitive mode of fastening the valves or folding-doors of a house runs thus:—

“Whilst to his couch himself the prince addressed,
The duteous nurse received the purple vest:
The purple vest with decent care disposed,
The silver ring she pulled, the door reclosed;
The bolt, obedient to the silken cord,
To the strong staple’s inmost depth restored,
Secured the valves.”

Most of the other great nations of antiquity resembled either the Egyptians or the Greeks and Romans, more or less closely, in their domestic and domiciliary arrangements; or, at any rate, so far as such humble matters as locks and keys are concerned, we need not seek far from those nations for examples. The Nineveh and other Assyrian explorations have, however, revealed many curious and unexpected facts; from the temples and the palaces we may by and by penetrate into the houses and rooms of the citizens sufficiently to know how their doors were fastened. In the mean time ancient Egypt awaits our notice.

Sir J. Gardner Wilkinson, in his Manners and Customs of the Ancient Egyptians, gives the following information concerning the doors and door-fastenings of that remarkable people, on the authority of models, sculptures, and paintings, still existing. The doors were frequently stained so as to imitate foreign and rare woods. They were either of one or two valves, turning on pieces of metal, and were secured within by a bar or by bolts. Some of these bronze pins have been discovered in the tombs of Thebes; they were fastened to the wood with nails of the same metal, the round heads of which served also as ornaments. In the stone lintels and floors behind the thresholds of the tombs and temples are still frequently to be seen the holes in which the pivot-pins turned, as well as those of the bolts and bars, and the recess for receiving the opened valves. The folding-doors had bolts in the centre, sometimes above as well as below; a bar was placed across from one wall to the other.

In many of the ancient Egyptian doors there were wooden locks fixed so as to fasten across the centre at the junction where the two folds of the door met. It is difficult, by mere inspection of the bas-reliefs and paintings, to decide whether these locks were opened by a key, or were merely drawn backwards and forwards like a bolt; but if they were really locks, it is probable that they were on the same principle as the Egyptian lock still in use. For greater security, these modern locks are occasionally sealed with a mass of clay; and there is satisfactory evidence that the same custom was frequently observed among the ancient inhabitants of that country. Sir J. G. Wilkinson gives a representation of an iron key, now in his possession, which he procured among the tombs at Thebes, and which looks very much like a modern burglar’s picklock. In relation to keys generally, and after mentioning the use of bronze for their manufacture, he says: “At a later period, when iron came into general use, keys were made of that metal, and consisted of a straight shank about five inches in length, and a bar at right angles with it, on which were three or more projecting teeth. The ring at the upper extremity was intended for the same purpose as that of our modern keys; but we are ignorant of the exact time when they were brought into use; and the first invention of locks distinct from both is equally uncertain; nor do I know of any positive mention of a key, which, like our own, could be taken out of the lock, previous to the year 1336 before our era; and this is stated to have been used to fasten the door of the summer parlour of Eglon, the king of Moab. The description here adverted to is that contained in Judges iii. 23-25: ‘Ehud went forth through the porch, and shut the doors of the parlour upon him, and locked them ... his servants ... took a key, and opened them.’”

The curious and ingenious wooden lock of ancient Egypt is still in use in Egypt and Turkey. In Eton’s Survey of the Turkish Empire, published towards the close of the last century, the locks then and there in use are thus described: “Nothing can be more clumsy than the door-locks in Turkey; but their mechanism to prevent picking is admirable. It is a curious thing to see wooden locks upon iron doors, particularly in Asia, and on their caravanserais and other great buildings, as well as upon house-doors. The key goes into the back part of the bolt, and is composed of a square stick with five or six iron or wooden pins, about half an inch long, towards the end of it, placed at irregular distances, and answering to holes in the upper part of the bolt, which is pierced with a square hole to receive the key. The key being put in as far as it will go, is then lifted up; and the pins, entering the corresponding holes, raise other pins which had dropped into these holes from the part of the lock immediately above, and which have heads to prevent them falling lower than is necessary. The bolt, being thus freed from the upper pins, is drawn back by means of the key; the key is then lowered, and may be drawn out of the bolt. To lock it again, the bolt is only pushed in, and the upper pins fall into the holes in the bolt by their own weight.” Mr. Eton, probably seeing how well the tumbler-principle is here understood, says: “This idea might be improved on; but the Turks never think of improving.” The locks on the doors of modern houses in Cairo seem to be of this long-established form, except where iron locks have been imported from Europe.

A letter was inserted in the Journal of Design for July 1850 from Mr. W. C. Trevelyan; in which, after adverting to the Egyptian lock, he says: “It is remarkable that the locks which have been in use in the Faröe Islands, probably for centuries, are identical in their construction with the Egyptian. They are, lock and key, in all their parts made of wood; of which material, if I mistake not, they have also been found in Egyptian catacombs; and so identical with the Faröese in structure and appearance, that it would not be easy to distinguish one from the other.”

fig. 1.

fig. 2.

fig. 3.

fig. 4.

The construction of this remarkable Egyptian or pin-lock will be understood from the accompanying engravings. The quadrangular portion, a a [fig. 1], is the case of the lock, screwed or otherwise fastened to the door, having a wooden bolt, b b, passing horizontally through a cavity in it. In the part of the case above the bolt are several small cells containing headed pins, arranged in any desired form; and in the top of the bolt itself are an equal number of holes similarly arranged. The effect of this arrangement is such that, when brought into the right positions, the lower ends of the headed pins drop into the corresponding holes in the bolt, thereby fastening the bolt in the lock-case. A large hollow, or cavity, is made at the exposed end of the bolt, the cavity extending as far as and beyond the holes occupied by the pins. The key consists of a piece of wood (shewn in two positions, [figs. 3] and [4],) having pins arranged like those in the lock, and projecting upwards just to a sufficient distance to reach the upper surface of the bolt. This being the arrangement, whenever the key is introduced and pressed upwards, its pins exactly fill the holes in the bolt, and by so doing dislodge those which had fallen from the upper part of the case. The bolt may, under these circumstances, be withdrawn (as shewn in [fig. 2]), leaving the headed pins elevated in their cells, instead of occupying the position shewn by the dotted lines in [fig. 1]. The cavity in the bolt must of course be high enough to receive the thickness of the key, and also the length of the pins protruding from the key.

This primitive lock comprises many of the best features of the tumbler or lever-locks of later days, as will be seen in a future chapter. There will also be opportunities of shewing how the pin-action has been applied in other ways in some of the modern locks.

CHAPTER III.
LOCK CLASSIFICATION. THE PUZZLE-LOCK AND THE DIAL-LOCK.

In approaching the subject of modern locks it becomes necessary to decide upon some method of treating the widely-scattered and diverse materials which are presented to our notice. One plan would be to trace the subject chronologically, by describing, in the order of their invention, the most important locks which have been presented to public notice. But this would be attended with some disadvantages: the peculiar characters of the several locks would not be brought out with sufficient distinctness; and the result, so far as the reader is concerned, would rather tend to confusion than to a clear appreciation of the subject. There are more advantages belonging to a classification of locks under certain headings, according to some marked peculiarities in their modes of action. This is a convenient plan, but it is not an easy one to put in execution; for inventors have not sought to place their locks in any particular class, but rather to call attention to their merits. Moreover, many locks embody two or three distinct principles so equally, that it will often be difficult to decide in which class to place them. This, nevertheless, may be done with an approach to correctness. It is necessary first, however, to explain certain technical terms by which locks are distinguished one from another.

Locks, in truth, admit of an immense variety, which, however important to be known to locksmiths, carpenters, and others employed on them, need only be glanced at very cursorily by the general reader. Some locks are named according to the purposes to which they are to be applied; others according to their shape, or the principles of their construction. In the first place, there is the distinction between in-door and out-door locks. Of in-door locks, one principal kind is the draw-back lock, for street-doors, in which the bolt is capable of maintaining any one of three positions: it may be locked by the key, or left half-way out by the pressure of a spring, or be drawn back by a handle. In the first position, it can only be withdrawn by the key; in the second, it closes the door, but can easily be withdrawn by the handle; and in the third, it leaves the door unfastened. If these locks are made of iron and carefully finished, they are further called iron-rim; but if made of wood, suitable for back-doors and inferior purposes, they are spring-stock. For the doors of rooms, there are the iron-rim, the brass-case, and the mortise lock; the second supplants the first, and the third the second, as we advance in the elegance of the door-fittings. Other designations for room-locks depend on the number of the bolts: thus, if there be only one bolt, it is a dead lock or closet lock; if there be a second bolt, urged by a spring and drawn back by a handle, it is a two-bolt lock; and if there be also a third, a private bolt acting only on one side of the door, it is a three-bolt lock. Again, according to the kind of handle employed, it may be a knob lock or a ring lock. According to which edge of the door it is to be fixed, it becomes a right-hand or a left-hand lock. If the wards of the lock are of somewhat superior quality, and bend round nearly to a circle, the lock is one-ward round, two-ward round, and so forth. If the lock has no wards at all, it is plain; if the wards are of common character, they are often called wheels, and then the lock becomes one-wheel, two-wheel, &c. Sometimes the lock is named from certain fancied resemblances in the shape of the ward, as the L-ward, T-ward, or Z-ward. If the wards are cast in brass, instead of being made of slips of iron or copper, the lock is termed solid ward.

Of the numerous but smaller varieties known by the collective name of cabinet locks, there are the cupboard, the bookcase, the desk, the portable desk, the table, the drawer, the box, the caddy, the chest, the carpet-bag, and many other locks. All these locks are further called straight, when the plate is to be screwed flat against the wood-work; cut, when the wood is to be so cut away as to let in the lock flush with the surface; and mortise, when a cavity is excavated in the edge of the door for the reception of the lock.

Out-door locks are usually wooden stock locks, for stables, gates, &c.; comprising many varieties of Banbury, bastard, fine, &c. There are D locks and P locks, for gates, designated from their shapes; and there are the numerous kinds of padlocks.

The above terms are employed chiefly between the makers of the locks and the persons who fix them in their places; but there are other terms and names, more familiarly known, which will come under notice in future pages.

It is scarcely worth while to descant upon the “middle age” of lock-making—to impart to the subject so much of dignity as to be susceptible of regular historical treatment. True, we know that wards were employed before tumblers (unless, indeed, the pins of the Egyptian lock be considered as tumblers—a character to which they present considerable claim), and that wards may be taken as the representative of the medieval period of lock-making; but it may be more profitable to proceed in our notice of the different kinds of locks in an order which will in itself partake somewhat of the historical character.

Apart from all the warded and tumbler locks are the very curious puzzle or letter-locks; a construction which we propose to dismiss out of hand in the present chapter, before treating of those which have more commercial importance.

The puzzle-lock is generally in the form of a padlock, which is opened and closed without the use of a key, and which has certain difficulties thrown in the way of its being opened by any one who is not in the secret of the person who closed it. It is, in fact, one of the locks in which the doctrine of permutation is made to contribute to the means of security. The key to open it is a mnemonic or mental one, instead of one of steel or iron. Two centuries ago, the puzzle-lock attracted far more attention than any other. It has always certain movable parts, the movement of which constitutes the enigma. Some of these very curious and out-of-the-way locks are so formed as to receive the name of dial-locks; but the chief among them are ring-locks—a name the meaning of which will be presently understood.

The puzzle or letter-lock of the ring kind, then, consists essentially of a spindle; a barrel, encompassing the spindle; two end-pieces, to keep the spindle and barrel in their places; and the shackle, hinged to one of these end-pieces. To unfasten the lock, one of the end-pieces must be drawn out a little, to allow the shackle or horse-shoe to be turned on its hinge; and the question arises, therefore, how this end-piece is to be acted upon. This is effected in a very ingenious way: there are four studs or projections in a row on the spindle, and as the spindle fits pretty closely in the barrel, the former cannot be drawn out of the latter unless there be a groove in the interior of the barrel, as a counterpart to the studs on the exterior of the spindle; four rings fit on the barrel, on the interior of each of which there is a groove; and unless all these four grooves coincide in direction, and even lie in the same plane as the groove in the barrel, the studs will not be able to pass, and the spindle cannot be drawn out. Each ring may be easily made to work round the barrel by means of the fingers, and to maintain any position which may be given to it. There are outer rings, one over each of the rings just described, with the letters of the alphabet (or a considerable number of them) inscribed on each; and these outer rings, by means of notches on the inside, govern the movements of the inner rings.

The action is, therefore, as follows: when the padlock is to be locked, the rings are so adjusted that all the grooves shall be in a right line; the spindle is thrust in, the end-piece is fixed on, and the shackle is shut down. The padlock is now fastened; but a reverse order of proceeding would as easily open it again, and therefore the “safety” or “puzzle” principle is brought into requisition. The outer rings are moved with the finger, so as to throw the various interior grooves out of a right line, and thus prevent the withdrawal of the spindle. As each ring may be turned round through a large or a small arc, and all turned in different degrees, the variations of relative position may be almost infinite. The letters on the outer rings are to assist the owner to remember the particular combination which he had adopted in the act of locking; for no other combination than this will suffice to open the lock. There may, for instance, be the four letters L O C K in a line, which line is brought to coincide with two notches or marks at the ends of the apparatus; and until all the four outer rings are again brought into such relative position as to place the letters in a line, the lock cannot be opened.

There are many allusions to locks, apparently belonging to the letter or puzzle principle, in authors who flourished two or three centuries ago. Thus, in Beaumont and Fletcher’s play of the Noble Gentleman, written in the early part of the seventeenth century, one of the characters speaks of

“A cap-case for your linen and your plate,
With a strange lock that opens with A·M·E·N.”

And in some verses by Carew, written about the same time, there is an analogy drawn, in which one of the things compared is—

“A lock
That goes with letters; for till every one be known,
The lock’s as fast as if you had found none.”

In the Memorabilia of Vanhagen von Ense, written about the middle of the seventeenth century, a commendatory notice is given of a letter-lock, or combination-lock, invented by M. Regnier, Director of the Musée d’Artillerie at Paris. “Regnier,” we are told, “was a man of some invention, and had taken out a patent for a sort of lock, which made some noise at the time. Every body praised his invention, and bought his locks. These consisted of broad steel rings, four, five, or eight deep, upon each of which the alphabet was engraved; these turned round on a cylinder of steel, and only separated when the letters forming a particular word were in a straight line with one another. The word was selected from among a thousand, and the choice was the secret of the purchaser. Any one not knowing the word might turn the ring round for years without succeeding in finding the right one. The workmanship was excellent, and Regnier was prouder of this than of the invention itself. The latter point might be contested. I had a vague recollection of having seen something of the sort before; but when I ventured to say so, my suspicions were treated with scorn and indignation, and I was not able to prove my assertion; but many years afterwards, when a book, which as a boy I had often diligently read, fell into my hands, Regnier’s lock was suddenly displayed. The book was called Silvestri a Petrasancta Symbola Heroica, printed at Amsterdam in 1682. There was an explanation at p. 254, attached to a picture; these were the words:—Honorius de Bellis, serulæ innexæ orbibus volubilibus ac literatis circumscripsit hoc lemma—Sorte aut labore.[3] However, neither luck nor labour would have done much more towards discovering the secret of opening Regnier’s locks, from the variety of their combinations; and their security seemed so great, that the couriers’ despatch-boxes were generally fastened with them.”

[3] “Honorius de Bellis wrote this inscription,—By chance or by labour,—round a lock composed of revolving rings graven with letters.”

This curious extract, which was brought forward by Mr. Chubb, in a paper on locks and keys (read before the Institution of Civil Engineers in 1850), seems to take away the credit from one (Regnier) with whose name the letter-lock has been most intimately associated. We shall presently explain, however, what it was that Regnier effected towards perfecting the letter-lock. In the meantime it may be interesting to note that the British Museum contains a copy of the work mentioned by Vanhagen. At the page indicated there is an engraving (a fac-simile of which is given in [fig. 5]) containing a drawing of a veritable puzzle or letter-lock; the lock consists of a cylinder or barrel, on which seven rings work; each of these rings is inscribed with letters, and the ends of the cylinder are grasped by a kind of shackle.

fig. 5. Puzzle-lock of the seventeenth century.

It was a natural result of the arrangement of the letter-lock, as invented (conjecturally) by Cardan, that only one particular word or cipher or key could be used in each lock; and it was to increase the puzzle-power of the lock that Regnier doubled all the rings, making each pair concentric, and enabling the user to vary the cipher at pleasure.

The principle of the letter-lock, when applied to doors, requires that sort of modification which renders it what is termed a dial-lock. There are to such a lock one or more dials, with a series of letters or figures stamped on them; there is to each dial a hand or pointer connected by a spindle with a wheel inside the lock; on the wheel is a notch which has to be brought to a certain position before the bolt can be moved. There are false notches, to add to the difficulty of finding the true notch in each wheel. To adjust the notches to their proper position, a nut on the back of the wheel is loosened, and the pointer is set at any letter or figure chosen by the user. The pointers and the dials perform the part of the outer rings, the wheels that of the inner rings; and it is easy to see that the same leading features prevail in the two kinds of lock, however they may differ in detail.

These dial-locks have not been numerous; they require wheel and pinion work within the body of the lock, which gives delicacy and complication to the mechanism. The letter padlock, be its merits great or small, is strong and durable, not liable to get out of order; and in so far as it requires no key or key-hole, it occupies rather a special position among locks. One of our great “merchant-princes” has been a letter-lock inventor, as the following will shew.

Early in 1852, Mr. William Brown, the distinguished member for South Lancashire, read a paper before the Architectural and Archæological Society of Liverpool, of much interest in relation to our present subject. His object was to describe a letter-lock which he had invented, and which had up to that time given high satisfaction. We cannot do better than transcribe the paper, as reported in one of the Liverpool Journals, with a few abridgments.

“As your society are desirous of seeing any improvements or attempts at them, I send you a stock-lock for inspection. The idea for its construction I took from a letter-padlock. I had a lock of this description made by Mr. Pooley twenty-five years ago, which has been in use ever since on Brown, Shipley, and Co.’s safe....

“Its advantages I conceive to be—First, it cannot be picked, for there is no key-hole. Second, it cannot be blown up by gunpowder, for the same reason. Third, you cannot drill through the door so as to reach the lock, for you are intercepted by a steel plate on which your tools will not act: thus you cannot introduce gunpowder that way to force the lock off. Fourth, you cannot bounce off the wheels in the interior with a muffled hammer, for vulcanised India-rubber springs resist this. Fifth, you cannot drill the spindles out, as their heads are case-hardened. Sixth, you cannot drive them in, for they are countersunk in the door about half-way through....

“Now let us set the lock to the word W O O D (any other four letters might be used). When you set the lock, make a private record of them, so that you may not forget them. If parties do not know your letters, nothing but violence, applied by some means or other, can enable them to get into your safe; for the lock will not open to any thing but its talisman. Take off all the large wheels and open the lock: you will see that the large wheels have a number of false chambers; if you get the spurs of the bolt into three real chambers and one false, you are as fast as ever, for all four must be right.

“Having placed your key and pointer outside the door to point to W on brass-plate No. 1, the small wheel inside obeys the same impulse; then maintain your small wheel steadily on this point, and the large wheel No. 1 will only fit on at the right place, the true opening compartment being opposite the spur of the bolt. It being necessary at the time you set your lock that it should be open, proceed with Nos. 2 and 3 in the same way, your pointer standing steadily at O. No. 4 is the same, the pointer being held steadily at D. You should then shoot your lock two or three times, to be sure you have made no mistake. Every time you shoot your bolts out, turn your wheels away from the true chamber, and see when you again turn your pointers to W O O D that your lock opens freely; it is the proof that you have made no mistake, and you may now venture to lock your safe. When you unlock the door, and find it necessary to leave it open for a time, you should shoot the bolts as if locked, and turn the wheels, so that no one may find what your real letters are; and again adjust them to their proper places, in order that the bolt may go back and enable you to re-lock. Once having locked the door and turned the wheels from your real letters, you need not trouble yourself with carrying the key, but leave it in any place beside the lock.

“I believe two wheels would make a perfectly safe lock; three would be quite so. I adopted four to make security doubly sure, as it would be impossible in any given time to work the changes. On two wheels by chance the lock might open; you can, however, calculate the chances against this; and also three or four, the false compartment on the outer rim being taken into calculation. ***

“If this lock is of any value, it should be known; if it has weak points, let them be pointed out, and they may admit of a remedy; for we ought not to be led to believe a lock is safe which is not so.”

In relation to the “first advantage” which Mr. Brown not unreasonably supposed to be possessed by his lock—viz. that “it cannot be picked, because it has no keyhole”—we shall have something to say in a future page, where certain fallacies on this subject will be noticed. In the meantime we may remark, that it is not a little creditable that a leading Liverpool merchant should have invented a lock worthy of occupying a position on his own safe for a quarter of a century; for we may be quite certain that he would not have allowed the lock to maintain that post of honour unless it had really (so far as experience had then gone) served worthily as a safeguard to his treasures. And if it were possible to collect all the by-gone specimens of lock-oddities, we should probably find among them many highly-ingenious letter-locks; for supposing a man to have a mechanical turn of mind, a lock is by no means an unworthy medium for displaying it; the pieces of metal are so small as to be easily manageable at a small work-bench in a small room. The fondness for this sort of employment evinced by the unfortunate Louis XVI. of France led to the common remark, “He is a capital locksmith, but a very bad king.”

In an amusing article in the Observer, during the progress of the “lock controversy,” was the following paragraph relating to combination-locks of the letter or puzzle kind: “The French, in their exposition of 1844, availing themselves of the permutation principle, produced some marvels in the art; but the principle has not been adopted in this country. The Charivari had an amusing quiz upon these locks when they first came out. It said the proprietor of such a lock must have an excellent memory: forget the letters, and you are clearly shut out from your own house. For instance, a gentleman gets to his door with his family, after a country excursion, at eleven o’clock at night, in the midst of a perfect deluge of rain. He hunts out his alphabetical key, and thrusts it into his alphabetical lock, and says A Z B X. The lock remains as firm as ever. ‘Plague take it!’ says the worthy citizen, as the blinding rain drives in his eyes. He then recollects that that was his combination for the previous day. He scratches his head to facilitate the movement of his intellectual faculties, and makes a random guess B C L O; but he has no better success. In addition to his being well wet, his chances of hitting on the right combinations and permutations are but small, seeing that the number is somewhere about three millions five hundred and fifty-three thousand five hundred and seventy-eight. Accordingly, when he comes to the three-hundredth he loses all patience, and begins to kick and batter the door; but a patrol of the National Guard passes by, and the disturber of the streets is marched off to the watch-house.”

CHAPTER IV.
WARDED LOCKS, WITH THEIR VARIED APPENDAGES.

The more ordinary locks are of an oblong quadrangular shape. In nearly all of them, either a bolt shoots out from the lock, to catch into some kind of staple or box, or a staple enters a hole in the edge of the lock, and is there acted upon by the bolt. A common room-door lock will illustrate the first of these kinds, a tea-caddy lock the second. The key, as is well known, enters a receptacle made for it; and the shaft of the key generally serves as a pivot or axis around which the web or flat part of the key may move in a circular course. During this movement the web acts directly or indirectly on the bolt, driving it in or out according to the direction in which the key is turned; the key impels the bolt one way, certain springs act upon it in another, and the balance between these two forces determines the locking and unlocking of the bolt. Wards, or wheels, are contrivances for rendering the opening difficult without the proper key; and it is of warded locks that we shall chiefly treat in this chapter.

fig. 6. Interior of a back-spring warded lock.

The annexed cut, [fig. 6], represents the interior of an ordinary back-spring lock, without tumblers. Such a lock may usually be known from a tumbler-lock by this simple circumstance, that it emits a smart snapping noise during the process of locking, occasioned by the pressure of the spring when the bolt is in a particular position. In the woodcut the bolt is represented half out, or half shot. At a a are two notches on the under side of the bolt connected by a curved part; b is the back spring, which becomes compressed by the passage of the curve through a limited aperture in the rim c c of the lock. When the bolt is wholly withdrawn, one of the notches a rests upon the rim c c; and the force with which the notch falls into this position, urged by the spring b, gives rise to the snapping or clicking noise. When the bolt is wholly shot, the other notch rests in like manner upon the edge of the aperture in the rim.

It must be obvious at a glance, that this back-spring lock is objectionable on the score of security, on account of the facility with which the bolt may be forced back by any pressure applied to its end, a pressure which may often easily be brought to bear. At the centre of the lock is seen the end of the key acting on a notch in the bolt, and surrounded by wards.

fig. 7. Section to shew the action of wards.

It is not at a first glance that the relation between the clefts in a key and the wards of a lock can be duly appreciated; because the wards present themselves to view as portions of circles to which nothing in the key seems to correspond; but if it be borne in mind that the key has a rotary motion within the key-hole around the pipe or barrel as an axis, the circular form of the wards will be accounted for, and their section will be regarded as exhibiting the looked-for relation to the wards of the key. In the annexed cut, for example ([fig. 7]), which represents a portion of the interior of a warded lock, the curved pieces of metal are the wards (two in this case); and there are two clefts in the bitt of the key to enable the latter to take its circular course without interruption from the wards. If the clefts were other than they are, either in number, position, or size, this freedom of the key’s movement could not be obtained.

fig. 8. End sections of keys.

When once the opinion became established that a lock is rendered secure by virtue of its wards, (a theory which we shall have to discuss in a later page,) much ingenuity was displayed in varying the wards of the lock, the clefts of the key, and the shape of the keyhole. Even if the two former were unchanged, a change in the latter might add to the puzzlement of the arrangement. For instance, in the annexed cut (fig. 8), all the six keys represented may have clefts or cuts exactly alike, all alike adapted to the wards of one particular lock; yet the differences in the thickness of the web are such, that if the keyholes were shaped in conformity therewith, each keyhole would be entered by one of these keys; b and c differing from a in the relative thickness at different points, and d, e, and f having certain curvatures and cavities not to be found in the other three.

fig. 9. Examples to shew the action of “master,” or “skeleton keys.”

But without waiting for the detailed examination of the relative security and insecurity of locks, we may at once shew how simple is the principle which renders the warded system fallacious. In [fig. 9] we shall be able to illustrate this. Numbers 1, 2, and 3, all appear very different keys, and it is quite true that neither one would open a lock adapted for either of the other two; and yet the very simple arrangement No. 4 would open all three. This No. 4 is called a skeleton-key; and the relation which it bears to the others may be expressed in the form of a proposition thus: at any point where there is solid metal in all the keys, there must (or may) be solid metal in the corresponding part of the skeleton-key; but at any point where there is a vacancy or cavity in any of the keys, there must be a cavity in the corresponding part of the skeleton-key. If Nos. 1, 2, 3, 4, be examined, this proposition will be found to be borne out; there is so much cavity in No. 4 that it avoids the wards in all the three locks, nothing being required but the tongue of metal to move the bolt. Sometimes, to add to the safety, wards are attached to the front as well as the back plate of the lock; and then there may be a double series of notches required in the key, such as in No. 5; but if this be compared with Nos. 9, 10, 11, it will be found that although no one of the four would open a lock adapted for either of the other three, yet the skeleton-key No. 12 would master them all, having cavities wherever any of the others have cavities. This is the theory of the master-key, by which one key may be made to command many locks. Nos. 6 and 7 have complicated wards; but the key is so much cut up as to be weakened more than is desirable. No. 8 enables us to point out the difference between two distinct classes of keys. Keys with pipes or barrels fitting on a pin or pipe-shaft can only open a lock on one side of the door or box; but a key with a solid stem, as No. 8, has the clefts so cut as to open the lock from either side, as in a street-door lock: it is, in fact, two warded keys fixed end to end, only half of which is employed at one time in opening the lock.

fig. 10. Wards of an old French lock.

Some of the warded locks of the last century are curious. While the idea prevailed that a complicated ward gave security, there was room for the exercise of ingenuity in varying the shape of the wards. [Fig. 10] is copied from the great French work. It represents the cuts in the key, and also (seen perspectively) the complicated forms of the pieces of metal which constitute the wards corresponding with those cuts. The aperture in the key at 16 fits upon the metal surrounding the keyhole at 18; and the M-shaped cuts at 17 fit in like manner upon the similarly-shaped metal pieces at 19.

Another example of a similar kind is shewn in [fig. 11], where an anchor appears to have been the favourite form. The anchor cuts in the key are shewn at 26; while in the wards the bottom of the anchor is near the keyhole at 28, and the top at 29.

fig. 11. Wards of an old French lock.

fig. 12. Wards of an old French lock.

A similar illustration occurs in [fig. 12], where the star-like cuts at 34 on the key correspond with the star-like wards at 33.

fig. 13. Exterior of an old secret lock.

fig. 14. The same, with a portion of the front let down, shewing the key-hole.

From the fifteenth to the eighteenth centuries locks were made in France, on which a vast amount of care and expense was bestowed. They were, in an especial degree, decorative appendages as well as fastenings. They were of three kinds: room-locks, buffet-locks, and chest-locks; they were fixed on the outside of the door or lid, so as to be fully visible. The key had a multitude of perforations which bore no particular relation to the wards of the lock, but which were regarded as tests of the workman’s skill. The honorary distinctions awarded to apprentices and aspirants in the art depended very much on the number and fine execution of these perforated keys. The locks, considered as fastenings, had slender merit; although usually throwing four bolts, they were not very secure. [Fig. 13] represents the exterior of a lock made about the year 1730, by Bridou, a celebrated Parisian locksmith. It was a lock belonging to a coffer or strong chest; all the works being sunk below the level of a carved architectural moulding or ornament. There is a secret opening near the part C, forming a portion of the ornamental design; it allows a bolt, shewn at D, [fig. 14], acted on by the spring E, to be touched, by which a doorway opens upon the hinges at B B. A A are a sort of pilasters, which aid in forming a hold for the bolts. The little ornament at C is drawn down by the hand, opening the secret door and revealing the key-hole G. S S, O O, Z Z, are ornaments fastened on at b c d, [fig. 14], by nuts and screws, intended to display the skill of the workman. The lock itself, access to the keyhole of which is obtained within the secret door, has nothing very remarkable about it.

fig. 15. Examples of true and false keys.

Mr. Chubb, in his paper read before the Institute of Civil Engineers, illustrated the insecurity of the warded lock by the example of one which had actually been placed in the strong-room of a banking house, and which is represented in the annexed cut ([fig. 15]). The wards are here shewn, surrounding the central key-pin; and from the appearance of the key, shewn at a, it is evident that these wards must have been rather complex. But the uselessness of the wards was proved by the result. A burglar employed an instrument, shaped like that at b, having on one of its faces, or sides, a layer of wax and yellow soap; this instrument, being introduced through the keyhole and turned a little way round, brought the soft composition in contact with the ends of the wards, and these ends thus left their impress on the composition. A false key was then made, as at c, which, however clumsy it may appear, has a cavity, or vacuity, where there is a cavity in the true key; and by such a surreptitious instrument was the lock opened. Even so rude an instrument as d, by passing round the wards, might open such a lock.

We are somewhat anticipating the full consideration of this subject; but it is desirable at once to explain how and why an improvement on the warded lock was sought for.

In connexion with the fanciful eighteenth-century locks, lately adverted to, we may remark, that no less a man than Louis XVI. was an amateur workman in this department of mechanical art—or at least in smith’s work, which in France is generally considered to include lock-making. Sir Archibald Alison says, in his History of Europe:—“He had an extraordinary fondness for athletic occupation and mechanical labour; insomuch that he frequently worked several hours a-day with a blacksmith of the name of Gamin, who taught him the art of wielding the hammer and managing the forge. He took the greatest interest in this occupation, and loaded his preceptor in the art with kindness; who returned it by betraying to the Convention a secret iron recess which they had together worked out in the walls of the cabinet in the Tuileries, wherein to deposit his secret papers during the storms of the Revolution.” There are not wanting indications that the unfortunate monarch wrought upon locks, as well as upon safes and strong-rooms.

Besides wards, there have been numerous other contrivances for adding to the security of locks—including screws, escutcheons, spiral springs, wheel-and-pinion work, alarums, and multiple bolts. As these are not of sufficient importance to be treated in separate chapters, we shall here give just so much notice of them as will illustrate their general character. Some of them are found combined with the “tumbler” principle, presently to be described; but all of them, it is now well known, were employed in various, ways when the tumbler lock was but little understood, and when the warded lock was held in esteem.

The Marquis of Worcester, whose curious Century of Inventions, written nearly two hundred years ago, contains so many suggestions which ingenuity has since developed into practical completeness, gives four of his inventions in the following words:—

69. “A way how a little triangle screwed key, not weighing a shilling, shall be capable and strong enough to bolt and unbolt, round about a great chest, an hundred bolts, through fifty staples, two in each, with a direct contrary motion; and as many more from both sides and ends; and, at the self-same time, shall fasten it to the place beyond a man’s natural strength to take it away; and in one and the same turn both locketh and openeth it.

70. “A key with a rose-turning pipe and two roses pierced through endwise the bit thereof, with several handsomely contrived wards, which may likewise do the same effects.

71. “A key, perfectly square, with a screw turning within it, and more conceited than any of the rest, and no heavier than the triangle screwed key, and doth the same effects.

72. “An escutcheon, to be placed before any of these locks, with these properties: First, the owner, though a woman, may with her delicate hand vary the ways of causing to open the lock ten millions of times beyond the knowledge of the smith that made it, or of me that invented it. Second, if a stranger open it, it setteth an alarum a-going, which the stranger cannot stop from running out; and besides, though none shall be within hearing, yet it catcheth his hand as a trap doth a fox; and though far from maiming him, yet it leaveth such a mark behind it as will discover him if suspected; the escutcheon or lock plainly shewing what money he hath taken out of the box to a farthing, and how many times opened since the owner had been at it.”

Mr. Partington, in his edition of the marquis’s singular work, makes a few comments on these lock-and-key contrivances. He says that the lock is evidently intended to operate on the principle of applying a screw for the purpose of moving the bolt, instead of using a key as a lever for this purpose. That such a plan might be applied to locks generally, he observes, there can be no doubt; and by a similar contrivance the large keys at present in use for outer doors, iron chests, &c. might be advantageously reduced by this means. By employing the escutcheon mentioned by the marquis, much additional security would be obtained. It must be confessed, however, that many of the marquis’s statements are difficult to credit.

The escutcheon has been a favourite resource with lock-makers. Mr. Mordan’s escutcheon, for instance, introduced before the Society of Arts in 1830, is a contrivance to be placed temporarily over the keyhole of a door, to prevent the picking of the lock during the owner’s absence. The escutcheon, or “protector,” has a short pipe which, after the door has been locked, is thrust into the keyhole; attached to the pipe is a small lock, on Bramah’s or any other convenient principle, so contrived that, on turning its key, two lancet-shaped pieces fly out laterally and bury themselves in the wood. The escutcheon cannot be removed until the small key has reacted upon the small lock; and until this removal has taken place, the large key cannot reach the keyhole.

A curious application of the escutcheon principle attracted some attention among locksmiths about seventy years ago. One of the first premiums awarded by the Society of Arts, after the commencement of their “Transactions,” was to Mr. Marshall, for a “secret escutcheon,” in 1784. In his description of his new invention, he adverts to the marquis of Worcester’s wonderful escutcheon, and to the many attempts which have since been made to produce an apparatus which should realise the marquis’s description. He supposes that the letter padlock originated as one among many varieties of these imitative inventions; but this may be doubted. Mr. Marshall’s contrivance, however, was in effect an endeavour to improve upon the letter-lock. He considered it an objection that, in ordinary locks of this kind, the letter-rings admit of no variation of place; and he sought to remedy this defect. It is not so much a new lock, as an escutcheon for a lock, which he produced. There is a studded bar passing through a barrel; there are five rings which work concentrically on this barrel; there are letters on the outer surfaces of the rings, and notches on the inner surface; but when, by the usual puzzle-action of the rings, the notches in them have been brought into a right line with the studs of the bar, the result is, not that the hasp of a padlock is raised, but that the escutcheon is removed from the keyhole of an ordinary lock. Mr. Marshall’s contrivance, therefore, is not so much a ring padlock, as a puzzle-ring security for the escutcheon of a fixed lock.

Some locks work by a screw and a spiral spring, instead of an ordinary key. Mr. W. Russell received a silver medal from the Society of Arts, about thirty years ago, for a new mode of locking the cocks of liquor-casks. Under ordinary circumstances, as is well known, the cock of a barrel or cask is in no way secure from the action of any one who can approach near enough to touch it; and different methods have been adopted of obtaining this security or secrecy. One plan is to employ a perforated cap, soft-soldered to the barrel of the cock, immediately over the grooved plug, the top of which plug is formed to the shape of the perforation, and a socket-key of the same form is introduced to turn the plug or open the lock. Another plan is to employ an iron saddle or staple, passing over the plug and below the bottom of the cock, through which a bolt is put, and a pendent padlock attached. The first method is very inefficient; the second is much superior, and has been largely adopted for locking the cocks of coppers, stills, vats, and other large vessels. But Mr. Russell thought some further improvement wanted. He caused a hole to be bored through the barrel, and to some depth into the plug when the latter is in the position for closing the cock. A stud works into this hole in such a way, that when the stud is driven home, the plug cannot be turned or the lock opened. The stud is attached at its other end to a spiral spring connected with a screw; a key is employed, the hollow pipe of which has an internal screw; and when this key is inserted in the cock-barrel and turned twice round, it draws back the stud, and allows the plug to be turned round in the proper way for opening the cock.

It is not often that wheel-and-pinion work is introduced into locks; the delicacy, the costliness, the weakness, and the tendency to get out of order, would all militate against the frequent adoption of such a course. It is, however, adopted occasionally. Mr. Friend’s secret-lock, introduced to the notice of the Society of Arts in 1825, had a train of wheels which acted upon the bolt, driving it out whenever the circular arcs of three wheels moved against it, but allowing a spring to force it back again whenever a deep cleft in each of the wheels locked into a stud on the bolt. There were certain numbers on a guide-plate, and a power of combining these numbers in great variety; and a provision that the bolt could be unlocked only by the same combination of numbers which had locked it. The guide-plate was a separate piece of apparatus, carried in the pocket of the user as a companion to the key. The key was of no use without the guide-plate, nor the guide-plate without the key. The user ‘set’ the numbers on the guide-plate, then applied it to the face of the lock, then introduced the key into the key-hole, and turned the key partially round; the bolt was now shot, and the guide-plate removed. If the key were used without the guide-plate, the bolt might be locked, but it was always unlocked again by the time the key had made a complete circuit. There was considerable ingenuity in the idea of this lock; but we believe it never went further than a model. Indeed many of the locks elaborately described in books have never had an existence as acting working locks.

A very ingenious principle has been occasionally introduced, in which clock-work regulates the interval of time which must elapse before a lock can be opened, even with its proper key. The object is, to ensure the safety of the lock during a journey, or until a particular person be present, or until the locked article is conveyed to a particular room. A patent was taken out in 1831 for a lock on this principle by Mr. Rutherford, a bank agent at Jedburgh. Against the end of the bolt of the lock is placed a circular stop-plate, so adjusted that the bolt cannot be withdrawn until a particular notch in the rim of the circular plate is opposite the end of the bolt. The plate is put in rotation by clock-work. As the notch can be set at pleasure to any required distance from the end of the bolt, the lock may be secured against being opened, either by its own or any other key, until any assigned number of minutes or hours after it has been locked; for the plate may be made to revolve either slowly or quickly, by varying the number of wheels in the clockwork. When the lock is used for boxes or portable packages, the clockwork must be moved and regulated by a spring; but when it is applied to closets or safes, a descending weight and a pendulum may be employed. It is manifest that this system is susceptible of being greatly varied in its mode of application; and it has many points of interest about it. That a man cannot open his own lock with his own proper key, until the lock gives permission by assuming a particular state or condition, certainly strikes one as being susceptible of many useful applications, where time is an element taken into the account.

A curious alarum-lock was invented by Mr. Meighan, in 1836, in which the bell or alarum is not placed behind a door, as in many alarum contrivances, but within the lock itself. Two or more studs are placed on the bolt, which press against the lower end of a small tumbler; the movement of the tumbler elevates a hammer; but as soon as the point of the tumbler becomes released from the stud, a spring presses the hammer down forcibly, and causes it to strike against a small bell placed near it. This sounding of the bell will be repeated, during the shutting of the bolt, as many times as there are studs to act upon the point of the tumbler.

Much of the ingenuity which has been displayed in locks depends on the employment of multiple bolts, there being all the additional strength which results from the use of two or more bolts instead of simply one. Ordinary doors seldom afford us examples of these double bolts; but they may be frequently seen in cabinets and desks, where two staples fixed to the lid fall into two holes in the lock, and are retained by two bolts. The most remarkable and complicated varieties, however, are those in which the bolts, instead of shooting parallel and nearly together, shoot in wholly different ways; one up, one down, one to the right, one to the left, and so on. It is on safes, strong boxes, and the doors of strong rooms containing valuable treasures, that such locks are usually placed. The mechanism is such that the key acts upon all the bolts at once, through the intervention of levers and springs of various kinds.

fig. 16. Multiple bolts of an old chest-lock.

The above [woodcut] represents a very curious specimen of these multiple-bolt locks. It is copied from the great French work; and the ponderous chest to which it is attached is, we are told by Réaumur, “known at Paris by the name of the strong German coffer.” He further says, “nothing is wanting in these coffers on the score of solidity. They are made entirely of iron; or if of wood, they are banded both within and without with iron; and can only be broken open by very great violence. Their locks are almost as large as the top of the coffer, and close with a great number of bolts. The one which we have engraved has twelve fastenings; they have been made with twenty-four, or more.” His next remark on the subject is a sensible one: “Notwithstanding the large size of these locks, and all the apparatus with which they are provided, they correspond but ill with the solidity of the rest of the coffer. If we have given a representation of one, it is chiefly to shew how little confidence one could have in such a lock, and what are its defects, in order that we may avoid them.” It is not difficult, by tracing the action of the several levers, to see how one movement of the key, in the centre of the lid, would act upon all the bolts. In the engraving ([fig. 16]) a, f, h, c, are the four corner bolts; six others, a d e, a d e, are on the long sides, three on each; and two, b g, on the short sides. Every bolt is provided with a spring, of which three or four are shewn at Z Z Z. There is no staple or box to receive each bolt; but all shoot or snap beneath the raised edge E running round the top of the box just within the exterior at A A. The keyhole in the front of the box at D is a deception or mask; the real keyhole is in the middle of the lid concealed by a secret door opened by a spring. When the key has moved the great central bolt, this acts upon the other bolts P Q R S T, &c.; V V are studs which act upon two of the bolts; Y Y are staples confining the great bolt; k, l, c, p, x, are small levers which transmit the action to the corner bolts; q, r, s, t, n, are the small levers which render a similar service to the side and end bolts; L L within the chest, and M M on the lid, are contrivances for limiting the movement of the latter; C H, H C are iron straps or bands by which the interior of the chest is strengthened. After all, this is not so much a lock as a series of spring latches.

If a lock can be picked, the picking is as effective whether the lock has one bolt or twelve bolts. This fact led Mr. Duce, in 1824, to construct, instead of a four-bolt lock, four distinct one-bolt locks, fixed in the same frame and opened by the same key; the bolts to be moved in succession instead of simultaneously. It would require four times as long to pick this as a four-bolt lock of similar action.

There have been many other varieties of the multiple bolt, but we need not stop to describe them.

CHAPTER V.
ON TUMBLER, OR LEVER LOCKS.

Security being the primary object in all locks, any considerations as to mechanical ingenuity and graceful decoration give place to those which relate to safety. A spring lock may be ingenious and even beautiful in its construction, but an imitative key will easily open it. Hence arose the invention of wheels or wards; and as wards failed in trustworthiness, they in their turn yielded to something better. We have already explained how the insecurity of mere warded locks arises; and we shall have something more to say on the subject in a future chapter. It is sufficient here to remark, that wards, springs, screws, alarums, wheel-work, escutcheons,—all, however useful for particular purposes, are wanting in the degree of surety which we require in a lock. Hence the invention of tumblers, levers, or latches, which fall into the bolt and prevent it from being shot until they have been raised or released by the action of the key. We have been unable to ascertain at what time, or in what country, or by whom, tumbler-locks were invented. The invention has been claimed by or for persons subsequently to the year 1767, when the celebrated French treatise (Art du Serrurier) already referred to was published; and yet this treatise contains numerous examples of simple tumbler locks of ingenious construction, as will presently be shewn.

fig. 17. Simple tumbler lock.

One of the most elementary forms of tumbler-lock is shewn in [fig. 17]. In this case the bolt, instead of having two notches in the bottom edge, like those in the back-spring lock, [fig. 6], has two square notches or slots in the upper edge; and as the key acts upon the bolt, these notches must of course share in whatever movements the bolt is subjected to. Behind the bolt is a kind of latch or tumbler (the lower part of which is shewn by dotted lines), with a stump or projecting piece of metal at a; the tumbler moves freely on a pivot at the other end, and is made to rise through a small arc whenever the key acts upon the bolt. When the bolt is wholly shot, the stump falls into one notch and prevents the motion of the bolt; when wholly unshot or withdrawn, the stump falls into the other notch, and equally prevents the motion of the bolt. It is not, therefore, until the key, by elevating the tumbler, has raised the stump out of the notch, that the bolt has freedom of movement. If the shape of the key does not enable its web to effect this elevation to a sufficient degree, the bolt remains immovable; and to this extent a certain additional security is obtained by making the shape of the key significant as well as the wards.

fig. 18.

fig. 19. Old French lock.

The tumbler-principle, as we have said, is difficult to trace to its origin on account of the various aspects which it presents; but the great French treatise proves that the locksmiths of France were familiar with tumbler-locks a century ago. The plates of that work represent the details of numerous locks, on the upper edge of the bolts of which were notches called encoches, as at o k [fig. 18]; into these notches sank a small iron stud or stump called the arrêt du pêne, or bolt-stop, shewn in [fig. 19], attached to the upper portion of the gâchette or tumbler, which, for the sake of economy of metal, is made in the form of a triangular spring in front of the bolt k i; and not until the key, by its circular action, had raised this stud out of one or other of the notches, could the bolt move to the right or left. The stud was generally fixed to a spring which forced it down again into the notch as soon as the action of the key had ceased. Sometimes, however, the stud was fixed to the bolt, and the notches were in a separate tumbler or gâchette (see E E, [fig. 21]); and in other instances, again, the stump was fixed to the case of the lock and caught into notches in the bolt. It will be seen, when we come to treat of tumbler-locks of later date, that there was much in these early locks to point out the way. [Fig. 19], copied from the French work, represents a lock of the box or casket kind. Two staples, fixed into the cover, fall into two cavities or receptacles at C d; and a short bolt in each receptacle catches into each staple, one near g and one near h. The small bolt q is attached to the upper extremity of the lever q r s, [fig. 19], and shewn separately in [fig. 20]; and by the pressure of a spring a ([fig. 19]) upon this lever, the bolt q is kept locked in the staple. The vertical portion of this spring presses at its lower end on another spring p ([fig. 19]) of singular curvature; and attached to the horizontal part of this second spring is the stud, which falls into a notch in the top of the bolt. The action of these parts, then, is as follows: when the key is placed upon the key-pin at Z, and turned round in the direction in which the hands of a watch move, the bitt presses against the tail s of the lever, moves it upon its centre Z, [fig. 19], v, [fig. 20], to the left, and consequently moves the upper part q to the right, drawing it out of the receptacle and liberating the staple within C. Thus it will be seen that the lever q r s, held in one position by the spring a, forms in itself a simple kind of spring catch-lock, and was, in fact, formerly used as such, without any other appendages except the staple in the lever, into which the catch q fitted on shutting down the lid. So also we may regard the other portion, [fig. 18], or k i p h ([fig. 19]), as forming a separate lock; for the key after having passed S comes in contact with the triangular spring, which it raises thereby, lifting the stud out of the bolt, and exerting pressure against the barbs of the bolt n. [Fig. 18] shoots the bolt k, and also the short bolt l, which passes through the staple in the cavity d, [fig. 19].

fig. 20.

The lock represented in the four following figures is also from M. de Réaumur’s chapter on locks in the work referred to. In this lock the tumbler-principle is carried out in a very elaborate manner, for not only is the stump or stud H ([fig. 23]) attached to a very strong spring (best shewn at H, [fig. 22]), which holds it with considerable force in one of the three notches of the principal bolt R S ([fig. 24]); but there is also a second set of notches E E in the gâchette G O ([fig. 21]), and a pin attached to one of the plates of the lock fits into one of these notches, thereby preventing the bolt from being moved until the gâchette is lowered by the revolution of the key; so that in attempting to pick this lock, not only must the spring H be raised so as to release the stud from the notches of the great bolt, but the gâchette must be lowered to disengage the fixed pin from the notches. There is yet a third source of security. Attached to the large bolt are short projecting pins F ([fig. 21]), against which an arm or detent, G F, of the gâchette projects, thus preventing the bolt from being shot back by any pressure applied to its extremity S.

fig. 21. Details of an old French lock.

fig. 22. Another view of the same.

fig. 23. Another view of the same.

fig. 24. The two bolts detached.

There are a few details relating to this remarkable lock, which may as well be introduced here in order to complete the description. The principal bolt can be shot twice, or be double-locked; hence it is furnished with three barbs for the key to act against, and with three notches for the spring-stud. The lower bolt I K can be shot by the horizontal pressure of the button P ([figs. 22], [23]), which is situated on the inner side of the door to which this lock is attached, so that a person inside the room can secure the door against any one on the outside who is not furnished with the proper key, for it must be remarked that the small bolt as well as the large one is acted on by the key. Now supposing the small bolt to be shot or locked, it is kept so by the pressure of the coiled spring Q ([figs. 21], [22]). But this small bolt is connected with the large one by means of the bent lever O N M ([figs. 21], [24]), which turns on a pin N attached to the main bolt. Now, when both bolts are either fully shot or unshot, the arm O N lies flat against and parallel with the main bolt; but when the large bolt is unshot and the small one not moved, the arms O N, N M, fall into an inclined position, and the arm O N passing a little below the main bolt comes within the range of the web of the key, which in its revolution causes the bent lever to move upon its centre N, thereby restoring O N to its horizontal position, and at the same time causing the arm N M to move from right to left, or in the direction for unshooting the small bolt; the end of this arm thus catches into a mortise V ([figs. 21], [24]) in the small bolt, and immediately unlocks it.

But to return to the subject of tumbler-locks. About the year 1778, Mr. Barron introduced that species of double-action (as it may perhaps be termed) which so greatly increases the security of the simple tumbler, [fig. 17]. In the tumbler-locks previously made, if the tumbler were raised sufficiently high, the lock could be opened: there was no such possibility as raising it too high; but Mr. Barron, by his invention, patented 31st October, 1778, rendered it absolutely necessary that a limit should be put to the height to which the tumbler should be raised, by rendering the bolt equally immovable whether the tumbler were too much or too little raised. Another important improvement was the introduction of two tumblers instead of one. The bolt has in its middle a slot or gating notched on both edges, the notches being fitted for the reception of studs fixed to the tumblers. Supposing the studs or stumps of the tumblers to be resting in the lower notches, they require to be elevated to the general level of the gating before the bolt can be moved; whereas, on the other hand, if the tumblers were raised ever so little too high, the studs will enter the upper notches, and prevent the shooting of the bolt. The lower edge, or belly, of each tumbler is acted on by the steps of the key during its circular movement; the leverage of the key being so exactly adjusted as to raise the tumbler to the desired height and no further. The tumblers are made unequally wide, so that steps or inequalities in the bit of the key are requisite to lift them both to the proper height. There are thus two improvements introduced: there are two tumblers instead of one, and each tumbler has a double instead of a single action.

This ingenious and very useful lock is represented, so far as regards its governing principle, in [fig. 25]. The bolt is here seen to have a peculiar slot or hole cut in it, consisting of a narrow horizontal passage or gating, with three notches above it and three below it. These double notches might be available even for one tumbler only; but Barron used two or more for the sake of additional security. In [fig. 25] there are two tumblers shewn, expressed by dotted lines; both are hinged to one pivot, both are raised by the same action of the key, but the stump on the one tumbler does not coincide in position with that on the other. It will be seen that if the studs of the tumblers rested in the lower notches, they would require to be elevated to the level of the gating before the bolt could be moved; while, on the other hand, if lifted too high, the stumps would be caught in the upper notches, and would equally prevent the passage of the bolt, The tumblers are unequally wide; and the bitt of the key is stepped or notched in a corresponding way, that there may be one step fitted to act upon each tumbler. Mr. Barron also adopted the reverse arrangement of having the stump on the bolt, and the openings in the tumblers; so that the principle of his patent may be concisely expressed as being “an arrangement to allow a stump on the tumbler to pass through an opening in the bolt, or a stump on the bolt to pass through an opening in the tumbler.”

fig. 25. Action of Barron’s tumbler-lock.

A very elaborate tumbler-lock, patented 23d February, 1790, by Mr. Rowntree, contrasts remarkably with the simplicity of Barron’s lock. Mr. Rowntree’s lock consisted of tumblers combined with revolving discs or wheels. Its mechanism may be understood from the following description and engravings. The same letters refer to the same parts in the several figures.

fig. 26.

fig. 28.

fig. 27.

fig. 29.

fig. 30.

Details of Rowntree’s tumbler-lock.

A A is the plate which encloses the whole mechanism of the lock, and fastens it to the door; B B is the bolt, guided in its motion by sliding under the bridges C D; E E are pillars which support a plate covering the works; F are the circular wards surrounding the centre or key-pin; and a shews the position of the key, which, in turning round, acts in a notch r in the bolt, and propels it; G, the tumbler, is a plate situated beneath the bolt, and moving on a centre-pin at d; it has a catch or stump e projecting upwards, which enters the notches s or g in the bolt, and thereby retains the latter for backward or forward motion, as the case may be; H is a spring which presses the tumbler forward. The key a, in turning round, acts first against the part c c of the tumbler, and raises it so as to remove the stump from the notches; it can then enter the notch r in the bolt, and move it. So far there is no particular security; but Mr. Rowntree sought to obtain it by the following means. There is a piece of metal h fixed to the lower side of the tumbler, called the pin; when the tumbler is caught in either notch of the bolt, the pin applies itself to a cluster of small wheels I, fitted on one centre-pin beneath the tumbler; the edges of these wheels stop the pin, and prevent the tumbler from being raised. But each wheel has a notch cut in its circumference I; and it is only when the wheels are so placed that all their notches lie in a right line, that the pin can enter this compound notch and allow the tumbler to rise. The wheels must therefore be all adjusted to position; and this is effected by a number of levers K centred on one pin at k; at the opposite end each lever has a tooth m entering a notch in the wheel belonging to it; so that when any lever is pressed outward, it turns its wheel round. Now this pressure of the levers is brought about by a spring n applied to each; and when so pressed, the levers rest against a pin o fixed in the plate. The key is so cut as to determine the extent to which the levers shall act upon the wheels. The key first operates from the curved part p p of the levers K, and raising them, turns all the wheels I at once into the proper positions; in turning further round, it then operates on the part c c of the tumbler, causing the latter to rise and to release the bolt; and in turning still further round, it (the key) seizes the notch r of the bolt, and shoots it. The key is cut into steps of different lengths, as shewn at V V; each step operates on its respective lever K in a different degree from the others; the notch at s acts upon the tumbler, and the plain part t moves the bolt.

We now proceed to notice the modern tumbler-lock. This was arranged by Bird, whose patent, bearing date 29th October, 1790, was for a series of four double-acting tumblers, differing in no respect from those patented by Barron, and closely resembling those in use at the present time in the best tumbler-locks. We will describe the modern tumbler-lock more particularly when we have gone through a few historical details on the subject.

Messrs. Mitchell and Lawton obtained a patent bearing date 7th March, 1815, for a lock in which were combined with the bolt and double-acting tumblers, a series of movable wards, and a revolving curtain for closing the key-hole. The action of the wards was peculiar. On introducing any key or instrument, and passing it round, a number of movable wards or pieces were thrown out so as to prevent the key from being turned back or withdrawn. It was necessary therefore to pass round the key so as to unlock the lock, and if that were not possible, as in the case of a false key being used, it was held permanently, and could only be released by destroying the lock, When the bolt was once shot, the wards were carried up so as to leave a clear passage for the key. This lock does not appear ever to have come into use, on account of the violence required in case a wrong key should be used either by accident or design.

The detention of a wrong key in this lock appears to have suggested the contrivance of a detector. This was first made by Ruxton, whose patent is dated 14th May, 1816. His detectors were of various kinds, the object of each kind being to give information to the owner in case any one of the tumblers should be overlifted in an attempt to pick the lock, which fact would be discovered on the next application of the true key. This is precisely the object of the detector in tumbler-locks at the present day, and Ruxton accomplished it by somewhat similar means. He also had a contrivance for holding a false key, as in Mitchell and Lawton’s lock; and he recommended this form of detector in the following words: “It is true that in this case the lock will have to be destroyed in order to open the door: the result is frightful; but we think the more terrible the result, the less likely would any one be to tamper with it.”

We now come to Chubb’s lock, patented 3d February, 1818, which consisted of double-acting tumblers and a peculiar kind of detector. This lock has been made the subject of various patents obtained in the years 1824, 1833, 1846, and 1847. This lock[4] consists of six separate and distinct double-acting tumblers, all of which must be raised to a particular height, neither more nor less, in order that the bolt may pass. It also comprises a detector, by which, should any one of the tumblers be lifted too high in an attempt to pick or open the lock by a false key, it would be immediately detected on the next application of the proper key. The tumblers are flat pieces of iron or steel, with the plane of the surface vertical, and pivoted at one end; and the following is the mode in which the key, the tumblers, and the bolt, are brought into mutual action.

[4] The lock about to be described is the latest and most complete form of Chubb lock up to the date of the Great Exhibition. The various additions and alterations which have been made in the lock since that date will be noticed in a subsequent chapter.

The bolt shoots in and out of the lock in the usual way. It has a square stud or stump riveted on one surface; and it is to furnish obstructions to the passage of this stud that the tumblers are provided. All the six tumblers are pivoted to one pin at the end, giving to each of them a small leverage, each independent of the others. There are six springs which press these tumblers downwards, one to each tumbler. There is a longitudinal slot or gating in each tumbler, large enough to receive the stud of the bolt; and unless all the six slots (supposing there to be six tumblers) coincide in height or position, the stud will not have a clear passage for moving to and fro. Now the slots are purposely made nearer the upper edge in some of the tumblers than in others, all the six being different in this respect; so that if they are all lifted equally, the slots do not coincide, and the bolt and its stud will not pass. The tumblers must then be raised unequally, those to be most raised which have the slot nearest to the lower edge. To effect this, the bit of the key is cut into six steps or inequalities, each to act upon one particular tumbler, and each cut or stepped to the exact depth which will suffice for the proper raising of the tumbler. The key is inserted in the keyhole, and is turned; the six steps raise the six tumblers all to the proper height, to leave a clear passage along the slots; and the extreme end of the key then acts upon the bolt itself, and shoots it. To unlock it again, the same or a duplicate key must be used; for if another key be employed, differing by ever so little from the proper one, some one or more of the tumblers will be lifted either a little too much or not quite enough; and in either case the stud of the bolt will catch above or below the slot, instead of having a clear line of movement along the slot itself. After both locking and unlocking, the springs force the tumblers down as far as they can go, burying the stud in the recesses above the slot; so that the tumblers must be raised by the key both for locking and unlocking.

The doctrine of chances has wide play in determining the relative position of the six tumblers. In Mr. Chubb’s essay this part of the subject is treated in the following way: “The number of changes which may be effected on the keys of a three-inch drawer-lock is 1 × 2 × 3 × 4 × 5 × 6 = 720, the number of different combinations which may be made on the six steps of unequal lengths (on a six-tumbler lock), without altering the length of either step. The height of the shortest step is, however, capable of being reduced 20 times; and each time of being reduced, the 720 combinations may be repeated; therefore 720 × 20 = 14,400 changes. The same process, after reducing the shortest step as much as possible, may be gone through with each of the other five steps; therefore 14,400 × 6 = 86,400, which is the number of changes that can be produced on the six steps. If, however, the seventh step, which throws the bolt, be taken into account, the reduction of it only ten times would give 86,400 × 10 = 864,000, as the number of changes on locks with the keys all of one size (that is, with one key of definite size in all save the lengths of the steps). Moreover, the drill pins of the locks and the pipes of the keys may be easily made of three different sizes; and the number of changes will then be 864,000 × 3 = 2,592,000, as the whole series of changes which may be gone through with this key. In smaller keys, the steps of which are capable of being reduced only ten times, and the bolt-step only five times, the number of combinations will be 720 × 10 × 6 × 5 × 3 = 648,000. On the other hand, in larger keys, the steps of which can be reduced thirty times, and the bolt-step twenty times, the total number of combinations will be 720 × 30 × 6 × 20 × 3 = 7,776,000.”

These enormous numbers have been the cause of much of the wonderment which the six-tumbler locks have excited; and, as we shall see further on, the Bramah lock presents still more of the marvellous in respect to this ringing of the changes.

fig. 31. Chubb lock, with detector and six tumblers.

The construction and action of the Chubb lock may be further illustrated by means of an engraving, [fig. 31], in which b is the bolt of the lock, with a stump riveted to it marked s. The six tumblers are shewn perspectively, the front or anterior one being marked t; they all move on the centre-pin a, but are nevertheless perfectly distinct and separate, to allow of being elevated to different heights. At d is shewn one end of a divided spring, the divisions being equal to the number of tumblers, one to each, and so bent that each spring may press upon its particular tumbler. At e is the detector-spring, so placed that a projecting piece in the hindmost tumbler shall be near it; this tumbler having also fixed into it a stud or pin p. This being the arrangement, especially in relation to the stump s and the tumblers, it follows that all the tumblers must be lifted to exact and regulated heights in order that the stump may pass through the longitudinal slits of the tumblers; unless it can do so, the bolt cannot be withdrawn. As there are gaps or notches in each tumbler both above and below the proper line of passage, and as there are no ordinary means of ascertaining when any one tumbler is lifted too high or not high enough, the safety of the lock is greatly increased by this uncertainty; especially when it is considered that this uncertainty is multiplied sixfold by the different modes in which the six tumblers are slotted. If, through the insertion of a false key, or by any other cause, any one of the tumblers be raised above its proper position, the detector spring e will catch the hindmost tumbler, and retain it so as to prevent the bolt from passing; and thus, upon the next application of the true key, it will be instantly felt that some one of the tumblers has been overlifted, because the true key will not unlock it. To relieve the bolt from this temporary imprisonment, the key must be turned the reverse way, as for locking; all the tumblers will thus be brought to their proper position, and allow the stump to enter the notches n n´; the bevelled part of the bolt will then lift up the detector-spring, and allow the hindmost tumbler to fall down into its proper place; and all this being effected, the lock may be opened and shut in the ordinary way. The pin p is so adjusted that if any one of the tumblers—front, back, or intermediate—be lifted too high, the pin will be lifted with it, and will catch into the detector-spring, thus producing the result just described.

fig. 32.
Key to Chubb’s lock.

The key is represented in [fig. 32]. It has six steps, besides a terminal step to act upon the bolt. The height of each step, or the distance to which it extends from the pipe of the key, depends of course on the height to which its corresponding tumbler is to be lifted; and it matters not whether the steps of the key are adjusted to the slots of the tumblers, or the slots to the steps, provided the agreement be brought about. It is simply a matter of manufacturing convenience that the key-steps are cut first and the tumbler-slots afterwards. We may here remark that bit, or bitt, is the name given, somewhat indefinitely, either to the whole flat part of a key, or to the small stepped portions of it. The flat part was formerly termed the web of the key, probably from the webbed appearance of the keys to complex warded locks.

After the reading of Mr. Chubb’s paper before the Institution of Civil Engineers, Mr. Owen narrated one or two circumstances connected with the early history of Chubb’s lock. A convict on board one of the prison-ships at Portsmouth dockyard, who was by profession a lock-maker, and who had been employed in London in making and repairing locks for several years, and subsequently had been notorious for picking locks, asserted that he had picked with ease one of the best of Bramah’s locks, and that he could pick Chubb’s locks with equal facility. One of the latter was secured by the seals of the late Sir George Grey, the Commissioner, and some of the principal officers of the dockyard, and given to the convict, together with files and all the tools which he stated were necessary for preparing false instruments for the purpose, as also blank keys to fit the pin of the lock. A lock exactly the same in principle was placed in his hands, that he might examine it and make himself master of its construction. If he succeeded in opening the lock, he was to receive a free pardon from the Government, and a reward of 100l. from Messrs. Chubb. After trying for two or three months to pick the sealed lock—during which time, by his repeated efforts, he frequently over-lifted the detector, which was as often re-adjusted for his subsequent trials—he gave up the attempt. He stated that Chubb’s were the most secure locks he had ever met with, and that it was impossible for any man to pick or to open them with false instruments.

Mr. Owen further stated, that in order to compare the merits of Bramah’s and Chubb’s locks, he had suggested a mechanical contrivance, which was applied to one of Bramah’s six-spring padlocks belonging to the Excise. It was hung upon a nail, in a vertical position, secure from lateral oscillation. A self-acting apparatus was then applied, consisting of a pipe with hexagonal grooves, and a stud or bit corresponding with the division of the lock, and secured to it by a spring. In the grooves of this pipe small slides were inserted, which pressed against the spring keys of the lock; to these slides were attached levers, acted upon by eccentrics, moved by a combination of wheels, whose teeth differed in number so as to perform the permutation required for the different depths of the spring keys, corresponding with those of the proper key to the lock. The automaton machine was set in motion by a line working over a barrel, and acted upon by a weight; and was thus left acting upon the mechanism for a considerable time. At right angles to the pipe or false key was attached a rod and weight; and when the notches in the spring keys were brought in a line with the plane of the plate or diaphragm of the lock, the rod and weight turned the false key, opened the lock, and stopped the further motion of the automaton. In that state the slides indicated the exact depth of the grooves in the proper key, and gave the form of a matrix by which to make a key similar to the original one. The automaton worked during a period varying from half an hour to three hours, according to the state of permutation of the apparatus at the moment of being applied, compared with that of the slides in the lock. We confess that it is difficult to understand the action of this automaton from Mr. Owen’s description. We imagine that the false notches would effectually prevent the operation of the instrument, and openings would be required on each slide to bring it back, so as to meet the motions of the machine.

Mr. Owen did not state whether his apparatus had been successful with one only of Bramah’s locks or with several; nor did he describe any apparatus invented with the view to the picking of Chubb’s locks. He stated, however, that in order to ascertain the effect of friction on one of these last-named locks, it was subjected to the alternate rectilinear motion of a steam-engine in Portsmouth dockyard, and was locked and unlocked upwards of 460,000 times consecutively, without any appreciable wear being indicated by a gauge applied to the levers and the key, both before and after this alternate action. Mr. Owen concluded by expressing his individual opinion that Chubb’s lock had never been picked. “The detector was the main feature of its excellence; and additional precaution, therefore, was only departing from its simplicity, and adding to the expense, without any commensurate advantage.”

In a subsequent chapter the degree of security afforded by various descriptions of locks, and the obstacles which they present of being picked, will come under notice; we therefore now proceed to describe briefly a few other tumbler-locks, or application of the tumbler-principle.

In Mr. Somerford’s lock, for which the Society of Arts gave a premium in 1818, an attempt was made to improve upon the ordinary action of tumblers. In most such locks, all the tumblers must ascend, although to different heights, before the stud of the bolt can pass through the slots; “which arrangement,” says Mr. Somerford, “gives an opportunity of introducing a nail, or a piece of stout wire, into the lock, and thus raising the tumblers without the necessity of using the key.” In his new lock, however, he made one lever to ascend while the other descended, by a somewhat complicated arrangement of slotted plates above and below the bolt. The key was so perforated as to be much endangered in respect to strength.

In Davis’s lock there is a double chamber with wards on the side of the key-hole. The key is inserted into the first chamber and turned a quarter round; it is then pushed forward into the inner chamber, where there is a rotating plate containing a series of small pins or studs, which are laid hold of by the key. By turning the key, the plate is moved round, the tumbler is raised, and the bolt is shot backwards and forwards. This lock, which is somewhat expensive, is used to some extent on Cabinet despatch-boxes.

The lock invented by Mr. Nettlefold is so constructed, that when the bolt is shot out by the key, two teeth or quadrants are projected from the sides of the bolt, which take a firm hold of the plate fixed on the door-post or edge. This construction is said to answer well for sliding-doors.

Mr. Alfred Ainger, in 1820, received a silver medal from the Society of Arts for a draw-back spring latch, in which the objects proposed were the two following—to render the lock more difficult of violation by a pick than those ordinarily in use; and to apply to it a key of which no ordinary person could take an impress, and which would be difficult of access even in a workman’s hand. The key is very peculiar; its pipe consists of three divisions, the section of the upper and lower divisions being circular, and that of the middle division triangular; the triangular portion is intended to give motion to some part of the interior of the lock during the rotation of the key. There are collars fixed on the extremity of the key, to act each on one tumbler; and there are modes, by varying the arrangement of these collars on an octagonal stem, to give something like a permutation to the number of variations to which the action of the key may be subject. The notches or slots are rather in the bolt than in the tumblers; and there are many peculiarities in the general arrangement.

In a lock invented and patented by Mr. Parsons, the tumblers are of a particular form, being hinged on a pivot at their centres, and working into and out of two notches cut in the under side of the bolt. It must be obvious that many variations in the adjustment of the tumblers of locks might be made, without vitiating the principle on which the action depends.

Many inventors have tried the use of an expanding web to the key, so planned that if the step of the web be long enough to reach the tumbler, it would be too long to pass through the key-hole; and therefore a principle of safety would operate by enabling the key to adjust itself at one moment to the size of the key-hole, and at another to the height of the tumbler. Mr. Machin of Wolverhampton invented such a key in 1827. The web of the key is movable on a countersunk pin, on which it can so far slide as to be drawn one-eighth of an inch from the barrel. The key-hole is of such a size as to admit the key only when the web is pressed close up to the barrel. When the key in this state is introduced, and is begun to be turned round, one of the notches in the web works into a raised circular edge of steel, placed eccentrically with regard to the lock-pin; so that as the key is turned, the web becomes drawn out, and is at its greatest elongation when it arrives at the tumblers: in the second half of its circular movement, the key becomes contracted to its original dimensions, and can then be removed from the lock.

Another mode of modifying the key has been introduced by Mr. Mackinnon, the object being to enable any person to change at will the pattern or arrangement of the movable parts of a lock and key; or to keep the key, when not actually in use, in such a state as to render it unavailing to any one but himself. It was a complex arrangement, which does not seem to have come much into use.

The lock invented by Mr. Williams, in 1839, may be designated a pin-lock, involving a principle analogous in many points to that of the Egyptian lock. This lock has a series of pins which reach through the cap, and are pressed to their places with a key like a comb or a rake-head. On the inner end of each pin is a flat piece of steel, in which is cut a notch for the passage of the bolt; but this passage is not clear until the notches in all the pieces of steel are in a right line. The pins are movable, and can be pushed either too far or not far enough to bring about the coincidence of position in the notches; and on this ground they are “double-acting.” Now the teeth of the key are of irregular lengths, each having a length just suited for pushing the pin to the proper depth: any other lengths of teeth would fail to open the lock. There is a mechanism of springs and levers to shoot the bolt when the pins in the plate are rightly adjusted. The arrangements in respect to the key are singular and somewhat awkward. The teeth which lock the bolt are not the same as those which unlock it, the user having to change ends and adjust the bit to a socket-handle. This is one among many examples in which a lock embodies several principles, the inventor having set himself the task of combining the excellences of many diverse locks.

In respect to the tumbler-locks generally, the simplicity of action, the strength of construction, and the non-liability of disarrangement, have given them a high place among safety-locks. The only danger seemed to be, that any person once obtaining possession of the key could take an impression from it, and thence form a key which would command the lock. Attempts have been occasionally made to obviate this danger, by supplying the key with movable bits which could be changed at pleasure, so as to constitute any number of effectively different bits in succession. But the locks being so constructed that the bolt could only be moved when the tumblers were in a certain position, the owner was placed in this predicament: that it was useless to alter the arrangement of the bits in the key, unless the tumblers were altered in a corresponding manner; and this would entail the removal of the lock from the door, and the re-arrangement of the interior mechanism.

One of the great defects of tumbler-locks made previously to the last ten years was, that the tumblers, when lying at rest in the lock, presented at their bellies or lower edges precisely the same arrangement as the steps of the key. Indeed, in many locks of the present day, a good idea of the form of the key may be gained by feeling the bellies of the tumblers. The bellies are in fact cut out so as to compensate for the circular motion of the key, to allow them to remain at rest while the stump is passing through the gating. Even in tumbler-locks of the best construction the tumblers will vibrate more or less during the motion of the key; a defect which must be provided against in adjusting the lock, or the stump will be caught in its passage through the gating. Mr. Hobbs provides a simple remedy by enlarging the back part of the gating, the effect of which is as follows: when, in shooting back the bolt, as in unlocking, the key has got to its highest point, the stump enters the narrow end of the gating; but in shooting the bolt forward, as in locking, the stump enters the gating before the key has got to its highest point, and to allow for the slight vibratory motion of the tumblers during the passage of the stump, the gating is widened. The usual method of adjustment is to alter the forms of the bellies of the tumblers, thus greatly risking the security of the lock, a defect which was clearly perceived by Bramah [see [pp. 67]-[70]], and was one of the reasons which induced him to construct locks with slides instead of tumblers.

American locks on the tumbler-principle, and the relation which all such locks bear to the Bramah lock, will be better understood after the details of the following chapter.

CHAPTER VI.
THE BRAMAH LOCK.

The lock which was invented by the late Mr. Bramah deservedly occupies a high place among this class of contrivances. It differs very materially from all which has gone before it; its mechanical construction is accurate and beautiful; its key is remarkable for smallness of size; and the invention was introduced by the publication of an essay containing much sensible observation on locks generally. The full title of this essay runs thus: “A dissertation on the Construction of Locks. Containing, first, reasons and observations, demonstrating all locks which depend upon fixed wards to be erroneous in principle, and defective in point of security. Secondly, a specification of a lock, constructed on a new and infallible principle, which, possessing all the properties essential to security, will prevent the most ruinous consequences of house-robberies, and be a certain protection against thieves of all descriptions.” A second edition of this Dissertation was published in 1815; but the work is now extremely scarce, and hardly attainable.

It is remarkable to observe the boldness and self-relying confidence with which Mr. Bramah, some sixty years ago, declared that all locks were, up to that time, violable; he felt that this was strictly true, and he hesitated not to give expression to his conviction. The following is from his Dissertation:—

“It is observable that those who are taken in the desperate occupation of house-breaking are always furnished with a number and variety of keys or other instruments adapted to the purpose of picking or opening locks; and it needs no argument to prove that these implements must be essential to the execution of their intentions. For unless they can secure access to the portable and most valuable part of the effects, which in most families are deposited under the imaginary security of locks, the plunder would seldom recompense the difficulty and hazard of the enterprise; and till some method of security be adopted by which such keys and instruments may be rendered useless, no effectual check or opposition can be given to the excessive and alarming practice of house-breaking.

“Being confident that I have contrived a security which no instrument but its proper key can reach; and which may be so applied as not only to defy the art and ingenuity of the most skilful workman, but to render the utmost force ineffectual, and thereby to secure what is most valued as well from dishonest servants as from the midnight ruffian, I think myself at liberty to declare (what nothing but the discovery of an infallible remedy would justify my disclosing), that all dependence on the inviolable security of locks, even of those which are constructed on the best principle of any in general use, is fallacious. To demonstrate this bold and alarming proposition, I shall first state the common principles which are applied in the art of lock-making; and by describing their operation in instruments differently constructed, prove to my intelligent readers that the best-constructed locks are liable to be secretly opened with great facility; and that the locks in common use are calculated only to induce a false confidence in their effect, and to throw temptation to dishonesty in the way of those who are acquainted with their imperfections, and know their inefficacy to the purpose of security” (p. 5).

Tumblers had been so little thought of and used at the time Bramah wrote, that his attention was almost exclusively directed to warded locks. The mysterious clefts in a key, connected with some kind of secret mechanism in the lock, had given the warded locks a great hold on the public mind, as models of puzzlement and security; and it was to shew that this confidence rested on a false basis, that he to a great extent laboured. The following is his exposition of the principle and the defects of the warded lock.

“Locks have been constructed, and are at present much used and held in great esteem, from which the picklock is effectually excluded; but the admission of false keys is an imperfection for which no locksmith has ever found a corrective; nor can this imperfection be remedied whilst the protection of the bolt is wholly confided to fixed wards. For if a lock of any given size be furnished with wards in as curious and complete a manner as it can be, those wards being necessarily expressed on what is termed by locksmiths the bit or web of the key, do not admit of a greater number of variations than can be expressed on that bit or web; when, therefore, as many locks have been completed of the given size as will include all the variations which the surface of the bit will contain, every future lock must be the counterpart of some former one, and the same key which opens the one will of course unlock the other. It hence follows that every lock which shall be fabricated on this given scale, beyond the number at which the capability of variation ends, must be as subject to the key of some other lock as to its own; and both become less secure as their counterparts become more numerous. This objection is confirmed by a reference to the locks commonly fixed on drawers and bureaus, in which the variations are few, and these so frequently repeated, from the infinite demand for such locks, that, even if it were formed to resist the picklock, they would be liable to be opened by ten thousand correspondent keys. And the same observation applies in a greater or less degree to every lock in which the variations are not endless.

“But if the variation of locks in which the bolt is guarded only by fixed wards could be multiplied to infinity, they would afford no security against the efforts of an ingenious locksmith; for though an artful and judicious arrangement of the wards, or other impediments, may render the passage to the bolt so intricate and perplexed as to exclude every instrument but its proper key, a skilful workman having access to the entrance will be at no loss to fabricate a key which shall tally as perfectly with the wards as if the lock had been open to his inspection. And this operation may not only be performed to the highest degree of certainty and exactness, but is conducted likewise with the utmost ease. For the block or bit, which is intended to receive the impression of the wards, being fitted to the keyhole, and the shank of the key bored to a sufficient depth to receive the pipe, nothing remains but to cover the bit with a preparation which, by a gentle pressure against the introductory ward, may receive its impression, and thus furnish a certain direction for the application of the file. The block or bit being thus prepared with a tally to the first ward, gains admission to the second; and a repetition of the means by which the first impression was obtained, enables the workman to proceed, till by the dexterous use of his file he has effected a free passage to the bolt. And in this operation he is directed by an infallible guide; for, the pipe being a fixed centre on which the key revolves without any variation, and the wards being fixed likewise, their position must be accurately described on the surface of the bit which is prepared to receive their impression. The key therefore may be formed and perfectly fitted to the lock without any extraordinary degree of genius or mechanical skill. It is from hence evident that endless variations in the disposition of fixed wards are not alone sufficient to the purpose of perfect security. I do not mean to subtract from the merit of such inventions, nor to dispute their utility or importance. Every approach towards perfection in the art of lock-making may be productive of much good, and is at least deserving of commendation; for if no higher benefit were to result from it, than the rendering difficult or impossible to many that which is still practicable and easy to a few, it furnishes a material security against those from whom the greatest mischiefs and dangers are to be apprehended.”

There can be little doubt, in the present day, that Bramah did not over-rate the fallacies embodied in the system of wards for locks. He was sufficiently a machinist to detect the weak points in the ordinary locks; and, whatever may have been his over-estimate of his own lock (presently to be described), he was certainly guilty of no injustice to those who had preceded him; for their locks were substantially as he has described them. To understand the true bearings of his Dissertation too, we must remember that housebreaking had risen to a most daring height in London at the time he wrote (about the middle of the reign of George III.); and men’s minds were more than usually absorbed by considerations relating to their doors and locks.

Mr. Bramah, after doing due justice to the ingenuity of Barron’s lock, in which, if the tumbler be either over lifted or under lifted the lock cannot be opened, pointed out very clearly the defective principle which still governed the lock. “Greatly as the art is indebted to the ingenuity of Mr. Barron, he has not yet attained that point of excellence in the construction of his lock which is essential to perfect security. His improvement has greatly increased the difficulty but not precluded the possibility of opening his lock by a key made and obtained as above described (by a wax impression on a blank key); for an impression of the tumblers may be taken by the same method, and the key be made to act upon them as accurately as it may be made to tally with the wards. Nor will the practicability of obtaining such a key be prevented, however complicated the principle or construction of the lock may be, whilst the disposition of its parts may be ascertained and their impression correctly taken from without. I apprehend the use of additional tumblers to have been applied by Mr. Barron as a remedy for this imperfection.” Mr. Bramah thought that Barron had a perception of a higher degree of security, but had failed to realise it; because, by giving a uniform motion to the tumblers, and presenting them with a face which tallies exactly with the key, they still partake in a very great degree of the nature of fixed wards, and the security of the lock is thereby rendered in a proportionate degree defective and liable to doubt.

To shew how this insecurity arises, Mr. Bramah illustrates the matter in the following way: “Suppose the key with which the workman is making his way to the bolt to have passed the wards, and to be in contact with the most prominent of the tumblers. The impression, which the slightest touch will leave on the key, will direct the application of the file till sufficient space is prepared to give it a free passage. This being accomplished, the key will of course bear upon the tumbler which is most remote; and being formed by this process to tally with the face which the tumblers present, will acquire as perfect a command of the lock as if it had been originally made for the purpose. And the key, being thus brought to a bearing on all the tumblers at once, the benefit arising from the increase of their number, if multiplied by fifty, must inevitably be lost; for, having but one motion, they act only with the effect of one instrument.”

It is worthy of notice, that even while thus shewing the weak points of the Barron lock, Mr. Bramah seems to have had in his mind some conception of infallibility or inviolability attainable by the lock in question. After speaking of the defect arising from the bad arrangement of the tumblers, he says: “But nothing is more easy than to remove this objection, and to obtain perfect security from the application of Mr. Barron’s principle. If the tumblers, which project unequally and form a fixed tally to the key, were made to present a plane surface, it would require a separate and unequal motion to disengage them from the bolt; and consequently no impression could be obtained from without that would give any idea of their positions with respect to each other, or be of any use even to the most skilful and experienced workman in the formation of a false key. The correction of this defect would rescue the principle of Mr. Barron’s lock, as far as I am capable of judging, from every imputation of error or imperfection; and, as long as it could be kept unimpaired, would be a perfect security. But the tumblers, on which its security depends, being of slight substance, exposed to perpetual friction—as well from the application of the key as from their own proper motion—and their office being such as to render the most trifling loss of metal fatal to their operation, they would need a further exertion of Mr. Barron’s ingenuity to make them durable.”

It may perhaps be doubted whether the principle of Bramah’s lock is not more clearly shewn in the original constructed by him than in that of later date. In appearance it is totally different, but the same pervading principle is observable in both; and the cylinder lock can certainly be better understood when this original flat lock has been studied. The annexed [woodcut] is taken from the first and very scarce edition of Mr. Bramah’s Dissertation; the description is somewhat more condensed, but perhaps sufficient for the purpose.

fig. 33. Bramah’s first model.

The lock is supposed to be lying flat, with the bolt B half-shot. Ranged somewhat diagonally are six levers, turning on a horizontal joint or pivot at A, each lever having a slight extent of vertical motion independent of the others. Each lever rests on a separate spring of sufficient strength to sustain its weight, or, if depressed by a superior force, to restore it to its proper position when the force is withdrawn. F is a curved piece of metal, pierced with six grooves or passages; these grooves are exactly equal in width to the thickness of the levers, but are of sufficient depth to allow the levers a free motion in a perpendicular direction. The ends of the levers are inserted in these grooves, and have this freedom of motion, whether lifted by the elastic power of the springs or depressed by a weight from above. In the bolt B is a notch to receive a peculiarly-shaped lever, which shoots or withdraws the bolt according as it traverses to the right or the left. This lever, the six long levers, the springs beneath them, the bent piece F, and the pivot, all alike are fixed to a circular platform P, which turns on a centre; so that if any force can make this platform turn partially round, the bolt must be shot or unshot by the lever which works in the notch. The six long levers are the contrivances whereby the platform shall not be allowed to turn until the proper moving agent (the key) shall have been applied, the plate p being one of the assistants in this obstruction. This plate, which is hollow underneath, has six notches in one of its edges; the points of the levers catch into these notches; and while so caught, the levers cannot move horizontally, and all the machinery is at a stand-still. To enable the key to set the mechanism in action, other contrivances are necessary. Each lever has a notch at its extreme end, and the six are notched very irregularly in respect one to another. These notches must be brought all into one plane, to enable the levers to pass horizontally out of the notches in the plate, in the same way as the two prongs of a fork might traverse one above and the other below the blade of a knife; and when the lever-notches are in this position, all in one plane and in the plane of the plate, the levers can be moved, and with it the stump which shoots the bolt. To ensure this due pressing down of the levers, a key is used such as is shewn in the [cut], having six steps or bits to correspond with the six levers; this key, put upon the pin K, presses down all the levers to the exact distance necessary for bringing their notches into one plane, viz. the plane of the plate; the key then being turned round turns the movable platform P, and shoots the bolt. It is evident at a glance, that unless the various steps of the key are so cut, that each shall press down its own lever to the proper extent, the ends of the levers cannot pass the notches in the plate, and the bolt can neither be locked nor unlocked.

It may be well to give Bramah’s own words in relation to this lock: “I may safely assert that it is not in art to produce a key or other instrument by which a lock constructed on this principle can be opened. It will be a task, indeed, of great difficulty, even to a skilful workman, to fit a key to this species of lock, though its interior face were open to his inspection; for the levers being raised by the subjacent springs to an equal height present a plane surface, and consequently convey no direction that can be of any use in forming a tally to the irregular surface which they present when acting in subjection to the proper key. Unless, therefore, a method be contrived to bring the notches on the ends of the levers in a direct line with each other, and to retain them in that position till an exact impression of the irregular surface which the levers will then exhibit can be taken, the workman will in vain attempt to fit a key to the lock, or by any effort of art to move the bolt. And when it is considered that this process will be greatly impeded, and may perhaps be entirely frustrated, by the action of the springs, it must appear that great patience and perseverance, as well as great ingenuity, will be required to give any chance of succeeding in the attempt. I do not state this circumstance as a point essential or of any importance to the purpose of the lock, but to prove more clearly what I have before observed upon its principle and properties; for if such difficulties occur to a skilled workman, as to render it almost, if not altogether impracticable to form a key when the lock is open to his inspection and its parts accessible to his hand, it pretty clearly demonstrates the impossibility of accomplishing it when no part of the movement can be touched or seen.”

It is evident that Mr. Bramah had his thoughts directed to that mode of picking locks which depends on taking impressions of the moving parts, rather than to the mechanical or pressure method which has been developed in later times. There can be little doubt that a lock was, to his mind, a beautiful and admirable machine, far elevated above the level of mere blacksmith’s work; and his name will ever be associated with what may be termed the philosophy of lock-making.

After the model-lock, which has just been described, was constructed, and found to corroborate the idea which was working in Mr. Bramah’s mind, he proceeded to the construction of his barrel or cylinder-lock, embracing similar elements placed in more convenient juxta-position. In his Essay he gives an engraving to illustrate the principle on which his lock acts, rather in the manner of a diagram than as depicting any lock actually made; his main object being to impart a clear notion of the action of the slides which form such a distinguishing feature in his lock.

fig. 34. Diagram to illustrate the Bramah lock.

Viewed in this sense, therefore, simply as an illustrative diagram, the annexed [cut] may represent the action of the safety slides. B is a sliding bar or bolt, having a power of longitudinal motion in the frame F. This frame has six notches cut on each of its long sides, the two series being exactly opposite each other; and there are six similar notches cut in the bolt B. The concurrent effect of all these eighteen notches is, that the six slides a b c d e f can move freely up and down across the bolt. When the slides are thus placed, the bolt cannot move, and may in this case be considered to be locked. There are six clefts or notches in the six slides, one to each (1, 2, 3, 4, 5, 6); and until all these are brought in a right line, the bolt cannot move through them. If a tally or key be prepared, as shewn at T in the lower part of the cut, with six projections, and if these projections thrust up the six slides till their clefts rise to the plane of the bolt, then can the bolt be withdrawn or the lock opened. This serves to illustrate the relation between the slides and the key, as carried out in the way now to be described.

One peculiarity of the Bramah lock is, that from the essential part of the apparatus being a barrel or cylinder, much of the working can be conducted in the lathe; and this has given a beauty to the details generally and deservedly admired. Mr. Bramah, when he worked out the theory of his lock, resolved to discard altogether the use of fixed wards, and also the use of tumblers working on a pivot at one end; substituting in their stead a system of slides, working in a very novel way. The body of a Bramah lock may be considered as formed of two concentric brass barrels, the outer one fixed, and the inner rotating within it. The inner barrel has a projecting stud, which, while the barrel is rotating, comes in contact with the bolt in such a way as to shoot or lock it; and thus the stud serves the same purpose as the bit of an ordinary key, rendering the construction of a bit to the Bramah key unnecessary. If the barrel can be made to rotate to the right or left, the bolt can be locked or unlocked; and the problem is, therefore, how to ensure the rotation of the barrel. The key, which has a pipe or hollow shaft, is inserted in the keyhole upon the pin, and is then turned round; but there must be a very nice adjustment of the mechanism of the barrel before this turning round of the key and the barrel can be ensured. The barrel has an external circular groove at right angles to the axis, penetrating to a certain depth; and it has also several internal longitudinal grooves, from end to end. In these internal grooves thin pieces of steel are able to slide, in a direction parallel with the axis of the barrel. A thin plate of steel, called the locking-plate, is screwed in two portions to the outer barrel, concentric with the inner barrel; and at the same time occupying the external circular groove of the inner barrel; this plate has notches, fitted in number and size to receive the edges of the slides which work in the internal longitudinal grooves of the barrel. If this were all, the barrel could not revolve, because the slides are catching in the grooves of the locking-plate; but each slide has also a groove, corresponding in depth to the extent of this entanglement; and if this groove be brought to the plane of the locking-plate, the barrel can be turned, so far as respects that individual slide. All the slides must, however, be so adjusted that their grooves shall come to the same plane; but as the notch is cut at different points in the lengths of the several slides, the slides have to be pushed in to different distances in the barrel, in order that this juxta-position of notches may be ensured. This is effected by the key, which has notches or clefts at the end of the pipe equal in number to the slides, and made to fit the ends of the slides when the key is inserted; the key presses each slide, and pushes it so far as the depth of its cleft will permit; and all these depths are such that all the slides are pushed to the exact position where their notches all lie in the same plane; this is the plane of the locking-plate, and the barrel can be then turned.

fig. 35. Exterior of a Bramah lock.

fig. 36. Details of the Bramah lock.

This is the principle which Mr. Bramah adopted; and we have now to trace it, step by step, by means of illustrative details. [Fig. 35] represents the exterior of a box or desk lock, one among many varieties which the Bramah lock presents. A A shews the bolt, formed something like two hooks rising out of a bar of metal, which bar has a backward and forward motion upon the plate B B. The upper edge of this plate is turned over at right angles, forming a small horizontal surface through which two openings are cut to receive the two hooked portions of the bolt. The movements of the bolt are otherwise guided by the edges of square holes through which it works; the holes being made in the edge-pieces of the lock, riveted to the main plate. The bolt is further prevented from rising out of its place by means of a plate of metal C, which is secured to the edge-pieces by two screws 1, 1, and by two steadying pieces. This plate has on its surface a cylindrical projection D, which contains in effect all the working mechanism of the lock. The pins 4 4 are employed for securing a plate, which we shall have to describe presently. When such a lock is fixed upon a desk or box, the portion D projects to a small distance through a hole in the wood-work, forming in itself a very neat escutcheon, with a key-hole in the centre.

fig. 37. The slides.

So much for the exterior. We must now proceed to examine the interior of the lock, especially the part contained within the cylinder. In [fig. 36], for convenience of arrangement, the several parts are exhibited separately, and as if the plane of the lock were horizontal, with the key acting vertically. The essential part of the mechanism is a barrel or cylinder E, pierced or bored with a cylindrical hole down its centre. The inside of the bore has six narrow grooves, cut parallel with the axis, and in the direction of radii; the grooves are not cut through the thickness of the cylinder, but leave sufficient substance of metal for strength. In every groove is fitted a steel slide of peculiar form, such as is shewn at a´ a´ in [fig. 37]. Each slide is split in its thickness (seen in section), so that it may move up and down in its groove with a slight friction, and thereby not fall simply by its own weight. Each slide has three small notches (3, 2, 3´), the use of which will presently appear. Reverting to [fig. 36], the lower part of the opening through the cylinder E is closed by a circular plate of metal, fixed to it by two screws; this plate is represented at F, in the lower part of the figure. This plate has a vertical pin rising from its centre (also seen at b, [fig. 39]), and serving as a key-pin on which the pipe of the key may work or slide; and it has also a short circular stud c projecting from its under side, and fitted to enter into a curved opening in the bolt presently to be described.

The point to be now borne in mind is this, that if the cylinder E turns round, the plate F will also turn round, and with it the stud c; and as this stud works into the peculiarly formed cavity d in a portion of the bolt ([fig. 38]), it causes the bolt to be shot backwards or forwards. Now, in order to prevent this rotating of the cylinder unless the proper key be employed, the following mechanism is introduced: the cylinder has a groove cut round its circumference at e e, extending sufficiently near to the internal bore to produce the desired effect without too much weakening the metal. Into this notch is introduced the thin circular plate of metal f f, it being divided into two halves for this purpose; and when so placed, it occupies the position shewn by the dotted portion e e. When this plate is screwed to the case of the lock by the screws 4, 4, it cannot of course turn round; but the cylinder itself will or will not turn round according to the position of the slides. The plate f f has six notches, 5, 5, 5, &c. in the inner edge or circle; so adjusted that, when the plate is in its place, the slides a a can move up and down. The cylinder cannot move round in a circle without carrying the slides with it; and these cannot so move unless they are all depressed to such exact distances in their respective grooves, that the deep notch of each slider (shewn at 2 in [fig. 37]) shall come into the plane of the circular plate: when all are so brought, the cylinder can be turned. If any one of the slides be pressed down either too low or not low enough, this turning of the cylinder cannot be effected, because the slides will be intersected by the edges of the notches 5, 5; and it is the office of the key, therefore, to press all the six slides down to the exact distances required. When the slides are not pressed upon by the key, they are forced upwards to the top of the cylinder by a spiral spring 6, coiled loosely round the pin b; this pressure forces up a small collet, 7, on which the upper part of the slides rest by a sort of step.

fig. 38. The bolt.

The first locks were made with a separate and independent spring to each slide; but it is a very great improvement, the introduction of one common spring to raise up the whole number; because if a person attempts to pick the lock by depressing the slides separately by means of any small pointed instruments, and by chance brings two or more of them to the proper depth for turning round, should he press any one too low, it is difficult to raise it again without relieving the spring 6, which immediately throws the whole number of slides up to the top, and destroys all that had been done towards picking the lock. Another improvement of this lock, and one which very much increased the difficulty of picking, and its consequent security, was the introduction of false and deceptive notches cut in the sliders, as seen at 3, 3. It was found that in the attempt to pick this lock, an instrument was introduced by the keyhole to force the cylinder round. At the same time that the slides were depressed by separate instruments, those slides which were not at the proper level for moving round were held fast by the notches 5, 5 in the plate f f bearing against their sides; but when pressed down to the proper level, or till the notch 2 came opposite f f, they were not held fast, but were relieved. This furnished the depredator with the means of ascertaining which slides were pressed low enough, or to the point for unlocking. The notches 3, 3 in the slides are sometimes cut above the true notch 2, sometimes below, and at other times one on each side (one above and one below); they are not of sufficient depth to allow the cylinder to turn round, but are intended to mislead any one who attempts to pick, by his not knowing whether it is the true notch or otherwise, or even whether the slider be higher or lower than the true notch.

We have not yet sufficiently described the key of the Bramah lock. One merit of the lock is the remarkable smallness of the key, which renders it so conveniently portable. The key, as shewn in the upper part of the figure, has six notches or clefts at the end of its pipe or barrel; these clefts are cut to different depths, to accord with the proper extent of movement in the slides. There is a small projection, 10, near the end of the pipe, fitted to enter the notch D in the cylinder; this forces the cylinder round when the parts are all properly adjusted. The bolt of the lock, when properly shot or locked, is prevented from being forced back by the stud c on the bottom, F, of the cylinder coming into a direct line with its centre of motion, as shewn in [fig. 39]; in this position no force, applied to drive the bolt back, would have any tendency to turn the cylinder round.

fig. 39. Section of the Bramah cylinder.

To facilitate the comprehension of this very curious and beautiful mechanism, the cylinder is shewn in section in the annexed [fig. 39], the same letters and figures of reference being used as before. In the whole of this description we have spoken of six slides, and six only; but Bramah locks may be, and have been, constructed with a much larger number.

There have been several attempts made to modify the action of Bramah’s lock, or to combine this action with that of some other inventor. It will suffice to describe one of these. The lock invented by Mr. Kemp of Cork, and for which a patent was obtained in 1816, is called by him the Union lock, as combining the principles of Barron’s and Bramah’s locks. It contains two, three, or more sliders or tumblers, operated upon by two, three, or more concentric tubes. These concentric tubes are of different lengths, and are placed inside the barrel of the key; so that the barrel may, in fact, be conceived to consist of a series of concentric tubes. These tubes are made of such respective lengths as to push back the tumblers, sliders, or pins which detain the bolt; and this to the precise extent that will bring certain notches in all the sliders to the position which will allow the bolt to pass. The inventor gives this lock its distinctive appellation because it combines something of the pushing motion which Bramah gives to his key, with something of the tumbler-motion observable in Barron’s locks. The principle of safety is considered here to rest chiefly on the extreme difficulty of imitating the key.

Mr. Bramah calculates the number of changes of position which the slides of his lock are capable of assuming before the right one would be attained. “Let us suppose the number of levers, slides, or other movables by which the lock is kept shut, to consist of twelve, all of which must receive a different and distinct change in their position or situation by the application of the key, and each of them likewise capable of receiving more or less than its due, either of which would be sufficient to prevent the intended effect. It remains, therefore, to estimate the number producible, which maybe thus attempted. Let the denomination of these slides be represented by twelve arithmetical progressionals; we find that the ultimate number of changes that may be made in their place or situation is 479,001,600; and by adding one more to that number of slides, they would then be capable of receiving a number of changes equal to 6,227,020,800; and so on progressively, by the addition of others in like manner to infinity. From this it appears that one lock, consisting of thirteen of the above-mentioned sliders, may (by changing their places only, without any difference in motion or size,) be made to require the said immense number of keys, by which the lock could only be opened under all its variations.”

CHAPTER VII.
AMERICAN LOCKS.

The lock-manufacture in America has undergone some such changes as in England. The insufficiency of wards to the attainment of security has been for many years known; and the unfitness of even tumblers to attain this end, without auxiliary contrivances, has been fully recognised for a dozen years back. In this, and in other mechanical arts, the American machinists depended primarily on the invention of the artisans in the mother country, rather than on those of any continental European state. But the development of the art in the United States has not been wanting in originality; the varieties of locks have been very numerous, and many of them exceedingly ingenious. It is not necessary, however, to describe or depict any of those of simple form. The warded locks of different countries very much resemble each other; the intricate warded locks made in France in the last century have long fallen into disuse, in consequence of the general conviction that no arrangement of wards, however intricate, can afford the degree of security required in a good lock. It will be more to the purpose, therefore, to proceed at once to a notice of those American locks which, during the last few years, have acquired some celebrity; first, however, noticing one of older date.

Stansbury’s lock, invented in the United States about forty years ago, may be regarded as a modification of the Egyptian lock. It had a bolt, case, and key-hole somewhat similar to those of modern locks; but there were peculiarities of construction in other respects. There was a revolving plate, pierced with a series of holes, and having a bit or pin which moved the bolt. On the lock-case were a series of springs, each having a pin at one end; and the arrangement was such that, when the bolt was locked or unlocked, each pin would be pressed into some one of the holes. Like as in the Egyptian lock ([figs. 1] to [4]), each pin had to be pushed out, and all of them simultaneously, to allow the plate to turn and move the bolt. The key was made with a barrel and bit; and on the front end of the bit was a series of pins corresponding in position with the holes in the plate. The mode of locking or unlocking was as follows: the key was inserted in the key-hole, and turned to a certain position; it was then pressed in with some force, until the pins on the key met those in the plate; when the latter, yielding to the pressure, left the plate free to turn and move the bolt. Modifications of the Egyptian lock, more or less resembling this, have been brought out in some variety on both sides of the Atlantic; but scarcely any have equalled in simplicity the curious wooden relic of by-gone ingenuity in the art of lock-making.

A lock made a few years ago by Mr. Yale, in the United States, somewhat resembles the Bramah lock in having a cylinder or barrel, or rather two concentric cylinders, one working within the other. These cylinders are held together by pins which pass through them both into the key-hole. On the back of the inner cylinder is a pin that fits into a slot in the bolt, and moves it whenever the cylinder is turned. The pins that hold the cylinders together are each cut in two; the pieces of the various pins differing in lengths as irregularly as possible. The key is so peculiarly formed, that, on inserting it in the key-hole, it thrusts the pins radially outwards; each pin being pushed just so far that the joint of the pin shall coincide with the joint between the two cylinders. The inner cylinder can then be turned, by which the bolt is locked or unlocked. If, by the use of a false key, any pin be pushed in too far, it will be as ineffectual in opening the lock as if it were not thrust in far enough; and some of these locks having been made with as many as forty pins, the chances are very numerous against the right combination being hit upon. There is a combination of something like the Egyptian with something like the Bramah lock, here attempted.

One of the principal constructions adopted in America a few years back for bank-locks is that of Dr. Andrews of Perth Amboy, in New Jersey. It was up to that time (1841) believed that the best locks, both of England and America, were proof against any attempts at picking derived from knowledge obtained by inspection through the key-hole; but there still remained the danger that the sight of the true key, or the possession thereof, for only a few minutes, would enable a dishonest person to produce a duplicate. It was to contend against this difficulty that Dr. Andrews directed his attention; and he sought to obtain the desired object by constructing a lock, the interior mechanism of which could be changed at pleasure. The lock of his invention is furnished with a series of tumblers and a detector. The tumblers are susceptible of being arranged in any desired order; and the key has movable bits which can be arranged so as to correspond with the tumblers. When the lock is fixed in its place, no change can be made in the tumblers, and consequently only one arrangement of the bits of the key will suit for the shooting and withdrawing of the bolt. The owner can, however, before the fixing of the bolt, adopt any arrangement of tumblers and bits which he may choose. But though the tumblers cannot be actually re-arranged in any new order within the lock while the latter is fixed, yet by an ingenious contrivance the tumblers can be so acted upon as to render the lock practically different from its former self. The purchaser receives with his lock a series of small steel rings, each ring corresponds in thickness with the thickness of some one of the bits of the key; so that, by suitable adjustment, any one of the bits may be removed from the key, and a ring be substituted in its place. The effect of this substitution is, that the particular tumbler which corresponds with the ring is not raised by it; it is drawn out with the bolt, as if it were part of the bolt itself. Supposing the lock to be locked by this means, the original key would not now unlock it; for one of the tumblers has now been displaced, and can only be re-adjusted by the same ring which displaced it. If an attempt be made to open the lock by the original key, or by the key in its original adjustment, a detector is set in action, which indicates that a false key or other instrument has been put into the lock. One, or more than one, of the bits may be removed from the key, and rings be substituted, and consequently one or more of the tumblers may be disturbed in this peculiar way; so that the lock may change its character in all those permutating varieties which are so observable in most “safety-locks.” The shape of the tumblers is, of course, such as to facilitate this action; they have each an elongated slot, and also two notches; when a tumbler is raised by one of the bits of the key, one of the notches closes around a stump fitted into the case of the lock, and prevents the tumbler from being moved onward with the bolt; but when a ring has been substituted for a bit on the key, the tumbler cannot be raised at all; it is carried onward by a stump on the bolt.

Dr. Andrews is also the inventor of a lock which he terms the snail-wheel lock. In this lock a series of revolving discs, or wheels, taking the place of the tumblers, are mounted on a central pin, on which the pipe of the key is inserted. Each disc has a piece cut out of it, into which the bit of the key enters, and in turning round moves the discs according to the various lengths of the steps on the key. On the outer edge of each disc is a notch, and by the turning of the key all these notches are brought into a line, so that a moveable tongue, or toggle, attached to the bolt, falls into the notches; the key is then turned the reverse way, by which means the bolt is projected.

About the time when Dr. Andrews invented his first lock, Mr. Newell, of the firm of Day and Newell of New York, constructed a lock which possessed the same distinctive peculiarity as that of Andrews, viz. that the key might be altered any number of times without rendering it necessary to remove the lock or change its internal mechanism. This was brought about, however, in a different manner. Instead of having, as in the Andrews lock, a two-fold movement to every tumbler, Mr. Newell employed two sets of tumblers, the one set to receive motion from the other, and having different offices to fill, to be acted upon by the key in respect to the first series, and to act upon the bolt in respect to the second. Calling these two sets primary and secondary, the action of the lock may be briefly described as follows. A primary tumbler being raised to the proper height by the proper bit in the key, raises the corresponding secondary tumbler; the secondary tumbler is held up in a given position during the locking, while the primary becomes pressed by a spring into its original position. It results from this arrangement that the bolt cannot be unlocked until the primary tumbler has been raised to the same height as before, so as to receive the tongue of the secondary tumbler. And as this is the case in respect to any one primary and its accompanying secondary tumblers, so is it the case whether each set comprises four, five, or any other number. The key may be altered at pleasure, and will in any form equally well shoot the bolt; but the lock can only be unfastened by that arrangement of key which fastened it.

It is, however, desirable to trace the course of improvements more in detail, because every successive change illustrates one or other of the several properties required in a good lock. Messrs. Day and Newell’s lock was not finally brought to an efficient form without many attempts more or less abortive. Mr. Newell conceived the idea of applying a second series of tumblers, so placed as to be acted on by the first series. Each of these secondary tumblers had an elongated slot, such that a screw could pass through all of them; the screw having a clamp to overlap the tumblers on the inside of the lock. The head of the screw rested in a small round hole on the back of the lock, so placed as to form a secondary key-hole, to which a small key was fitted. There was thus a double system of locking, effected in the following way: when the large key had been applied, and had begun to act on the primary tumblers, the small key was used to operate on the clamp-screw, and thus bind all of the secondary tumblers together, ensuring their position at the exact heights or distances to which the primary key had caused them to be lifted. The bolt was then free to be shot, and the first series of tumblers reverted to their original position.

But such an arrangement has obvious inconveniences. Few persons would incur the trouble of using two keys; and besides this, there were not wanting certain defects in the action and reaction of the several parts; for if the clamp-screw were to be left unreleased, the first series of tumblers would be upheld by the second series in such a way that the exact impression of the lengths of the several bits of the key could be obtained through the key-hole while the lock was unlocked or the bolt unshot. To remedy one or both of these evils was the next object of Mr. Newell’s attention. He made a series of notches or teeth in each of the secondary tumblers, corresponding in mutual distance with the steps or bits of the key; and opposite these notched edges he placed a dog or lever, with a projecting tooth suitable to fall into the notches when adjusted properly in relation to each other. When the key was used, the primary tumblers were raised in the usual way, and acted on the secondary tumblers; these latter were so thrown that the dog-tooth caught in the notches and held them fast, thereby rendering the same service as the clamp-screw and the small key in the former arrangement. No other relative position of the bits of the key could now unlock the lock.

Still, improvement as it was, this change was not enough; Mr. Newell found that his lock, like all the locks that had preceded it, was capable of being picked by a clever practitioner; and candidly admitting the fact, he sought to obtain some new means of security. He tried what a series of complicated wards would do, in aid of the former mechanism; but the result proved unsatisfactory. His next principle was to provide a number of false notches on the abutting parts of the primary and secondary tumblers, with alterations in other parts of the apparatus. The theory now depended upon was this, that if the bolt were subjected to pressure, the tumblers would be held fast by false notches, and could not be raised by any lock-picking instrument. To increase the security, a steel-curtain was so adjusted as to cover, or at least protect, the key-hole. Great anticipations were entertained of this lock, but they were destined to be negatived. A clever American machinist, Mr. Pettit, accepted Messrs. Day and Newell’s challenge (500 dollars to any one who could pick this lock); he succeeded in picking the lock, and thus won the prize.

Once again disappointed, Mr. Newell re-examined the whole affair, and sought for some new principle of security that had not before occurred to him. He had found that, modify his lock how he might, the sharp-eyed and neat-fingered mechanician could still explore the interior of the lock in such a way as to find out the relative positions of the tumblers, and thus adapt their means to the desired end. How, therefore, to shut out this exploration altogether became the problem; how to make a lock, the works of which should be parautoptic—to coin a word from the Greek, which should signify concealed from view. The result of his labours was the production of the American bank-lock now known by that name. The details of this lock may now conveniently be given.

fig. 40. The American Parautoptic lock; bolt unshot.

fig. 41. The same with the bolt shot.

In [fig. 40] the lock is represented in its unlocked state, with the cover or top-plate removed; the auxiliary tumbler and the detector-plate are also removed. In [fig. 41] it is represented as locked, with the cover and the detector-plate also removed, and the auxiliary tumbler in its place. In these two figures, the same letters of reference apply to the same parts, unless otherwise stated. B B is the bolt; T¹ are the first series of movable slides or tumblers; s shews the tumbler-springs; T² the secondary series of tumblers; and T³ the third or intermediate series—these latter coming between the first and secondary series; P P are the separating plates between the several members of the first series of tumblers; s¹ are the springs for lifting the intermediate tumblers. On each of the secondary tumblers T² is a series of notches, corresponding in mutual distance with the difference in the lengths of the movable bits of the key. It thence happens that, when the key is turned in the lock to lock it, each bit raises its proper tumbler, so that some one of these notches shall present itself in front of the tooth t in the dog or lever L L. When the bolt B is projected by the action of the key, it carries with it the secondary tumblers T², and presses the tooth t into the notches; in so doing, it withdraws the tongues d from between the jaws j j of the intermediate tumblers T³, and allows the first and intermediate tumblers to fall to their original position. By the same movement, the secondary tumblers T² become held in the position given to them by the key, by means of the tooth t being pressed into the several notches, as shewn in the closed state of the lock ([fig. 41]). Now let us see what results if any attempt be made to open the lock with any arrangement of key but that by which it has been locked. In such case, the tongues d will abut against the jaws j j, preventing the bolt from being withdrawn; and should an attempt be made to ascertain which tumbler binds and requires to be moved, the intermediate tumbler T³ (which receives the pressure), being behind the iron wall I I, which is fixed completely across the lock, prevents the possibility of its being reached through the key-hole; and the first tumblers T are quite detached at the time, thereby making it impossible to ascertain the position of the parts in the inner chamber behind the wall I I. K is the drill-pin, on which the key fits; and C is a revolving ring or curtain, which turns round with the key, and prevents the possibility of inspecting the interior of the lock through the key-hole. Should, however, this ring be turned to bring the opening upwards, a detector-plate D, [fig. 42], is immediately carried over the key-hole by the motion of a pin p¹ upon the auxiliary tumbler T⁴, which is lifted by the revolution of the ring C, thereby effectually closing the key-hole. As an additional protection, the bolt is held from being unlocked by the stud or stump S bearing against the detector-plate; and, moreover, the lever l l holds the bolt, when locked, until it is released by the tail of the detector-plate pressing the pin p¹; l¹ is a lever which holds the bolt on the upper side, when locked, until it is lifted by the tumblers acting on the pin p¹; X are separating-plates between the intermediate tumblers T³; u u¹ are the studs for preserving the parallel motion of the different tumblers.

fig. 42. The detector plate of the Parautoptic lock.

[Fig. 43] represents the key in two different forms, or with the bits differently arranged. Either form will lock the lock, but the other will not then unlock it. The end of the key is represented in [fig. 44], shewing the screw which fixes the bits in their places. The bits for a six-bitted key are shewn separately in [fig. 45].

fig. 43. Key of the Parautoptic lock.

fig. 44. End view of the key.

fig. 45. Separate bits of the key.

In 1847 the parautoptic lock was exhibited at Vienna before the National Mechanics’ Institute of Lower Austria; and towards the close of the year Mr. Belmont, consul-general of Austria at New York, placed in the hands of Messrs. Day and Newell a letter, a diploma, and a gold medal, forwarded by the Institute. The letter was from the president of the Institute to Mr. Newell, and was couched in the following terms:

“The Institute of Lower Austria, at its last monthly session, has passed the unanimous resolution to award to you its gold medal, as an acknowledgment of the uncommon superiority of the combination-lock of your invention; and this resolution was ratified in its general convention held on the 10th instant.

“Whilst I, as president of this Institute, rejoice in seeing the services which by this invention you have rendered to the locksmith’s art thus appreciated and recognised, I transmit to you, enclosed, the said medal, together with the documents relating to it; at the same time availing myself of this opportunity to assure you of my esteem.

“Colloredo Mannsfeld.

“Vienna, May 31st, 1847.”

The diploma and the medal were similar to other honorary distinctions of the same class, and need not be described here; but the report of the special committee may be given, as it expresses the opinions of the Viennese machinists on the relative principles by which safety is sought to be obtained in different kinds of locks.