Life of Richard Trevithick, with an Account of His Inventions. Volume 2 (of 2)

The Project Gutenberg eBook, Life of Richard Trevithick, Volume II (of 2), by Francis Trevithick, Illustrated by W. J. Welch

LIFE
OF
RICHARD TREVITHICK,
WITH AN ACCOUNT OF HIS INVENTIONS.
By FRANCIS TREVITHICK, C.E.

ILLUSTRATED WITH ENGRAVINGS ON WOOD BY W. J. WELCH.

VOLUME II.

LONDON:
E. & F. N. SPON, 48, CHARING CROSS.
NEW YORK:
446, BROOME STREET.
1872.

LONDON: PRINTED BY WILLIAM CLOWES AND SONS, DUKE STREET,
STAMFORD STREET AND CHARING CROSS.

CONTENTS OF VOLUME II.

ILLUSTRATIONS TO VOLUME II.

[LIFE OF TREVITHICK.]

[CHAPTER XVII.]

VARIOUS INVENTIONS.

"About 1804 Captain Trevithick put up in Dolcoath Mine a stone-crushing mill, having large cast-iron rollers, for breaking into small pieces the large stones of ore; it was spoken of as the first ever used for such a purpose; the same form of crusher is still used in the mines. It caused a great saving compared with breaking by a hand hammer."[1]

"I saw at the Weith Mine in 1805 a portable high-pressure engine, made by Captain Trevithick.

"It was called a puffer; the cylinder was in the boiler; the steam about 30 lbs. on the inch above the atmosphere. A wooden shed sheltered the engine and man.

"The facility of manufacture and cheapness of those engines caused them to be much used in the mines, and also elsewhere."[2]

Mrs. Trevithick, about the time we are speaking of, accompanied her husband through one of the Staffordshire china manufactories. Trevithick said to the manufacturer, "You would grind your clay much better by using my cast-iron rolls and high-pressure steam-engine." The manufacturer begged him to accept a set of china. Mrs. Trevithick was disappointed at hearing her husband say "No! I have only told you what was passing in my mind."

Driving rolling-mills was among the early applications of the high-pressure steam-engines; but pulverizing hard rock by the use of iron rollers was a novelty: though his patent of 1802 shows the proposed rolls driven by steam for crushing sugar-canes, yet no one had dreamt, prior to 1804, of economy in crushing stone and clay by such a means. The plan, however, remains in use to this day in many mines, and is frequently spoken of under the name of quartz-crusher.

"Mr. Giddy,

"Coalbrookdale, September 23rd, 1804.

"Sir,—Yours of the 13th this day came to hand. I left Wales about eight weeks since, and put an engine to work in Worcester, of 10-horse power, for driving a pair of grist-stones, and a leather-dressing machine, and another in Staffordshire for winding coals; each of them works exceedingly well.

"From Coalbrookdale I went to Liverpool, where a founder had made two of them, which also worked exceedingly well; one other was nearly finished, and three others begun. Some Spanish merchants there saw one of them at work, and said that as soon as they returned to Spain they would send an order for twelve engines, of 12-horse power, for South America. In South America and the Spanish West Indies water is very scarce; in several places there is scarcely water for the inhabitants to drink, therefore there is no water for any engine. By making inquiry, I found that ten mules would roll as much cane in an hour as would produce 250 gallons of cane-juice, which they boil until the water is evaporated, and the sugar produced.

"I told them that the engine-boiler might be fed with this juice, and by a cock in the bottom of the boiler constantly turning, and by taking a greater or smaller stream from it, they might make the juice as rich as they liked. In this process the juice would be so far on towards sugar, and the fire that worked the engine would cost nothing, because it would have taken the same quantity of fuel under the sugar-pans to evaporate the water, as it would in the engine-boiler.

"The steam from the engine might be turned around the outside of the furnace for distilling rum, as the distilleries require but a slow heat.

"I think the steam would answer a good purpose around the outside of the pan.

"If this method answers, the cost of working the engine would be nothing, and the engine would be then working, as it were, without fire or water.

"The Spaniards told me that if this plan answers, they would take a thousand engines for South America and the Spanish West Indies. I shall be very much obliged to you for your opinion on this business. These merchants make a trade of buying up sugar mills and pans, with every other thing they want from England, and exchange them with the Spaniards for sugar.

"At Manchester I found two engines had been made and put to work; they worked very well: three more are in building. From there I went to Derbyshire. The great pressure-engine I expect will be at work before the middle of October. A foundry at Chesterfield is building a steam-engine as a sample; two foundries in Manchester are at full work on them, and one in Liverpool. There are six engines nearly finished at Coalbrookdale, and seven in a foundry at Bridgenorth.

"I am making drawings for several other foundries. Any number of them would sell. A vast number are now being erected, and no other engine is erected where these are known. The engine for the West India Docks was neglected during my absence from the Dale, but I expect it will be ready to send off in ten days.

"In about three weeks I shall be in London to set it up. It will please you very much, for it is a very neat and complete job, and I have no doubt will answer every purpose exceedingly well. At Newcastle I found four engines at work, and four more nearly ready; six of these were for winding coal, one for lifting water, and one for grinding corn.

"That grinding corn was an 11-inch cylinder, driving two pair of 5-feet stones 120 rounds per minute; ground 150 winchesters of wheat in twelve hours with 12 cwt. of small coal. It worked exceedingly well, and was a very complete engine, only the stroke was much too short, not more than 2 feet 6 inches, which made very much against the duty.

"The other engine that was lifting water had a 5½-inch diameter cylinder, with a 3-feet stroke, drawing 100-gallon barrels, twenty-four every hour, 80 yards, burning 5 cwt. of coal in twenty-four hours.

"This work it did with very great ease. I believe you will find this an exceeding good duty for a 5½-inch cylinder engine.

"Below I send a copy of Mr. Homfray's and Mr. Wood's letters to me:—

"Mr. Homfray's, of the 10th September.—'Our great engine goes on extremely well here, nothing can go better; the piston gives no trouble; it goes about three weeks, and we work it with blacklead and water; the cylinder is as bright as a looking-glass; it uses about 2 lbs. of blacklead in a week; about once in twelve or fifteen hours we put a small quantity of blacklead, mixed with a little water, through the hole in the cylinder screw, and we never use any grease. We rolled last week 140 tons of iron with it, and it will roll as fast with the both pair of rolls, as they can bring to it.'

"Mr. Wood's letter, September 12th.—'We are going on, as it is likely we always shall, in the old dog-trot way, puddling and rolling from the beginning of the week till the end of it. Your engine is the favourite engine with every man about the place, and Mr. Homfray says it is the best in the kingdom.'

"I have not the smallest doubt but that I can make a piston without any friction or any packing whatever, that needs not to have the cylinder screw taken up once in seven years. It is a very simple plan, and will be perfectly tight; it is by restoring an equilibrium on both sides of the piston. I expect to see you in London soon, and then will give you the plan for inspection before I put it in practice.

"I am very much obliged to you for recommending these engines in Cornwall, but you have not stated in what manner they are to be applied; whether to work pumps, or barrels, or both. They may be made both winding and pumping engines at the same time, if so required.

"A rotative engine will cost more than an up-and-down-stroke, on account of the expense of the fly-wheel and axle. An engine capable of lifting 180 gallons of water per minute 20 fathoms would cost, when complete and at work, patent right included, about 220l. If it is a rotative engine, with a winding barrel, it will cost 270l. I expect that a 7-inch cylinder would be sufficient for winding at Penberthy Crofts, which might have a Crank on the fly for lifting water in pumps, and a winding barrel on its back. This would cost about 170l.; the erection of them, when on the spot, will cost nothing. You do not say when you intend to be in town. I hope you will be present when the dock-engine is set to work.

"The engines first sent to Cornwall, must be from Coalbrookdale; then they will be well executed, but from Wales it would not be so.

"You may depend on having a real good engine sent down, with sufficient openings given to the passages.

"The engineer from the Dale has been lately in London, and has just returned; he gives a wonderful account of the engines working in London. There are twelve now at work there. They have well established their utility in different parts of the kingdom, and any number would sell. The founders intend to make a great number, of different sizes, and send them to different markets for sale, completely finished, as they stand.

"You do not say anything about wheels to the engine for Penberthy Crofts. There are several engines here nearly finished; if they suit in size for Penberthy, one may be sent down in four or five weeks, otherwise it may be two months.

"I am, Sir,
"Your very humble servant,
"Richard Trevithick.

"Direct for me at the Talbot Inn, Coalbrookdale."

Trevithick worked hard and successfully in making his steam-engines useful, and firmly believed that he could and would make them universal labourers. Even the Spanish merchants, unacquainted with steam, talked of giving an order for several engines for South America; and their glowing account of the wide field open to him may have been instrumental to his going to that country by making his engines known there. His proposal to make the sugar-cane convert itself into sugar by the use of his patent high-pressure steam-engine may be more theoretical than practical; but many more unlikely things have come to pass.

At that time several of his engines were at work in Wales, Worcester, Staffordshire, Coalbrookdale, Manchester, Derbyshire, Liverpool, Cornwall, and Newcastle-upon-Tyne. Twelve were at work in London, and so familiar were people with them, that founders intended to construct them of different sizes, and send them for sale at the large market or county towns; their cost complete, ready for work, to be 200l., more or less, according to size, with a range of application unlimited. His one letter, casually written sixty-seven years ago, mentions them as grinding corn, dressing leather, winding coal, crushing sugar-cane, prepared to boil sugar, and distil rum; pumping water, rolling iron, railway locomotion, portable steam fire-engine, portable steam-crane, mine engines on wheels; so that it may almost be said he was not too sanguine in hoping to send in 1804 a thousand of his engines to South America, for in those cursory remarks he draws attention to no less than thirty-six high-pressure steam-puffers at work.

The Penberthy Croft Mine portable engine could be placed on wheels or otherwise, according to the wish of the purchaser, as though steam locomotion was an every day occurrence in 1804.

"Mr. Giddy,

"Camborne, January 13th, 1811.

"Sir,—From calculating the quantity of blast given to a blast-furnace, I find a considerable quantity more of coal consumed by the same quantity of air in this way, than by the usual way in common engine chimneys. Of course the more cold air admitted to pass through the fire, the more heat carried to the top of the stack. Crenver 63-inch cylinder, double-power, 8-feet stroke, with but one boiler, works five strokes per minute. This gives about 1600 square feet of steam per minute, and burns about 8 tons of coals in twenty-four hours. The stack for this boiler is 3½ feet square, and the draught rises 10 feet per second, and will set white paper in a flame at the top of it in about a minute. Therefore, this chimney delivers 7200 square feet of air per minute, which is four and a half times the quantity of heated air, at nearly four times the temperature of heat that there is of steam produced from the same fire, and delivered to the cylinder.

"A blast-furnace that burns 100 tons of coal per week is blown by a 5-feet diameter air-cylinder, 4-feet stroke, ten strokes per minute, double-power, giving about 1600 square feet of air per minute, to consume 100 tons of coal, besides giving a melting heat to 350 tons of ore and limestone.

"Crenver engine has 7200 square feet of air to burn 56 tons of coal per week, which is above eight times the quantity of air used by air fire-places to what is used in a blast-furnace, and of course must carry off a great proportion of the heat to the top of the stack, that might be saved if the engine-fire was a blast instead of an air fire.

"But suppose the idea to be carried still further, by making an apparatus to condense and take the whole of the heat into the cylinder instead of its passing up the chimney. By having a very small boiler, and a blast-cylinder to blow the whole of the blast into the bottom of the boiler, under a cylinder full of small holes under the water, to make the heated air give all its heat to the water.

"The furnace must be made in a tight cast-iron cylinder. Both the fire-door and the hole through which the blast enters must be quite tight, as the pressure will be as strong in the fire-place as in the boiler. The whole of the air driven into the fire-place, with all the steam raised by its passage up through the water in the boiler, must go into the cylinder. There will also be the advantage of the expansion of the air by the heat over and above what it was when taken cold into the blast-cylinder.

"From the great quantity of coal burnt in blast-furnaces you will find that a very small blast-cylinder would work a 63-inch cylinder double. If there is as much heat in a square foot of air as in steam of the same temperature, the saving will be beyond all conception; but for my own part I cannot calculate from theory what the advantages will be, if any, and for that reason, before I drop or condemn the idea, I must request you will have the goodness, when you have an hour to spare, to turn your thoughts to this subject, and inform me of your sentiments on it.

"Perhaps it is like many other wild fancies that fly through the brain, but I did not like to let it go unnoticed without first getting your opinion. I hope you will excuse me for so often troubling you.

"St. Ives plans will be delivered to them on Tuesday, when I expect they will be forwarded to you.

"I hear there is a good course of ore in the adit end at Wheat Providence Mine.

"A Mr. Sheffield, of Cumberland, writes to Mr. Gould that he has turned idle his air-furnaces, and smelted his ores by a blast near a year since.

"His furnace is but 10 feet high and 4 feet diameter, and it melts 28 tons of ore, of from 4 to 5 in the 100 per week, and makes a regel of from 65 to 70 in the 100, and answers beyond what we calculated for them.

"Suppose a furnace 20 feet high and 4 feet diameter, it would smelt eight times the quantity of his, which would be near 900 tons per month, or nearly double the quantity raised by any one mine in the country. The expense of the ... would be very trifling.

"To-morrow Dolcoath account will be held, when I expect to have orders to begin to erect a furnace on the spot.

"This trial of Mr. Sheffield's has put it out of my power to get a patent, and now I do not know how to get paid.

"I should be content with 5 per cent. on the profits gained by this plan, and would conduct the business for the mines without salary. Should you chance to fall on the subject with his Lordship, be pleased to mention something about the mode of my payment, as his Lordship is by far the properest person to begin with about my pay, for after his Lordship has agreed to the sum, and Dolcoath Mine the first to try the experiment, I think all the county will give way to what he might propose. But I wish something to be fixed on before all the agents in the mines know how to be smelters themselves, after which I expect no favour, unless first arranged.

"I remain, Sir,
"Your very humble servant,
"Richard Trevithick.

How great was the practical insight his genius gave him, and how imperfectly his followers have acted on this advice given sixty years ago!

The chimney that at its top would ignite paper, threw to waste four and a half times more heated air than was requisite to supply the quantity of heat which passed through the working cylinder in steam, and at a temperature nearly four times greater than the temperature of the steam. It needs only to observe the burnt appearance of a steamboat funnel of the present day to know how wasteful we still are, or how very ignorant of improved methods of economizing fuel.

To prevent this waste of heat up the chimney be proposed to do away with the chimney altogether; the fire-place was to be a close one, having a blast under the fire-bars of a strength sufficient to force the air, heated by its passage through the fire, direct through a small valve into the water in the boiler, by which means all the heat given by ignition would pass into the steam, and his steam-puffer become an aërated steam-engine.

From the following it appears that this plan of Trevithick's is now coming into use as something quite new:—

"In your last impression, under the head of 'Air and Steam combined, as a Motive Power,' you state 'the invention was described to be that of Mr. Warsop, but we have recently heard that a few years back (1865) the same invention had been protected in an earlier patent than Mr. Warsop's, by Mr. Bell Galloway.'"[3]

Trevithick thought of patenting a plan for reducing copper ore by the use of a blast, in preference to the usual air-furnace and chimney, but something similar had been tried by Mr. Gould, and he therefore proposed to erect a blast-furnace in Dolcoath Mine, receiving a portion of the saving of fuel as his remuneration. Such a furnace worked there for many years, until copper smelting was removed from Cornwall to Wales. The plans for a breakwater at St. Ives were for an undertaking that has since been in many hands, but without success, except perhaps for the convenient making of members of Parliament. Some slight progress has been made by engineers and contractors, but vessels are not willingly taken to the port, and ratepayers grumble at unprofitable harbour taxes.

"Dear Trevithick,

"London, January 20th, 1811.

"I have not lost any time in mentioning your wishes respecting a compensation for the plan of smelting copper to Lord Dedunstanville, who intends mentioning the affair in his next letter to Mr. Reynolds. Lord Dedunstanville wishes you extremely well, but it is impossible for him to settle anything apart from the adventurers.

"I am very sorry that anyone should have executed the plan of reducing copper ore by a blast-furnace before you had put into practice the idea suggested to me ten years ago. It ascertains, however, that the contrivance will succeed, although you are certainly reduced to ask moderate terms, and I know not what can be more moderate than those you have asked, except that I would recommend some limit as to time.

"The plan you suggest for an engine on a new construction is, I fear, very doubtful.

"According to the data furnished to me, the air in the blast would be to that in a common fire-place as 6¼ to 1 very nearly, provided their densities were the same; but you have measured one entering the furnace at the common temperature, and the other going to the stack so hot as to set on fire a piece of paper held at the top. Thus the increase of temperature that augments the elasticity of a fluid confined, would expand it in the same degree. It is therefore uncertain from these statements which furnace consumes the greater quantity of air. I apprehend the general principles of an engine worked by hot air, through the medium of a blast, would be as follows:—

"Let any quantity of air be driven into a furnace with the pressure of an atmosphere, and let it be there expanded ten times. It should then be taken off ten times as quick, but in that case no power whatever would be produced, so the external atmosphere would balance the internal. Now, let the blast be two atmospheres strong, and let them be expanded ten times, and be taken off ten times as fast, each stroke will be opposed by one, equal in all to ten; subtract two for the blast, there remain eight.

"But air so hot would burn every vegetable or animal substance, and such a furnace I suppose could scarcely be kept air-tight. If the heated air is made to act on water, then it becomes a mere question of how much absolute heat is given out by the fuel, and whether that excess is more than sufficient to compensate the burden of the blast; for the water will absorb an immense quantity of heat in changing itself into steam, and thus reduce the force of the air as to make it almost impossible for that addition to add so much power as the blast takes away.

"I have, therefore, no hesitation in saying that this plan will certainly not do. Write to me by all means whenever anything strikes you, and you may always depend on having my best advice.

"I am, dear Sir,
Ever most truly yours,
Davies Giddy."

Trevithick saw without apparent reasoning, while his friend's reasonings failed to make plain the full bearing of the questions, and so cramped the position as to make a change of front difficult—an operation in which Trevithick excelled. We learn, however, that in 1801 he suggested a blast in copper-ore furnaces, and in 1811 was on the verge of a discovery that has since revolutionized the iron-smelter's art by the use of hot blast. Wasted heat from a blast-furnace 10 feet high led him to the conclusion that by doubling the height of the furnace, enabling the cold mineral thrown in at the top to take up the heat wasted through the top of the low furnace, seven-eighths of the coal would be saved. His idea of sending blast through the furnace of his steam-boiler to economize heat could have been readily applied to the iron furnace, and we should have had the modern hot-blast iron furnaces.

[Rough draft.]

"Gentlemen,

"Camborne, March 5th, 1812.

"Your favour of the 15th February, with a sketch of your brewery, I have received; and from which I find the head of water is 30 feet above the brewery, which makes it difficult to erect the chain and buckets so as to take advantage of the whole height of water; and as the stream is so very small, it will not admit of losing any part of the power.

"To erect a machine so high, to engage the whole fall, would be, I fear, more expense than the power you would get would warrant; therefore I would recommend it to be made use of in a cylinder, in the same way as we use falls of water of 200 feet in our Cornish copper mines. We allow one-third loss for friction and leakage in those machines; but your machine being so very small, the loss will exceed that proportion; therefore I cannot promise you above one-half of the real weight and fall to be performed on your machinery, and that must be by a well-executed machine, for a small defect would destroy the value of so trifling a power.

"As there is no expansion in water, it will be somewhat difficult to make the machine turn the centres with a fly-wheel, for if the valve shuts a little too early or too late for the turn of the crank over the centre, the fly-wheel's velocity must break something by confining the water between the piston and the bottom of the cylinder, which, after the valve is shut, cannot make its escape, and not having an elastic principle, the piston will strike as dead on the water as on a piece of iron, because, unless the valve is shut by the engine before the stroke is finished, it cannot shut at all.

"I know persons who have attempted to put fly-wheels on pressure-engines of this kind, but never yet has one been made to work rotative. I do not see much difficulty in making an engine of this kind to work a crank and fly-wheel, by connecting an air-vessel with the cylinder to receive the pressure and contract and expand and shut the valves, the same as in steam-engines.

"A machine on this plan ought to be placed as near the low level as possible. If I furnish you with drawings and directions for the executing of the work yourselves, I shall charge you fifteen guineas for them. If I send the machine finished, the charge will be 50l.

"Your objections respecting steam-engines I do not doubt are correct, when executed by persons who do not understand the construction of them. In England some persons privately erected my engine to evade the patent premium, but have severely paid for their saving knowledge by accidents and defects in their engineering ability. I have erected above 100 steam-engines on this principle, but never met with one accident or complaint against them. To prevent mischief from bad castings, or from the fire injuring the surface of cast iron, I make the boilers of wrought iron, and always prove them with a pressure of water, forced in equal to four times the strength of steam intended to be worked with.

"Some persons have worked those engines under a pressure above 100 lbs. on the square inch, but in general practice I do not exceed 20 lbs., finding under this pressure the piston will stand six or eight weeks, and the joints remain perfect, and no risk of bursting the boiler, it being made of wrought iron, and proved by pressure before sent off; but cast-iron boilers may, by defects not discernible, and are very apt to break by the water being left low in the boiler, and if heated red hot, exploding without the smallest notice; but wrought-iron boilers, when defective, give way only partially, without injury to anyone. With respect to the erecting and management of the engine, you need not have an engineer, for any common tradesman can do this from the drawings and directions sent with the engine; for, as I before informed you, farmers and their labourers set up and keep in order the thrashing-machine engines without my going on the spot or sending any person to assist them. I never saw a steam-engine rolling malt, therefore cannot judge the quantity the engine would roll, only by a comparison with horse labour, against the consumption of coal, which will be in some cases as about 42 lbs. to one horse; but where great speed is required in the machine, the coal will be less, as steam-engines make more revolutions in a minute than horse mills, therefore the work is done with less friction.

"I have several times applied the steam, after it has worked the engine, to boil water and other purposes, with as good effect as if the engine had not been there, therefore the work of the engine will be a clear profit.

"You say about a 1-horse engine. The boiler would be so small that it would not be worth applying that steam to any other purpose, as any large quantity of water would be but slowly heated.

"I find that it does not answer either the purpose of the vendor or the user of an engine, to make less than a 2-horse power, as the expense on a very small engine is nearly as much as one of the power I use for thrashing, those being only 80l., and a 2-horse is 60l. Respecting the mashing with steam, I never before heard of it, but from the theory of the plan I think it cannot fail to answer a far better purpose than any other that can possibly be applied for extracting the essence of the malt. However, should it not answer your purpose, it is only the loss of the expense of a few yards of 1-inch lead pipe.

"In an engine of the size used for thrashing, if the fire is kept brisk, it will boil, by the steam sent into a separate vessel, near 300 gallons of water per hour.

"The room required to work in is about 7 feet diameter, and 12 feet high. It would be useless to put you to the expense of drawings, until you have made up your minds on what you intend to have done.

"I am,Gentlemen,
"Your most obedient humble servant,
"Richard Trevithick.

"To Robinson and Buchanan, Brewers,
"Londonderry, Ireland."

Engineers of the present day do not volunteer such general information without charge, or give such a variety of practical mechanism slightly but clearly described, and principles reduced to practice. An endless chain with buckets is a form of water-wheel not then in use. A water-pressure engine for so small a quantity of water, with a fall of about 30 feet, would cause a loss of 50 per cent. from friction and small defects. The non-elastic character of water made it unsuitable for a machine requiring a fly-wheel. Air-vessels should be used to lessen the rigidity of water. Cast-iron boilers dangerous. Wrought-iron boilers to be tested with a water pressure four times as great as the proposed working steam pressure. A steam pressure of 20 lbs. to the inch most suitable for engines in charge of inexperienced persons. The brewers' mash tub to be heated by the waste or surplus steam.

[Rough draft.]

"Gentlemen,

"Camborne, December 5th, 1812.

"I have yours of the 20th November. The letter you directed for Truro never came to hand. I find by your letter that you have been trying to put into practice the hints I gave you about the chain and buckets, and that you expect it will answer if properly executed. You are not the first that has picked up my hints, and stuck fast in their execution. I make it a rule never to send a drawing until I have received my fee, and when you remit to me fifteen guineas I will furnish you with proper drawings and directions to enable you to make and erect the machine.

"I remain, Gentlemen,
"Your very humble servant,
"Richard Trevithick.

"Robinson and Buchanan, Brewers,
"Londonderry."

What a pocket encyclopædia of inventions! from which, as by stealth, Robinson and Buchanan selected the least applicable, declining a suitable steam-engine at a very small cost, rather than pay an engineer for his opinion.

[Rough draft.]

"Sir Charles Hawkins, Bart.,,

Camborne, April 26th, 1812.

"Sir,—I have received yours of the 7th, respecting the small breakwater at St. Ives. As far as I can judge from a rough calculation, I think it an undertaking likely to pay well; but as you wished me not to mention anything about your intentions, and not receiving your orders to make a minute inquiry and estimate, I cannot answer your letter so fully as I should wish, fearing that giving a random and imperfect statement might be apt to lead you into errors, and also make me look simple. If an engineer were employed to survey and estimate after me, every information in my power is at your service; therefore be pleased to state particularly what information you wish, and I will attend to the business and answer your questions as early as possible.

"I have received a letter from Sir John Sinclair requesting correct drawings and statements of the thrashing engine to be forwarded to the President of the Board of Agriculture, which I shall attend to. He also says that he has sent my letter to the Navy Board, in hopes that the experiment of propelling vessels by steam may be tried under its sanction and expense.

"Perhaps it might be proper to wait the answer of the Navy Board before writing to Mr. Praed about propelling the canal boats. I am very much obliged to you for writing to Captain Gundry, about the Wheal Friendship engine. I expect to have a portable steam-whim and stamps at work at my own expense in a few days, which will prove for itself its utility; that being the only way to introduce new things. I would be very much obliged to you to say if Mr. Halse is to pay me for my past attendance at St. Ives about the breakwater. Enclosed you have a letter to Sir John Sinclair, unsealed for your inspection, which, if you approve of, please to forward.

"I remain, Sir,
"Your very humble servant,
"Richard Trevithick.

Trevithick's skill did not prevent his being reasonably modest, or cause him to be envious of others; neither did his dear-bought experience, that one's own pocket must pay for making public one's own inventions, prevent his again soliciting the assistance of persons of influence, though it does not seem that Mr. Praed helped forward the screw-propeller, or that Sir John Sinclair gave direct help, though he probably made known the high-pressure steam-engine to the marine experimenters on the Clyde.

[Rough draft.]

"Mr. Rastrick,

"Camborne, December 7th, 1812.

"Sir,—I have been waiting your answer to my last, and especially that part respecting the West India engine, as I have not nor could not answer their letter to me without first hearing from you; therefore must beg you will be so good as to answer me by return of post on that subject. If they get impatient about the time, and refuse to take the engine, I have no doubt the Plymouth people will take it and several others; but I very much wish to send one to the West Indies, as there is a large field open there for engines of this kind. I have received an order for a thrashing engine for Lord de Dunstanville, of Tehidy; and as I wish those thrashing engines to be known through the country, I intend to take one of the engines ordered for Padstow and send it to Tehidy. One of the Padstow farmers can wait until you make another for him. Therefore I would thank you to send the first finished by ship from Bristol for Portreath or Hayle. Send a drum with everything complete, of which you are a better judge than I. Probably about 3 feet in diameter and 3½ feet long will be sufficient.

"There must be a fly-wheel with a notch to carry the rope, and also a small notch-wheel on the drum-axle. I think 6½ feet diameter for the fly, and 9½ inches diameter for the small wheel, will give speed enough to the drum. Mind to cast a lump, or screw on a balance, of about 1 cwt., on one side of the fly-wheel. There must be two stands on the boiler, and a crank-axle, or otherwise a crank-pin, in the fly-wheel, whichever you please; with a shaft 3 feet long with a carriage.

"The engine is to stand in a room under the barn, about 7½ feet high, 7 feet wide, and 14 feet long. The fly-wheel will stand across the narrow way of the room. The rope will go up through the floor, and the drum be shifted by a screw, horizontally, on the barn floor, so as to tighten the rope. I shall put down the top of the boiler level with the surface, with an arched way to the fire and ash-pit under ground, to prevent the chance of fire, which the farmers are very much afraid of. I send you a sketch showing how it is to stand.

"I do not bind you to the size of the drum or wheels, only the room that the fly-wheel works in is but 7 feet wide.

"Now to Mr. Richards' mill.

"Query 1st.—The length of the piston, and the small variation that the beam will give it, is so trifling that it will not be felt.

"The cylinders that have been working on their sides for seven years past, are now working as well as any engine with upright cylinders, which is a proof that the little rubbing is of no consequence.

"Query 2nd.—The passage in the cock is equal to the passage we make in our large engines, which is only one-fortieth part of the piston; and as we shall work with high steam, we do not mind the pressing through the steam-passage; and as the steam will be very much expanded, it will not be felt in the passage to the condenser. I know where we have removed cylinders and put larger ones on the same nozzles and condensing work, and the engines did good duty.

"Query 3rd.—I find by experience that if you give double the quantity of injection to an engine one stroke, and none the other, that the quicksilver in the gauge will stand nearly the same; the cold sides of the condenser are sufficient to work an engine a great many strokes without any injection.

"Query 4th.—You may put a hanging to the air-pump bucket, and foot-valve; either that or a rising one will do very well, but I think the rising cover and wood face on the top, best.

"Query 5th.—The air-pump bucket is large enough. At Wheal Alfred they have a 64-inch cylinder; the air-pump is 20 inches, and the stroke is half that of the engine. They were afraid that it was too small; they then put another of 14 inches by the side of the first, the same stroke. The quicksilver tube stands as high with the one 20-inch bucket as with the two buckets; the engine works best with the one bucket. I have found by experience that size to be sufficient, and (especially in an engine that works quickly) make the cistern high enough to cover the condensing work well with water.

"Query 6th.—My reason for making the forcing pump with duck-valves is, because they do not bum like the others, and we find them seldom out of repair; but make it whichever way you think best, and work it in any way you like.

"Query 7th.—I mean by ¾ expansive, that the steam is to be shut off from the cylinder when the piston has moved up from the bottom one quarter of its stroke. Make the cam to your own mind.

"Query 8th.—I do not think the engine will require a heavier fly-wheel, as the stones will act as a fly, and the power, though so very irregular, will be so sudden in its changes, that the speed of the machinery will not let it be felt. If you make a crank, you may make the fly-wheel 3 or 4 feet more in diameter. But if with a pin in the fly-wheel, the beam would come down on the top of it; therefore, I think it will be better to put a crank, and put the fly-wheel in the middle of the shaft.

"Query 9th.—The steam will be raised to 25 lbs. to the inch above the atmosphere, or 40 lbs. to the inch on a vacuum; but I think you need not calculate for much more strength on that account. It is not the power that breaks the machinery, but bangs, and not the uniform weight that this will give.

"Query 10th.—Twenty strokes per minute I propose, which I think a fair speed.

"Query 11th.—The fire-bars must be of wrought iron; we find them answer much better than cast iron. Let them be 5/8ths of an inch from bar to bar, 1 inch thick at the top, 3/8ths of an inch at the bottom, 2 inches deep, 4 feet long, with bits on them at the ends, to prevent their getting too close together. I find the nearer the fire is to the door, the better and handier it is to work. All the large engines are in this way, and we do not find the door or front plate get hot, as they are lined with brick. Cast the door with a rib to hold a brick on its edge. Tube, 2 feet 9 inches by 1 foot 11 inches; manhole, 15 by 10 inches.

"Query 12th.—A governor will be required; perhaps as good a place as any for it, out of the way, will be on the cast iron that carries the beam; you may turn the fly-wheel whichever way you please. If this engine is worked with steam of 25 lbs. to the inch above the atmosphere, and the steam shut off at one-twentieth part of the ascending stroke of the piston, the power will be as three is to two of Boulton and Watt's single engines.

"Only two pairs of stones for the present, but calculate those stones to stand in such a way that another pair may be placed, on a future day, if wanted. I have not seen Mr. Richards lately. I wish you to write a form of an order, in your next, such as you wish, and I will get him to write to you accordingly. Put the engine and drum for Lord de Dunstanville out of hand neat and well, as it will be well paid for; and make the stands, &c., in your own way.

"Rd. Trevithick."

Mr. Richards' flour-mill engine may claim to be the first practical smoke-burner: keeping the fire much thinner at the inner end of the grate-bars than at the fire-door end of the grate, allowed of the freer passage of air through the thinner layer of coal, near the fire-bridge, causing the combustion of the passing gas. This idea has, since the date of Trevithick's letter, led to several smoke-burning patents. The boiler fire-tube was oval, 2 feet 9 inches by 1 foot 11 inches. The open-topped cylinder was supplied with a heavy and deep piston serving as a counterweight, and also as a guide in the cylinder for correcting the angle of the connecting rod. Experience had taught him that the cold sides of the condenser were sufficient to work an engine a great many strokes without a supply of injection; and he had already used high-pressure steam of 25 lbs. to the inch above the atmosphere, cut off from the cylinder when the piston had performed one quarter of its course: thus both these things were as first steps leading to the modern expansive steam-engine and surface condensation.

The simplicity of the engine is remarkable—a high-pressure, expansive, condensing engine, worked by a single four-way cock, without cylinder-cover, or parallel motion.

The low first cost, and non-liability to derangement, were always kept in view; and his confirmed experience in the satisfactory working of horizontal cylinders prior to 1812 illustrates their extended application; for at that time scarcely any other engineer had constructed other than upright cylinder engines. No detail escaped his observant gaze. The fire-bars were to be 2 inches deep, 1 inch thick at the top edge, tapered to ¾ths of an inch at the bottom, giving the required strength, with free room for air, which in its passage cooled the bar, carrying the heat into the fire. Years before and after that period the fire-bar in common use by thoughtless people was a square iron bar that was always burning and bending.

The letter is descriptive of the high-pressure steam-engine in the sixteenth year of its age; and its expansive steam, made practical by Trevithick's high-pressure boilers. This engine only took steam during the first quarter of its stroke, the remaining three-quarters were by the expansion. Had it taken steam only during one-twentieth of its stroke, it would have been more powerful than Boulton and Watt's low-pressure steam vacuum engine of the same size.

[Rough draft.]

"Sir,

"Camborne, November 8th, 1812.

"I have your favour of the 3rd inst., informing me that Messrs. Fox and Williams have engaged to quarry the stone for e breakwater at Plymouth, but does not say whether you hold any share with them in the contract or not. Therefore I cannot understand from your letter whether you wish to see an engine fitted to the purpose of the breakwater, or for pumping the water from the foundations of the Exeter Bridge. Please to inform me which of the two purposes you wish to see the engine calculated for, and about what time you think you shall want it, and I will get one finished suitable to the purpose you intend it for.

"Yours, &c.,
"R. T.

"Jas. Green, Esq., St. David's Hill, Exeter.

"N.B.—To what extent have Messrs. Fox engaged, and what parts of the work do they perform? I think more good might be done by loading, carrying, and discharging, than by quarrying only."

Trevithick was equally ready with the application of steam-power either for pumping of water or for boring and removing rock. The use of chisels and rock-breakers in the Thames in 1803[4] had prepared the way for the more perfect engine for boring, lifting, and carrying rock from the quarries to its destination at the Plymouth Breakwater in 1812.[5]

"Sir,

"106, Holborn Hill, November 26th, 1812.

"I am in receipt of yours of the 22nd inst. Mr. Giddy informs me that Mr. Fox and Mr. Williams are to have 2s. 6d. per ton for making the breakwater at Plymouth, and he considers that they can do it for 2s., which he thought would give them 50,000l. profit. If you meet those gentlemen, I have to caution you not to LEARN THEM anything until you make a bargain, as I know Mr. Williams will endeavour to learn all he can and then you may go whistle.

"If 6d. per ton will give 50,000l. profit, a halfpenny per ton would give upwards of 4000l. Would they agree to give you that for your labour only? However, this will depend in a great measure on the time it will take in doing. If it takes eight years it would be 500l. a year for you (according to Mr. Giddy's calculation).

"Your well-wisher,
"Henry Harvey.

"Mr. Rd. Trevithick, Camborne."

Mr. Harvey knew Trevithick's weakness in money matters. Rennie had been employed to report on the proposed Plymouth Breakwater, and in 1811 was desired by Lord Melville, the head of the Admiralty, to proceed with the work. "The price paid in 1812 for taking and depositing rubble in the breakwater was 2s. 9d. per ton; it was afterwards reduced to 1s. per ton. A piece of ground was purchased from the Duke of Bedford at Oreston, up the Catwater, containing 25 acres of limestone, well adapted for the purposes of the work; and steps were taken to open out the quarry, to lay down railways to the wharves, to erect cranes."[6] The idea of the plan to be followed in conveying stone with greater economy and dispatch than was contemplated by Rennie, originated with Trevithick, while the former received the credit and the pay, as he before had done with the steam-dredger.

[Rough draft.]

"Mr. Fox Jun.,

"Camborne, January 29th, 1813.

"Sir,—Since I was at Roskrow I have been making trial on boring lumps of Plymouth limestone at Hayle Foundry, and find that I can bore holes five times as fast with a borer turned round than by a blow or jumping-down in the usual way, and the edge of the boring bit was scarcely worn or injured by grinding against the stone, as might have been expected. I think the engine that is preparing for this purpose will bore ten holes of 2½ inches in diameter 4 feet deep per hour. Now suppose the engine to stand on the top of the cliff, or on any level surface, and a row of holes bored, 4 feet in from the edge of the cliff, 4 feet deep, and about 12 inches from hole to hole for the width of the piece to be brought down at one time, and wedges driven into the holes to split the rock in the same way as they cleave moorstone, only instead of holes 4 inches deep, which will cleave a moorstone rock 10 feet deep when the holes are 14 or 15 inches apart, the holes in limestone must go as deep as you intend to cleave out each stope, otherwise the rock will cleave in an oblique direction, because detached moorstone rocks have nothing to hold them at the bottom, and split down the whole depth of the rock. In carrying down a large piece of solid ground the bottom will always be fast, therefore unless it is wedged hard at the bottom of the hole the stope cannot be carried down square. In a hole 2½ inches diameter and 4 feet deep put in two pieces of iron, one on each side of the hole, having a rounded back, then put a wedge between the two pieces, which might be made thus, if required to wedge tighter at the bottom of the hole than at the top.

"If this plan answers, the whole of the stones would be fit for service, even for building, and would all be nearly of the same size and figure. Each piece would be easily removed from the spot by an engine on a carriage working a crane, which would place them into the ship's hold at once. It would all stand on a plain surface, and might be had in one, two, three, or four tons in a stone, as might best suit the purpose, which would make the work from beginning to end one uniform piece. Steam machinery would accomplish more than nine-tenths of all the work, besides saving the expense of all the powder. I find that limestone will split much easier than moorstone, and I think that a very great saving in expense and time may be made if the plan is adopted.

"Please to think of these hints and write me when and where I may see you to consult on the best method of making the tools for this purpose before I set the workmen to make them. Any day will suit me, except Monday, the 8th of February. The sooner the better, as I cannot set to work to make the tools until we have arranged the plan.

"I am, Sir,
"Your humble servant,
"Rd. T."

The successful completion of the Mont Cenis Tunnel in 1871 was mainly due to an ingenious application of combined mechanical force to boring tools, before limited to man's strength; but the applied principle existed sixty years ago, and though not so perfect in detail, yet more comprehensive. Trevithick's high-pressure steam boring engine enabled him to penetrate the rock five times as fast as the quarryman's power. Ten holes, 2½ inches in diameter, 4 feet deep, could be bored in an hour, and he sagaciously suggested that in quarrying the limestone for the breakwater, a row of holes should be bored by his engine 4 feet in from the face of the rock, 2½ inches in diameter, 4 feet deep, and 12 inches apart; and by dropping into each hole two half-round pieces of iron, to be driven asunder by a steel wedge, large blocks would be forced off without the use of gunpowder. The high-pressure steam-puffer having bored the stone, moved itself toward the broken mass, lifted it into waggons, and again changing its powers from steam-crane to steam-locomotive, conveyed it to the port, and lifted it into the ship's hold. The whole operation was thus aptly described by the inventor, who then counted on contracting for the breakwater work:—"Steam machinery will accomplish more than nine-tenths of all the work, besides saving the expense of all the gunpowder."

[Rough draft.]

"Mr. Robert Fox, Jun.,

"Camborne, February 4th, 1813.

"Sir,—Since I was with you at Falmouth I have made a trial of boring limestone, and find that the men will bore a hole 1½ inch in diameter 1 inch deep in every minute, with a weight of 500 lbs. on the bit. I had no lump more than 12 inches deep; but to that depth I found that having a flat stem to the bit of the same width as the diameter of the hole, twisted like a screw, completely discharged the powdered limestone from the bottom of the hole without the least inconvenience.

"From the time the two men were employed boring a hole 12 inches deep, I am convinced to a certainty that the engine at Hayle will bore as many holes in one day as will be sufficient to split above 100 tons of limestone, and would draw that 100 tons of stone from the spot and put them into the ship's hold in one other day. The engine would burn in two days 15 bushels of coal, four men would be sufficient to attend on the engine, cleave the stone, and put it into the ship's hold. I think it would not amount to above 9d. per ton, every expense included, but say 1s., which I am certain it will not amount to. Perhaps it may not be amiss to withhold the method of executing this work until the partners have more fully arranged with me the agreement as to what I was to receive for carrying the plan into execution. I do not wish that anyone but your father should be made acquainted with the plan, and have no doubt he will have sufficient confidence in the scheme to adopt it. I shall be glad to hear from you soon, as I intend to go to Padstow in a few days and shall not return under a fortnight.

"Your humble servant,
"Rd. Trevithick.

"N.B.—I this day received a letter from Mr. Gould, requesting to know what the expense of an engine and apparatus would be for clearing Falmouth Harbour, which I have sent by the post."[7]

It had been and still is the custom to bore rock either with a long and heavy jumper-chisel, lifted a foot or two, and falling by its own weight, pounding to powder a portion of the rock, or by the use of a much smaller chisel called a borer, struck by a hammer. Trevithick having made his steam-engine perform those jumper and borer movements, turned his attention to the improvement of the borer, and found that a revolving bit was more suitable for drilling limestone than the borer-chisel. The powdered stone was removed from the hole by giving a screw form to the stem of the bit. Many years afterwards precisely similar bits for boring wood were patented as new things, and are still used. Within five months of his first communication with the contractors for the Plymouth Breakwater he had designed and made an engine to bore, lift, and convey to the ship's hold 50 tons of stone daily at less than half the cost Rennie was then paying for it.

[Rough draft.]

"Sir,

"Camborne, February 4th, 1813.

"I have your letter of the 31st January requesting to know the time in which the engine will be ready for the bridge at Exeter, and also about giving an additional power to it.

"The engine shall be ready in six weeks from the end of January, and shall be capable of lifting the 10-inch bucket you have ordered instead of the 9-inch before proposed, which was to have delivered 500 gallons of water 12 feet high per minute; but now the engine shall be made to lift in the same proportion as a 9-inch is to a 10-inch bucket, which will be 617 gallons of water per minute instead of 500 gallons, as was before agreed on, and I shall charge you accordingly. I observe that you have ordered the pump, and from the description you give of it, I think it will answer very well. If you wish a perpendicular cylinder instead of a horizontal, I can construct it in that way, but it will not be so convenient for a portable engine. I have now engines with horizontal cylinders at work above ten years, and find them answer equally as well as a perpendicular cylinder.

"I remain, Sir,
"Your very humble servant,
"Richd. Trevithick.
"Jas. Green, Esq., Exeter."

Engineers nowaday are not in the habit of designing and constructing a steam-engine in six weeks, or willing to alter the agreed form from the horizontal to the vertical without charge.

[Rough draft.]

"Mr. Robert Fox, jun., informed me the other day that you had the sole direction of the work at Plymouth. Had I known it at the time you were at Scorier I should have communicated to you my ideas relating to the application of machinery there; but until a few days since I had an idea that the young Mr. Fox was about to take an active part in the management, which I now find was never his intention, only he very much wishes to have an experiment tried to see to what extent an engine was capable of performing as against men. An engine is now preparing for that purpose."

"Sir,

"Camborne, February 24th, 1813.

"On my return from Padstow this evening, where I have been for the last fortnight, I found your letter of the 11th inst. respecting the getting an apparatus ready for the Plymouth undertaking. Before I set about it I wish to see you and Mr. Fox, and will call any day you may appoint. Waiting your reply,

"I remain, Sir,
"Your very humble servant,
"R. Trevithick.

"Mr. Robert Fox, Jun., Falmouth"

After three months of experimental scheming, without a thought of keeping his inventions secret, Trevithick for a moment became worldly wise, and asked for a written agreement before sending his locomotive boring engine to the breakwater.

[Rough draft.]

"Mr. Fox,

"Camborne, 14th March, 1814.

"Sir,—I expect to be called to London immediately after the end of this month. The engine with the boring apparatus for Plymouth remains at Redruth. I very much wish to see you on that business before I leave home, and would be much obliged by your dropping me a note by post, saying what day it would be convenient for me to wait on you.

"R. T."

The rock-boring machine was completed, and reached the breakwater two months after his interview with the Foxes, who were prominent in the quarrying work. "The engine for Plymouth will be put to break the ground as soon as I can find time to go up there."[8] It was impossible for any one man, single-handed, to make perfect such numerous practical inventions as were undertaken by Trevithick at that time. His letter of a few months before[9] reveals the facility with which he moulded the steam-engine to his requirements. "The ploughing engine that I sent you a drawing for, after being used for that purpose, was to have been sent to Exeter for pumping water. I have been obliged to take the small portable engine from Wheal Alfred Mine, and have a new apparatus fitted to it for Plymouth Breakwater. A small engine which I had at work at a mine I have been obliged to send to the farmers for thrashing." Messrs. Fox would probably require many engines for the Plymouth Breakwater, having engaged with Government to deliver three million tons of stone; and to prevent delay, the boring apparatus was applied to an engine made for another purpose, while drawings for a new and more suitable engine for boring stone were sent to Mr. Rastrick.

He engaged that an engine should bore holes to split 100 tons of limestone a day; and that on the following day it should, as a locomotive and steam-crane, load that quantity in waggons, convey it from the quarry to the port of shipment, and then by steam-crane place it in the hold of a vessel. The whole of the work to be done by 11 cwt. of coal and four men. The gross cost would be 1s. per ton for breaking and removing, though at that time Mr. Rennie was paying 2s. 9d. a ton, which in after years was reduced to 1s., just what Trevithick said was a fair price.

While this ready application of the high-pressure steam-engine was going on in England, it had also extended to, and was coining money in the Mint at Lima, where Trevithick contemplated going to look after it, intending to land at Buenos Ayres, and make his way across the continent of South America and the mountains of the Cordilleras as best he could, leaving the home field he had made so fertile to be reaped by others, and the stone-boring locomotive to be forgotten for many years.

[Rough draft.]

"Sirs,

"Penzance, December 9th, 1815.

"Your very great neglect in not writing.... Herland engine will work, I expect, in about fifteen days. It is a plunger of 33 inches diameter, 10-feet stroke, with a double packing around the top of the plunger-pole, in the same way as the steam is turned into the stuffing box of a double engine to exclude the air, only there is a small tube from the bottom of the boiler to the middle of the stuffing box to prevent the escape of steam.

"I am sorry to find by Mr. Uville's letter that the Mint engine does not go well. I wish you had put the fire under the boiler and through the tube, as I desired you to do, in the usual way of the long boilers; then you might have made your fire-place as large as you pleased, which would have answered the purpose and worked with wood just as well as with coal. I always told you that the fire-place in the boiler was large enough for coal, but not for wood; also if you found that the cock did not open and shut in proper time, to make the gear to it work the same as the Dolcoath puffer whim-engine instead of the circular gear. The boiler is strong enough and large enough to work this engine with 30 lbs. to the inch, thirty strokes per minute. I hope to leave Cornwall for Lima about the end of this month, and go by way of Buenos Ayres, and cross over the continent of South America, because I cannot get any other passage. None of the South Sea whalers will engage to take me to Lima, as they say they may touch at Lima or they may not. Unless I give them an immense sum they will not engage to drop me there. To be brought back to England after a two years' voyage without seeing Lima would be a very foolish trip. To make a certainty I shall take the first ship for Buenos Ayres, preparations for which I have already made."

This unfinished rough draft was intended for one of the men who had gone to Lima, less fruitful in emergency than Trevithick, who, without a moment's hesitation, would have constructed a fire-place outside the boiler, when the internal tube fire-place was found to be too small for a wood fire. Trevithick's proposing sixty years ago to make his way over the almost unknown track from Buenos Ayres, on the Atlantic, to Lima, on the Pacific, was perhaps characteristic of his daring spirit, that turned all things to good account; but he dreamed not that his grandson and namesake would at this time be conducting the steam-horse on the same line of march on the Central Argentine Railway from Rosario to Cordoba, in the Argentine Republic.

[Rough draft.]

"Gentlemen,

"Camborne, August 19th, 1813.

"I received yours at Bridgenorth of the 19th July, ordering a steam-engine for rolling sugar-cane. I immediately set the founders to work on one for you, which is to be ready by my return to Bridgenorth about the end of September. I intend to ship it for Bristol, and will call on you on my journey down to Cornwall, as I intend to set it to work at Bristol for your inspection before it is put on board ship. The price I cannot accurately say at present, as the engine now making is on a new principle; and as it will be more simple in construction, I hope to be able to render it within the price before stated to you. As it is on a new plan I cannot fix the price until I know the cost of making. All I can say at present is that it shall not exceed what I stated to you in my former letter.

"I remain, Sirs,
"Your humble servant,
"Rd. Trevithick.

"Messrs. Pinneys and Ames, Bristol."

The engine for the sugar plantations in Jamaica, on an improved plan, was to be constructed in the short space of six weeks, and if a saving in cost was effected, the inventor would hand the whole of it to the purchaser.

[Rough draft.]

"Sir,

"Penzance, Cornwall, March 8th, 1816.

"I received your favour of the 25th January, but did not answer it in due course, because I was then erecting a very large engine, which is the first on a new plan. This engine, which has been at work about a month, performs exceedingly well. The cost of erection and the consumption of coal are not above one-third of a Boulton and Watt's, to perform the same work. An engine of 4-horse power will not require a space of more than 5 feet high, 5 feet long, and 3 feet 6 inches wide. In some instances I employ a balanced wheel 5 feet in diameter. The water required will be a pint and a half per minute. The coal, one quarter of a bushel or 21 lbs. per hour. The price of a machine, finished and set to work, 100 guineas. It does not require either wood or mason work, but stands independent of every fixture, and may be set to work in half an hour after being brought on your premises.

"Your obedient servant,
"Richd. Trevithick.

"Dr. Moore, M.D., Exeter."

A 4-horse-power portable high-pressure steam-puffer engine cost 105l., with internal fire-tube and machinery attached to the boiler, ready for work in half an hour after lighting the fire, consumed 21 lbs. of coal and 11 gallons of water for each hour's work, at a cost of threepence.

The reader's attention has been very imperfectly drawn to the numerous subjects touched on in these remnants of Trevithick's correspondence between the years 1804 and 1816; among them may be traced the portable high-pressure steam-engine, the tubular cylindrical boiler of wrought iron, the economy of expansive working with steam of 100 lbs. on the inch, but limiting it to 20 lbs. when not in the charge of experienced workmen, and testing boilers by water pressure to four times the intended working pressure.

The economy of heat in smelting furnaces and in the aërated steam-engine were bold means to large results. The cheap 100l. steam-engine of 1812, with open-top cylinder and rigid simplicity of gear, resembling Newcomen's first atmospheric engine, was really a high-pressure steam expansive engine, with the germ of surface condensation, as ready to convey itself from mine to mine or from farm to farm, and to join in performing labourer's work, even to boring and conveying rock by land or sea, as the most perfect of modern engines; and yet this unadorned engine, as seen in the agricultural engine of the following chapter, followed the excellent mechanism of the double-acting Kensington model of 1798, and the still more beautiful engine of the 1802 patent and London locomotive.

[CHAPTER XVIII.]

AGRICULTURAL ENGINES.

The late Mrs. Trevithick said "that during the difficulties in London in 1808 and 1810, when Trevithick was overwhelming himself with new experiments and the cost of patents, and law expenses, lawyers and bailiffs took everything worth having from her house, including account-books, drawings, papers, and models, which she never saw again."

His earlier account-books left in safety in his Cornish home, though very disconnected, give trustworthy traces of his work up to 1803. From that time only detached accounts or papers are found until 1812, when the unused pages in two old mine account-books of his father served as his letter (rough-draft) books; and judging from their number and style, his correspondence was most extensive and varied.

[Rough draft.]

"Hayle Foundry, February 13th, 1812.

"To Sir Christopher Hawkins, Baronet.

Sir I now send you, agreeable to your request, a plan and description of my patent steam-engine, which I lately erected on your farm for working a thrashing mill. The steam-engine is equal in power to four horses, having a cylinder of 9 inches in diameter. The cylinder, with a moderate heat in the boiler, makes thirty strokes in a minute, and as many revolutions of the fly-wheel, to every one of which the drum of the thrashing mill (which is 3 feet in diameter) is turned twelve times. The boiler evaporates 9 gallons of water in an hour, and works six hours without being replenished. The engine requires very little attention—a common labouring man easily regulates it.

Trevithick's High-pressure Steam-puffer Thrashing Engine, 1812.

"The expense of your engine of 4-horse power, compared with the expense of four horses, is as follows:—

"Two bushels or 164 lbs. of coal will do the work of four horses, costing 2s. 6d.

"Four horses at 5s. each, gives 20s. Cost of coal, 2s. 6d. as compared with 20s. for horses.

"I remain, Sir,
"Your obedient servant,
"Richard. Trevithick.

"Cornwall, February 20th, 1812.

"Having been requested to witness and report on the effect of steam applied to work a mill for thrashing corn at Trewithen, we hereby certify that a fire was lighted under the boiler of the engine five minutes after eight o'clock, and at twenty-five minutes after nine the thrashing mill began to work, in which time 1 bushel of coal was consumed. That from the time the mill began to work to two minutes after two o'clock, being four hours and three-quarters, 1500 sheaves of barley were thrashed clean, and 1 bushel of coal more was consumed. We think there was sufficient steam remaining in the boiler to have thrashed from 50 to 100 sheaves more barley, and the water in the boiler was by no means exhausted. We had the satisfaction to observe that a common labourer regulated the thrashing mill, and in a moment of time made it go faster, slower, or entirely to cease working. We approve of the steadiness and the velocity with which the machine worked; and in every respect we prefer the power of steam, as here applied, to that of horses.

(Signed) "Matthew Roberts, Lamellyn.
"Thomas Nankivill, Golden.
"Matthew Doble, Barthlever."

This first high-pressure steam thrashing machine was working on the 13th February, 1812, at Trewithen, the property of Sir Christopher Hawkins, as proved by Trevithick's drawing of the machine, his account of the work performed, and the report of the three wise men that the power of steam was preferable to the power of horses. Its first cost was less than that of a horse machine; but to make the calculated amounts come right Trevithick charged 15 per cent. for wear and tear on the horse machinery, and but 5 per cent. on the steam-engine; overlooking the cost of the horses, which would have made the outlay for the horses and machinery greater than for the steam-engine.

The whole design evidences simplicity and consequent cheapness; no complication of valves or valve-gear, no cylinder cover, parallel motion, guide-rods, or air-pump, with its condenser and injection-water.

The 4-horse engine, with boiler complete, cost 90l. A common labourer worked it, and as it needed no supply of feed-water during six hours of work, the cost and attention of supplying feed were avoided. If a supply was required during the day it could be given by a pipe with two taps.

This first use of steam in agriculture was immediately followed by Lord Dedunstanville of Tehidy, Mr. Kendal of Padstow, and Mr. Jasper of Bridgenorth. Sir Charles' request for a more official report signed by disinterested persons brought a reply that the thrashing engine continued to work well. "It far exceeds my expectation. I am now building a portable steam-whim, on the same plan, to go itself from shaft to shaft." "If you should fall in with any West India planter that stands in want of an engine, he may see this at work in a month, which will prove to him the advantage of a portable engine to travel from one plantation to another. The price complete is 105l."[10]

"Dear Sir,

"Argyle Street, 19th March, 1812.

"I am sorry it is not convenient for me to advance you the money for Wheal Liberty; adventurers having the dues very low, ought to furnish the needful. I am very glad you have succeeded with your portable steam-engine, and am persuaded they will be more and more adopted. I have shown your account of your thrashing by steam, and Sir John Sinclair and Mr. —— very highly approve it. Sir John Sinclair wished the communication had been made to the Board of Agriculture. Sir John wished me to transmit you the enclosed on coals moved by steam ... whether you had a plan of this sort, as they would be very serviceable in passing the friths in Scotland. He seems to think you ought to advertise your steam-engines for thrashing; indeed, I think so too.

"By the enclosed letter, Sir John Sinclair wishes you to send him an account of your improved steam-engines. You will be careful in drawing up your letter to Sir John, because it will probably be read to the Board of Agriculture, and perhaps inserted in their publication. You will begin by acknowledging his letter, of date ... respecting the American passage boat ... and your improved small steam-engine. You will give him an account of the saving you have effected at Dolcoath, and a certificate of the same by the mining captains; the engine for thrashing you built for me, and the work it did, and the coals it consumed; the expense of the steam-engines, and the uses they may be applied to.

"I remain, dear Sir,
"Yours most obediently,
"C. Hawkins."

In 1812 Trevithick advertised the use and sale of steam-engines, weighing 15 cwt., costing 63l., for thrashing, grinding, sawing, or other home work; and also a more powerful engine for the steam-plough, or the harrow and spade machine for 105l., to travel from farm to farm. He wrote to Sir John Sinclair:[11]—

"I received from Sir Charles Hawkins a copy of Dr. Logan's letter to you, also a note from you to Sir Charles Hawkins, both respecting the driving boats by steam; respecting the engine for thrashing, chaff-cutting, sawing, &c. I am now making one of about two-thirds the size of Sir Charles Hawkins', which will be portable on wheels. By placing the engine in the farm-yard, and passing the rope from the fly-wheel through the barn-door, or window, and around the drum on the machine axle, it may be driven.

"The steam may be raised, and the engine moved a distance of two miles, and the thrashing machine at work, within one hour.

"The weight, including engine, carriage, and wheels, will not exceed 15 cwt.; about the weight of an empty one-horse cart.

"The size is 3 feet diameter, and 6 feet high. If you wish to have one of this size sent to the Board of Agriculture as a specimen, the price delivered in London will be sixty guineas."

This engine differed from that referred to in the drawing of Sir Charles Hawkins, mainly in the boiler having the fire-place in the fire-tube, requiring no brickwork, and having the advantage of portability. It was very like the earlier locomotive boiler, except that it was placed upright, as steam-cranes now use boilers, instead of being horizontal.

[Rough draft.]

"Camborne, Cornwall, April 26th, 1812.

"To Sir John Sinclair.

"I have your favour of the 4th instant, informing me that you had sent my letter respecting propelling ships by steam to the Navy Board; and also requesting a drawing and statement of the thrashing engine to be sent to the President of the Board of Agriculture, which shall be forwarded immediately.

"I beg to trouble you with a few wild ideas of mine, which perhaps may some future day benefit the public, but at this time remain buried, for want of encouragement to carry it into execution.

"The average consumption of coals in large steam-engines is about 84 lbs. (or one bushel), to lift 10,000 tons of water or earth 1 foot high.

"The average cost of this coal in the kingdom is sixpence. The average of a horse's labour for one day is about 4000 tons lifted 1 foot high, costing about 5s.

"A man's labour for one day is about 500 tons lifted 1 foot high, costing 3s. 6d.

"I have had repeated trials of the water lifted by coals, horses, and men, proving that where a bushel of coal can be purchased for sixpence, that sixpence is equal to 20s. of horse labour, and to 3l. 10s. of men's labour.

"If you calculate a man to lift 500 tons 1 foot high, it is equal to 100 tons lifted 5 feet high; a very hard task for a man to perform in a day's work.

"This calculation proves the great advantage of elemental power over animal power, which latter I believe can in a great part be dispensed with if properly attended to, especially as we have an inexhaustible quantity of coals.

"To prove to you that my ideas are not mere ideas, in general my wild ideas lead to theory, and theory leads to practice, and then follows the result, which sometimes proves of essential service to the public.

"About six years ago I turned my thoughts to this subject, and made a travelling steam-engine at my own expense to try the experiment.

"I chained four waggons to the engine, each loaded with 2½ tons of iron, besides seventy men riding on the waggons, making altogether about 25 tons, and drew it on the road from Merthyr to the Quaker's-yard (in South Wales), a distance of 9¾ miles, at the rate of four miles per hour, without the assistance of either man or beast, and then, without the load, drove the engine on the road sixteen miles per hour.

"I thought this experiment would show to the public quite enough to recommend its general use; but though promising to be of so much consequence, has so far remained buried, which discourages me from again trying, at my own expense, for the public, especially when my family call for the whole of my receipts from my mining concerns for their maintenance.

"It is my opinion that every part of agriculture might be performed by steam; carrying manure for the land, ploughing, harrowing, sowing, reaping, thrashing, and grinding; and all by the same machine, however large the estate.

"Even extensive commons might be tilled and effectually managed by a very few labourers, without the use of cattle.

"Two men would be sufficient to manage an engine, capable of performing the work of 100 horses every twenty-four hours; requiring no extensive buildings or preparations for labourers or cattle, and having such immense power in one machine as could perform every part in its proper season, without trusting to labourers.

"I think a machine that would be equal to the power of 100 horses would cost about 500l.

"My labour in invention I would readily give to the public, if by a subscription such a machine could be accomplished and be made useful.

"It would double the population of this kingdom, for a great part of man's food now goes to horses, which would then be dispensed with, and so prevent importation of corn, and at a trifling expense make our markets the cheapest in the whole world; because there are scarcely any coals to be found except in England, where the extreme price, duty included, does not exceed 2s. per bushel.

"I beg your pardon for having troubled you with such a wild idea, and so distant from being carried into execution; but having already made the experiment before stated, which was carried out in the presence of above 10,000 spectators, who will vouch for the facts, I venture to write to you on the subject, for the first and only self-moving machine that ever was made to travel on a road, with 25 tons, at four miles per hour, and completely manageable by only one man, I think ought not to be dropped without further experiments, as the main point is already obtained, which is the power and its management.

"Your most obedient servant,
"Richard Trevithick."

The Board of Agriculture in 1812 had their attention drawn to the feasibility of using the steam-engine to save agricultural labour and lessen the cost of working land. Trevithick's intuitive knowledge told him his application would be in vain, though an engine was at work proving the saving of horse-power in the item of thrashing corn.

"I beg to trouble you with a few wild ideas of mine, which perhaps may some future day benefit the public."

A steam-engine could exert as much power by the consumption of 6d. worth of coal as could be given by 20s. of horse-power, or by 70s. worth of men's power.

"Ideas lead to theory, theory leads to practice, then follows the result, which sometimes proves of essential service to the public."

"It is my opinion that every part of agriculture might be performed by steam. Carrying manure for the land, ploughing, harrowing, sowing, reaping, thrashing, and grinding; and all by the same machine, however large the estate."

"Two men would manage an engine capable of performing the work of 100 horses."

Such a use of the steam-engine, judiciously managed, "would double the population of this kingdom, and make our markets the cheapest in the world; because England is the country best supplied with coal and iron for steam-engines, and the land now growing food for horses would be available for man."

Its cost would be 500l., and its power sufficient to propel the largest subsoil ploughs and tormentors; and had the Board of Agriculture supplied such a sum of money as is now ordinarily given by a farmer for a steam-plough, we should have had in 1812 ploughing, harrowing, sowing, reaping, &c., by steam. Years before, the same kind of engine had been made to work pumps, wind coal from shafts, drive rolling mills, tilt hammers, and steamboats, and convey material from place to place; and why should not his promise to the farmer be also made good with his increased knowledge derived from eight years of active experience? Receiving small encouragement in England, he applied to sugar-cane planters to give his engines a trial in the West Indies.

[Rough draft.]

"Sir Charles Hawkins, Bart.,

"Camborne, 1st May, 1812.

"Sir,—I have your favour of the 27th April, respecting a steam-engine for your friend for the West Indies, of the power of ten mules employed at one time. This power we calculate equal to forty mules every twenty-four hours, as six hours' hard labour is sufficient for one mule for one day.

"The expense of an engine of this power complete delivered in London would be 200l. The consumption of coals about 84 lbs., or one bushel, to equal the labour of three mules, or from 13 to 14 bushels of coal every twenty-four hours to perform the full work of forty mules (or in proportion for a lesser number), with a waste of about 15 gallons of water per hour, unless a reservoir was made to receive the steam, and then to work the same water over again.

"Where water is scarce, nearly the whole may be saved.

"You remarked that the rope might slip round the notch in the wheel; but to prevent any risk of that kind, I apply a small chain instead of the rope, which works the same as a chain on the barrel of a common thirty-hour clock.

"The speed of the periphery of the fly-wheel is about eight miles per hour, which I think is nearly double the speed of the mules when at work in the mill. This would reduce the size of the part which carries the chain on the cattle mill to half the diameter of the present walk of the cattle, which might be done without altering or interfering with the present cattle mills, and might, if required, either work separately or in conjunction with the mules in the same mill at the same time.

"To inform your friend of the power and effect of such an engine, I prefer his sending some person down to Cornwall, to see it tried on some of the cattle mills or whims in the mines.

"Engines that have been sent to the West Indies hitherto have cost nearer 2000l.; very large, heavy, and complicated machines, requiring 2500 gallons of water per hour for condensing, and could only be managed by a professed engineer, while any common labourer can keep in order and work these engines. If you prefer to send a person with it, the cost will be about 40s. per week.

"I remain, Sir,
"Your most obedient servant,

"Richard Trevithick."

This letter indirectly points out two long-standing radical errors in engineering phraseology. An early method of describing the value of an engine was by stating the number of pounds it would lift one foot high by the burning a bushel of coal, called the duty of an engine. Trevithick's bushel was 84 lbs., while other engineers, under the same term of bushel, meant various weights, up to 120 lbs.

Another form of speaking was the horse-power of an engine; meaning that a horse could lift a certain number of pounds one foot high in a minute, and that a steam-engine lifting ten times as much was a 10-horse engine; but, as Trevithick points out, a horse only works at that rate for six hours out of twenty-four, while the steam-engine works continuously, performing the work of forty horses, yet is called a 10-horse engine.

The high-pressure engine suitable for the West Indies was to be adapted to the existing horse or mule machinery, that either power might be used. Its first cost and expense in working to be much less than that of the Watt low-pressure steam vacuum engine.

[Rough draft.]

"Sir Charles Hawkins, Bart.,

"Camborne, June 13th, 1812.

"Sir,—Yours of the 15th of last month I received, enclosing a drawing of a sugar-mill from Mr. Trecothick, which I should have answered per return, but was at that time in treaty for an engine for a sugar-mill with a Mr. Pickwood, who is in St. Kitts in the West Indies.

"The engine is now being erected at Hayle Foundry, of the power of twelve mules at a time, or equal to forty-eight mules during twenty-four hours.

"The cost is 210l. complete, with numerous duplicate parts.

"I hope she will be finished and sent off in a short time.

"I have now so fully proved the use of those engines, that I have engaged to take this one back if it does not answer their purpose, and to refund the whole sum if they return the engine to me in working order within four years.

"This gentleman says, if this engine answers he shall have two more for his own use, and four of his friends are waiting to see the result before ordering their engines.

"The mules that will be turned out of use by Mr. Pickwood's engine will sell for five times the sum the engine will cost him, exclusive of the wear of mules, with their keep and drivers, besides the greater dispatch and pleasantness of working a machine instead of forcing animals in so hot a climate.

"If your friend wishes an engine of this power and on the same terms, I can get two made and sent to London nearly in the same time as one. Enclosed I send to you a rough sketch of the engine and mill. I am of your opinion, that Sir John Sinclair has taken a useless journey by calling on the Navy Board, for nothing experimental will ever be tried or carried into effect except by individuals.

"If I could get an Act of Parliament for twenty-one years for only one-tenth part of the saving which I could gain over animal power and expense, I have no doubt but that I could get money to carry the plan fully into effect for propelling ships, for travelling with weights on roads, and doing almost every kind of agricultural labour.

"But a patent is but for fourteen years, and open to constant infringement; for the inventor of general and useful machinery is a target for every mechanic to shoot at, and unless protected or encouraged by some better plan than a common patent, will have the whole kingdom to contend with in law, and most likely receive ruin for his reward, which has too often been the case.

"A plan of such magnitude as this promises to be of, I think ought to be carried into effect by subscription, and as soon as accomplished, the subscribers to be repaid, and the invention thrown open for the use of the kingdom at large. I think about 1000l. or 1500l. would test the designs.

"It is expected that Mr. Praed will spend some time in this neighbourhood; I hope I shall be able to prove to you and to him the great use of propelling barges by steam. I have a small engine now at foundry, and would put it on board one of their barges for your inspection. I am very much obliged for your continued favours, and beg pardon for so often troubling you. I have so fully proved the great advantages resulting from those portable engines, that I very much wish the public to have the full use of them.

"I remain, Sir,
"Your most humble servant,
"Richard Trevithick."

A 12-mule-power engine for St. Kitts was being erected at Harvey's foundry at Hayle; Trevithick making himself liable for the whole cost, in case it should not answer the purpose. The mules thrown out of work by the engine would sell for five times as much as the engine cost, to say nothing of the saving in wear and tear of drivers and mules, and the unpleasantness of driving a mule in hot weather as compared with a machine.

If an Act of Parliament would give him one-tenth of the saving he could effect during twenty-one years, a company might be formed for carrying into full effect his plans for propelling ships, travelling with weights on roads, and performing almost every kind of agricultural labour, while a patent for fourteen years was open to constant infringement, and the inventor of useful machinery was a target for every mechanic to shoot at, had law suits with the kingdom at large, and ultimate ruin, as a reward for his labours. Inventions of such general application, when fairly established, should be thrown open to the public, Government paying the inventors their expenses, and reasonable reward for their time.

[Rough draft.]

"Mr. Pickwood,

"Cornwall, Camborne, 17th June, 1812.

"Sir,—Yours of the 17th April I received about twenty days since, and from that time to the present have been in treaty with Messrs. Plummer, Barham, and Co., for your engine. We have now closed for an engine complete, of the power of twelve mules at a time, with suitable duplicates, chains, &c., for 210l. I very much wish for your engine to be set to work by your own workmen, to show the planters the simplicity and easy management of the machine, and also save the expense of an engineer, which will tend to promote their use. The engine will be set to work before it is sent off, and every possible care taken to execute it in the most perfect order. From the experience I have had with common labourers keeping these engines in order, since I wrote to you, I have no doubt you will get on satisfactorily.

"I hope to get the engine ready in five or six weeks, but I fear there will be loss of time in shipping it. You may rest assured that I will spare no time or attention to promote the performance of this engine. I am so far satisfied with the probability of its fully answering your purpose that I voluntarily offered Messrs. Plummer, Barham, and Co., that if you return it to me for working repairs within four years, I will refund the whole of the sum I am to receive for it. I will take particular care to mark every part and send you a full description.

"Enclosed I send you a sketch of the engine attached to a sugar-mill. Please write to me by return of the packet; it may be in time, before the engine is shipped, to alter, or send you such things as I may not be acquainted with. I shall be glad to know the number of yards your mules travel in an hour when going at what you call a fair speed, in the mill, and also what number of rounds you wish the centre roll to make in an hour when worked by the engine.

"I remain, Sir,
"Your very humble servant,
"Rd. Trevithick.

"R. W. Pickwood, Esq.,
"St. Kitts, West Indies."

These are not the remarks of an uncertain schemer; every sentence having the impress of the ability and fixed intention of perfecting the work, and the belief that the simplicity of the engine would enable a common labourer to use it.

[Rough draft.]

"Sir Ch. Hawkins, Bart.,

"Camborne, 5th July, 1812.

"Sir,—If your friend Mr. Trecothick intends to have a sugar-mill engine immediately finished and sent out with the one I am now making for Mr. Pickwood, he ought not to lose any time in giving his orders. I have made inquiry at Falmouth about sending out Mr. Pickwood's engine for St. Kitts on board a packet, which would save much time, but I fear it cannot be granted unless application is made by some person of note to the Post Office in London. Mr. Banfield of Falmouth told me that if application was made to send out a model as a trial, he had no doubt but it would be granted.

"This experiment with the portable engine that will travel from one plantation to another and work without condensing water, is certainly of the greatest consequence to the planters, and as the whole weight will not exceed 1¾ ton, I should hope that the Commissioners at the Post Office will grant this request. I am sorry to trouble you so often about my business, but I beg the favour of your goodness to inform me through what channel I ought to make this application.

"I remain, Sir,
"Your very humble servant,
"Rd. Trevithick.

This experiment with the 1¾ ton portable engine to travel from one plantation to another, needing no condensing water, was certainly of the greatest consequence to the planters in the West Indies, and should have been of equal importance to the people in England.

Judging from the weight and cost, as compared with agricultural engines of the present day, Trevithick was nearer the mark then than we are now; its working without condensing water the engineers of that day believed to be impracticable, a fundamental error which greatly retarded the use of the high-pressure steam-engine. The providing sufficient condensing water was often a most serious item of cost, and as water mains were not in use, a deep well was a necessary part of a steam vacuum engine.

[Rough draft.]

"Gentlemen,

"Cornwall, Camborne, October 16th, 1812.

"Yours of the 30th of September I found at my house on my return yesterday from a journey. I am sorry to inform you that Mr. Pickwood's engine is not ready. Near three months ago I set my smiths and boiler-makers to work to complete an engine for Mr. Pickwood, which parts were finished five or six weeks ago. The other parts of the engine, which were to have been made of cast iron, were ordered and commenced at a foundry in this county, belonging to Blewett, Harvey, and Vivian, and would have been finished and the engine shipped long since had not these partners in the iron foundry quarrelled with each other, and the Lord Chancellor has laid an injunction and set idle their foundry. I have since ordered the castings to be made at a foundry at Bridgenorth, in Shropshire, belonging to Hazeldine, Rastrick, and Co., who will complete the engine and send it to you in about two months, at which time I intend to be in town to set it to work before it is shipped for the West Indies.

"I remain, Sir,
"Your very humble servant,
"Rd. Trevithick.

"Messrs. Plummer, Barham, and Co.,
"London.

"P.S.—Immediately on my receiving your order to prepare an engine for Mr. Pickwood I wrote to inform him that I had begun it, and enclosed a drawing of the engine with the method of connecting the engine to the cattle-mills, and requested he would remit to me his remarks on it, which I received by the last packet, from which it appears for the best that the engine is not in a forward state, because the parts would not have been so suitable to the purpose as they will now be."

Fortune was against Trevithick. A difficulty between his brother-in-law Harvey, and his old partner Vivian, with Blewett, retarded the completion of the engine; and the castings so anxiously waited for were ordered from Hazeldine and Rastrick. The wrought-iron work was made by the old smiths in his neighbourhood, who had long been in the habit of hammering his schemes into shape. This patchwork way of constructing engines made success much more difficult.

Trevithick often laughed heartily at the following incident which occurred during this quarrel at Harvey's works:—Blewett sent a handsome silver teapot to Miss Betsy Harvey, who kept her brother's house, called Foundry House. Trevithick was sitting with them when the box was brought in and opened. Mr. Henry Harvey was indignant at Mr. Blewett sending a bribe or make-peace to his sister, and threw the silver teapot under the fire-place. Trevithick, however, quietly picked it up, pointed out the dinge it had received, wrapped his pocket handkerchief around it, and saying, if it causes bad feeling here it will do for Jane, marched away home with the pot. The writer drank tea from it recently, and also laughed at the dinge.

The following was written to Mr. Rastrick in December, 1812:[12]—

"I have been waiting your answer to my last, and especially that part respecting the West India engine, as there is a large field there for engines of this kind. I have received an order for a thrashing engine for Lord de Dunstanville of Tehidy, and as I wish those thrashing engines to be known through the country, I intend to take one of the engines ordered for Padstow and send it to Tehidy; one of the Padstow farmers can wait until you make another for him; therefore I would thank you to send the first finished by ship from Bristol for Portreath or Hayle. Send a drum with everything complete, of which you are a better judge than I; probably about 3 feet in diameter and 3½ feet long will be sufficient. There must be a fly-wheel, with a notch to carry the rope, and also a small notch wheel on the drum-axle. I think 6½ feet diameter for the fly and 9½ inches diameter for the small wheel, will give speed enough to the drum. Mind to cast a lump or screw on a balance of about 1 cwt. on one side of the wheel. There must be two stands on the boiler, and a crank-axle or otherwise a crank-pin in the fly-wheel, whichever you please; with a shaft 3 feet long with a carriage. The engine to stand in a room under the turn-about, 7½ feet high, 7 feet wide, and 17 feet long. The fly-wheel will stand across the narrow way of the room. The rope will go up through the floor and the drum be shifted by a screw, horizontally on the barn floor, so as to tighten the rope. I shall put down the top of the boiler level with the surface, with an arched way to the fire and ash-pit underground to prevent the chance of fire, which the farmers are very much afraid of.

"I send you a sketch showing how it is to stand. I do not bind you to the size of the drum or wheels, only the room that the fly-wheel works in is but 7 feet wide. Put the engine and drum for Lord de Dunstanville out of hand neat and well, as it will be well paid for, and make the stands, &c., in your own way."

This description of Lord Dedunstanville's thrashing machine illustrates the drawing of that supplied to Sir Charles Hawkins.

[Rough draft.]

"Camborne, January 26th, 1813.

"Mr. Rastrick,

"Sir,—I have your favour of the 10th inst., in which you do not state the time when you expect I shall have either of the engines that you are executing. As so much time has elapsed since the orders were given, the persons that ordered them are quite impotent. The ploughing engine that I sent you a drawing for, after being tried for that purpose, was to have been sent to Exeter for pumping water out of the foundations of a new bridge; but as they intend to begin their work at the bridge before the end of March, the engine must be there before that time, or they will erect horse machines and not use the engine. I have therefore been obliged to send the small boiler that I had for that purpose to Hayle Foundry, and get the castings made there for this engine to get it in time to prevent losing the order. I have also been obliged to take the small portable engine from Wheal Alfred Mine and have new apparatus fitted to it, to apply this engine for Plymouth Breakwater. A small engine, from the same patterns as Sir Charles Hawkins' thrashing engine, which I had at work in a mine, I have been obliged to send to one of the farmers at Padstow for thrashing, instead of one of those engines that I ordered from you. I expect that the people who ordered the engine for the West Indies are also tired of waiting. I have two other applications for engines for the West Indies, and the Messrs. Fox will want a great many engines of that size for the Plymouth Breakwater. They are to provide machinery, with every other expense, and I am to have a certain proportion of what I can save over what it now costs them to do it by manual labour. I think I have made a very good bargain, for if the plan succeeds I shall get a great deal of money, and if it fails I shall lose nothing. They have engaged with the Government to deliver 3,000,000 tons, for which they have a very good price, even if it was to be done by men's labour. I hope I shall get the engine soon on the spot, and will then let you know the result. As the boiler that was intended for the ploughing engine is to be sent to Exeter, I wish you to finish that engine with boiler, wheels, and everything complete for ploughing and thrashing, as shown in the drawing, unless you can improve on it. There is no doubt about the wheels turning around as you suppose, for when that engine in Wales travelled on the tramroad, which was very smooth, yet all the power of the engine could not slip around the wheels when the engine was chained to a post for that particular experiment.

"That new engine you saw near the seaside with me is now lifting forty millions 1 foot high with 1 bushel of coal, which is very nearly double the duty that is done by any other engine in the county. A few days since I altered a 64-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting to erect a new engine equal in power to a 63-inch cylinder single, which I hope to be able to send to you for. I have also an appointment to meet some gentlemen at Swansea, to erect two engines for them, one to lift water, the other coal, which you will hear more about, I expect, soon. If I can spare a few days when at Swansea, I will call to see you at Bridgenorth. I have not seen Mr. Richard since you left, but will call on him in a few days and do as you request. If you think the fly-wheel is not sufficiently heavy for his engine, add half a ton more to the ring.

"If you cannot finish all these engines at the same time, I would rather the smaller ones should be finished first and Mr. Richards' stand a little, because if his engine was now ready he would not pull down his thrashing machine until he had nearly thrashed all his corn, and the machine now stands on the spot where the mill is to be erected.

"If I call on you from Swansea I think I shall be able to show you a new idea, which I think will, if carried into practice, be of immense value. Please to write to me and say particularly how you are getting on, and when you are likely to finish the engines ordered.

"R. T."

Trevithick had sent a drawing of a ploughing engine to Rastrick at Bridgenorth, that the castings might be made, while he himself was having the boiler and wrought-iron work constructed in Cornwall. The engine had been ordered as a portable pumping engine, for removing water from the foundation of a bridge at Exeter; but before sending it to its destination, he had arranged to plough with it, as a means of perfecting the plans and drawings for a more suitable ploughing engine then in construction, to be fitted "with boiler, wheels, and everything complete for ploughing and thrashing, as shown in the drawing." The friction of the wheels on the ground would be greater than the power of the engine; therefore they would not slip when the full power was applied to draw a plough any more than the Welsh engine, the wheels of which did not slip though resting on smooth iron.

One of his small engines, which had been at work in a mine, was sent as a thrashing engine to Padstow. It is evident that, having given a portion of his attention for a year or two to the question of steam agriculture, he had so far progressed in 1813 as to construct thrashing machines, portable agricultural engines, and steam-ploughs to be moved by wheels as in locomotives; reaping, sowing, and other work, was also in future to be the work of the steam-engine.

A drawing by Trevithick—having as usual neither name, date, nor scale, nor writing of any kind, but the watermark in the paper is 1813—illustrates his ideas expressed to Sir Charles Sinclair in 1812:—"It is my opinion that every part of agriculture might be performed by steam." The thrashing and grinding engines were at work, and the tormenting harrowing engine was probably designed for bringing under steam cultivation the extensive commons referred to. In those days, before the practice of underground drainage, the surface of cultivated land was thrown into furrows, or a series of small hills and vales, the latter acting as the surface drain for carrying off the water.

Suppose the first step in cultivating a common to be the breaking of the soil, and throwing it into uniform lines of rise and fall that facilitated drainage without inconveniencing the tillage, what better machine could have been devised than Trevithick's? A combination of the modern tormentor and harrow loosened the ground to the required depth, which was then, by a revolving wheel with spades, thrown on one side, resulting in uniform lines of ridges and hollows. The steam-shoveller was removed, or the tormentor irons raised, when only the harrow was required.

The absence of the ordinary shafts at the front end of the framing indicates that the spade-tormentor was not to be drawn by horses, but whether by a locomotive or by a fixed engine is not self-evident.

Trevithick's Steam Spade-tormentor, 1813.

[Rough draft.]

"Camborne, January 26th, 1813.

"Mr. Kendal,

"Sir,—I have yours of the 17th inst. The thrashing machine engine is ready for you, and shall be sent up immediately. I wish you to get about 100 fire bricks, 200 common bricks, 20 loads of stone, and 20 bushels of lime. The house will get finished while I am fixing the engine. About 1500 or 1600 weight of iron for your engine has been sent to the Blue Hills Mine, St. Agness. I wish you could send down your cart to fetch it from there to Padstow. There is no part of these castings but may be easily conveyed in a common butt or cart. When you have the stone, brick, and lime ready, and a cart to send to St. Agness for the castings, please to write me, and I will come to Padstow at the same time with them, and finish the engine. The sooner you get ready the better, as I expect to have an engagement in about four weeks' time, that would prevent my coming to Padstow for some time; therefore I wish to get your engine finished before that time. Please to write me as early as possible, and let me know when you will be ready for me, and what day I shall meet your cart at St. Agness for the castings.

"Your obedient servant,
"Rd. Trevithick.

Real inventors hesitate not to erect their own engines, lend a hand in building the house, walk to the scene of action, or take a lift in a cart; and by such steps was the gift of genius moulded to the wants of daily life; while the modern engineer of eminence, living in large cities, knows little of the minutiæ of his work, or even of the working mechanics on whose skill the success of his ideas is dependent.

"In 1815, Mr. Kendal, the proctor of Padstow, sent for me to repair his steam-engine. To prevent the old disputes in collecting his corn tithes, he had at work one of Captain Trevithick's steam thrashing machines. The small farmers sent their corn produce to him to be thrashed; the grain was measured, the tenth taken out, the remainder returned to the farmer. The three-way cock, which worked the engine, was joined in its shell; on freeing it the engine continued to work very well."[13]

"In 1818 I put a new four-way cock to a thrashing engine that Captain Trevithick had made for Mr. Kendal, of Padstow, who was the receiver of tithe corn. The boiler was a tube of wrought iron, about 4 feet in diameter and 6 feet long, standing on its end. The cylinder was fixed in the top of the boiler; an upright from the top of the cylinder supported the fly-wheel shaft; a connecting rod from the crank-pin in the fly-wheel was fastened to a joint-pin in the piston. The cylinder had no cover. The four-way cock was worked by an excentric on the shaft, moving a lever, which was kept in contact with the excentric by a spring."[14]

"About 1824 I worked in Binner Downs Mine one of Captain Trevithick's puffer whim-engines. The boiler was cylindrical, made of wrought iron. It stood on its end, with the fire under it, and brick flues around it. The cylinder was let down into the top of the boiler. A four-way cock near the top of the cylinder turned the steam on and off. The fly-wheel and its shaft were fixed just over the cylinder. A lever and rod worked the four-way cock and feed-pole. The waste steam puffed through a launder into the feed-cistern. The cylinder was about 12 inches in diameter, with a 3-feet stroke."[15]

Mr. Kendal's steam thrashing machine remained at work at least six years, during which time the only apparent repair was the four-way cock, worked by an excentric, which, if neglected, was apt to stick fast in its shell.

One of the puffer-whims erected about this time was similar to the thrashing engine for Padstow, differing from the earlier one made for Sir C. Hawkins, in having a portable boiler so arranged that if necessary it could be easily placed on wheels.

[Rough draft.]

"Camborne, March 15th, 1813.

"Sir,

"I have your favour of the 11th inst. respecting a steam-engine for thrashing. I have made several, all of which answer the purpose exceedingly well. They are made on a very simple construction so as to be free from repairs, and are kept in order and worked by the farm labourers, who never before saw a steam-engine. The first I made on this plan was for Sir Christopher Hawkins, who resides at this time in Argyll Street, Oxford Street, London. If you call on him, he, I doubt not, would give you every information you require respecting its performance. This was a fixed engine, because it was only required to work on one farm. It has been at work nearly eighteen months, and has not cost anything in repairs, nor any assistance but from the labourer who puts in the corn; he only gives three or four minutes every hour to put on a little coal. A few pails of water, put into the furnace in the morning, is sufficient for a day's work. They have at different times tried what duty the engine would perform with a given quantity of coal, and found that two Cornish bushels, weighing 168 lbs., would get up steam and thrash 1500 sheaves of wheat in about six hours.

"Before this engine was erected, they usually thrashed 500 sheaves, with three heavy cart-horses for a day's work. I cannot say exactly the measurement of the corn that it thrashed, but it was considerably above 60 winchesters of wheat with 168 lbs. of coal; not a halfpenny in coal for each winchester of wheat.

"The engines that I have since erected have performed the same duty.

"The horse machinery is thrown out of use, but the same drum is turned by the engine.

"A fixed engine of this power I would deliver to you in London for 100 guineas; it would cost you about 15l. more to fix the furnace in brickwork.

"A portable engine costs 160 guineas, but it would cost nothing in erecting, as it will be sent with chimney and every thing complete on its own wheels (the drum, &c., excepted), which you may convey with one horse from farm to farm as easy as a common cart.

"If you have not sufficient work for it you can lend it to your neighbours. The last engine I erected was about three weeks since, for a farmer that kept four horses and two drivers. The parts of the horse machine thrown out of use, together with the four horses, sold for more money than he gave me for the engine, exclusive of 4l. per week that it cost him in horse keep and drivers to thrash 3000 sheaves per week.

"Now the engine performs more than double that work, and does not cost above 10s. per week; and the labourer in the barn does double the work he did before for the same money. If you wish the same engine to have sufficient power to turn one pair of mill-stones, the cost will be 220 guineas.

"R. Trevithick.

"Mr. J. Rawlings, Strood, Kent."

"Camborne, 28th August, 1813.

"Dear Trevithick,

"Camborne, 28th August, 1813.

"Messrs. Hazeldine, Rastrick, and Co.,

"Gentlemen,—Lord Dedunstanville's engine thrashed yesterday 1500 sheaves in 90 minutes with 40 lbs. of coal.

"Rd. Trevithick."

The first steam thrashing engine was worked by a labouring man for eighteen months, without needing repair, or even attention beyond three or four minutes each hour to put on a little coal.

Necessary stoppages for various purposes caused a day's work to be no more than the engine could perform in half a day. No additional feed-water was required during an ordinary day's work to thrash 1500 sheaves of wheat with 168 lbs. of coal, while on a special occasion that quantity was thrashed in an hour and a half, consuming only 40 lbs. of coal. Three horses during three days were required to do the same amount of work. A farmer sold his horses used in thrashing for more money than his engine cost, which did twice as much work at a reduced expenditure, and also saved the feed of the horses.

Such an engine could be delivered in London for 100 guineas, while a portable engine on wheels with a differently constructed boiler, requiring no mason work, would cost 160 guineas.

[Rough draft.]

"cornwall. Camborne, 19th August, 1813.

"Gentlemen,

"I have your favour of the 9th August, respecting steam-engines for St. Kitts. I fear it will not be possible to get an engine ready by the 1st of November.

"As you say the gentleman that is about to take them out is a clever man, and likely to promote the use of them, I will make immediate inquiry, and, if possible, will get one ready, of which I will inform you in a short time.

"I very much wish that every person who intends to employ a steam-engine of mine would first examine the engine, and be satisfied with the construction before giving an order, for which reason I must request you to send your friend down to Messrs. Hazeldine and Rastrick's foundry, Bridgenorth, Shropshire, where he may see the portable steam-engine that was made for Mr. Pickwood, which the founders will set to work for his inspection in half an hour after his arrival. As this gentleman has a taste for machines, and wishes to make himself fully acquainted with the principle and use of the steam-engine, he will be much gratified with the sight of this curious machine and with the information he will receive from the founders, which will be essentially necessary to him before leaving England.

"I am extremely disappointed that this engine was not forwarded to Mr. Pickwood, as I find from his letter that he has an exceedingly clever and active mind, and is a very fit person to take the management of introducing a machine into a new country.

"This engine is engaged by a Spanish gentleman, who is going to take out nine of my engines with him to Lima, in South America, in about six weeks.

"I remain, your obedient servant,
"Rd. Trevithick.

"Messrs. Plummer, Barham, and Co.,
"London.

"N.B.—If your friend goes to Bridgenorth, let him show this letter to the founders."

The engine, intended for the West Indies, so pleased Mr. Uville, that he begged to have it made over to him for South America, where it worked the machinery for rolling gold and silver in the Mint at Lima.

"About 1815, while erecting a high-pressure pole-engine at Legassack for Mr. Trevithick, and doing some repairs to Mr. Kendal's thrashing engine, a Creole, I think called Nash, brought a note from Captain Trevithick, stating that the bearer was anxious to be taught to erect and work the portable engines for Jamaica.

"Sir Rose Price, who had property in the West Indies, had sent him to Mr. Trevithick for that purpose."[16]

It is therefore probable that some of Trevithick's engines reached Jamaica. Sir Rose Price was well known to Lord Dedunstanville and Sir Charles Hawkins, and living near them, saw the engines at work and their fitness for his property in Jamaica.

Lord Dedunstanville's engine of 1812 was sold as old iron to Messrs. Harvey and Co. not long before 1843. Having remained for some time on the old-scrap heap, it was in that year again worked to drive machinery. Instead of the original rope-driver on the fly-wheel, a chain was used, the links of which caught on projecting pins on the driving wheel. In that form it continued to work until 1853, before which it was frequently seen by the writer prior to its removal to make room for a more powerful engine.

What greater proof could be given of the fitness of design of this early engine, than its long life of forty years under such rough treatment, and the facility with which it was applied to different uses. Mr. Bickle, who, from recollection, had made a sketch of this engine before the writer had found Trevithick's sketch, says that after the engine had ceased to work, the boiler was turned to account in heating tar in the ship-builder's yard.

"In 1854 I saw working in a shed at Carnsew, in the ship-building yard of Harvey and Co., of Hayle, an engine working a stamps for pounding up the slag and furnace bottoms from the brass-casting foundry.

"I was then the foreman hammerman in Harvey and Co.'s smiths' shop and hammer-mill, and frequently noticed this old engine and inquired about it. It had been brought from Lord Dedunstanville's, at Tehidy Park, where it at one time worked a thrashing machine. The boiler was of wrought iron, built in brickwork, and looked like a big kitchen-boiler. A flattish cover was bolted on to the top of the boiler, and the cylinder was let down into this top.

"The cylinder had no cover; it was about 8 or 10 inches in diameter and 2 or 3 feet stroke. The piston was a very deep one, with a joint for the connecting rod which went direct to the crank, which was supported on two upright stands from the cover on the boiler. The fly-wheel had a balance-weight for the down-stroke. A pitch-chain for driving passed over the wheel, which had pins in it, or projections, to catch into the square links of the driving chain; it was worked by a four-way cock."[17]

"About 1843, when we were building iron boats for the Rhine, the old engine was put to work to drive the tools or machinery in the yard. She was very useful to us and worked very well. She worked about ten years, and was then thrown out to make room for a new and larger engine for our saw-mills. The chain-wheel for driving was made here, it did not belong to it originally."[18]

"My father (then the foreman boiler-maker) about twenty-four years ago took the old engine from the scrap heap, where it had been for many years, and set it to work in the tool shop. My father said it had come from Tehidy as old iron."[19]

The use of the high-pressure steam agricultural engine was not confined to Cornwall. Mr. H. Pape, still carrying on business in Hazeldine and Rastrick's old engine manufactory at Bridgenorth, says:—

"My father worked as a smith under Mr. Rastrick. Mr. Hazeldine had the foundry when Trevithick's engines were made, and have heard my father speak of them. I have seen three of them at work in Bridgenorth; one of them at Mr. Jasper's flour-mill, it drove four stones, and continued in work up to 1837; one at Sing's tan-yard worked up to 1840; and one was on Mr. Jasper's farm at Stapleford for doing farm work. Mr. Smith, now on the farm, worked it up to about 1858.

"The engines that worked in Bridgenorth had cast-iron cylinders for the outer casing of the boiler, one cylinder for small engines, three or four cylinders bolted together for the larger ones. The fire-tube was wrought iron, the chimney stood up by the fire-door. The cylinder was let down into the boiler; it worked with a four-way cock. There was a piston-rod, cross-head, two guide-rods on the top of the cylinder, and two side rods to the crank and pin in 'the fly-wheel.'"[20]

"My first husband had to do with the foundry; his father, Mr. Hazeldine, was a partner with Mr. Davies and Co. in 1816. In 1817 the partnership was broken up, and the foundry carried on by Hazeldine. I used to have two or three drawers full of drawings and account-books that were brought from the works. I kept them for many years, but now the greater part of them have gone to light the fire; all the drawings are gone."[21]

The engines described by Mr. Pape are of the type made by Trevithick, in Wales, about 1804, having a fire-place in the boiler, and similar in form to the Welsh locomotive.

The drawings which served to light the fires certainly included Trevithick's plans for the steam-locomotive, ploughing engine, the screw-propeller, and many others of equal interest.

"Stableford, March 26th, 1870.

"Dear Sir,

"My grandfather's name was John Jasper, Esq., of Stableford; he must have been one, if not the first, user of a steam-engine for thrashing, winnowing, and shaking the straw all at one operation; it may have been erected eighty years ago, for an old servant of the family just now dead, aged ninety, worked when a boy in the steam-mill at Bridgenorth erected by my grandfather about the same time.

"The thrashing engine was a side-lever engine, worked with a three side-way cock and tappet, a cylinder about 8¼ inches in diameter, and a 3 feet 4 inch stroke, cast-iron crank-shaft, cross-head, and guides. The boiler was placed underneath the engine, the fire under it, with brick flues. The boiler was about 9 feet long and 4 feet diameter.

"The old side rods made of wood are still here, and so was the engine until about twelve years ago. I sent the cylinder, &c., to Coalbrookdale.

"I am, Sir,
"Yours truly,
"Thomas Smith.

The Stableford agricultural engine was probably made in 1804. The cylinder, of 8¼ inches in diameter, is precisely the size of that in the Welsh locomotive, but the stroke was reduced from 4 feet 6 inches to 3 feet 4 inches, being very nearly the same as the Newcastle locomotive. The cross-head, side rods, and boiler were very similar to the Welsh stationary engines of that date. This engine remained in use more than fifty years.

The engines specially referred to in this chapter fully prove, from their length of service, the practical character of Trevithick's inventions, and of his having persevered with his high-pressure portables until their usefulness as locomotives and as agricultural helps had been established; but the ploughing, though fully designed, and probably put into practice, was not followed up to the same approach to perfection, or the record of its progress has been lost.

Since the foregoing was written, the following has been received:—

"Trewithen, Probus, May 17th, 1872.

"Dear Sir',

"The engine you refer to is still occasionally used here; when first erected there was a large quantity of corn thrashed by it, but of late years it has not been much used except for chaffing, bruising, &c.

"I remain, dear Sir,
"Your truly,
"Wm. Trethnoy.

"F. Trevithick, Esq."

Trevithick's Trewithen engine, which sixty years ago was more manageable than horses going momentarily faster or slower at the will of a common labourer,[22] remains in use unchanged.

His preparations for South America, and application of high steam in the large Cornish pumping engines, interfered with the perfecting the smaller agricultural work.

[CHAPTER XIX.]

POLE STEAM-ENGINE.

When in the autumn of 1810 Trevithick returned to Cornwall, the experience of ten busy years had established the practicability and usefulness of the high-pressure engine. The principles of the invention were now to be applied on engines of the largest size.

In 1811, the late Captain S. Grose, a young pupil of Trevithick's, was employed to erect at Wheal Prosper Mine, in Gwythian, the first high-pressure steam pole condensing engine. It was placed immediately over the shaft and pump-rods, requiring no engine-beam. The air-pump, feed-pump, and plug-rod were worked from the balance-bob. The pole was 16 inches in diameter, with a stroke of 8 feet. The boilers were two wrought-iron tubes, 3 feet in diameter and 40 feet long. The fire was external. Shortly after Captain H. A. Artha erected several of those pole-engines for Trevithick. The drawing shows the simplicity of parts of this highly expansive steam-engine, beginning the up-stroke with steam of 100 lbs. to the inch above the atmospheric pressure, expanding it during the stroke down to a pressure of 10 lbs., and then condensing to form a vacuum for the down-stroke. It cost 750 guineas.

The drawings of this expansive pole condensing engine are from the dimensions given by Captain Grose who erected it, and by Captain Artha who knew it well.

Wheal Prosper High-pressure Expansive Steam-condensing Pole-Engine, 1811.

Trevithick's Cylindrical Boiler for Wheal Prosper Engine, 1811.

a, cast-iron pole, 16 inches diameter, 8-feet stroke; b, pole-case, a small bit larger in internal diameter than the pole; c, cross-head, fixed on top of pole; d, guides for cross-head; e, side rods connecting the two cross-heads; f, bottom cross-head; g, pump-rod; h, balance-beam, with box for weights; i, connecting rods from balance-beam to bottom cross-head; k, guides for air-pump cross-head; l, cross-head and side rods for working air-pump; m, air-pump, condenser, and water-cistern; n, feed-pump worked from air-pump cross-head; o, plug-rod worked from balance-beam; p, exhaust-valve; q, steam-valve; r, exhaust-pipe; s, steam-pipe; t, bracket for carrying working gear; u, expansive steam-horn and tappets; v, handles for working valves.

Detail of Boilers:—a, two wrought-iron boilers, 3 feet in diameter, 40 feet long, using steam of 100 lbs. on the square inch above the atmosphere; b, cast-iron manhole door and safety-valve; c, ash-pit; d, fire-place; e, flues, the fire going first the whole length under the bottom of the boiler, then back again over the top, and into the chimney; f, brickwork; g, ashes or other convenient non-conductor of heat; the fire-place ends of the boilers were 15 inches lower than the opposite ends, increasing the safety, with less liability to prime, and greater surface for superheating.

"When a boy I was placed as an apprentice or learner with Captain Trevithick, before he left Cornwall for London. On his return to Cornwall, about 1810, he employed me to erect his first high-pressure expansive pole pumping engine at a mine in Gwythian.

"The pole was 16 inches in diameter; the stroke was very long, but I do not exactly recollect the length. It had a condenser and air-pump. There were two boilers made of wrought iron, 8 feet in diameter and 40 feet long. The fire was placed under them at one end, and flues went round them. A feed-pump forced water into the boilers; each had a safety-valve with a lever and weight. The steam in the boiler was 100 lbs. to the square inch. The pole was raised by the admission of the strong steam under its bottom. The steam-valve was closed at an early part of the stroke, and the steam allowed to expand; at the end of the stroke it was reduced to 20 lbs. or less, when the exhaust-valve allowed the steam to pass to the condenser, and the pole made its down-stroke in vacuum. A balance-bob regulated the movement of the engine.

"Trevithick's character in those days was, that he always began some new thing before he had finished the old."[23]

Captain Artha, one of his assistants, said:—

"I erected several of Captain Trevithick's pole-engines. My brother Richard worked the one at Wheal Prosper when first erected. The pole made an 8-feet stroke. The case was fixed over the engine-shaft on two beams of timber from wall to wall. A cross-head was bolted to the top of the pole, and from it two side rods descended to a cross-piece under the pole-case, from which the pump-rod went into the shaft. A connecting rod worked a balance-beam, which worked the air-pump, feed-pump, and plug-rod for moving the valves. The steam, of a very high pressure, worked expansively."[24]

The first admission of the high-pressure steam under the pole was equal to a force of 8 or 9 tons, causing it and its attached pump-rods to take a rapid upward spring. Having travelled 1 or 2 feet of its stroke of 8 feet, the further supply of steam from the boiler was cut off, and its expansion, together with the momentum of the mass of pump-rods, completed the upward stroke. The pressure of the steam in the pole-case at the finish of the up-stroke would be reduced to say 10 or 20 lbs. to the inch, according to the amount of work on the engine. The steam then passed to the condenser and air-pump, and the engine made its down-stroke by the vacuum under the pole, and by the weight of the descending pole and pump-rods.

Each boiler was a wrought-iron tube 3 feet in diameter and 40 feet long, the fire-place under one end, with brick flues carrying the heated air under the whole length of the bottom of the boiler, and back again over the top or steam portion for superheating.

[Rough draft.]

"Camborne 28th February, 1813.

"I will engage to erect a puffer steam-engine, everything complete at the surface, on the Cost-all-lost Mine, capable of lifting an 8-inch bucket, 4½-feet stroke, twenty-four strokes per minute, 30 fathoms deep, or 280 gallons of water per minute from that same depth, being a duty equal thereto, for 550 guineas. But if a condensing engine, 600 guineas. If of the same size as Wheal Prosper, 750 guineas.

"Richard Trevithick."

The engines, erected in 1811 or 1812, combined the novelty of the steam pole-engine, with the use of high-pressure steam of 100 lbs. on the square inch, and the comparatively untried principle of steam expansion, carried to what in the present day is thought an extreme and unmanageable limit.

The Wheal Prosper engine fixed near the sea-shore at Gwythian is referred to in Trevithick's note to Mr. Rastrick,[25] as "that new engine you saw near the sea-side, with me, is now lifting forty millions, 1 foot high, with 1 bushel of coal" (84 lbs.), "which is very nearly double the duty that is done by any other engine in the county."

This was probably the first application of high-pressure steam to give motion to pump-rods. The engine, as compared with the neighbouring Watt low-pressure steam vacuum pumping engines, was small, but the principles of high steam, expansive working, and vacuum, were combined successfully to an extent scarcely ventured on by modern engineers.

Trevithick's high-pressure condensing whim-engines had been for some years at work in Cornwall, but mine adventurers had not dared to risk the application of high-pressure steam to the large pumping engines, fearing its great power would prove unmanageable, and its rapid movement cause breakage of the pump-rods and valves.

Two distinct inventions or improvements, each of which was actually followed up in different mines, show themselves in this engine: one being the form of boiler to give with economy and safety high-pressure expansive steam for large engines; the other, the application of a pole in lieu of a piston, as a more simple engine for working with strong expansive steam, and more easily constructed by inexperienced mechanics, who had none of the slide lathes or planing machines so much used by engine builders of the present day.

"About 1814 Captain Trevithick erected a large high-pressure steam-puffer pumping engine at the Herland Mine. The pole was about 30 inches in diameter, and 10 or 12 feet stroke. There was a cross-head on the top of the pole, and side rods to a cross-head under the pole-case. The side rods worked in guides. The pole-case was fixed to strong beams immediately over the pump-shaft. The steam was turned on and off by a four-way cock. The pressure was 150 lbs. to the inch above the atmosphere. The boilers were of wrought iron, cylindrical, about 5 feet 6 inches in diameter and 40 feet long, with an internal tube 3 ft. in diameter. The fire-place was in the tube. The return draught passed through external brick flues.[26]

"When a young man, living on a farm at Gurlyn, I was sent to Gwinear to bring home six or seven bullocks. Herland Mine was not much out of my way, so I drove the bullocks across Herland Common toward the engine-house. Just as the bullocks came near the engine-house the engine was put to work. The steam roared like thunder through an underground pipe about 50 feet long, and then went off like a gun every stroke of the engine. The bullocks galloped off—some one way and some another. I went into the engine-house. The engine was a great pole about 3 feet in diameter and 12 feet long. A cast-iron cross-head was bolted to the top of the pole. It had side rods and guides. A piece of iron sticking out from the cross-head carried the plug-rod for working the gear-handles. The top of the pole worked in a stuffing box. A large balance-beam was attached to the pump-rods, near the bottom cross-head.

"There were two or three of Captain Trevithick's boilers with a tube through them, the fire in the tube. They seemed to be placed in a pit in the ground. The brick flues and top of the bricks were covered with ashes just level with the ground. A great cloud of steam came from the covering of ashes.

"I should think the pressure was more than 100 lbs. to the inch. People used to say that she forked the mine better than two of Boulton and Watt's 80-inch cylinder engines. We could hear the puffer blowing at Gurlyn, five or six miles from the Herland Mine.

"In 1813 I carried rivets to make Captain Trevithick's boilers in the Mellinear Mine; they were 5 feet in diameter and 30 or 40 feet long, with an internal fire-tube. It took four or five months to build them. In the present day (1869) a fortnight would build them. The largest boiler-plates obtainable were 3 feet by 1 foot. We had to hammer them into the proper curve. The rivet-holes were not opposite one another. A light hammer was held against the rivet-head in riveting, in place of the present heavy one, so the rivet used to slip about, and the plates were never hammered home so as to make a tight joint."[27]

Lest the reader should doubt the comparative power of the Watt low-pressure vacuum and Trevithick's high-pressure steam-engines, a short but sufficiently close calculation shows that taking Stuart's[28] estimate of the effective power of the Watt engine at 8½ lbs. on each square inch of the piston, and Trevithick's engine at anything approaching to 150 lbs. on each square inch, it becomes evident that the latter would be ten or twenty times more powerful than the former. A few figures will put the question in more practical form.

The Wheal Prosper 16-inch pole high-pressure expansive steam vacuum engine commenced its up-stroke with steam of 100 lbs. on the inch, acting on the 122 square inches of the pole, which steam at the finish of the stroke was reduced by expansion to 10 lbs., giving, say, an average steam pressure of 55 lbs. The down-stroke was caused by a vacuum under the pole of 14 lbs. on the inch, reduced by, say, one-third loss in working the air-pump to 9 lbs., giving from the compound stroke a force of 64 lbs. on each square inch, which, multiplied by the area of the pole, gives a net force of 7808 lbs.

The Herland 33-inch pole high-pressure expansive steam puffer-engine commenced its up-stroke with steam of 150 lbs. on the inch, acting on the 855 square inches of the pole, which steam at the finish of the stroke—we will suppose—was reduced by expansion to 75 lbs., giving an average steam pressure of, say, 112. As this puffer-engine used no vacuum, the down-stroke gave no increase of power; its compound stroke was therefore a force of 112 lbs. on each square inch, which, multiplied by the area of the pole, gives a net force of 95,760 lbs.

To compare the Trevithick high-pressure steam pumping engine, with the Watt low-pressure steam pumping engine, take one of the largest of the latter, made about that time, say, with an 80-inch cylinder, which commenced its down-stroke with steam of, say, 3 lbs. on the inch, acting on the 5000 square inches of the piston, which steam at the finish of the stroke—the writer is describing the usage at that time, for Watt himself advocated a less steam pressure—was reduced by expansion to, say, 1 lb., giving an average steam pressure of, say, 2 lbs. on the top of the piston, whose under side was in vacuum equal to 14 lbs. on the inch, reduced by, say, one-third loss in working the air-pump to 9 lbs., which power, from vacuum added to the 2 lbs. from steam, gives a net force of 11 lbs. on each square inch of the piston. As the Watt pumping engine moved in equilibrium during its up-stroke, it thereby gained no increase of power; its compound stroke was therefore a force of 11 lbs. on each square inch, which, multiplied by the area of the piston, gives a net force of 55,000 lbs.

The practical comparison therefore stands,—Trevithick's 16-inch pole high-pressure steam, and vacuum, on each inch 64 lbs., net force 7808 lbs.; Trevithick's 33-inch pole high-pressure steam, without vacuum, on each inch 112 lbs., net force 95,760 lbs.; Watt's 80-inch piston, low-pressure steam, and vacuum, on each inch 11 lbs., net force 55,000 lbs. As the first cost was mainly dependent on the size, the Trevithick engine was commercially much more valuable than the Watt engine.

"I saw Captain Trevithick's puffer working at the Herland Mine. The steam used to blow off like blue fire—it was so strong. The lever on the safety-valve was about 3 feet long, with a great weight on it, more than a hundredweight. The engine did not answer very well, for the packing in the pole stuffing box used to burn out, and a cloud of steam escaped. The greatest difficulty was in the leaking of the boilers. You could hardly go near them. Before that time we always put rope-yarn between the lap of the boiler-plates to make the seams tight. Captain Dick's high-pressure steam burnt it all out. He said, 'Now you shall never make another boiler for me with rope-yarn.' Everybody said it was impossible to make a tight boiler without it. We put barrowfuls of horse-dung and bran in Captain Dick's boilers to stop the leaks."[29]

This difficulty of making a tight and safe boiler, that puzzled Watt, was moonshine to Trevithick. When the strained boiler and flinching rivets allowed the boiler-house to become full of dense steam, Trevithick told them to cover it up with ashes, they would not see it quite so much then, and it would keep the heat in the boiler. Bran or horse-dung inside was a good thing as a stop-gap, though it added not to the strength of the boiler. Trevithick was himself in a cloud of steam in the engine-house; yet, with such surroundings, he turned on and off his gunpowder steam, from his cannon of a pole-case, of 40 tons force, sending his bolt-shot pole, 33 inches in diameter, its destined course of ten feet, and back again, as though it were a shuttlecock, several times in a minute.

Having by one or two years of experience proved the value of his new pole-engine, he applied for a patent on the 13th June, 1815,[30] of which the following is the portion referring particularly to the pole-engine:—

"Instead of a piston working in the main cylinder of the steam-engine, I do use a plunger-pole similar to those employed in pumps for lifting water, and I do make the said plunger-pole nearly of the same diameter as the working cylinder, having only space enough between the pole and the cylinder to prevent friction, or, in case the steam is admitted near the stuffing box, I leave sufficient room for the steam to pass to the bottom of the cylinder, and I do make at the upper end of the cylinder for the plunger-pole to pass through a stuffing box of much greater depth than usual, into which stuffing box I do introduce enough of the usual packing to fill it one-third high. Upon this packing I place a ring of metal, occupying about another third part of the depth of the stuffing box, this ring having a circular groove at the inside, and a hole or holes through it communicating with the outside, and with a hole through the side of the stuffing box; or, instead of one ring containing a groove, I sometimes place two thinner rings, kept asunder by a number of pillars to about the distance of one-third of the depth of the stuffing box, and I pack the remaining space above the ring or rings, and secure the whole down in the usual manner. The intention of this arrangement is to produce the effect of two stuffing boxes, allowing a space between the two stuffings for water to pass freely in from the boiler or forcing pump through a pipe and through the hole in the side of the stuffing box, so as to surround the plunger-pole and form the ring of water for the purpose of preventing the escape of steam by keeping up an equilibrium between the water above the lower stuffing and the steam in the cylinder. By this part of my said invention I obviate the necessity of that tight packing which is requisite when steam of a high pressure is used, and consequently I avoid a greater proportion of the usual friction, because a very moderate degree of tightness in the packing is quite sufficient to prevent the passage of any injurious quantity of so dense a fluid as water. And I do further declare that I use the plunger-pole, working in a cylinder and through a double stuffing, either with or without a condenser, according to the nature of the work which the steam-engine is to perform."

Though Trevithick has been spoken of as a visionary, intractable schemer, observation shows that he adhered with tenacity to original ideas, proved to be good. The plunger-pole pump, the water-pressure engine, the Camborne locomotive, the pole steam-engine, were all built on the same groundwork originally started with, of greatest simplicity of form, and absence of many pieces; and it may be observed that he never applied for a patent until the value of the idea had been proved by experiment.

In practice the difficulty of keeping the pole-packing in order was one of the objections to the plan; for it either leaked, or, if packed tight, caused much friction and wearing away of the middle of the pole faster than the ends, from the greater speed at the middle of the stroke. The steam-ring was therefore of importance in the engine, in those days of inaccurate workmanship; like the water cup on the gland of the plunger-pump packing, it prevented external air from injuring the vacuum.

""Camborne, July 8th, 1815.

""Mr. Giddy,

"Sir,—About a fortnight since I received letters from Lima, and also letters to the friends of the men who sailed with the engines. They arrived on the 29th January, after a very good passage, and without one hour's sickness. Both their and my agreements were immediately ratified, and they are in high spirits. The ship finished discharging on the 11th February, which was the day those letters sailed from Lima with $12,000 for me, which has all arrived safe.

"I shall make another fit-out for them immediately. I expect that all the engines will be at work before the end of October; half of them must be at work before this time. The next day, after their letters sailed for Europe, they intended to go back to the mines. Woolf's engine is stopped at Herland, and I have orders to proceed. A great part of the work is finished for them, and will be at work within two months from the time I began. I only engage that the engine shall be equal to a B. and Watt's 72-inch single, but it will be equal to a double 72-inch cylinder. It is a cast-iron plunger-pole, over the shaft, of 33 inches diameter, 10-feet stroke. The boiler is two tubes, 45 feet long each, 3 feet diameter, 1/2 an inch thick, of wrought iron, side by side, nearly horizontal, only 15 inches higher at the steam end of the tubes, to allow the free passage of steam to the steam-pipe. There are two 4-inch valves, one the steam-valve, the other the discharging valve. I have made the plunger-case and steam-vessel of wrought iron ¾ of an inch thick. The steam-vessel is 48 inches in diameter. The plunger stands on beams over the shaft, with the top of it at the level of the surface, with a short T-piece above the plunger-pole, and a side rod on each side, that comes up between the two plunger-beams in the shaft; this does away with the use of an engine-beam, and the plungers do away with the use of a balance-beam.

Pole-Engine.

"The fire is under the two tubes, and goes under them for 45 feet, and then returns again over them, and then up the chimney. Those tubes need no boiler-house, because they are arched over with brick, which keeps them from the weather, and scarcely any engine-house is needed, only just to cover the engineman.

"Suppose a 72-inch cylinder (having 4000 inches), at 10 lbs. to the inch, an 8-feet stroke, working nine strokes per minute (which is more strokes of that length than she will make when loaded to 10 lbs. to the inch).

"Suppose a 33-inch plunger-pole, 10-feet stroke, ten strokes per minute (which is not so fast by three or four strokes per minute as this engine will go, because she will have no heavy beam to return, neither will she have to wait for condensing, like B. and Watt's, which, when loaded, hangs very long on the injection).

"I should judge that less than 50 lbs. to the inch above the atmosphere would be quite enough to do the work of a 72-inch cylinder single, which is but a trifle for those wrought-iron tubes to stand. This engine, everything new, house included, ready for work, will not exceed 700l. Two months are sufficient for erecting it. The engine of Woolf's, at Wheal Vor, which is but two-thirds the power of a 72-inch cylinder, single power, cost 8000l., and was two years erecting. I would be much obliged to you for your opinion on this business.

"I remain, Sir,
"Your very humble servant,
"Rd. Trevithick.

"I am sorry to say that the mines in general are very poor."

He shows that with steam of 34 lbs. to the inch, his Herland pole puffer steam-engine of 33 inches in diameter would be equal in power to the Watt low-pressure steam vacuum engine, with a 72-inch cylinder. Herland, like Dolcoath and Wheal Treasury, was the chosen battle-ground of rival engineers; fifty years after Newcomen had there erected his famously large 70-inch cylinder engine, Watt surpassed it in size by a cylinder 2 inches more in diameter, and, after personally superintending its erection in 1798, declared that "it could not be improved on." Mr. Davey, the mine manager, considered that it did twenty millions of duty, though Mr. Watt had made it twenty-seven millions with a bushel of coal.[31] This difference is probably explained by the then Cornish bushel weighing 84 lbs., while Watt generally calculated a bushel at 112 lbs.

Trevithick declining to believe Watt's prognostication, a public test of Watt's engines in the county was demanded; Mr. Davies Gilbert, with Mr. Jenkin, were requested to report on their duty, and gave it in 1798 as averaging seventeen millions.[32] During the same year the adventurers in Herland Mine engaged Trevithick and Bull, jun., to erect a 60-inch cylinder Bull engine to compete with Watt's 72-inch cylinder. The result of this fight is not traceable, nor what took place there during the succeeding fifteen years; when in 1814 Woolf erected in Cornwall his double-cylinder engine to compete with Watt's engine, and Trevithick attacked them both with his Herland high-pressure pole puffer in 1815, when he erected at his own risk and cost a 33-inch pole-engine, engaging that it should, both in power and economical duty, equal the Watt 72-inch engine. The boilers were similar in form to those used a year before in Wheal Prosper high-pressure steam vacuum pole-engine, being two wrought-iron tubes, each 45 feet long and 3 feet in diameter, made of plates half an inch thick. The fire was in external flues. The engine was fixed directly over the pump-rods in the shaft, using neither main beam nor air-pump.

Trevithick's rough hand-sketch shows the steam-ring in the stuffing box and the steam-vessel; the particular use of the latter he has not described: probably it was because Cornish pumping engines, not having the controlling crank to limit the movement of the piston, are obliged to trust to the very admirable, but little understood, steam-cushion, without which the ascending piston would inevitably strike and break the cylinder-cover, while in the pole puffer-engine this danger was during the descent of the pole, and therefore the discharge-steam valve was closed, while the steam in the pole-case was still of ten or more pounds to the inch, so that by the time the pole reached the finish of its down-stroke, it had compressed this steam-cushion, filling also the steam-vessel, with a pressure approaching to that in the boiler, and equal to the weight of the pole and pump-rods. A comparatively small supply of steam from the boiler into the steam-vessel brought it up to the boiler pressure, sending the pole and pump-rods upwards with a spring. The steam-valve then closed, allowing the momentum of the great weight of pump-rods, together with the expanding steam, to complete the up-stroke. The discharge-valve was then opened for a moment, allowing a blast of steam to escape, reducing the pressure say to one-half. The weight of the rods caused their downward movement, raising the load of water in the plunger-pole pumps, and at the same time compressing the steam from the pole-case into the steam-vessel, equal at the finish of the stroke to the support of the pole and pump-rods. This most simple steam-engine combined in the greatest degree the two elements of expansion and momentum.

The up-stroke began with a much higher pressure of steam than was necessary to raise the load; having given momentum to the rods, the supply of steam was cut off, and the stroke was completed by expansion. The down-stroke began with a comparatively low pressure of steam under the pole. The unsupported pump-rods fell downwards, setting in upward motion the column of water in the plunger-pole pumps. The discharge-valve was closed long before the completion of the down-stroke, and the momentum of the moving mass of rods and water compressed the steam driven from the pole-case into the steam-vessel up to a pressure equal to the support of the pole and pump-rods. The pole was, therefore, continually floating or rising and falling in steam of ever-varying pressure.

Trevithick' s figures show the working power of the 33-inch pole as much greater than Watt's 72-inch cylinder engine, even when the steam pressure in the former was much reduced, and that Woolf's double-cylinder engine, of less power, cost ten times as much as the pole-engine. This sum probably included the costly buildings required for the beam-engines, which Trevithick's plan dispensed with.

The reader may judge of the perfection of mechanism in this plain-looking engine from the fact that a pole, with 150 lbs. of steam to the inch in the boiler, was equal to 50 or 60 tons weight, thrown up and down its 10-feet stroke ten or fourteen times a minute, with a limit of movement perfectly under control, while modern engineers are building ships' turrets because of the difficulty of raising and depressing a 30-ton gun from the hold to above the water level.

[Rough draft.]

"Camborne, September 12th, 1815.

"Sir,

"I received a letter dated the 20th of August, from Mr. Davies, in which he did not mention the name of Herland castings. On the 24th of the same month I wrote to you, informing you of the same, and requesting to know what state of forwardness the castings were in. On the 30th of August I received another letter from Mr. Davies, not saying what state of forwardness the castings were in, nor when they would be finished, only that they would set their hands about them, and that I might expect a letter from you stating the particulars, which has not yet come to hand. I have waited so long that I am quite out of patience. You will know that it is now nearly double the time that the castings were to have been finished in, and you have not yet answered my letters as to the state of the castings nor when they will be finished. I must again request you to write to me on this subject, otherwise I must immediately remove the orders to some other founders that may be a little more attentive to their customers. I must be informed in the positive, whether the castings will be at Bristol by the next spring-tide, as a vessel is engaged for the purpose of taking them to Cornwall.

"Yours, &c.,
"R. T..

"Mr. John Rastrick,
"Chepstow, South Wales."

Rastrick, whom he had known at the Thames Driftway, had become the managing engineer at the Bridgenorth Foundry.

[Rough draft.]

"Camborne, September 29th, 1815.

""Mr. George Cowie,

"I received your favour of the 20th, and on the 23rd called on Mr. Wm. Sims, your engineer, who went with me to Beeralstone Mine the same day. We arranged on the spot what was necessary for the engine. I hope it will be at work in good time, before the winter's floods set in. Nothing can prevent it, unless the castings are detained by contrary winds. The boilers are nearly finished in Cornwall. The castings at Bridgenorth are in a forward state. I intend leaving this evening for Bridgenorth, to ship the castings, both for Herland and Beeralstone. It was the wish of the agents on the mine that these castings might be sent to Swansea, and taken from thence to the mine with a freight of coal. I shall, if possible, get the Herland castings in the same ship. The workmen making your boilers want an advance of cash to enable them to finish. They provide both iron and labour, for which they are to receive 42l. per ton for the boiler when finished; the weight will be about 8 tons. You may send this money to Mr. Sims or to me, or otherwise you may direct it to Mr. N. Holman, boiler-maker, Pool, near Truro. 100l. will satisfy them for the present. I hope to be in London this day week, and will call at your office.

"Yours, &c.,
"R. Trevithick.".

The pole-engine was not only used in several mines shortly after its first introduction, but Mr. Sims, the leading engineer of the eastern mines, not generally favourable to Trevithick, advocated its application in the traditional Watt district.

Scarcely had he smoothed the way with one opponent than another sprung up in an unexpected quarter. His brother-in-law, Harvey, with his once friend, Andrew Vivian, then a partner with Harvey, opposed his plans at the Herland. They were annoyed at Trevithick's sending his orders for castings and machinery to Bridgenorth, and may have had doubts of the success of the new inventions. They had authority in the mine, probably as shareholders, a position generally acquired in Cornwall by those who supply necessary mine material, as well as by the smelters who buy the mineral from the mines. The Williamses and Foxes, controlling the eastern district of mines, were also shareholders and managers, supplying machinery and buying the mine produce.

[Rough draft.]

"Penzance, 13th December, 1815.

""Sir,

"Yesterday I was at Herland, where I was informed that Captain Andrew Vivian had been the day before, on his return from Mr. Harvey's, and discharged all the men on the mine, without giving them a moment's notice. Before the arrival of the castings the pitmen, sumpmen, carpenters, and smiths were very busy getting the pit-work ready; at which time H. Harvey and A. Vivian were exulting in reporting that the iron ore was not yet raised that was to make the Herland castings. The day that they heard of their arrival they discharged all the labourers, and ordered the agents not to admit another sixpence-worth of materials on the adventurers' account, or employ any person whatever.

"The agents sent a short time since to Perran Foundry[33] for the iron saddles and brasses belonging to the balance-bob, the property of the adventurers; but they refused to make them, with a great deal of ill-natured language about my engine.

"I am determined to fulfil my engagement with the adventurers, and yesterday ordered all the smiths, carpenters, pitmen, and sumpmen to prepare the adventurers' pit-work, and ordered the agents to get the balance-bob and every other thing that may be wanted at my expense, so as to fork the first lift, which I hope to have dry by Monday three weeks. The engine will be in the mine this week, and in one fortnight after I hope the engine will be at work, and in less than a week more the first twenty fathoms under the adit will be dry.

"In consequence of the Perran people refusing to send the saddles and brasses for the balance-bob, we will make shift in the best way we can without them. The brasses I have ordered on my own account at Mr. Scantlebury's. The coals for the smiths I have also ordered, and the same for the engine to fork the first lift. This is very uncivil treatment in return for inventing and bringing to the public, at my own risk and expense, what I believe the country could not exist without. I am determined to erect the engine at all events and upset this coalition before I leave Europe, if it detains me one year to accomplish it.

"I remain, Sir,
"Your very humble servant,
"Rd. Trevithick.

"Mr. Phillip,
"George Yard, Lombard Street.

"P.S.—I should be glad to hear from you what is going forward respecting an arrangement of the shares."

[Rough draft.]

"Penzance, 23rd December, 1815.

""Gentlemen,

"I have received the Herland castings, and am very seriously sorry to say, after we had fixed together the castings on the mine and made the joints, on attempting to put the plunger-pole into the case it would not go down; neither would either of the rings go to their places into the cylinder and on to the pole; therefore the whole engine must be again taken to pieces and sent to a turning and boring mill to be newly turned and bored. How to get this done I cannot tell, for the founders here will not do it because they had not the casting them. Already great expenses have been incurred by delays, and now to send them back to Bridgenorth at an immense loss of time and money will be a very serious business indeed. I think that either the cylinder is bored crooked or the plunger-pole turned crooked, or both, as it will sink farther down into the cylinder on turning it round on one side than it will on the other. The whole job is most shamefully fitted up, and was never tried together before sent off. Write to me by return of post and say what I am to do in this dilemma.

"Yours, &c.,
"Richard Trevithick.

"Hazeldine, Rastrick, and Co.,
"Bridgenorth."

The new engine-work from Bridgenorth on arrival was found to be so inaccurately made that the pole would not go into the pole-case. Henry Phillips,[34] who saw the engine make its first start, says:—

"I was a boy working in the mine, and several of us peeped in at the door to see what was doing. Captain Dick was in a great way, the engine would not start; after a bit Captain Dick threw himself down upon the floor of the engine-house, and there he lay upon his back; then up he jumped, and snatched a sledge-hammer out of the hands of a man who was driving in a wedge, and lashed it home in a minute. There never was a man could use a sledge like Captain Dick; he was as strong as a bull. Then, he picked up a spanner and unscrewed something, and off she went. Captain Vivian was near me, looking in at the doorway; Captain Dick saw him, and shaking his fist, said: 'If you come in here I'll throw you down the shaft.' I suppose Captain Vivian had something to do with making the boilers, and Captain Dick was angry because they leaked clouds of steam. You could hardly see, or hear anybody speak in the engine-house, it was so full of steam and noise; we could hear the steam-puffer roaring at St. Erth, more than three miles off."

By the end of January, 1816, the engine was ready for work, and after ten days of experience, he thus described the result:—

"Penzance, 11th February, 1816.

""Mr. Davies Giddy,

Sir,—I was unwilling to write you until I had made a little trial of the Herland engine. It has been at work about ten days, and works exceedingly well; everyone who has seen it is satisfied that it is the best engine ever erected. It goes more smoothly than any engine I ever saw, and is very easy and regular in its stroke. It's a 33-inch cylinder, 10½-feet stroke. We have driven it eighteen strokes per minute. In the middle, or about two-thirds of the stroke, it moved about 8 feet per second, with a matter in motion of 24 tons; and that weight returned thirty-six times in a minute, with 2 bushels of coal per hour. This of itself, without the friction, or load of water, is far more duty than ever was done before by an engine. I found that it required about 80 lbs. to the inch to work the engine the first twelve hours, going one-third expansive, twelve strokes per minute, 10½-feet stroke, with 24 bushels of coal. The load of water was about 30,000. This was occasioned by the extreme friction, the plunger-pole being turned, and the plunger-case bored, to fit so nicely from end to end, that it was with great difficulty we could at all force the plunger-pole down to the bottom of the plunger-case. This is now in a great degree removed, and since we went to work we have thrown into the balance-box 4 tons of balance, and it would carry 3 tons more at this time. We must have carried that load in friction against the engine, therefore, if you calculate this, you will find it did an immense duty, going twelve strokes per minute, 10½-feet stroke, with 2 bushels of coal per hour. The engine is now working regularly twelve strokes per minute, with 60 lbs. of steam, 10½-feet stroke, three-quarters of the stroke expansive, and ends with the steam rather under atmosphere strong, with considerably within 2 bushels of coal per hour. I would drive her faster, but as the lift is hanging in the capstan rope under water, they are not willing to risk it. I have raised the steam to 120 lbs. to the inch, the joints and everything perfectly tight. I took the packing out of the stuffing box and examined it, and found that the heat had not at all injured it; the packing is perfectly tight, not a particle of steam is lost.

"I have offered to deposit 1000l. to 500l. as a bet against Woolf's best engine, and give him twenty millions, but that party refuses to accept the challenge. I have no doubt but that by the time she is in fork she will do 100 millions, which is the general opinion here. The boilers are certainly the best ever invented, as well as the other parts. The draught is the best you ever saw; I have only one-quarter part of the fire-bars uncovered, yet from one-quarter part of the fire-place that I first made, I find plenty of steam. The greatest part of the waste steam is condensed in heating the water to fill the boiler; what escapes is a mere nothing. The engine will be loaded, when in fork, about 52 lbs. to the inch. Now suppose I raise the steam so high at the first part of the stroke as to go so expansive as to leave the steam, at the finish, only atmosphere strong, shall I, in that case, use any more coal than at present? The materials and joints will stand far more than that pressure; 500 lbs. to the inch would not injure them. When the engine gets on two lifts, I will write to you again, and in the meantime please to give me your thoughts on the engine. Every engine that was erecting is stopped, and the whole county thinks of no other engine.

"Your very obedient servant,
"Rd. Trevithick.

The new pole puffer-engine worked so satisfactorily and its movements were so manageable that the length of the stroke was increased by the spare 6 inches, which had been allowed as a margin in case of its overrunning its intended stroke. It would bear being worked at eighteen strokes a minute, while the Watt 72-inch engine did not exceed nine strokes a minute; with steam in the boiler of 80 lbs. to the inch it performed its work when the steam supply was cut off at two-thirds of the stroke, completing it by expansion. It also worked well with steam of 120 lbs. to the inch; but the want of strength in the pump-rods and the requirements of the mine caused the regular working pressure of steam to be reduced to 60 lbs. on the inch, and to be cut off when the pole had moved through the first quarter of its stroke. The excellent draught causing the fire-bars to be reduced to one-quarter of their original surface, and the heating the feed-water by the waste steam in this powerful pumping engine, indicate the use of the blast-pipe as at that time worked in the Welsh puddling-mill engine. Watt's engine was for a moment forgotten, that he might challenge Woolf to a trial, giving him as a help twenty millions, or the understood duty of the Watt engine. This non-condensing pole-engine, with 20 tons of pump-rods, moved at a maximum speed of 8 feet a second, and was equal to its work with a steam pressure of 52 lbs. on the inch. Trevithick contemplated extending the expansive principle even further than he had done in the Wheal Prosper pole condensing engine, so that at the finish of the up-stroke the steam should only be about the pressure of the atmosphere, or say from 1 to 10 lbs. on the inch, having commenced it with steam of from 100 to 200 lbs. on the inch, and cutting off the supply from the boiler when the pole had gone but a very small part of its upward stroke, more or less as the mine requirements admitted of it. The principle of expansive working and momentum of moving parts was of necessity modified in its application to pump-work.

"Eastbourne, February 15th, 1816.

"Dear Trevithick,

"I have been called here by the decease of my wife's uncle, and consequently your letters of the 11th did not reach me till this day.

"The account you give me of your new engine has been extremely gratifying. The duty performed by the engine in giving a velocity of 8 feet in a second, thirty-six different times in a minute, to 24 tons of matter, by the consumption of 2 bushels of coal in an hour, is indeed very great, amounting to about fifty-seven and three-quarter millions. So that when you obtain a proper burden, and the extraordinary friction arising from the too close fitting of the plunger-pole and case is reduced, there seems to be no doubt of your engine performing wonders.

"I am of opinion that the stronger steam is used, the more advantageous it will be found. To what degree it should be applied expansively must be determined by experience in different cases. It will depend on the rate at which the engine requires to be worked, and on the quantity of matter put into motion, so that as large a portion as possible of the inertia given in the beginning of the stroke may be taken out of it at the end.

"Some recent experiments made in France prove, as I am told, for I have not seen them, that very little heat is consumed in raising the temperature of steam. And if this is true, of course there must be a great saving of fuel by using steam of several atmospheres' strength, and working expansive through a large portion of the cylinder. I have really been impatient for a week past to receive some account of your machine, having learned nothing about it, except from a paragraph dated Hayle in the Truro paper of last Saturday week, and somehow or other the next paper has not reached me,

"I hope to be in London about Tuesday next, but at all events direct to me there, as my letters are regularly forwarded.

"Believe me, dear Sir,
"Yours ever most faithfully,
"Davies Giddy."

[Rough draft.]

"Bromsgrove, 8th March, 1816.

""Mr. John Adams,

"Sir,—I received your favour of the 12th February, but did not answer it in due course, because I was then erecting an engine on the new plan, which is now at work, and performs exceedingly well. It is equal in power to a 72-inch diameter cylinder, double power of B. and Watt's. The expense of erection, and the consumption of coals in this engine, are not one-third of a B. and Watt's to perform the same work. I am the same Trevithick that invented the high-pressure engine. I have sent out nine steam-engines to the gold and silver mines of Peru. I intend to sail for that place in about a month or six weeks, but shall appoint agents in England to erect these engines.

"No publication or description whatever has been in circulation, neither is it required, for I have a great many more orders than I can execute.

"I have not seen anything of Mr. Losh's patent engine, or Mr. Collins'.

"If you should go to London I advise you to call on Mr. Jas. Smith, Limekiln Lane, Greenwich, who is an agent for me, and will soon be able to show you an engine on this plan at work.

"I remain, &c.,
"R. Trevithick.

Unless the foregoing letters are based on error, the only conclusion to be drawn is that Watt, on the expiry of his patent right and of twenty-eight years of labour, having erected his masterpiece in Cornwall, was within a few years so beaten that Trevithick, in his challenge to Woolf, offered to throw in the Watt engine as a make-weight, and with such odds to bet him two to one that his comparatively small and cheap high-pressure engine should beat the two big ones, both in power, in first cost, and in economical working. The Watt engine was one of his largest, with a 72-inch cylinder. Its power was equal to Trevithick's 33-inch pole-engine, when worked with steam of 34 lbs. to the inch; but the latter also worked with three times that pressure of steam, whereby its power was increased threefold. The first cost of these engines was probably in inverse proportion to their power. Trevithick's cost 700l., while three times that sum would not pay for the Watt engine. The reported duty of Watt's Herland engine was twenty-seven millions; and if the trial was with his ordinary bushel of 112 lbs. of coal, the duty would only be equal to twenty millions with 84 lbs. of coal, which constituted the Cornish bushel.

Trevithick's pole high-pressure steam-engine did fifty-seven millions; in other words, performed the same work as the Watt engine with less than half of the daily coal. This large economy led to orders for many engines, on his promise that they should cost much less than those of Watt of equal power, and should perform the work with one-third of the coal. Some believed him, though others were stony-hearted, and as obstinate as donkeys.

[Rough draft.]

"Penzance, 8th March, 1816.

""Mr. Phillip,

"Sir,—I long since expected to have heard from you that my agreement with the Herland adventurers was executed. I have in every respect fulfilled my part of the engagement with the adventurers, and expect that they will do the same with me. The engine continues to work well. Every person that has seen it, except Joseph Price, A. Vivian, Woolf, and a few other such like beasts, agrees that it is by far the best engine ever erected. Its performance tells its effects, in spite of all false reports.

"Joseph Price and A. Vivian reported that the engine was good for nothing, that it would not do four millions, and that at the next Tuesday meeting they would turn it idle. On the evening before the meeting they met at Camborne for that purpose.

"Captain A. Vivian did not attend the meeting. I could not help at the meeting threatening to horsewhip J. Price for the falsehoods that he with the others had reported.

"I hear that he is to go to London to meet the London committee on Monday. I hope the committee will consider J. Price's report as from a disappointed man. It is reported that he has bought very largely in Woolf's patent, which now is not worth a farthing, besides losing the making my castings, which galls him very sorely.

"The water sinks regularly 20 fathoms per month, including every stoppage. On Monday next I expect they will be putting down the second lift. The water rises about 8 inches per hour when the engine is idle, and when at work will sink it again at the same rate, showing that the engine is equal to double the growing stream. When drawing from the pool the sinking is not much above 4 inches per hour, which shows that the water drains from a great distance from the country. The engine is going fourteen strokes per minute, 10-feet stroke, 14½-inch box. When Herland worked last they drew a 14-inch box, 7-feet stroke, twelve strokes per minute in winter, and seven strokes per minute in summer. Therefore it appears that the winter water is about from seven to eight strokes per minute, and the summer water from four to five strokes per minute for this engine.

"The engine has forked faster the last week than she did before. I think that the great quantity of water that was laying round the mine at the surface is nearly drawn down, and that as we get down to a closer ground the drainage will not be so much. If we have dry weather the water will, at the next shallow level, fall off two strokes per minute before the next lift is in fork. If it continues the same we can continue to sink 20 fathoms per month, exclusive of the time it will take to fix the lifts. As we get down the house of water will lessen considerably. The expense of the engine is about 100l. per month. The sumpmen and others attending on the forking the water, about 100l. per month more. They have all the materials on the mine for the pit-work, therefore a very trifling sum will bring the water down to the 60-fathom level, when the mine will pay her own expense.

"I will thank you for an account of the meeting.

"Your obedient servant,
"R. Trevithick.

Mr. Phillip was the financial managing shareholder—more particularly with the Londoners—at that resuscitation of Herland Mine; and though the new engine was comparatively cheap, both in its first cost and in its consumption of coal, and satisfactorily reduced the water in the mine, payment for it was withheld because the currents of self-interest were against Trevithick. Mr. Joseph Price was the manager of a steam-engine manufactory at Neath Abbey, in South Wales, and had been in the habit of supplying castings for Cornish mines. Arthur Woolf was then striving to bring into use his patent double-cylinder engine, and patent high-pressure steam-boiler, which Trevithick looked on as copies from Hornblower and himself. This, added to Woolf's sarcastic manner of speech, roused Trevithick's anger.

Putting aside the words of the disputants, the fact is stated that the pole-engine, with a reduced steam pressure, worked a pump 14½ inches in diameter, 10-feet stroke, fourteen strokes per minute; while the largest and best engine by Watt in Cornwall, placed on the same mine, with a 72-inch steam-cylinder, gave motion to a pump of 14 inches in diameter, 7-feet stroke, at twelve strokes a minute; being in round numbers just one-half the amount of the work performed by Trevithick's comparatively small engine, which had not a single feature of the Watt engine in it.

[Rough draft.]

"Penzance, March 7, 1816.

""Captain Joe Odgers,

"Sir,—I have your favour of the 27th February, and requested Mr. Page to send to you a sketch of the agreement. On seeing him yesterday, I found that he had neglected to send it to you. He will leave the country for London in a few days, and intends to call on you at Dolley's as soon as he arrives. I do not know that the agreement matters much for a few days up or down. The terms are well understood between us, which is that the adventurers and I equally share the advantages that may arise from this new engine over Boulton and Watt's. When you have fully arranged with your adventurers about the engine, please to write me, and I will immediately proceed to order the engine; and in the interim the agreement will be drawn up by Mr. Page, and executed either here or in London, just as may suit.

"I remain, &c.,
"R. Trevithick.

"P.S.—Herland engine goes on better and better. Your adventurers will get a satisfactory account by applying in town to Mr. Wm. Phillip, No. 2, George Yard, Lombard Street. He is the principal of the London adventurers."

Trevithick believed that mine adventurers would agree to pay him one-half the saving caused by his engines, as compared with the cost of fuel in the Watt engine. The duty performed by the latter was understood and agreed to generally; persons were chosen by the adventurers to experiment and report on the duty of Trevithick's pole-engine, that the amount of payment might be ascertained in proportion to the saving effected.

"Penzance, April 2, 1816.

""Mr. Giddy,

"Sir,—I have long wished to write to you about the Herland engine, but first wished to see the engine loaded with a second lift, and a trial made of the duty. Yesterday was fixed on, before ordering another engine for the eastern shaft.

"The persons attended. The arbitrators gave the duty as forty-eight millions, and said they had no doubt the engine would perform above sixty millions before getting to the bottom of the mine.

"They were much within the duty, but I did not contend with them, as they said it was quite duty enough.

"The engine worked 9¼ strokes per minute, with 2 bushels of coal per hour for the whole time, 10-feet stroke. There were two pump-lifts of 14½-inch bucket, making 43 fathoms, and 26 fathoms of 6-inch for house-water.

"The steam was from 100 to 120 lbs. to the inch. The valve open while the plunger-pole ascended 20 inches, then went the remainder of the 10-feet stroke expansive.

"It went exceedingly smooth and regular. Some time since, by way of trying the power of the engine, we disengaged the balance-bob. The engine worked twenty strokes per minute, with 17 tons of rods, &c., and drew 14½-inch bucket 23½ fathoms, and a 6-inch bucket 26 fathoms, 10-feet stroke, twenty strokes per minute.

"This was about 45,000 lbs. weight, with the speed of 200 feet per minute, which makes the duty performed more than the power of three 72-inch cylinders, single, of Boulton and Watt, say of 8-feet stroke, 10 lbs. to the inch, nine strokes per minute, which is more than these engines will perform. I have all the orders for every engine now required in the country, which is not to be wondered at, for one-tenth part of the expense in the erection will do, and the duty is not less than three times as much as other engines. This will be proved before we get to the bottom.

"The engine now works at about two-fifths of the load which she will have when at the bottom. When the next lift is in fork I will write to you again.

"I am, Sir, your humble servant,
"Richard Trevithick.

Independent examiners reported that the Herland pole-engine did forty-eight millions of duty, under various pressures of steam, up to 120 lbs. to the inch, working five-sixths of the stroke expansively, with a speed of twenty strokes a minute, or double the speed of the Watt engine; and the importance of those facts deserves the scrutiny and close study of youthful engineers. A small cheap engine, of 33-inch cylinder, similar in general construction to the Wheal Prosper pole-engine, but still more simple from the absence of air-pump and condenser, did as much work as three of Watt's largest engines with cylinders of 72 inches in diameter. This great stride in the useful value of the steam-engine was forced on the public by Trevithick's single-handed energy, when every man was against him, even Henry Harvey, his brother-in-law and friend, his former partner, Andrew Vivian, and his once carpenter and assistant, Arthur Woolf. As a closing attempt to finally crush him, he was made personally responsible for the payment of an engine erected for the benefit of others. This was the great trial test of the power and economy of the purely high-pressure expansive steam-engine as compared with the Watt low-pressure vacuum engine applied to large pumps.

"Hayle Foundry, 18th April, 1816.

"Sir,

"I was at Herland to-day. Captain Grose received a letter while I was there, signed by Captain William Davey and Joseph Vivian, requesting him to appoint others to attend the trial of the engine, as it would not be convenient for them to do it.

"Captain Samuel Grose, jun., brought down the drawing for your engine. He said he had taken off the working gear only. If you would wish it, we will make the working-gear and all the wrought-iron work on the drawing for the two engines ordered, and will take on a man or two immediately for that purpose. You will let me know about this before you set off, and also if any alteration is to be made in the beam for Wheal Treasure engine, since you have altered the size of the pole. We had cast the case, but I suppose it will suit some place else.

"Your obedient servant,
"Henry Harvey.

"Mr. Richard Trevithick."

"About 1815 or 1816 I was employed by Captain Trevithick to erect various pole-engines, one of them at Saltram Stream. It had worked at Tavistock; it was a horizontal high-pressure pole puffer. Captain Samuel Grose was then erecting for Captain Trevithick a 24-inch high-pressure pole-engine at Beeralstone, on the Tamar, to drain a lead mine. I assisted Captain Grose. The stroke was about 8 feet. It worked with cross-head and side rods. There were two wrought-iron boilers about 3 feet 6 inches in diameter and 40 feet long. The fire and flues were outside. The steam pressure, 60 lbs. to the inch. I also erected a similar engine with a 20-inch pole at Wheal Treasure, now called Fowey Consols Mine; and one at Logassack, near Padstow. Those two had brass poles. It was found that the poles cut and wore in their passage through the stuffing box, the middle wearing more than the ends, causing steam to escape. A similar pole of Captain Trevithick's erecting was then working at Wheal Regent, near St. Austell.

"In 1818 I saw working at Wheal Chance Mine, near Scorrier, an old 60-inch cylinder Boulton and Watt engine. A pole of Trevithick's was fixed between the cylinder and the centre of the main beam. High-pressure steam was first worked under the pole and then expanded in the cylinder."[35]

The late Mr. William Burral, for many years manager of the boiler-making department at Messrs. Harvey and Co., at Hayle, said:—

"About the year 1815 or 1816 I helped to erect at Treskerby Mine an engine for Captain Trevithick. Mr. Sims was the engineer of the mine. The engine had the usual cylinder, and close to it one of Captain Trevithick's poles was fixed. The boilers were Captain Trevithick's high-pressure. The steam was first turned on under the pole. When she had finished her up-stroke the steam passed from under the pole on to the top of the piston in the cylinder. There was a vacuum under the piston. The steam-cylinder was 58 inches in diameter, about 9 or 10 feet stroke. The pole was 36 inches in diameter, and a less stroke than the piston, because it was fixed inside the cylinder, nearer to the centre of the beam. There was a pole-engine then working at Wheal Lushington, also at Poldice, and at Wheal Damsel."

"Captain Artha recollects at Wheal Alfred Mine in 1812 the 66-inch cylinder pumping engine used a pole air-pump; one or two whim-engines on the same mine also used them. Wheal Concord pumping engine, in 1827 had a similar air-pump. Old Wheal Damsel, near Treloweth, used one as late as 1865. The condensing water and air passed through a branch with a valve on it near the top of the pole-case, just under the stuffing box There was a foot-valve at the bottom of the pole-case."[36]

The writer has had the pleasure of personal acquaintance with each of those three gentlemen, who as young engineers commenced their labours in the erection of Trevithick's engines.

No sooner had Trevithick perfected the pole condensing engine and then the pole puffer-engine, than he, in conjunction with Sims, who had just taken part in the erection of one of his high-pressure steam pole-engines for working the pumps at Beeralstone Mine, combined the pole with the ordinary Watt vacuum engines, supplying them with steam from his high-pressure boilers, in other words, converting them from their original form of low-pressure vacuum engines to high-pressure expansive compound steam-engines.

The old 60-inch cylinder Boulton and Watt engine, at Wheal Chance (one of Watt's favourite engines), was in 1818 transformed into a high-pressure engine, with Trevithick's pole placed between the centre of the main beam and the steam-cylinder. The high-pressure steam from Trevithick's new boilers was turned under the pole for the up-stroke, after which it was expanded in the old and much larger cylinder on the top of the piston causing the down-stroke; it then, by its passage through the equilibrium valve, allowed the piston in the large cylinder to make its up-stroke, by equalizing the pressure of steam on its top and bottom, while a fresh supply of strong steam from the boiler admitted under the pole gave power to the up-stroke; and finally, the comparatively low-pressure steam under the large piston passed to the condenser and air-pump to form a vacuum for the down-stroke, as in the Watt engine.

Sims, the engineer at Wheal Chance, one of the mines in the eastern or Watt district, was converted and became in 1815 or 1816 a partner with Trevithick, and erected, at Treskerby Mine, Trevithick's high-pressure pole of 36 inches in diameter, as an addition to the old Watt engine working with a cylinder 58 inches in diameter.

Watt, then, within a year or two of his death, was too old to any longer take part in the contest; his engine in the hands of others was converted and became a high-pressure expansive engine.

Trevithick, as a further proof that he could do without the Watt patent air-pump bucket, with its piston and valves, removed it from a Watt engine at Wheal Alfred Mine in 1812, replacing it by one of his poles, answering the same purpose, but different in construction. Many other mines used them; one remained at work in Old Wheal Damsel in 1860. They have also been used in steamboat air-pumps.

Having traced during a period of five or six years the rise and progress of the high-pressure expansive pole condensing-engines, the high-pressure expansive pole puffer-engine, and the combined pole and cylinder high-pressure engine, their value in a commercial sense may be further tested by the public acts of the time. Lean, an authority on such matters, and certainly not given to unduly praise Trevithick, spoke as follows on the duty of those particular engines at various periods; and not the least noteworthy is the fact, that Herland, Poldice, and Treskerby, that were prominent in the early use of the Watt engine, threw off their allegiance but shortly before the last days of the great engineer, and converted his low-pressure steam vacuum engines into Trevithick high-pressures.

"In 1798 Messrs. Boulton and Watt, who on a visit to Cornwall, came to see it—'the Herland engine'—and had many experiments tried to ascertain its duty; it was under the care of Mr. Murdoch, their agent in the county. Captain John Davey, the manager of the mine, used to state that it usually did twenty millions, and that Mr. Watt, at the time he inspected it, pronounced it perfect, and that further improvement could not be expected.

"In 1811 the average duty of the three engines (Boulton and Watt's) on Wheal Alfred Mine was about twenty millions. These engines were at that time reckoned the best in the county.

"In 1816 Sims erected an engine at Wheal Chance, to which he applied the pole adopted by Trevithick in his high-pressure engine. This engine attained to forty-five millions; and in 1817 it did 46·9 millions.

"In 1814 Treskerby engine is reported as doing 17·48 millions.—Wm. Sims, engineer.

"In 1820 Treskerby engine, to which Trevithick's high-pressure pole had been adapted, had reached 40·3 millions."[37]

The Herland engine of Watt in 1798 did twenty millions; in 1816 Trevithick's high-pressure pole puffer in the same mine did forty-eight millions. In 1820 his high-pressure pole-engine was combined with a Watt low-pressure engine, thereby more than doubling its economical duty.

In 1813 Trevithick wrote:—

"That new engine you saw near the sea-side with me (Wheal Prosper high-pressure pole condensing engine) is now lifting forty millions one foot high, with a bushel of coal, which is nearly double the duty that is done by any other engine in the county. A few days since I altered a 60-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting, to erect a new engine equal in power to a 63-inch cylinder single."[38]

In the four or five years from his return to Cornwall in 1810, to his leaving for South America in 1816, he doubled the duty and the power of the steam-engine. Watt once said he had received an oblique look from Trevithick, sen. The time was now come for Trevithick, jun., to return the compliment; his improved engines having made their way into the eastern mine district, which Watt once looked upon as his own.

Trevithick was short of money and on the point of leaving England for South America, when Mr. Sims, in the employ of Messrs. Williams and Co., favourable to low pressure, was sent to negotiate for the purchase of a share in Trevithick's patent of 1815 for the high-pressure steam expansive pole-engine.

[39]"18th October, 1816.—Agreement between Trevithick and Mr. William Sims, prepared by myself and Mr. Day, solicitor for Mr. Sims, or for Mr. Michael Williams, under whom Sims acted, recites, that in consideration of 200l. paid by Sims, he was to have a moiety of the patent for Cornwall and Devon, and that I should have power to act and make contracts whilst Trevithick was out of England.

"The day after contract signed, Trevithick sailed in the 'Asp,' Captain Kenny, for South America. I was on board when the ship sailed.

"I see among my papers, in May, 1819, in reference to the patent, is the following note:—'Mr. Michael Williams said it was verbally agreed that Captain Trevithick should have one-quarter part of the savings above twenty-six millions.' This, I believe, was the average duty of the engines at that time.

"I had several assurances relative to Trevithick's claims, and much correspondence, but no allowance was made from any mines but Treskerby and Wheal Chance; though Trevithick's patent and boilers were used throughout the county without acknowledgment; and the duty of the engines had soon increased from twenty-six millions to about seventy millions.

"In 1819 I attended at the account-houses of Treskerby and Wheal Chance, of which the late Mr. John Williams, of Scorrier, was the manager, in consequence of some of the adventurers objecting to continue the allowances on the savings to Captain Trevithick, when Mr. Williams warmly observed, that whatever other mines might do, he would insist, as long as he was manager for Treskerby and Wheal Chance, the agreement made should be carried into effect.

"I remain, my dear Thomas,
"Your very affectionate father,
"Rd. Edmonds.

The agreement with Mr. Sims, or rather with Mr. Michael Williams, late M.P. for Cornwall, who exercised large authority in Cornish mines, was that he should have for 200l. one-half of the patent for the high-pressure pole-engine, as applied to Cornwall and Devon.

Trevithick had desisted from securing a patent for the large high-pressure steam-boilers and expansive working, on a verbal understanding that he should receive one quarter of the saving from the reduced consumption of coal by those two particular inventions, twenty-six millions of pounds of water raised one foot high by a bushel of coal of 84 lbs., being the duty of the best Watt engines, to be taken as a starting-point for the payment. Treskerby and Wheal Chance paid for the pole-engine, but the Trevithick boilers suitable for high steam, and the simple methods of working it expansively, had been made so generally public, that people professed to think they had a right to them, when but a few years before they had thrown the inventor off his guard by saying "everybody knows that the Cornish boiler is your plan, and as it cannot be denied, a patent will be of no service."

Mr. John Williams[40] stated "that whatever other mines might do, he would insist, as long as he was manager for Treskerby and Wheal Chance, the agreement made should be carried into effect." The Williamses paid to Trevithick 300l. for the saving of coal by the pole patent engine, as an "acknowledgment of the benefits received by us in our mines;" but no payment was made for the greater invention of the high-pressure steam-boilers then in general use.

In 1814 the Watt Treskerby engine did seventeen and a half millions. Trevithick's boiler and pole were applied, and the duty was increased to more than forty millions. In 1816 the same changes were made in Wheal Chance, and the duty rose to more than forty-six millions. The consumption of coal was reduced to one-half, amounting in round numbers to a gain of 500l. a month in those two mines alone.

"Trevince, near Truro,
5th January, 1853.

"Dear Sir,

"I am favoured with your letter of the 31st ult., enclosing also one from Mr. F. Trevithick, of the 24th idem, and have much pleasure in complying with your joint request to the best of my ability. I was well acquainted with the late Mr. Rd. Trevithick, having had frequent occasion to meet him on business and to consult him professionally; and I am gratified in having the present opportunity of bearing testimony to his distinguished abilities, and to the high estimation in which the first Cornish engineers of the day then regarded him. I need scarcely say that time has not lessened the desire in this county especially to do him justice. As a man of inventive mechanical genius, few, if any, have surpassed him, and Cornwall may well be proud of so illustrious a son.

"At this distance of time I can scarcely speak with sufficient exactness for your purpose of the numerous ingenious and valuable mechanical contrivances for which we are indebted to him, but in reference to his great improvements in the steam-engine I have a more particular recollection, and can confidently affirm that he was the first to introduce the high-pressure principle of working, thus establishing a way to the present high state of efficiency of the steam-engine, and forming a new era in the history of steam-power. To the use of high-pressure steam, in conjunction with the cylindrical boiler, also invented by Mr. Trevithick, I have no hesitation in saying that the greatly-increased duty of our Cornish pumping engines, since the time of Watt, is mainly owing; and when it is recollected that the working power now attained amounts to double or treble that of the old Boulton and Watt engine, it will be at once seen that it is impossible to over-estimate the benefit conferred, either directly or indirectly, by the late Mr. Trevithick, on the mines of this county. The cylindrical boiler above referred to effected a saving of at least one-third in the quantity of coal previously required; and in the year 1812 I remember our house at Scorrier paying Mr. Trevithick the sum of 300l. as an acknowledgment of the benefits received by us in our mines from this source alone. Mr. Trevithick's subsequent absence from the county, and perhaps a certain degree of laxity on his own part in the legal establishment and prosecution of his claims, deprived him of much of the pecuniary advantage to which his labours and inventions justly entitled him; and I have often expressed my opinion that he was at the same time the greatest and the worst-used man in the county.

"Amongst the minor improvements introduced by him, it occurs to me to notice that he was the first to apply an outer casing to the cylinder, and by this means prevent, still further than Watt had succeeded in doing, the loss of heat by radiation.

"As connected with one of the most interesting of my recollections of Mr. Trevithick, I must mention that I was present by invitation at the first trial of his locomotive engine, intended to run upon common roads, and of course equally applicable to train and railways. This was, I think, about the year 1803, and the locomotive then exhibited was the very first worked by steam-power ever constructed.

"The great merit of establishing the practicability of so important an application of steam, and the superiority of the high-pressure engine for this purpose, will perhaps more than any other circumstance serve to do honour through all times to the name of Trevithick. The experiment which was made on the public road close by Camborne was perfectly successful; and although many improvements in the details of such description of engines have been since effected, the leading principles of construction and arrangements are continued, I believe, with little alteration, in the magnificent railroad-engines of the present day. Of his stamping engine for breaking down the black rock in the Thames, his river-clearing or dredging machine, and his extensive draining operations in Holland, I can only speak in general terms, that they were eminently successful, and displayed, it was considered, the highest constructive and engineering skill. As a man of enlarged views and great inventive genius, abounding in practical ideas of the greatest utility, and communicating them freely to others, he could not fail of imparting a valuable impulse to the age in which he lived; and it would be scarcely doing him justice to limit his claims as a public benefactor to the inventions now clearly traceable to him, important and numerous as these are. From my own impressions I may say that no one could be in his presence without being struck with the originality and richness of his mind, and without deriving benefit from his suggestive conversation. His exploits and adventures in South America, in connection with the Earl of Dundonald, then Lord Cochrane, will form an interesting episode in his career; and altogether, I am of opinion that the Biography which you have undertaken will prove highly interesting and valuable, and I wish you every success in carrying it out.

"Believe me, my dear Sir,
"Yours very faithfully,
"Michael Williams.

"E. Watkin, Esq.,
"London and North-Western Railway,
"Euston Station, London."

Arthur Woolf shortly after that time (1811) erected his double-cylinder engines in Cornwall. The late Captain Samuel Grose, when giving the writer his recollections of Trevithick, said:—

"When he returned from London to Cornwall, about 1810 or 1811, he employed me to look after the erection of the Wheal Prosper high-pressure engine. Oats, Captain Trevithick's head boiler-maker, was constructing the boilers; Woolf came into the yard, and examined them. 'What do'st thee want here?' asked Oats. 'D—n thee, I'll soon make boilers that shall turn thee out of a job!' was Woolf's reply. He was a roughish man. When his brother Henry mutinied at the Nore, Woolf, who was then working an engine in Meux's brewery, and had married the lady's maid, made interest with his employer to save Henry from being hanged at the yard-arm, and afterwards found employ for him in Cornwall. He was but a clumsy mechanic. Woolf used to blow him up by saying, 'D—n thee, I wish I'd left thee to be hanged.'"

The writer, who knew Oats, has heard him tell similar stories of the rival engineers.

In 1800, Woolf, who had been a mine carpenter, went to London with the first high-pressure steam-engine which Trevithick had sent beyond the limits of Cornwall[41]—probably to Meux's brewery,[42] for he was there in 1803, and in the receipt of 30l. a year from Trevithick as engine-fireman. From the date of Woolf's patent in 1804, his pay from Trevithick ceased, and with it their friendship. Trevithick used to say, "Woolf is a shabby fellow."

Patents sprang up like mushrooms after Trevithick had so liberally cast forth the seeds of the high-pressure engine, making the security, or even the form of a patent, a doubtful matter. The perfecting of expansive high-pressure engines was like the boiler, the result of years of trial. When matured in 1816 it saved Cornwall and the world one-half of the coal that before had been consumed in low-pressure steam-engines. Every engineer became, more or less, an expansive worker, and Trevithick's saving of hundreds of thousands of pounds annually to the general public, gave to him little or no reward.

At the period of those high-pressure pole-engine experiments, Trevithick had devoted twenty years of constant labour to the improvement and extended use of the steam-engine, causing it to assume every variety of form except that of the Watt patent engine, an approach to which was unusual, as evidenced in the high-pressure steam Kensington model of 1796, without beam, parallel motion, air-pump, or condenser, having no one portion either in principle or detail similar to the Watt engine, being portable and not requiring condensing water, with single and double cylinders, placed vertically or horizontally. Having during twelve busy years constructed over a hundred high-pressure steam-engines, scarcely any two of which were exactly alike, he departed if possible still further from the Watt type, and went back apparently, though not in reality, to the Newcomen engine, simplifying it by the omission of the great bob, and use of condensing water, as in the nautical labourer and steamboat engine of about 1810,[43] and the South American mine engines of 1816,[44] which had open-top cylinders, more like a Newcomen than a Watt, but if possible even more simple and primitive-looking than the former. Again, compare the thrashing engine of 1812[45] with the Newcomen of 1712:[46] the great and all-important difference being that one was a high-pressure steam-engine, the other a low-pressure atmospheric engine. Then came the varieties of high-pressure steam pole-engines, working very expansively either as puffers or condensers, retaining the same dissimilarity to the Watt engine: and lastly, the combination of the high-pressure pole with the Watt patent engine, thereby causing the old Watt engine to do more than double the work it had done when new from the hands of the maker, and also to perform this increase of work with a decrease in the consumption of coal.

The following chapter will trace the adaptation of high-pressure expansive steam, from cylindrical boilers, to the form of pumping engine still in general use.

[CHAPTER XX.]

THE WATT AND THE TREVITHICK ENGINES AT DOLCOATH.

Having up to 1816 traced the progress of the steam-engine in Cornwall through a century, during the latter half of which Trevithick, sen., and his son were among its most prominent improvers, the latter having devoted a quarter of a century to the work, the effect of which is shown in the skeleton outlines of a few classes of engines, one important feature still remains for examination before a correct judgment can be formed of the events of this period and their prime movers.

The use of an increasing pressure of steam gave increased force and value to the improved steam-engine, but the power of constructing engines and boilers to render the increased pressure manageable was the result of a lifetime of labour.

Savery, whose engine was scarcely more than a steam-boiler, failed to control its force, and is said to have blown the roof from over his head. The mechanism of Newcomen's engine was well arranged, but suitable only for the working of pumps, and its power was limited to the weight of the atmosphere, from which it was called the atmospheric engine.

In 1756, an atmospheric engine with a cylinder of 70 inches in diameter worked at the Herland Mine, "the only objection to which was the cost of the coal, to lessen which several methods had been suggested for increasing the elasticity of the steam, and reducing the size of the boiler."[47]

In 1775 Richard Trevithick, sen., removed the flat top of a Newcomen boiler, and substituted a semicircular top, enabling it to contain stronger steam, and at the same time he improved the mechanical part of the engine by finding a better resting-place for the steam-cylinder than the top of the large boiler. Pryce gives a drawing of this engine as the best at that time in Cornwall.[48]

"It is known as a fact that every engine of magnitude consumes 3000l. worth of coal every year.

"The fire-place has been diminished and enlarged again. The flame has been carried round from the bottom of the boiler in a spiral direction, and conveyed through the body of the water in a tube (one, two, or three) before its arrival at the chimney.

"Some have used a double boiler, so that fire might act on every possible point of contact, and some have built a moorstone boiler, heated by three tubes of flame passing through it.

"A judicious engineer does not attempt to load his engine with a column of water heavier than 7 lbs. on each square inch of the piston."[49]

While Pryce's book was being printed, Watt in 1777 wrote of the Cornish steam-engines:—

"I have seen five of Bonze's engines, but was far from seeing the wonders promised. They were 60, 63, and 70 inch cylinders at Dolcoath and Wheal Chance. They are said to use each about 130 bushels of coals in the twenty-four hours, and to make about six or seven strokes per minute, the stroke being under 6 feet each. They are burdened to 6, 6½, and 7 lbs. per inch."[50]

The 63-inch was an open-top cylinder atmospheric engine at Dolcoath Mine under the management of Trevithick, sen.; and shortly after, in 1777 or 1778, Watt's first engine was erected in Cornwall.[51]

In 1783 Trevithick, sen., gave Watt an order for a patent engine for Dolcoath, in size similar to the old Newcomen atmospheric, having a cylinder 63 inches in diameter, that a working trial might be made between the rival engines. The Watt engine having a cylinder-cover, with the patent air-pump and condenser, was known in the county as the Dolcoath great 63-inch double-acting engine. Three steam-engines were then at work in that mine: Trevithick senior's Carloose (then called Bullan Garden) atmospheric 45-inch cylinder, the atmospheric 63-inch cylinder, and Watt's 63-inch cylinder double-acting vacuum engine; all of which continued in operation side by side for five years until 1788, when for a time Dolcoath ceased to be an active mine. Trevithick, jun., was then a boy of seventeen years.

After ten years of idleness and rust, as if mourning the death of Trevithick, sen., in 1798 Richard Trevithick, jun., as engineer, and Andrew Vivian as manager, induced shareholders to resuscitate the old mine. Fire was again given to the voracious jaws of the boilers, and the three engines recommenced their labours and their rivalries.

A year or two before this Trevithick had made models of high-pressure steam-engines. Davies Gilbert, in 1796, met him among other engineers, giving evidence in the Watt lawsuits, when he mentioned his ideas of an engine to be worked solely by the force of steam. Watt had claimed such an engine in his patent twenty-seven years before, but had failed to carry it into practice. Hornblower had tried something like it in his double-cylinder expansion engine, but he did not use high-pressure steam, and consequently also failed.

The idea, therefore, of expansive steam was not new, but the useful mastery of it was. Savery had tried expansive steam before Watt patented it; the latter went to law with Hornblower for an infringement of the idea, when neither of them had in truth constructed an expansive steam-engine. The low pressure of the steam from the boilers used by Hornblower and Watt did not admit of profitable expansion in the cylinder; at its full boiler pressure it constituted but a comparatively small portion of the power of the engine: to reduce that power by expansion was as apt to be a loss as a gain. The steam-engine was still dependent for its power mainly on steam as an agent for causing the required vacuum, until 1796, when Trevithick disclosed his method of constructing small cylindrical boilers and engines suitable for giving power from the strong pressure of the steam, irrespective of vacuum.

Lean, who favoured Watt rather than Trevithick, thus records the advent of Watt's expansive engine:—

"In 1779 to 1788 Mr. Watt introduced the improvement of working steam expansively, and he calculated that engines which would previously do nineteen to twenty millions would thus perform twenty-six millions; but I do not find any record of this duty being performed in practice. In 1785 Boulton and Watt had engines in Cornwall working expansively, as at Wheal Gons and Wheal Chance in Camborne; but in these the steam was not raised higher than before, and the piston made a considerable part of the stroke therefore before the steam-valve was closed.

"In 1798, on account of a suit respecting their patent, which was carrying on by Boulton and Watt, an account of the duty of all the engines in Cornwall was taken by Davies Gilbert, Esq., and the late Captain Jenkin, of Treworgie, and they found the average to be about seventeen millions."[52]

One of these so-called expansive Watt engines, erected at Wheal Chance, was converted into a real expansive engine by Trevithick, as described in the foregoing chapter, by his high-pressure steam-boilers and the addition of his pole-engine. The conversion of the other, a 63-inch low-pressure vacuum engine at Wheal Gons, will be traced in this chapter.

Mr. Taylor, who for many years took an active interest in Cornish mining, says:—

"In 1798 an engine at Herland was found to be the best in the county, and was doing twenty-seven millions, but being so much above all others, some error was apprehended. This engine was probably the best then ever erected, and attracted therefore the particular attention of Messrs. Boulton and Watt, who, on a visit to Cornwall, came to see it, and had many experiments tried to ascertain its duty. It was under the care of Mr. Murdoch, their agent in the county.

"Captain John Davey, the manager of the mine, used to state that it usually did twenty millions, and that Mr. Watt, at the time he inspected it, pronounced it perfect, and that further improvement could not be expected."[53]

This best engine from the hands of Watt and Murdoch in the Herland Mine in 1798 may be taken as a Watt stand-point, when its usual duty was twenty millions; and Trevithick and Bull erected a competing engine, probably with an increased steam pressure, for Trevithick's portable high-pressure engines were at that time coming into notice;[54] but no trace remains of the result of this contest of the Watt and the Bull engine, though it was one of the causes of the lawsuits.

"In 1799 Henry Clark worked as a rivet boy in Dolcoath, and carried rivets to construct Captain Trevithick's new boiler, said to be the first of the kind ever made. It looked like a great globe about 20 feet in diameter, the bottom hollowed up like the bottom of a bottle; under this the fire was placed: a copper tube attached to this bottom went around the inside of the boiler, and then passed out through the side of the boiler, the outside brick flues then carrying the heat around the outside of the boiler and into the chimney.

"Captain Trevithick's first plunger-pole lifts in Dolcoath were put in at this time and worked by this engine. Glanville, the mine carpenter, was head man over the engines when Captain Trevithick was away."[55]

"Charles Swaine worked as a rivet boy in making Captain Trevithick's cylindrical wrought-iron boilers for the Dolcoath engine. Several of Captain Trevithick's high-pressure boilers were working in the mines before that, but not made exactly like the Dolcoath engine boilers. When I was a boy about the year 1804, several years before I worked on the Dolcoath engine boilers, I carried father's dinner to the Dolcoath smiths' shop, where he worked, and used to stop and watch the wood beam going up and down of Captain Dick's first high-pressure steam-whim. She was not a puffer, but a puffer-whim worked near by, called the Valley puffer. At that time most of Captain Dick's high-pressure boilers were smallish, cast iron outside, and wrought-iron tube."[56]

In 1799, shortly after the reopening of Dolcoath Mine, Trevithick, jun., selected his father's second-hand atmospheric engine of 1775,[57] to further improve it by a new boiler of uniformly globular figure, with concave circular bottom, under which fire was placed; it was of wrought iron, 24 feet in diameter, surrounded by external brick flues; a large copper tube, starting from the boiler bottom, immediately over the fire, served as an internal flue, carrying the fire by a sweep around the interior in the water space, and then out through the side of the boiler into the external brick flue. It may be said that there was nothing new in a circular form of boiler, or in an internal tube; but it will be admitted that this repaired engine, in this its third stride in the march of advancement, made publicly known those principles which in a few years more than doubled the power, the economy, and the applicability of the steam-engine. His patent drawing of 1802 shows this form of boiler applied to a small portable engine, in which, for the sake of simplicity of structure and cheapness, cast iron was used instead of wrought iron, and the internal tube omitted.[58]

The full detail estimate, from which the following items are extracted, of the cost of alteration was written by Trevithick, jun., in the book and on the page adjoining that containing the account of the former alteration and re-erection of the same engine by Trevithick, sen., in 1775.

"A 45-inch cylinder engine, working 20 lbs. to the inch:—

The term "single" refers to its open-top cylinder as originally erected by Newcomen, when it was called the Carloose engine, and so it remained after its re-erection in 1775, under the name Dolcoath new engine, alias Bullan Garden; but after the last re-erection in 1799 it had a cylinder-cover, and was called the Shammal 45-inch engine; "working 20 lbs. to the inch" meant the force on each inch of the piston, including vacuum on the one side of 14 lbs. and steam on the other side of 6 lbs. to the inch.

Watt, on his first visit to Cornwall, in 1777, spoke disparagingly of the Newcomen atmospheric engines "burdened to 6 or 7 lbs. net to the inch." Fifty years later Stuart described Watt's engine as "using steam of a somewhat higher temperature than 212 degrees, so as to produce a pressure between 17 and 18 lbs. on each square inch of the piston; yet in practice, from imperfect vacuum and friction, it cannot raise more water per inch than would weigh about 8½ lbs.,"[59] or an increase of net force—when compared with the Newcomen atmospheric—of only a pound or two on the inch in the lapse of years embracing the active lifetime of Watt. The cause of this slight increase of power is so simple that it has been passed by unnoticed by very many. The steam pressure in the Newcomen atmospheric was continued unaltered in the Watt vacuum engine. Trevithick constructed the first boiler and engine capable of safely and economically using the power of high-pressure steam. Nelson was obliged to come to close quarters, that his shot, propelled by weak cannon and low-pressure powder, might penetrate wooden ships. We now manufacture and control high-pressure powder, so that 12 inches of iron armour-plates cannot resist its force; but this knowledge has taken nearly as long in growing to perfection as did the mastery of high-pressure steam, and its use in the much more complicated steam-engine.

Watt's engine, as described a quarter of a century after the expiration of his patent and the advent of the high-pressure steam-engine, still derived its gross force from 14 lbs. of vacuum and 2 or 3 lbs. of steam, resulting in a net force of 8½ lbs. Trevithick's engine of 1799, which heralded the last hours of the Watt patent authority, and may be taken as the first distinct evidence of comparatively high-pressure steam in large Cornish pumping engines, derived its power from 14 lbs. of vacuum and 6 lbs. of steam, being together but 2 or 3 lbs. on the inch more than the Watt engine, but its net force of 12 lbs. to the inch was half again as much as the net force of the Watt engine, the increase being wholly from the steam pressure, which was never practised by Watt, and which in its almost unlimited force gives the greatly increased power to modern steam-engines.

Trevithick's estimate for a new engine of the same size as the old was 2000l., but as the old one could be improved for 1300l., the latter course was adopted, the wooden main beam with its segment head was retained, a cover was added to the cylinder, and a new piston-rod and piston; a pole air-pump was used in lieu of the more usual Watt air-pump bucket; a feed-pole forced water into the boiler,—an indirect proof of increased steam pressure. The new globular boiler with internal tube weighed 8 tons; the engineer's charge for carrying out the work was 66l.

The use of strong steam as the prime mover of the steam-engine increased more rapidly beyond than within the limits of Cornwall, for in 1802 was erected at Coalbrookdale a high-pressure steam-puffer engine, to which Trevithick attached a pump which forced water through a column of upright pipes, that the power of the engine might be accurately measured. It worked with steam of from 50 to 145 lbs. on the inch, and wholly discarded the vacuum which had been Watt's mainstay.

"The boiler is 4 feet diameter, the cylinder 7 inches diameter, 3-feet stroke. The water-piston is 10 inches in diameter, drawing and forcing 35 feet perpendicular, equal beam. I first set it off with about 50 lbs. on the inch pressure against the steam-valve, for the inspection of the engineers about this neighbourhood. The steam continued to rise the whole of the time it worked; it went from 50 to 145 lbs. to the inch.

"The engineers at this place all said that it was impossible for so small a cylinder to lift water to the top of the pumps, and degraded the principle, though at the same time they spoke highly in favour of the simple and well-contrived engine.

"After they had seen the water at the pump-head, they said that it was possible, but that the boiler would not maintain its steam at that pressure for five minutes; but after a short time they went off, with a solid countenance and a silent tongue."[60]

This high-pressure steam pumping engine in 1802 may be taken as the first pumping engine of the puffer class using such strong steam.

In the spring of the following year[61] a somewhat similar engine was erected in London. "The cylinder is 11 inches in diameter, with a 3½-feet stroke. It requires the steam at a pressure of 40 to 45 lbs. to the inch to do its work well, working about twenty-six or twenty-seven strokes per minute. It is much admired by everyone that has seen it, and saves a considerable quantity of coal when compared with a Boulton and Watt. Mr. Williams, Mr. Robert Fox, Mr. Gould, and Captain William Davey were here, and much liked the engine; they gave me an order for one for Cornwall as a specimen." This particular engine was for driving machinery in a cannon manufactory. A high-pressure pumping engine was at work at Greenwich, and some were at work in Cornwall.

"Penydarran, near Cardiff,
"October 1st, 1803.

"Mr. Giddy,

"Sir,—In consequence of the engine bursting at Greenwich, I have been on the spot to inspect its effects. I found it had burst in every direction. The bottom stood whole on its seating; it parted at the level of the chimney. The boiler was cast iron, about 1 inch thick, but some parts were nearly 1½ inch; it was a round boiler, 6 feet diameter; the cylinder was 8 inches diameter, working double; the bucket was 18 inches diameter, 21 feet column, working single, from which you can judge the pressure required to work this engine. The pressure, it appears, when the engine burst, must have been very great, for there was one piece of the boiler, about 1 inch thick and about 5 cwt., thrown upwards of 125 yards; and from the hole it cut in the ground on its fall, it must have been nearly perpendicular and from a very great height, for the hole it cut was from 12 to 18 inches deep. Some of the bricks were thrown 200 yards, and not two bricks were left fast to each other, either in the stack or round the boiler. It appears the boy that had care of the engine was gone to catch eels in the foundation of the building, and had left the care of it to one of the labourers; this man, seeing the engine working much faster than usual, stopped it, without taking off a spanner which fastened down the steam-lever, and a short time after being idle it burst, killed three on the spot and another died soon after of his injuries. The boy returned that instant, and was then going to take off the trig from the valve. He was hurt, but is now recovering; he had left the engine about an hour. I would be much obliged to you if you would calculate the pressure required to burst this boiler at 1 inch thick, supposing it to be a sound casting, and what pressure it would require to throw the materials the distance I have before stated, for Boulton and Watt have sent a letter to a gentleman of this place, who is about to erect some of those engines, saying that they knew the effects of strong steam long since, and should have erected them, but knew the risk was too great to be left to careless enginemen, and that it was an invention of Mr. Watt, and the patent was not worth anything. This letter has much encouraged the gentlemen of this neighbourhood respecting its utility; and as to the risk of bursting, they say it can be made quite secure. I believe that Messrs. Boulton and Watt are about to do me every injury in their power, for they have done their utmost to report the explosion, both in the newspapers and in private letters, very different to what it really was; they also state that driving a carriage was their invention; that their agent, Murdoch, had made one in Cornwall and shown it to Captain Andrew Vivian, from which I have been enabled to do what I have done. I would thank you for any information that you might have collected from Boulton and Watt, or from any of their agents, respecting their even working with strong steam, and if Mr. Watt has ever stated in any of his publications the effects of it, because if he condemns it in any of his writings, it will clearly show from that, that he did not know the use of it. Mr. Homfray, of this place, has taken me by the hand, and will carry both the engines and the patent to the test. There are several of Boulton and Watt's engines being taken down here, and the new engines being erected in their place. Above 700 horse-powers have been ordered at 12l. 12s. for each horse-power for the patent right, and the persons that ordered them make them themselves, without any expense to me whatever. If I can be left quiet a short time I shall do well, for the engines will far exceed those of Boulton and Watt. The engine at Greenwich did fourteen millions with a bushel of coals; it was only an 8-inch cylinder, and worked without an expansive cock, and under too light a load to do good duty; also on a bad construction, for the fly-wheel was loaded on one side, so as to divide the power of the double engine, and connected to the pump-rods on a very bad plan. I remember that Boulton and Watt's 20-inch cylinders when on trial did not exceed ten millions; I believe you have the figures in your keeping. Let us have the 60-horse power at work that is now building, and then I will show what is to be done. It will be loaded at 30 lbs. to the inch on each side the piston, it has an 8-feet stroke with an expansive cock, and the blowing cylinder directly over the steam-cylinder, as free from friction as possible. There was no engine stopped on account of this accident; but I shall never let the fire come in contact again with the cast iron. The boiler at Greenwich was heated red hot and burnt all the joints the Sunday before the explosion.

"I have received a letter from a person in Staffordshire who has a cylinder-boiler at work with the fire in it, and he says the engine performs above all expectation; he requests me to give him leave to build a great many more. I shall put two steam-valves and a steam-gauge in future, so that the quicksilver shall blow out in case the valve should stick, and all the steam be discharged through the gauge. A small hole will discharge a great quantity of steam at that pressure. There will be a railroad-engine at work here in a fortnight; it will go on rails not exceeding an elevation of one-fiftieth part of a perpendicular and of considerable length. The cylinder is 8½ inches in diameter, to go about two and a half miles an hour; it is to have the same velocity of the piston-rod. It will weigh, water and all complete, within 5 tons.

"I have desired Captain A. Vivian to wait on you to give you every information respecting Murdoch carriage, whether the large one at Mr. Budge's foundry was to be a condensing engine or not.

"Is it possible that this engine might be burst by gas?

"I am, Sir,
"Your very obedient servant,
"Richard. Trevithick.

This high-pressure puffer pumping engine at Greenwich, in 1803, worked a pump of 18 inches in diameter. The engine boy having fixed the safety-valve while he fished for eels, caused an explosion of the boiler. This was the first mishap from the use of high-pressure steam. The boiler was globular, 6 feet in diameter, and from an inch to an inch and half in thickness, made of cast iron; the cylinder, of 8 inches in diameter, was partly let into and fixed on the boiler. Its general design is seen in the patent drawing of 1802, Fig. 1.[62] Trevithick determined in future to use two safety-valves, and also a safety steam-gauge. At that time one of his high-pressure puffer-engines, with a cylindrical boiler and internal tube, was working in Staffordshire.

The Greenwich high-pressure puffer-engine did fourteen millions of duty with a bushel of coals, 84 lbs. A 60-horse-power engine was being built in Wales, with an 8-feet stroke, to work expansively with 30 lbs. of steam on the inch in the boiler. For a more thorough test with the low-pressure vacuum engines, in competition, the Government intended to use the new engines, and some of Watt's engines having been removed to make room for them, Boulton and Watt wrote to a gentleman who was about to order an engine from Trevithick, "We knew the effects of strong steam long since, and should have erected them, but knew the risk was too great." Moreover, "it was an invention of Mr. Watt's, and the patent (Trevithick's) was not worth anything." This admission clearly shows not only that Watt did not make high-pressure steam-engines, but that he did his best to prevent others from making them.

"Penydarran, Cardiff, January 5th, 1804.

"Mr. Giddy,

"Sir,—I received yours a few days since, and should have answered it sooner, but I was at Swansea for the last four weeks, and wished to return here to give you as full an account of our proceedings as possible.

"We have had an 8-inch cylinder at work here by way of trial; it worked exceedingly well a hammer of the same size as is now being worked here by an atmospheric engine 28 inches diameter, 5-feet stroke, which does not master its work with greater ease than the 8-inch cylinder. The 8-inch is now removed to Swansea, and is winding coals; the baskets hold 6 cwt. of coal; it lifts 80 yards in a minute and a quarter, and burns 6 cwt. of coal in twenty-four hours. There were twelve horses on this pit before, lifting 80 tons of coal in the course of the twenty-four hours. You may fairly state that the 8-inch cylinder does between thirty and forty horses' work in twenty-four hours, with 6 cwt. of coal.

"One of Boulton and Watt's 18-inch double engine, about half a mile from it, lifting baskets of the same size, and with the same velocity, burns above three times the quantity of coal.

"The 8-inch engine requires the steam to be about 46 or 48 lbs. to the inch to do its work well. The standers-by would not believe that such a small engine could lift a basket of coal, but are now much pleased with it, and have given orders for several more. There will be another at work here for the same purpose in about six weeks, a 15-inch cylinder, 6-feet stroke, which is a great power for a winding engine.

"Mr. Watt says, in a letter to Mr. Homfray, that he could not make any of his experiments in strong steam answer the purpose. It is my belief that he never made any experiments of any consequence in strong steam.

"A great number are building at different foundries. Mr. Sharratt, a founder at Manchester, who has four in building, said that he would not pay the patent right; on giving him notice of a trial he agreed to pay the patent right.

"I have received a letter from London, saying that an engineer called Dixon has two engines on the same plan working; and says that he shall not pay anything to the patentee; that the words in Mr. Watt's specification are enough to indemnify him from my threats. We have had three counsels' opinions on the subject, and they all agree that the patent is good. Counsels Marratt and Gibbs principally treated on the construction of the engine, more than on the principle; but Erskine was principally on the principle of the engine, and said very little of its construction. They all say the words in Mr. Watt's specification will have no weight whatever against us.

"I shall leave this place to-morrow for London to make inquiry into those engines, and to get the business into court if they will contend. I shall be at No. 2, Southampton Street, Strand, and expect to be in town about five or six days, and if you will be so good as to return here, from Oxford, with me, I will call on you in my journey down. It is but 50 miles from Bristol, and not so much as 100 miles from Oxford, and the coach passes very near this place.

"There is a great deal of machinery and mining here, which would engage your attention for a few days, and very pleasant gentlemen about the neighbourhood.

"If I had not been called to Swansea to put up the winding engine, the road-engine would have been at work long since, but in my absence very little was done to it. The work is all ready, and a part of it put together. If I could tarry four or five days longer I could set it to work before going to London. They promise me that it shall be completed before my return. I think there is no doubt of its being finished, as I have Frank Bennetts here from Cornwall about it, and a plenty of hands to assist him.

"I have a thousand things to relate to you, too much for paper to contain, therefore must request you to be so good as to go down from Oxford with me, and I will promise, on warrant, that the road-engine shall be finished before my return. When it is set to work I shall return to Cornwall.

"I remain, Sir,
"Your humble servant,
"Richard. Trevithick.

In 1804 an 8-inch cylinder high-pressure puffer-engine, with steam of 48 lbs. to the inch, worked a large hammer as well as a 28-inch cylinder atmospheric engine, and more economically than a Watt low-pressure steam vacuum engine with an 18-inch cylinder, which was five times as large as the little high-pressure. In consequence of this superiority those who came to witness the trial ordered several more of Trevithick's engines, one of which with a 15-inch cylinder and 6-feet stroke was to be at work in a few weeks.

Watt wrote to Mr. Homfray "that he could not make any of his experiments in strong steam answer the purpose," and Trevithick declared Watt never could have tried any experiments with high steam.

Dixon refused to pay patent right because the words of Mr. Watt's specification, "in cases where cold water cannot be had in plenty, the engines may be wrought by the force of steam only, by discharging the steam into the open air after it has done its office," "are enough to indemnify him." Eminent counsel were of opinion that "the words in Watt's specification will have no weight whatever."

Marratt and Gibbs were inclined to rest on the difference in the construction of the two kinds of engines, while Erskine boldly said that the principle was different, and he cared little for the kind of construction.

The admission by Watt that he could do nothing with high steam after an experience of thirty years from the date of his patent, shows how difficult the work was to those who had to find the way; yet Trevithick had several at work within a few months of his first mental sight of a steam-engine without condensing water, fitful glimpses of which passed and repassed while he sat unobserved in the crowded law court in 1796 hearing the remarks of engineers and counsel.

"The public until now called me a scheming fellow, but their tone is much altered. An engine is ordered for the West India Docks, to travel itself from ship to ship, to unload and to take up the goods to the upper floors of the storehouses.

"Boulton and Watt have strained every nerve to get a Bill in the House to stop these engines, saying the lives of the public are endangered by them, and I have no doubt they would have carried their point, if Mr. Homfray had not gone to London to prevent it; in consequence of which an engineer from Woolwich was ordered down, and one from the Admiralty Office, to inspect and make trial of the strength of the materials."[63]

After a week or two another letter states,[64]—

"We are preparing to get the materials ready for the experiments by the London engineers, who are to be here on Sunday next. We have fixed up 28 feet of 18-inch pumps for the engine to lift water.

"These engineers particularly requested that they might have a given weight lifted, so as to be able to calculate the real duty done by a bushel of coal.

"As they intend to make trial of the duty performed by the coal consumed, they will state it as against the duty performed by Boulton's great engines, which did upward of twenty-five millions, when their 20-inch cylinders, after being put in the best order possible, did not exceed ten millions. As you were consulted on all those trials of Boulton's engines, your presence would have great weight with those gents, otherwise I shall not have fair play. Let me meet them on fair grounds and I will soon convince them of the superiority of the 'Pressure-of-steam engine.'"

Watt left no stone unturned to prevent the use of high-pressure steam-engines, and fortune favoured him, for after four or five days Trevithick again wrote:—

"I am sorry to inform you that the experiments that were to be exhibited before the London gents are put off, on account of an accident which happened to Mr. Homfray. I find myself much disappointed on account of the accident, for I was desirous to make the engine go through its different work, that its effect might be published as early as possible."[65]

While constructing those numerous high-pressure engines for rolling mills, winding engines, and pumping engines, the Welsh and Newcastle locomotives were being made and worked, yet he found time to teach the people of Stourbridge.

"Stourbridge, July 5th, 1804.

"Mr. Giddy,

"Sir,—I should have answered your letter some time since, but waited to set two other engines to work first. The great engine at Penydarran goes on exceedingly well. The engine will roll 150 tons of iron a week with 18 tons of coal. The two engines of Boulton's at Dowlais burn 40 tons to roll 160 tons; they are a 24-inch and a 27-inch double. The engine at Penydarran is 18½ inches, 6-feet stroke, works about eighteen strokes per minute: it requires the steam about 45 lbs. to the inch above the atmosphere. I worked it expansive first, when working the hammer, which was a more regular load than rolling; then with steam high enough to work twelve strokes per minute with the cock open all the stroke; then I shut it off at half the stroke, which reduced the number of strokes to ten and a half per minute, the steam and load the same in both; but I did not continue to work it expansively, because the work in rolling is very uneven, and the careless workmen would stop the engine when working expansive.

"When the cylinder was full of steam the rollers could not stop it; and as coal is not an object here, Mr. Homfray wished the engine might be worked to its full power. The saving of coal would be very great by working expansively.

"The trials we have made for several weeks past against Boulton's engines have been by working with the cylinder full of steam. The cock springs out of its seat when water gets into the cylinder, and prevents any mischief from the velocity of the fly-wheel.

"The tram-engine has carried two loads of 10 tons of iron to the shipping place since you left this. Mr. Hill says he will not pay the bet, because there were some of the tram-plates in the tunnel removed so as to get the road into the middle of the arch.

"The first objection he started was that one man should go with the engine, without any assistance, which I performed myself without help; and now his objection is that the road is not in the same place as when the bet was made.

"I expect Mr. Homfray will be forced to take steps that will force him to pay. As soon as I return from here there will be another trial, and some person will be called to testify its effects, and then I expect there will be a lawsuit immediately. The travelling engine is now working a hammer.

"At Worcester last week we put a 10-horse engine to work in a glover's manufactory. The flue from the engine is carried through the drying room and dries his leather. The steam from the engine goes to take the essence out of the bark, and also to extract the colour out of the wood for dyeing the leather. Then it boils the dye, and the steam that is left is carried into his hot-house. It works exceedingly well. This week I put another to wind coals at this place, a 10-horse power, which works very well. All the tradesmen are set against it; they say that there is no carpenter or mason work about it, and very little smith-work, and that it will destroy their business. The engineer on the spot is also against it very much. I do not expect that it will be kept long at work after I leave it, unless the proprietor takes care to prevent those people from doing an injury to it. Mr. Homfray was here yesterday, but is now returned to Penydarran. I shall go from here to Coalbrookdale.

"There is an engine there almost ready for the West India Docks. It will be ready to send off to London in about four weeks. It will be a very complete engine. The pumps for forcing the water will be fixed on the back of the boiler. It will force 500 gallons of water 100 feet high in a minute; above ten times the quantity that engines worked by men can do. Mr. Homfray and myself shall be in town as soon as the castings are sent off. I hope you will be there at the time. If you wish to see the engines already at work in London, call on Mr. David Watson, steam-engine maker, Blackfriars Road. He lives up about 500 or 600 yards above the bridge on the left-hand side; you will see his name over his door. If you have time to inspect those engines you will find by comparing them against Boulton's, doing the same work, that there is a great saving of coal above other engines.... I shall go to Liverpool and Manchester from here, and again to Coalbrookdale.

"There are three engines at the Dale begun, to work with condensers, for places where coal is scarce. I think it is better to make them ourselves, for if we do not, some others will, for there must be a saving of coal by condensing. But with small engines, or where coal is plentiful, the engine would be best without it. They say at the Dale about putting two cylinders, but I think one cylinder partly filled with steam would do equally as well as two cylinders.

"That engine at Worcester shuts off the steam at the first third of the stroke, and works very uniformly. I cannot tell what coal it burns yet, but I believe it is a very small quantity. I shall know in a short time what advantage will be gained by working expansive. I expect it will be very considerable. There are a great many engines making and ordered. Boulton and Watt and several others are doing everything to destroy their credit, but it is impossible to destroy it now that it is so well known. I have not taken any of the ground at Bristol to remove. I called on them and told them it was possible to break the ground without men, and they wish me to take a piece to clear out, but would not set but a small piece at a time; therefore it would be disclosing the business to no purpose. They were very desirous to know the plan, but I would not satisfy them, neither will I unless they pay me for it in some way or other. If you direct for me at the Dale it will find me. I am happy to find that you have a seat in the House. I wish every seat was filled with such.

"I remain, Sir,
"Your very humble servant,
"Richard. Trevithick.

Trevithick fully understood the value of the expansive principle in 1804: when working with steam of 45 lbs. to the inch, the engine went at a speed of twelve strokes a minute. On cutting off the steam at half-stroke, the speed and consequent work done fell to ten and a half strokes a minute; in other words, the work performed by the engine fell off only one-eighth part, while the quantity of steam and consequently of coal was reduced by one-half. The principle was established, but the application was practically incomplete from the want of heavier fly-wheels, to give out their momentum during the latter half of the stroke, when the expanding steam was lessening its force.

"The saving of coal would be very great by working expansively, but as coal is not an object here," Mr. Homfray was careless about the expansion. Thirty-three years after this indirect check to steam-engine economy, the writer, then living in the Sirhowey Iron Works, and within stone's-throw of Mr. Homfray's Works, recommended the removal of the Boulton and Watt's waggon boilers, to make room for Trevithick's boilers, on the plea of saving one-half the fuel, and at the same time increasing the power of the engine, and thereby the pressure of the blast in the iron furnaces. The proprietor was careless about the saving of coal, and was doubtful that an increased blast would increase the quantity of iron smelted. The promise that the wages of one-half of the number of boiler firemen would be saved, was understood. Trevithick's high-pressure boilers replaced the Watt low-pressure, resulting in a largely-increased quantity of iron from the greater power and pressure of blast in the furnaces, and at one-half the expenditure of coal in the boilers: ten men had been employed as firemen of the Watt boilers during twenty-four hours; with Trevithick's boilers, five men did the work.

The high-pressure puffer-engine, with an 18-inch cylinder, working with 45 lbs. of steam, rolled as much iron as the two larger low-pressure vacuum engines of Watt, of 24 and 27 inch cylinders, which together were more than three times the size of the high-pressure engine, and cost three times as much.

At Stourbridge, as elsewhere, everyone was against the new plan. The engineer in charge did not like it, and the carpenters, smiths, and masons saw the end of their occupation as engine erectors, if there was no longer a necessity for foundations, well-work, &c., for condensing water, and many other things, necessary to complete a Watt engine; while the high-pressure puffer was no sooner unloaded than it was ready to work.

A great charm in Trevithick's character was his freedom and largeness of view in questions of competition. He was then making three engines at Coalbrookdale, to be worked with high-pressure steam, combined with the Watt air-pump and condenser; and though smarting from the contest with his great rival, yet wrote, "I think it is better to make them ourselves, for if we do not, some others will, for there must be a saving of coal by condensing. But with small engines, or where coal is plentiful, the engine would be best without it."

Those words accurately describe the practice of the present day, though written sixty-six years ago, and were followed by others equally true in principle, though varied in form to suit special requirement. "They say at the Dale about putting two cylinders, but I think one cylinder partly filled with steam would, do equally as well as two cylinders."

These sagacious views required the untiring labour of the following twelve years to perfect and make practical, when applied to the largest engines of the time; which we shall now trace in the construction of a strong and economical boiler, supplying high-pressure steam to the cylinder during only a comparatively small portion of the stroke, completing it by expansion, so that at its finish the steam had become of low pressure when passed to the condenser. The moving parts and expansive gear were so simplified as to be applicable to the then existing low-pressure steam vacuum engines without the complication of the double cylinders of Hornblower and Woolf.

"Penydarran Place, December 26th, 1804.

"Dear Sir,

"I have been favoured with your letter, and in answer, respecting Mr. Mitchell, I am at a loss to know from your letter what kind of iron he may likely want. If you will direct him to write to me, and explain himself, I will immediately reply to him and do what I can to assist and serve him. I believe there are vessels going over frequently from Cardiff to Cornwall with coals, that he might have part in cargo and the remainder in coals. I am happy to give you the most satisfactory account of our 'Trevithick's engine' going on well. It has now been at work many months, and is by far the best engine we have. We have for weeks weighed the coal, and knowing the work it does, can speak with confidence. Its 18 inches diameter steam-cylinder consumes as near as can be 3 tons of coal in twenty-four hours, or 18 tons per week; and in this time it rolls with ease 130 tons long weight of iron from the puddling furnaces, at the same heat, into bars of 3 inches by about half an inch thick. Now, one on Messrs. Boulton and Watt's plan, of '24 inches' steam-cylinder, at our neighbouring works at Dowlais, employed in doing exactly the same kind of work, consumes full as much coal, and rolls only 90 tons in the week. These being facts, open for any person daily to see, must convince any dispassionate man of the superiority of 'Trevithick's engines,' and that the saving of fuel is nearly one-third, besides the other advantages of saving water and grease, which is no little. The packing of the piston now gives us little or no trouble, it goes from a fortnight to a month, opening the top now and then to screw it down, as it gets slack, which should be attended to. We use no grease or oil in packing the piston or working the engine, having found blacklead mixed with water, and poured 'a little now and then' through a hole on the top into the steam-cylinder, suits the packing of the piston much better, and is cheaper than anything else. About 1s. worth of blacklead will last our engine a week. We are now so thoroughly convinced of the superiority of these engines that I have just begun another of larger size. The boiler is to be 24 or 26 feet long, 7 feet diameter, fire-tube at wide end 4 feet 4 inches, and at narrow end, where it takes the chimney, 21 inches, steam-cylinder 23 inches diameter. This boiler, on account of the length of its tube withinside, will, I have no doubt, get steam in proportion, and work the engine with much less coals than our present one. Trevithick is at Coalbrookdale, Manchester, &c., &c., very busy, a great number of engines being in hand in that part of the world; and I think by perseverance the prejudice is wearing away very fast, and in spite of all Messrs. Boulton and Watt's opposition, they must and will take the lead of theirs. Any person now wanting engines, must be next kin to an idiot to erect one of Boulton's in preference to Trevithick's. I find there is a small one making near you by Mr. Vivian. I hope they have corresponded with Trevithick about the proportions of it; if they have not, I shall be particularly obliged to you to desire them to do so, for by his experience of what he has done they may be benefited, for it would be a shocking thing to have a bad engine put up for the first time in his native county.

"Mrs. Homfray unites with me in best compliments, and wishing you many happy returns of the season.

"I remain,dear Sir,
"Your most obedient servant,
"Samuel Homfray.

"To Mr. Davies Giddy."

The evidence in this contest between the Watt low-pressure steam vacuum engine and the Trevithick high-pressure steam-puffer engine is in favour of the new principle; for the steam-engine with an 18-inch cylinder did fifty per cent. more work than the vacuum engine with a 24-inch cylinder with an equal quantity of coal, though the latter was seventy-five per cent. larger than the former; and a still greater economy was expected from the larger boiler to be built, 26 feet long, 7 feet in diameter, with internal fire-tube 4 feet 4 inches diameter at the fire end, tapering to 21 inches at the chimney end.

Thus in 1804 the cylindrical boiler in Wales had nearly reached its present form, and Homfray thought that none but idiots would prefer the Watt engine; forgetting that Trevithick's near friends and neighbours were carrying on a similar contest at Dolcoath Mine.

"Penydarran Place, January 2nd, 1805.

"Mr. Davies Giddy,

"Dear Sir,—I have duly received your favour enclosing a letter for Mr. Trevithick, and which I, according to your desire, forwarded to him at Manchester, where he now is; and a letter directed to him, to the care of Mr. Whitehead, Soho Foundry, Manchester, will find him, as he will stay a little time there, being very busy. I had lately the pleasure of writing to you, and gave you the account of our engine working, and the satisfaction it gives; I have nothing more to add on the subject, but that it is now at work, going on as usual, and I should be happy for you to have a sight of it.

"We are beginning another of a larger size, and I have no doubt but by making the cylindrical boiler larger, so as to take a longer tube withinside it, by which means the fire will spend itself before it leaves the tube to go up the chimney, that we shall work to much better advantage in point of fuel than we do at this present one, as this boiler is so short that a great deal of the flame of the fire goes up the chimney. We are now better acquainted with the different proportions than we at first were, for which reason I am anxious that one now making by Mr. Vivian should be made according to the directions of Mr. Trevithick.

"I beg leave to offer you the compliments of the season, and many happy returns, and

"Remain, respectfully, dear Sir,
"Your most obedient servant,
"Samuel Homfray."

Trevithick, always busy, was just now doing the work of a host, for everybody had to be taught how to make high-pressure steam-engines; and the Newcastle locomotive, the Thames steam-dredging, and other special applications of steam-power required his presence, especially the fight with Watt at Dolcoath Mine, where Andrew Vivian, as mine manager, was erecting a high-pressure steam-puffer whim-engine to compete with a Watt low-pressure steam vacuum whim-engine.

"The adventurers grumbled because Captain Trevithick was so often away from the mine. Glanville, the mine carpenter, the head man over the engines, made a trial between Trevithick's high-pressure puffer whim and Watt's low-pressure condenser. When Captain Trevithick heard of it, he wrote down from London that he would bet Glanville 50l. that his high-pressure puffer should beat Watt's low-pressure condenser. Then he came down from London and found that the piston of his engine was half an inch smaller in diameter than the cylinder. When a new piston was put in, she beat Boulton and Watt all to nothing. Persons were chosen to make a three or four weeks' trial, and when it was over, 'a little pit was found with coal buried in it, that Glanville meant to use in the Watt engine.'"[66]

Pooly, Smith, and others, say that Trevithick's Dolcoath puffer had the outer case of the boiler of cast iron, the fire-tube of wrought iron, the cylinder horizontal, and fixed in the boiler. Captain Joseph Vivian saw Trevithick's whim in Stray Park Mine about 1800 or 1801, and a similar one was erected in Dolcoath, and after a year or two a Boulton and Watt low-pressure whim was put up to beat it. The trial was in favour of the Watt engine, but everybody said the agents were told beforehand which way the report ought to go; so the engine that puffed the steam up the chimney was beaten.

Trevithick, who was busily engaged in Manchester at that time, the early part of 1805, when informed of what was going on in Cornwall, wrote:—

"I fear that engine at Dolcoath will be a bad one. I never knew anything about its being built until you wrote to me about Penberthy Crofts engine, when you mentioned it. I then requested Captain A. Vivian to inform me the particulars about it, and I find that it will not be a good job. I wish it never was begun."[67]

"Camborne, February 18th, 1806.

"Mr. Giddy,

"Sir,—On my return from town I altered the pressure of the steam-engine at the bottom of the hill, Dolcoath. Before I returned there was a trial between mine and one of Boulton's; both engines in the same mine and drawing ores from the same depth. The result was, Boulton's beat the pressure-engine as 120 to 55. Since it was altered there have been three other trials; the result was 147 to 35 in favour of the pressure of the steam-engine. They are now on trial for another month, and at the next account they intend to order a new boiler for the great engine, and work with high-pressure steam and condenser, provided this engine continues to do the same duty as was done in the former trials. This engine is now drawing from a perpendicular shaft, and Boulton and Watt's from an underlay shaft; but to convince Captain Jos. Vivian, we put it to draw out of the worst shaft in the mine, and then we beat more than three to one; we lifted in forty-seven hours, 233 tons of stuff 100 fathoms with 47 bushels of coal. The engine was on trial sixty-six hours, but nineteen hours were hindered by the shaft and ropes, &c., which made the consumption of coals about ¾ths of a bushel per hour. The fire-tube is 2 feet 3 inches diameter, and the fire-bars were only 14 inches long. The fire-place was but 2 feet 3 inches wide by 14 inches long, and the fire about 4 or 5 inches thick; it raised steam in plenty; it was as bright as a star. The engine is now doing the work of two steam-whims; the other steam-whim in the Valley is turned idle, and both shafts will not more than half supply it. 233 tons are equal to nearly 2000 kibbals, which were drawn in forty-seven hours.

"Mr. Harris has a 12-inch cylinder making at Hayle, for Crenver, and Mr. Daniel has a 14-inch for Perran-sand, and a great number are waiting for the trial of this month, before altering their boilers to the great engines.

"The steam-whim that is now turned idle at the Valley was 13½-inch cylinder, 4-feet stroke; it turned the whim one revolution to one stroke, and lifted the kibbal the same height at a stroke as my engine did, and I think took the same number of gallons of steam to lift a kibbal as mine did. Their steam was not above 4 lbs. to the inch; mine was near 40 lbs. to the inch; yet I raised my steam of near 40 lbs. with a third of the coals by which they got theirs of 4 lbs. to the inch. This is what I cannot account for, unless it is by getting the fire very small and extremely hot. Another advantage I have is, that there is no smoke that goes off from my fire to clog the fire sides of the boiler, while the common boilers get soot half an inch thick, and the mud falls on the bottom of the boiler, where the fire ought to act; but in these new boilers the mud falls to the bottom, where there is no fire, and both the inside and outside of the tube are clean and exposed both to fire and water. This fire-place of 14 inches was 5 feet long when I came down, and then the coal did not do above one-seventh of the duty that it now does.

"I would be very much obliged to you for your opinion on what I have stated, and what advantage you think the great engine is likely to get from working with steam about 25 lbs. to the inch, and shut off early in the stroke, so as to have the steam about 4 lbs. to the inch when the piston is at the bottom. I think this, with the advantage of the fire-place, will make a great saving.

"The present fire-place is 22 feet from fire-door to fire-door, 9 feet wide, and 7 feet thick in fire. There is not one-tenth of the coals that are in the fire-place on fire at the same time; it will hold 30 tons of coals at one time, and I think that a great deal of coal is destroyed by a partial heat before it takes fire. A boiler on the new plan will not cost more than two-thirds of the old way, and will last double the time, and can be cleaned in three hours. It requires twenty-four hours in the old way, and we need to clean the boilers only one-fourth the number of times.

"Though these trials have shown so fairly that it is a great advantage, my old acquaintances are still striving with all their might to destroy the use of it; but facts will soon silence them.

"I am about to enter into a contract with the Trinity Board for lifting up the ballast out of the bottom of the Thames for all the shipping. The first quantity stated was 300,000 tons per year, but now they state 500,000 tons per year. I am to do nothing but wind up the chain for 6d. per ton, which is now done by men. They never lift it above 25 feet high. A man will now get up 10 tons for 7s. My engine at Dolcoath has lifted above 100 tons that height with 1 bushel of coals. I have two engines already finished for this purpose, and shall be in town in about fifteen days to set them at work. They propose to engage with me for twenty-one years. The outlines of the contract they have sent me down, which I think is on very fair terms. I would thank you for your answer before I leave this county.

"I am, Sir,
"Your very humble servant,
"R. Trevithick.

In the trial at Dolcoath during his absence the high-pressure steam-puffer whim was beaten by Watt's low-pressure steam vacuum whim-engine as 55 to 120; but having corrected some oversight in the puffer-engine, it then beat Watt as 147 to 35. The trial was to be continued for a month; and provided the superiority of his whim-engine could be maintained, the adventurers would allow him to apply his high-pressure boilers to their large Boulton and Watt pumping engine. The trial with the whim-engines was for the greatest number of kibbals of mineral raised to the surface by the least consumption of coal. A dispute arose on the difference of the shafts, the one causing more friction to the moving kibbal than the other, when Trevithick agreed to take the worst shaft in the mine. On a trial during sixty-six hours Watt's engine was beaten by more than four times; and as Trevithick's engine did the work that before required two engines, one of the low-pressure steam Watt engines was removed that the engine working with 40 lbs. on the inch might perform the whole work.

"My fire-tube is 2 feet 3 inches in diameter, and the fire-bars only 14 inches long, and the fire only about 4 or 5 inches thick; it raised steam in plenty, and was as bright as a star." These words certainly imply the use of the blast-pipe, making the fire as bright as a star, and enabling the small boiler to give the required supply of steam. Several high-pressure puffer-engines had been ordered, and many persons were waiting the conclusion of the month's public trial to enable them to judge between the Watt and the Trevithick engine.

"Camborne, March 4th, 1806.

"Mr. Giddy,

"Sir,—The day after I wrote to you the first letter, I received yours, and this day I have yours of the 1st instant.

"I am very much obliged to you for the figures you have sent me. I am convinced that the pressure of steam will not hold good as theory points it out, because on expanding it will get colder, and of course lose a part of its expansive force after the steam-valve shuts. I think there can be no risk in making this trial on Dolcoath great engine, as they intend to have a new boiler immediately, so as to prevent stopping to cleanse; and a boiler on this new plan can be made for one-third less expense than on the old plan, when you count the large boiler-house and ashes-pit, and brickwork round the boiler. It is not intended to alter any part of the engine or condenser, but only work with high steam from this new boiler; and if this boiler only performs as good duty as the old one, it will be a saving of near 300l. to them on the erection. The vast matter this great engine has in motion will answer in part the use of a fly-wheel: the whole of the matter in motion is near about 200 tons, at a velocity of about 160 feet a minute. This I know will not be sufficient; but it will be about equal to a fly-wheel of 20 feet diameter, 25 tons weight, twenty rounds per minute, if weight and velocity answer the same purpose.

"Since Monday, the 18th February, being Dolcoath account-day, both engines have been on trial, and are to be continued until the next account, 17th instant. The engines are kept on in the usual way, as at other times. Neither of the engines have done so much duty as on the first trials, as they have not been so strictly attended to. The average of the trial at this time stands 26 cwt. for a bushel of coals to Boulton and Watt's engine; mine, 83 cwt. for a bushel of coals.

"If I do not remain in Cornwall to attend next Dolcoath account, I shall be in town about the 15th instant, otherwise about the 20th instant. I shall call on you immediately on my arrival. In this time I should be glad to hear from you again. The Trinity business will answer exceedingly well; I have two engines ready for that purpose to put to work on my arrival in town.

"I am, Sir,
"Your very humble servant,
"Rd. Trevithick.

"P.S.—I would try the evaporation of water by both boilers, but Boulton and Watt's engine is so pressed with work, and being on the best part of the mine, they will not stop it a moment. A boiler of 8 feet diameter and 30 feet long will have as much fire-sides in the tube as there is now in Dolcoath great boiler. The fire-tube in this boiler would be 5 feet diameter, and a fire-place 6 feet long in it would be 30 feet of fire-bars. In the whim-engines I find that a fire-place 14 inches long and the tube 2 feet 3 inches diameter would, being forced, burn 1 bushel per hour. At this rate the great tube would burn near 12 bushels per hour, which is above the quantity that the great engine boiler can consume, now at work. Small tubes would have an advantage over large ones. Two boilers would not cost much more than one large one, and be much stronger."

The battle-ground of the fight between low and high pressure from 1806 to 1812 had also served for the personal encounter of Trevithick, sen., and Watt a quarter of a century before, when the Dolcoath great pumping engine was erected to compete with the two earlier atmospherics; all three were still at work, overlooked by Carn Brea hill and castle, once the resort of Druid priests, whose sacrificial rites are still traced, by the hollows and channels for the blood of victims on the granite rocks.

Carn Brea Castle. [W. J. Welch.]

"Camborne, March 21st, 1806.

"Mr. Giddy,

"Sir,—The trial between the two engines ended last Monday, which was Dolcoath day. Boulton and Watt's engine, per average of trial, 1 ton 20 cwt. 2 qrs., with 1 bushel of coals; the other, 5 tons 11 cwt. 3 qrs., with 1 ditto, the same depth of shaft. The adventurers ordered the new castings that were made for another of Boulton and Watt's engines to be thrown aside, and another new engine of mine to be built immediately. The great boiler for the old engine is not yet ordered.

"I have received orders for nine engines within these four weeks, all for Cornwall. Two 12-inch cylinders, two 16-inch ditto, three 9-inch ditto, one 8-inch ditto, one 7-inch ditto. I expect one will be put to work next week at Wheal Abraham, for lifting water.

"This day I shall leave Cornwall for London. Shall stop two days in the neighbourhood of Tavistock, and take orders for three engines. As soon as I arrive in town I will call at your lodgings. I expect that the patent will be brought into court about the end of May. A person in Wales owes us about 600l. patent premium, and he says that the patent is not good. More particulars you shall have on my arrival.

"The railroad is going forward. I have the drawings in hand for the inclined plane.

"I am, Sir,
"Your very humble servant,
"Rd. Trevithick.

The fact that expansion of steam caused reduction of heat was so evident to Trevithick that he ventured to doubt his friend's theory. The trials between the whim-engines having continued a fortnight, showed that the high-pressure steam-puffer had lifted 83 cwt., while the low-pressure steam vacuum only lifted 26 cwt. with the consumption of a bushel of coal. A suitable high-pressure boiler for the Watt low-pressure steam 63-inch pumping engine should be 30 feet long, 8 feet in diameter, with an internal fire-tube 5 feet in diameter; proportions approved of in the present day. The recommendation in 1806 to use small tubes may claim to be the first practical decision on the advantage of tubular boilers; and at the same time we read of the first hesitating step on the part of the public to use high-pressure steam in a Watt low-pressure engine, which was still deferred for further consideration, even with the limited pressure of 25 lbs. to an inch; so the large Watt pumping engines were doomed for another four or five years to struggle through their work with low-pressure steam, though at that time Cook's Kitchen high-pressure expansive condensing whim-engine had been for years at work close by.

The shareholders professed to have fear of explosion; but party-feeling and ignorance were the real causes of opposition, for working men had no dread of the new engines, while influential men leaned toward Watt's old-fashioned plans.

This fear of Trevithick's expansive plans and high steam is the more surprising, because at that time a new boiler was required for the Watt 63-inch cylinder pumping engine and Trevithick's cylindrical tubular boiler could be made for one-third less cost than the Watt waggon boiler, thus saving 300l., and in addition he promised to apply the higher pressure of steam to the Watt engine without any change in its parts or expenditure of money, and make it set in motion at the commencement of the stroke the 200 tons of pump-rods, the momentum of which would, with the expansion of the steam, when shutting it off soon after the first start in the movement of each stroke, carry it through to the end; and he practically compares this advantage from hoarded momentum in the pumping engine with his experience of the fly-wheel of the rolling-mill expansive engine in Wales.

The whim-engine with a fire-tube 2 feet 3 inches in diameter used 84 lbs. of coal per hour; and at that rate one cylindrical boiler 30 feet long, 8 feet in diameter, with internal fire-tube 5 feet in diameter, would supply steam for Watt's 63-inch cylinder; but in place of it he preferred two smaller boilers, because small tubes have an advantage over large ones, and are much stronger.

The whim trials—high-pressure puffer against low-pressure vacuum—went on for another fortnight, when high pressure, having done twice as much work as low pressure, with an equal consumption of coal, the adventurers threw aside the work that had been made for another Watt engine, ordering one in its stead from Trevithick; but they could not just then make up their minds to place the Watt 63-inch pumping engine in his hands.

"Camborne, May 30th, 1806.

"Dear Sir,

"I am very happy to find you have so far continued your agreement with the Trinity gents, and think the bargain is a good one. Must still beg leave to remind you not to proceed to show what your engine will do till the agreement is fully drawn up and regularly signed.

"Dolcoath agents, since they are informed of the accident at the iron-works in Wales, of the engine blowing to pieces, have requested me to have your opinion whether the old cylinder is strong enough for the boiler of the intended new engine, or whether you would recommend them to have a new one. Your answer to this as soon as possible, as Mr. Williams and some others are likely to make some objections.

"Mr. Sims, the engineer, has published in the Truro paper, that one of Boulton and Watt's engines at Wheal Jewell has drawn more than a ton of ore over and above that drawn by the Dolcoath engine from the same depth by a bushel of coal. On inquiry I found they had only tried for twenty-two hours. They said they left off with as good a fire as they began with. This I argued was not a fair trial. They say they are now on a trial for a month.

"The little engine at Wheal Abraham does its duty extremely well. The particulars as to consumption of coal cannot be fairly ascertained, as she has never been covered, is fed with cold water, and has not water to draw to keep her constantly at work.

"I wish I could give a better account of the mines than is in my power to give, or of the standard price for ore, though the latter is rather looking up than otherwise. Our friend, North Binner Downs, is better than paying cost, but very little. At present the levels are all poor; the lode in the west shaft has underlayed faster than the shaft, and we have not seen it for several fathoms. The ground lately in the shaft has been cleaner killas, and if any alteration, better ground. It is now 9 fathoms under the 55-fathom level, and we are driving to cut the lode. The ground in the cross-cut is harder than when you were on the spot. The water is sinking in old Binner; it is about 7 fathoms under the adit in the western part, and deeper in the eastern part; we do not account for this. Wheal St. Aubyn combined poor. Wheal Abraham looks promising, and Creuver about paying cost. Dolcoath is better than when you left us, or when I was in London. The last sale was only about 800 tons. The next sale on Thursday is upwards of 1100 tons, and we expect a little better standard.

"I wish you could discover who that old gent is that wanted a large slice in Dolcoath, that I might get at him through some unknown channel, for I want money sadly.

"Cook's Kitchen continues poor, Tin Croft ditto; Wheal Fanny not rich. We had a pretty little fight last account there with T. Kevill and W. Reynolds, Esquires: black eyes and bloody noses the worst effects. T. Kevill's face was much disfigured, and he might have found a new road out of his coat.

"At a meeting of Condurrow adventurers yesterday, twenty-four of them agreed to have one of our engines, cylinder 12 inches in diameter and 6-feet stroke, provided the Foxes do not object to it. When the order is given I shall write to Mr. Hazeldine, provided I do not hear from you that it is better to send the order to any other place.

"If you have occasion to write Mr. Hazeldine, I wish you would press him to hasten the engines for Wheal Goshen, &c.

"I am served with a Vice-warden's petition by Mr. Harris for not working the Weith mine in a more effectual manner, and he prays the Vice-warden to make the sett void. The trial will come on some time the beginning of July, and by that time I suppose we shall have two fire-engines working thereon.

"Had Mr. Harvey done as he was desired we should have had one working there at this time, but he has but now begun to do anything to it. We have the cylinder and ends home from Polgooth, and my cousin Simon Vivian is making the tubes. We have the other cylinder from Wheal Treasury, and I have ordered Horton to cast a cock for it the same as that at Dolcoath. We have cut the south lode at the adit level about 50 or 60 fathoms east of the engine, and have driven about 20 fathoms on it. It turns out about half a ton per fathom at 20l. a ton. The ground at 40s. per fathom; this all in a hole, and is better going down. The back is sett to four men at 3s. 11d.; their time is out this week, and I suppose they must have 5s. next. This may turn out a few thousands, and I think too promising a thing to give up to Mr. Harris.

"I am happy to inform you that all our friends are in good health, and beg my most respectful compliments to Mrs. Rogers and adopted son; and am,

"Dear, Sir,
"Yours very sincerely,
"Andw. Vivian.

"The promised news respecting the engine business I am very anxious to have, as it will I hope make me proud, as proud I shall be when I am able to pay everyone their demands, and have sufficient to carry on a little business to maintain my family and self without the assistance of others. May you succeed in your undertaking and also be independent, is the sincere wish of your friend. John Finnis and others are anxious to know when they will be wanted.

"A. V."

The explosion at Greenwich in 1803 was made much of, though the fault was clearly not in the boiler. Three years afterwards, in 1806, a steam-cylinder burst in Wales, therefore Mr. Williams, a large shareholder in Dolcoath, objected to the use of high-pressure expansive steam in their large Watt pumping engine, and desired their engineer, Mr. Sims, to make a competitive trial after his own fashion. At Condurrow Mine one of Trevithick's engines was to be ordered if the Foxes and Williamses did not object; and so it was that Trevithick's high-pressure steam-boiler was not ordered, and the Watt vacuum engine was for a longer time to receive no increase of power.

"Some of Captain Dick's early boilers had flattish or oval fire-tubes. In 1820 I repaired an old one in Wheal Clowance Mine in Gwinear. The flat top had come down a little; we put in a line of bolts, fastening the top of the tube to the outer casing.

"About 1818 I saw in Carsize Mine in Gwinear a pumping engine that Captain Dick had put up. The boiler was a cylinder of cast iron, with a wrought-iron tube going through its length in which the fire was placed. The steam-cylinder was vertical, fixed in the boiler. She had an air-pump and worked with a four-way cock. The steam was about 100 lbs. to the inch."[68]

"About 1820 I removed one of Captain Trevithick's early high-pressure whim-engines from Creuver and Wheal Abraham, and put it as a pumping engine in Wheal Kitty, where it continued at work for about fifteen years. The boiler was of cast iron, in two lengths bolted together, about 6 feet in diameter and 10 feet long. At one end a piece was bolted, into which the cylinder was fixed, so that it had the steam and water around it. There was an internal wrought-iron tube that turned back again to the fire-door end, where the wrought-iron chimney was fixed; the fire-grate end of the tube was about 2 feet 6 inches in diameter, and tapered down to about 1 foot 6 inches at the chimney end. It was a puffer, working 60 lbs. of steam to the inch; it worked very well. There were several others in the county at that time something like it. It was made at the Neath Abbey Works in Wales."[69]

These boilers were of the kind first tried in Cornwall about 1800. The oval tube in the Kensington model of 1798 continued in use in Cornwall for many years. The cast-iron outer casing was soon abandoned, though one of them in Wales remained in work fifty years, using steam of 60 lbs. to 100 lbs. to the inch.

"Hayle Foundry, August 26th, 1810.

"My dear Jane,,

"I saw Captain Andrew Vivian on Wednesday, who told me that he had been offered 150l. a year to inspect all the engines in the county, and report what duty they were doing, in order to stimulate the engineers. He declined accepting it, having too much to do already; and he thought it would be worth Trevithick's notice, as it would not take him more than a day or two in a month.

"I remain, my dear Jane,
"Yours sincerely,
"H. Harvey..

"I wrote this letter on Sunday, with an intention of sending it then, but thought it best to wait until this day, in hopes of hearing the determination of Government in your favour; but your letter has arrived without the desired information. All that I can now say is, to desire that Trevithick will make up his mind to return to Cornwall immediately.

"H. H."

The application to the Government for remuneration for benefits conferred on the public was unsuccessful. The office of registrar of Cornish engines was unsuitable; fortunately for mining interests, illness obliged Trevithick to revisit his native county, for by the increased power and economy of his engines Dolcoath Mine, so frequently mentioned, and so important in olden time, now returns 70,000l. worth of tin yearly.

Trevithick's first act on returning to Cornwall in 1810 was the erection of the high-pressure boilers and pole vacuum engine at Wheal Prosper; at the same time renewing his proposals to Dolcoath to use his improved boilers, which had been broken off in 1806, and to apply high-pressure steam to their low-pressure Watt engine, with the same safety and profit as in Wheal Prosper; the evidence was undeniable, so his plans were agreed to, and in the early part of 1811 the high-pressure boilers, called the Trevithick or Cornish boilers, were constructed in the Dolcoath Mine under his directions.

Old John Bryant, who worked the Dolcoath large engines both before and after the introduction of higher pressure steam, including the Carloose or Bullan Garden 45-inch cylinder engine, Wheal Gons 63-inch cylinder single engine, and the Watt 63-inch cylinder double, with the bee-but boiler, such as Trevithick, sen., used in 1775,[70] followed by the Watt waggon boiler, and afterwards by the globular boiler of Trevithick, jun., in 1799,[71] and still later also with the cylindrical boiler of 1811, gave the following statement, when seventy-four years old, to the writer:—

"In the old bee-but and the waggon boiler the steam pressure in the boiler was not much; we did not trouble about it so long as the engines kept going: when the steam was too high it blew off through the feed-cistern. When Captain Trevithick tried his high steam in Dolcoath we hoisted up the feed-cistern as high as we could; when the steam got up, it blew the water out of the cistern. Captain Dick holloed out, 'Why don't you trig down the clack?'

"The cylindrical boilers when they were first put in leaked very much; we could hardly keep up the fire sometimes. I reckon the steam was 30 or 40 lbs. to the inch. Captain Dick's boilers made him lots of enemies. I heard say in one mine where he was trying his boilers against Boulton and Watt's waggon, a lot of gunpowder was put into the heap of coal."[72]

The waggon or hearse Watt boiler was attached to his 63-inch cylinder double, and the old man recollected having raised the water cistern, when Trevithick's globe boiler gave an increased pressure in 1799, ten or twelve years before the cylindrical boilers were made in Dolcoath.

"Some time after Captain Dick's globe boiler and steam-whims had been at work in Dolcoath, a letter came down from London, saying that he would save the mine 100l. a month if they would put in one of his new plan boilers.

"They were put in hand in the mine, and I worked about them; they were wrought-iron cylindrical boilers, about 20 feet long, and 5 or 6 feet in diameter; the fire-tube was about 3 feet in diameter; the fire returned around the outside in brick flues. Three boilers were put in side by side.

"When Captain Dick first tried them, he said to the men, Now mind, the fire-bars must never have more than six inches of coal on them; give a shovel or two to one boiler, and then to another. When Captain Dick's back was turned, the men said they wasn't going to do anything of the sort, there would never be no rest for them. They used to say that the boilers saved more than 170l. the first month."[73]

Clark, when a boy, in 1799, helped to construct Trevithick's globular boiler in Dolcoath, and recollected the events of the few following years, during the contests with the whim-engines about 1806, and the introduction of the large cylindrical wrought-iron boilers for the pumping engines in 1811, and the struggle preceding the downfall of the Watt low-pressure steam vacuum engine, to make room for the high-pressure expansive steam-engine, with or without vacuum.

"About 1812 Captain Trevithick threw out the Boulton and Watt waggon boilers at Dolcoath and put in his own, known as Trevithick's boiler. They were about 30 feet long, 6 feet in diameter, with a tube about 3 feet 6 inches in diameter going through its length. There was a space of about 6 inches between the bottom of the tube and the outer casing. Many persons opposed the new plans. The Boulton and Watt low-pressure engine did not work well with the high steam, and the water rose in the mine workings. Captain Trevithick, seeing that he was being swamped, received permission from the mine managers to dismiss the old engine hands and employ his own staff. Captain Jacob Thomas was the man chosen to put things right. He never left the mine until the engine worked better than ever before, and forked the water to the bottom of the mine. Before that time the average duty in the county by the Boulton and Watt engines was seventeen or eighteen millions, and in two or three years, with Trevithick's boilers and improvements in the engines, the duty rose to forty millions. About 1826 he (Captain Vivian) was manager of Wheal Towan; their engines were considered the best in the county, doing eighty-seven millions; they had Trevithick's boilers, working with high-pressure steam and expansive gear; few if any of Boulton and Watt's boilers could then be found in the county. Sir John Rennie and other scientific men, who doubted the reports of the duty, came and made their own trials with the engines, and were satisfied that the duty was correctly reported.

"About that time a Mr. Neville requested him to report on the engines at his colliery at Llanelthy; one was an atmospheric of Newcomen's, doing six millions; and four or five of Boulton and Watt's patent engines averaged fourteen millions."[74]

When at last the cylindrical high-pressure boiler was admitted, and men had been taught to fire them, many persons still liked the old plans, and among them the easy-going low-pressure enginemen. The consequence was that the Watt engines under their management refused the early doses of Trevithick's high steam, not easily digesting it, and their obstinacy nearly swamped Trevithick and his plans.

"When a little boy, about 1812, I frequently carried my father's dinner from Penponds to Dolcoath Mine. One day, not finding him in the engine-house, I sought him in the account-house, but not knowing him in a miner's working dress, refused to give him his dinner. William West then worked with him. I heard there was difficulty in making the new boilers and the old engine work well; engineers from other mines looked on from a distance, not liking the risk of explosion. People seemed to be against the new plans; some labourers worked with them."

This narration—sixty years after the events—from Mr. Richard Trevithick, the eldest son of the engineer, shows that William West helped in applying high-pressure steam to the Watt low-pressure engine, and that but few sympathized with the innovators on old customs; but among them was Captain Jacob Thomas, who successfully fed the old engine with strong steam.

At that time the Watt engines in Cornwall had been doing seventeen or eighteen millions; Trevithick's new boilers increased their duty to forty millions.

"William Pooly[75] was working in Dolcoath before Captain Trevithick's new boilers were put in, and helped to put them in.

"The Shammal 45-inch engine was an open-top cylinder, with a chain to the segment-head wooden beam. So was the 63-inch cylinder Stray Park engine, then called Wheal Gons[76] in Dolcoath sett, and the Boulton and Watt 63-inch cylinder double-acting.

"There used to be great talking about different boilers; a boiler of Captain Trevithick's worked with higher steam than the others. Just before Captain Dick came back to the mine a Boulton and Watt hearse boiler had been repaired with a new bottom; it was never used. I and William Causan took a job to cut up the boiler at 1s. 6d. the hundredweight; it weighed 17 tons. Jeffrie and Gribble were the mine engineers; Glanville used to be considered Captain Dick's man in the mine. You could stand upright on the fire-bars in the middle hollow of the hearse boiler, and so you could in the outside brick flues; the middle hollow was like a horse-shoe. When Captain Dick put in his cylindrical boilers he altered the 63-inch single; there was hardly anything of her left but the main wall, with the wood bob and a chain to the piston-rod, and also to the pump-rods. There was an air-pump, and I think a second-hand cylinder was brought, but it was a 63-inch; the old Shammal engine had been altered, too.

"The new boiler put in was about 8 feet in diameter and from 30 to 40 feet long, two round tubes went through it; the fire-place in one end of one tube and in the other end of the other tube; after going through the tubes the draught went into the brick flues under the bottom and sides. When the new engine was put in, Gribble said, ‘Why, these little things will never get steam enough;’ everybody said so.

"In the Boulton and Watt engines we didn't trouble about feed-pumps and gauge-cocks.

"A wire came through a stuffing box in the top of the boiler; a biggish stone in the boiler was fastened to one end of the wire, the other end was fastened to a weighted lever near the water cistern, just above the boiler; when the water got low the stone opened the valve in the water cistern. That was when they were putting in Captain Dick's new cylindrical boilers to the old 63-inch engine. She did so much more work, with less coal, that in a year or so they agreed to throw out Boulton and Watt's engine, and to put in a stronger one that could stand Captain Dick's high steam. Jeffrie and Gribble were the mine engineers that put her up. The 76-inch cylinder came from Wales. The big beam was cast at Perran Foundry in 1815; you can see the name and date upon it now. The boiler and the gear-work were made in the mine. The exhaust-valve is exactly as when it was put in, worked by a rack-and-tooth segment. The equilibrium valve is unchanged, except that the rack is taken out and a link put in.

"The steam-valve was taken out soon after she went to work, and the present double-beat valve was put in; it is the first of the kind I ever saw. Some were made before that time with a small valve on the top of the big one, that opened first, to ease the pressure.

"John West[77] fitted up the valve-gear in the mine with the expansive tappets, the same as when she stopped a month or two ago, and the same as the present new one has.

"Captain Dick's cutting off his strong steam at an early part of the stroke, used to make the steam-valve strike very hard; so the new plan valve, with a double beat, was put in; that must have been about 1816 or 1817; and the valve and expansive horn for working were just exactly like what they have put into the present new engine in 1869. She was the engine that showed them how to fork the water, and burn only half the coal.

"I worked in this mine the old atmospheric engines, and then Boulton and Watt; and then Trevithick's boilers in Boulton and Watt; and then Trevithick's boilers and engine; and now I come every day to the new engine, though I can't do much. They give me 35s. a month; and my name is William Pooly, Dolcoath, 1869."

Three years ago (in 1869), when the writer entered the old engine-house in which Watt's 63-inch cylinder double had been erected in 1780, adjoining the old walls that then enclosed that early Newcomen 45-inch cylinder Carloose engine, re-erected by Trevithick, sen., in 1775 in Bullan Garden portion of Dolcoath, an old man sat near a small window in a recess in the thick wall of the engine-house, within reach of the gear-handles of the Jeffrie and Gribble 76-inch cylinder engine that Trevithick, jun., had erected in 1816 on the foundations of the removed Watt engine; he held in one hand a portion of slate from the roof, and in the other an old pocket-knife, one-half of the blade of which had been broken off, leaving a jagged fracture, with which he made the figures of some calculation on the rude slate; on his nose rested the brass frame of a pair of very ancient spectacles, with horn glasses. He answered the writer's question by, "Yes, I am William Pooly; I worked this engine, and the other engines before it—the great double and the little Shammal working out of the same shaft; and I am seventy-four years of age. The 63 single worked upon a shaft up there; she was called Wheal Gons." That old man, still living, had worked in Dolcoath Mine one of the first steam-engines of Newcomen; the 45-inch, modified by Trevithick, sen.; then the 63-inch double of Watt; and, finally, the high-pressure engines of Trevithick, jun.; he saw the open-top cylinders, atmospheric of Newcomen, in the Shammal 45-inch and Wheal Gons 63-inch, with their wooden beams with segment-headed ends, moving in rivalry with the Watt 63-inch double, with cylinder-cover and parallel motion; he saw the two former engines, as altered by Trevithick, jun., using the higher steam from the globular boiler on which Henry Clark worked in 1799, when "there used to be great talking about different boilers, and a boiler of Captain Trevithick's worked with higher steam than the others; and the waggon boiler of Watt, that had just been repaired, was discarded and cut up;" thus described by Trevithick, "the fire-place is 22 feet from fire-door to fire-door, 9 feet wide, and 7 feet thick in fire,"[78] which he proposed to replace in 1806 by a cylindrical boiler to give steam of 25 lbs. on the inch.

Pooly also saw the finishing stroke in 1811, when the boilers still known as the Trevithick or Cornish boilers, gave steam to the three engines; after a twelve years' fight between low and high pressure, commencing with Trevithick's globular boiler and internal tube, in Dolcoath, in the year 1799, from which time it gained step by step, though in comparatively small engines, up to 1811, when the cylindrical boilers took the place of the condemned hearse and globular boilers, and gave really strong and expansive steam to the three Dolcoath pumping engines that from time immemorial had been rivals, causing all three of them to lift an increased quantity of water, and at the same time to save one-half in the cost of coal; this continued for four or five years, when in 1816 the 63-inch double and the 45-inch, being the youngest and the oldest of the three, were removed, that a new 76-inch cylinder, better adapted to Trevithick's expansive steam might more cheaply perform their joint work. Prior to this change the three engines were known by the names Shammal 45-inch, formerly Bullan Garden,[79] but before that as Carloose, of the period and form of the Pool engine;[80] Stray Park 63 single, formerly Wheal Gons,[81] dated from 1770 to 1777; and the 63-inch double of Watt in 1780.

"Dolcoath Mine, March 29th, 1858.

"Sir,

"I have obtained the following information respecting the building of the first cylindrical boilers, as ordered by your late father for Dolcoath; and some information of the results as to the coals consumed, compared with the consumption by the boilers previously in use here.

"George Row, now about seventy-two years old, and working at Camborne Vean Mine, says he assisted to build the two first cylindrical boilers with internal tubes used in Cornwall. They were built in Dolcoath Mine in the year 1811; they were 18 feet long, 5 feet diameter, having an oval tube 3 feet 4 inches in the largest diameter at the fire end; the other or chimney end of the tube was somewhat smaller. They were found too small for the work to be done, and another boiler was built immediately, 22 feet long, 6 feet 2 inches diameter, and he believed a 4-feet tube.

"John Bryant, now seventy-four years old, works a steam-engine at West Wheal Francis. He worked at Dolcoath the 63-inch cylinder double-acting engine, upon Boulton and Watt's plan. When he first worked her she had the old bee-but boiler, 24 feet in diameter. They were taken out for the Boulton and Watt waggon boiler, 22 feet long and 8 feet wide, with two fire-doors opposite one another.

"Then the Boulton and Watt waggon was taken out for Captain Trevithick's boilers, which he worked for several years. Two boilers were put in, each 18 feet long, 5 feet diameter, with an internal oval tube, he thinks, 3 feet by 2 feet 6 inches. Shortly after, another boiler of similar form was added, 22 feet long, 6 feet diameter, 4-feet tube.

"He cannot say what the saving of coal was, but remembers that the duty performed by the engine with the waggon boiler was thirteen to fourteen millions. Mr. William West came to the mine as an engineer, and by paying great attention increased the duty of the Boulton and Watt engine and boiler to about fifteen millions. He does not recollect the duty the engine performed with the cylindrical boilers.

"Mr. Thomas Lean, of Praze, the present reporter of mine engines in the western part of Cornwall, in answer to a note I sent to him, says he has no account of any report of Dolcoath engines for the year 1812, but during the month of April in that year the engines did 21½ millions. During the whole of 1813 that engine was reported to average a duty of twenty-one millions. The whole of the above are at per bushel of 93 lbs., and the whole of the accounts furnished by Mr. Lean are for Trevithick's cylindrical boilers.

"From the Dolcoath Mine books I find the following: Paid for coals for the whole mine during the year 1811, 1150l. 15s. 10d., or per month, 931l. 14s. 7d. During the first three months of 1812 the coal averaged 1000l. per month. In May of this year, 1812, Captain Trevithick is entered on the books as paid 40l. on account of boilers; and in August of the same year, for erecting three boilers, 105l. I think the three boilers were at work in April, 1812, the month Mr. Lean gives as the first reported. From April, 1812, to December, during nine months, the cost of coals was 5512l. 6s., averaging 612l. 9s. 6d. per month. During the next year, 1813, the cost for coal was 7019l. 17s. 5d., or an average per month of 590l. 16s. 5d. I cannot find the price paid per ton for the coal in these years, but the average price during 1808 and 1815 was much alike, making it probable that the price per ton during 1811, 1812, and 1813, was nearly the same; and that the saving of the above 300l. per month in Dolcoath was wholly on account of the saving effected by Trevithick's cylindrical boilers.

"The testimony of John Bryant, that the duty with the waggon boiler was say fourteen millions, and that of Mr. Lean, giving twenty-one millions with the new Trevithick boiler, bear much the same proportion as the charges for coals in the respective periods above given.

"In the year 1816 a new 76-inch single engine was erected in the place of the old Boulton and Watt 63-inch double engine with Trevithick's cylindrical boilers. The average duty performed during the year 1817 was 43¾ millions. This same engine is still at work, and her regular duty is from thirty-six to thirty-eight millions.

"I am, Sir,
"Your most obedient servant,
"Charles Thomas.

"Francis Trevithick, Esq."

Captain Charles Thomas, who was one of the most experienced of Cornish miners, for many years the manager of Dolcoath, and in youth the acquaintance of Trevithick, states that the new high-pressure boilers were made in the mine in 1811, and gave their first supplies of strong steam to the three large pumping engines in April, 1812, with such good effect that the increasing water which had threatened to drown the mine was speedily removed, and that with a saving of nearly one-half of the coal before consumed. Prior to their use Dolcoath Mine paid 1000l. monthly for coal; but for the latter nine months of the year, in consequence of the new boilers, the cost was reduced to 612l. a month. This saving in the pumping cost of one mine crowned with success the high-pressure steam engineer, who had been steadily gaining ground during his fight of twelve or fourteen years on the battle-ground chosen by Watt thirty-three years before.

The low price of tin and copper, which caused so many engines to cease working about the close of the last century, had changed for the better, and the present century opened with an increasing demand for steam power. Trevithick's high-pressure portable engines had worked satisfactorily for several years; and as a means of making public the relative duty performed by Cornish pumping engines, and of solving conflicting statements on the rival systems of low and high pressure steam, it was determined that an intelligent person should examine and give printed monthly reports of the amount of duty done by the different engines, and in 1810 Captain Andrew Vivian was requested to take this work of engine reporter in hand; on his refusal it was offered to Trevithick. In August, 1811, Mr. Lean commenced such monthly reports, showing that the duty of twelve pumping engines at the end of that year averaged seventeen millions, exactly the duty done by the Boulton and Watt engines thirteen years before, as reported by Davies Gilbert and Captain Jenkin in 1798, proving the small inherent vitality of the Watt engine.

In 1814 the Dolcoath pumping engines, with Trevithick's cylindrical boiler and high steam expansion, are thus reported:—"The Boulton and Watt, Dolcoath great double engine, 63-inch cylinder, did a duty of 21½ millions; the Shammal 45-inch cylinder, single engine, did 26¾ millions; and the 63-inch single, Stray Park engine, 32 millions." Shammal engine, nearly 100 years old, beat the Watt engine of more than half a century later; and so did Stray Park 63-inch, which Watt had laughed at when he first tried his hand as an engineer in Cornwall in 1777.[82]

The marked change in these three engines, while for two or three years under Trevithick's guidance, becoming more powerful and economical, raised the usual swarm of detractors, and in 1815 a special trial was made, which lasted for two days, to test the reported increased duty by the cylindrical boilers and expansive working.

The unbelievers were then convinced, and agreed to throw out the Boulton and Watt great double engine 63-inch cylinder, together with its neighbour, the worn-out old 45-inch, and put in their stead one engine with a cylinder of 76 inches in diameter, with expansive valve and gear, and parts strong enough and suitable to the high-pressure steam, on Trevithick's promise that it should do more than the combined work of the other two with one-half the coal.

In 1816 this new engine commenced work, and did forty millions of duty, increasing it during the next two or three years to forty-eight millions, being three times the duty performed by the Watt 63-inch double engine before it was supplied with steam from Trevithick's boilers, and twice as much as it performed when so supplied. Lean says, "This was the first instance of such duty having been performed by an engine of that simple construction." The other mines followed Trevithick's advice, but never paid him a penny. On this Lean again says, "The engines at work in the county in 1835 would have consumed 80,000l. worth of coal over and above their actual consumption yearly, but for the improvements that had been made since 1814."

Trevithick's engines were very durable, as well as cheap in first cost and in working expense. This famous Dolcoath 76-inch engine remained in constant work night and day for fifty-four years; after which good service the steam-pipes, being thinned by rust, were held together by bands and bolts; the steam-case around the cylinder would no longer bear the pressure of steam; the interior of the cylinder from wear was one inch larger in diameter than when first put in, and had to be held together by strap-bolts. The original boilers were said to remain, only they had been repaired until not an original plate remained; but there they were in the old stoke-hole in 1869, when, from the fear of some part of the engine breaking and causing accident, it was removed.

Trevithick's Dolcoath 76-inch Cylinder Pumping Engine, erected in 1816, ceased working 1869.

a, steam-cylinder, 76 inches in diameter, 9-feet stroke; b, steam-jacket; c, steam expansion-valve, 11 inches diameter, double beat; the upper beat 11 inches diameter, the under beat 9½ inches, valve 8 inches long; d, expansive cam on plug-rod; e, plug-rod for moving the gear; f, expansive horn; g, equilibrium valve, 13 inches in diameter, single beat moved by a tooth-rack and segment; h, exhaust-valve, 14½ inches in diameter, single beat moved by a lever and link; i, equilibrium-valve handle; j, exhaust-valve handle; k, Y-posts for carrying the gear arbors; l, main beam in two plates of cast iron; m, parallel motion; n, feed-pump rod; o, air-pump bucket-rod, the pump, 2 feet 9 inches diameter; p, the main pump rods.

Cylinder, Main Beam, and Pump-rod of Dolcoath 76-inch Cylinder Engine.

In 1867 the writer was a member of the Dolcoath Managing Committee, when it was determined that the old engine of 1816 should be replaced by a new one. The cylinder sides were reduced in thickness by half an inch; the steam-pipes and nozzles were thinned by rust and decay; the valves and gear-work remained in good order. Captain Josiah Thomas, the present manager of the mine, offered to sell this old engine at scrap price, that it might be stored in the Patent Museum at Kensington as a memento of the early high-pressure expansive steam pumping engine.

Boilers erected in 1811 in Dolcoath, used in the Boulton and Watt 63-inch Engine, then in the new 76-inch until 1869.

a a, two wrought-iron cylindrical boilers, 5 feet in diameter, 18 feet long, with internal fire-tube, oval, 3 feet 4 inches by 3 feet; b, a boiler, 6 feet 2 inches diameter, 22 feet long, cylindrical tube, 4 feet diameter in the fire-place, the remainder 3 feet; c, brick bridge; d, fire-bars; e, brick external flues under boiler; f, brick side-flues; g, ashes, or other non-conductor; steam 30 to 50 lbs. on the inch above the atmosphere.

The steam-cylinder of 1816 was cast in South Wales; the beam still working in the new engine of 1869 was cast in the foundry of the Williams' at Perran. John West replaced the original flat expansive steam-valve with a double-beat valve; the gear was principally made by him on the mine, and remained in good working to the last. This double-beat valve is the first the writer has met with; it is of the same form as the modern double-beat valve; an earlier plan was to have a small valve on the top of the main valve. The steam in ordinary working was shut off when the piston had moved from an eighth to a quarter of its stroke.

The Gons, or Stray Park 63-inch cylinder, survived its companions, the 63 double, and 45 single, for some ten or fifteen years, having beaten both of them in duty. A memorandum in Trevithick's handwriting shows that he in 1798, when designing his large globular boiler with internal flue at the reworking of Dolcoath, tested the relative duty of the Watt 63-inch double and the 63-inch single engine, then called Wheal Gons, the latter in its original form of open-top cylinder atmospheric; shortly after which it probably received a cover about the same time as the 45-inch, for both those engines were thoroughly repaired by Trevithick at the reworking of the mine, twelve or fourteen years prior to the use of the cylindrical boilers.

"At the time that Boulton and Watt made their trial of Seal-hole engine against Hornblower's engine at Tin Croft, the engines were put in the best order, and good coals brought in for the purpose, to work for twenty-four hours. The trial was attended by the principal mining agents; the result was about ten millions by each engine.

"At Dolcoath Mine an old atmospheric engine continued to work for several years by the side of one of Boulton and Watt's engines of the same size; the water lifted and coals consumed were carefully taken and made known to the public, showing that Boulton and Watt's engine performed, when compared with the old engine, as 16 to 10."[83]

Hornblower was an active engineer in Cornwall before Watt; the patent of the latter claiming the sole right of working an engine by steam in the cylinder,[84] drove the former to use two cylinders, in one of which the expansion was carried out, as a means not described in Watt's patent; a lawsuit was the consequence. The two engines when tried by Trevithick[85] performed an equal duty of ten millions. In 1798 he tested the Dolcoath atmospheric 63-inch single against Watt's great 63-inch double action. "The atmospheric performed ten millions," precisely the duty of the patent Watt and the patent Hornblower contests of six years before; but the Watt Dolcoath engine, then considered the best he had made, did sixteen millions. These trials in 1792 and 1798 enable us to compare the Newcomen, the Hornblower, and the Watt engines; shortly after which Trevithick tried higher steam in one or more of those same engines from his globular boiler.[86]

"Camborne, March 10th, 1812.

""Sir Ch. Hawkins,

"Sir,—This day I shall attend the account at Wheal Prosper Mine, in Gwythian, to contract with the adventurers for erecting a steam-engine on my improved plan, for drawing the water 50 fathoms under the adit. I called on Wheal Liberty adventurers at St. Agnes last week, and found that several of them had given up their shares rather than put in a new engine, and the remainder of them very sick.

"I told them that I would fork the water with the present engine, and draw instead of 40 gallons each stroke, 47 fathoms deep (which she did), 85 gallons per stroke, 65 fathoms deep, by altering the engine on the same principle as I have done with the Dolcoath great engine, and several more that are now altering. The expense of altering the engine, and forking the water to bottom, and proving the mine, will not exceed 1000l.

"All the adventurers are very anxious to again resume their shares and make the trial, on condition that I will undertake the completion of the job at a certain sum, but not otherwise.

"I am certain, from what Dolcoath engine is doing, that I can far exceed the power above stated, and perform the duty with one-half the coal the engine consumed before, and would not hesitate a moment to engage the job on the terms they propose, but I have not money sufficient to carry it into execution, as I must lay out a large sum in erecting the engine on the Gwythian Mine, and unless I can be assisted with 500l., shall not be able to undertake the job.

"If you think it worth your notice to encourage this undertaking by lending me the above sum for six months, I will pay you interest for it, and before drawing any part of it from you would get materials in the mine that should amount to above that sum, and also give you an order on the adventurers to repay you the whole sum before receiving any part myself.

"As I have been a bankrupt, perhaps you may scruple on that account, but that business is finally settled, and I have my certificate; and indeed I never was in debt to any person; not one shilling of debt was proved against me under the commission, nothing more than the private debts of my swindling partner.

"At Wendron we are working an engine lately erected on a copper lode, which has a very promising appearance, and near this spot you have land at Besperson, where there is also a very kindly copper lode, which deserves trial; if you are inclined to grant a sett, I think I can find adventurers to join me to try the mine.

"I have lately read a letter from your hind, that the engine continues to mend; it far exceeds my expectation. I am now building a portable steam-whim, on the same plan, to go itself from shaft to shaft; the whole weight will be about 30 cwt., and the power equal to twenty-six horses in twenty-four hours.

"The only difference in this engine and yours will be the fire in the boiler, and without mason-work, on account of making it portable. I shall pass the rope from the fly-wheel round the cage of the horse-whim.

"If you should fall in with any West India planter that stands in want of an engine, he may see this one at work in a month, which will prove to him the advantage of a portable engine, to travel from one plantation to another. The price, completely finished and set to work, free of all expense, in London, 105l.

"I am, Sir,
"Your very humble servant,
"Richard. Trevithick.

"N.B.—Captain John Stephens informed me, a few days since, that the lead mine at Newlyn was rich."

In Wheal Prosper Mine the first high-pressure expansive steam-condensing pole-engine had been worked, just before the date of the foregoing letter, and that evidence of increased power and economy was immediately followed by the application of the same principles of high-pressure steam and very expansive working to the Watt low-pressure steam vacuum engines at Wheal Alfred, Dolcoath, and other mines, with such satisfactory results as to warrant his offering, on the battle-ground of his first attack on the Watt low-pressure steam vacuum principle at Seal-hole in St. Agnes, fourteen years before,[87] at his own pecuniary risk, to so apply those principles in the Wheal Liberty low-pressure steam-engine, which had failed to drain the mine, lifting only at the rate of 1880 gallons of water one fathom high at each stroke; that it should lift an increased quantity of water, and that, too, from an increased depth, making the load equal to 5525 gallons, and to perform such increase of work with one-half of the quantity of coal before used; in other words, he was willing to engage to make the old low-pressure steam-engine perform by its conversion into a high-pressure steam-engine threefold its original work, and also to increase its duty or economic value sixfold; resting his argument on the similar changes, then to be seen in operation at Wheal Alfred Mine, and especially in the Watt 63-inch double-acting engine at Dolcoath, whose history we have been tracing. Well might Sir Charles Hawkins hesitate to believe what the experience of sixty years has barely sufficed to make plain to us.

"Penzance, March 27th, 1813.

"Captn. Trevithick,

"Sir,—In consequence of the conversation that has passed between you and West Wheal Tin Croft adventurers, the said adventurers have resolved to put an engine on that mine, agreeable to the proposals offered by you; that is, the engine shall be capable of lifting a 5-inch bucket, 50 fathoms, 4-feet stroke, 15 strokes per minute, or a duty equal thereto; for which they will pay you 50 guineas one month after the engine shall be at work, and 50 guineas more at four months after that, and 50 guineas more at four months from that time, making the full payment of 150 guineas in nine months from the time the engine shall set at work, the adventurers paying all expense, except the engine materials, which shall be delivered on the mine. But in case the engine not performing the above duty, the adventurers to be at liberty to return the same engine, and you to pay back all the money that you had received for the said engine.

"Signed by Gabl. Blewett,
"in behalf of the Adventurers and Company."

Trevithick was willing to spend more than his last penny in establishing the superiority of his high-pressure steam expansive engines, but the selfishness of adventurers retarded their progress. The atmospheric, mentioned by Watt as working in Dolcoath in 1777,[88] did five or six millions of duty, yet in Trevithick's hands, about 1798 to 1800, when he erected his globular boiler with internal tube, one of them was tested with the 63-inch Watt low-pressure vacuum engine, when the latter did sixteen millions to ten millions by the atmospheric engine, being nearly double the duty it performed in its original form; and we shall still trace this same engine as Bonze or Gons until it increased to six times its first duty under the name of Stray Park 63-inch.

Trevithick having erected a high-pressure steam condensing whim-engine at Cook's Kitchen,[89] and in Dolcoath[90] a high-pressure puffer whim-engine, pleaded hard in 1806[91] to be allowed to supply the large pumping engines of Newcomen and Watt with higher pressure steam from his cylindrical boiler, which after years of consideration Dolcoath, in 1811, agreed to. In 1813 he wrote:—"That new engine you saw near the sea-side with me is now lifting forty millions, one foot high, with one bushel of coal, which is very nearly double the duty that is done by any other engine in the county. A few days since I altered a 64-inch cylinder engine at Wheal Alfred to the same plan, and I think she will do equally as much duty. I have a notice to attend a mine meeting to erect a new engine, equal in power to a 63-inch cylinder single."[92]

The beneficial results of those acts are too large to be here entered into in detail. In round numbers, the early pumping engines of Newcomen did five millions;[93] Trevithick caused them to do ten millions of duty with a bushel of coal. Watt, during thirty years of improvements, caused the duty to reach sixteen or twenty millions in 1800. Trevithick, on the expiry of the Watt patent, then came into play, and before he had reigned half the time of Watt, again doubled the duty of the steam-engine, as he states in 1813 "his new engine was doing forty millions, being nearly double the duty of any other engine in the county." These statements by Trevithick agree very nearly with the generally-received accounts of the progressive duty of the large pumping steam-engine.

"In 1798 Davies Gilbert, Esq., and the late Captain Jenkin of Treworgie, found the average of the Boulton and Watt engines in Cornwall to be about seventeen millions. In August, 1811, the eight engines reported averaged 15·7 millions. During the year 1814 Dolcoath great engine, with a cylinder of 63 inches in diameter, did twenty-one and a half millions nearly. Dolcoath Shammal engine, with a cylinder of 45 inches in diameter, did twenty-six and three-quarter millions. Dolcoath Stray Park engine, with a cylinder of 63 inches in diameter, did thirty-two millions.

"In 1815 a trial was made, to prove the correctness of the monthly reports. Stray Park engine at Dolcoath was chosen for the purpose, because its reported duty was such as led some persons to entertain doubts of its accuracy. The trial was continued for ten days, to the full satisfaction of all concerned.

"In 1816, Jeffrie and Gribble erected a new engine, 76-inch cylinder, single, at Dolcoath, which did forty millions. This was the first instance of such duty having been performed by an engine of that simple construction.

"In 1819, Dolcoath engine performed the best during this year, and at one time reached forty-eight millions.

"In 1820, Treskerby engine, to which Trevithick's high-pressure pole had been adapted, reached 40·3 millions.

"In 1816, Sims also erected an engine at Wheal Chance, to which he applied the pole adopted by Trevithick in his high-pressure engines. This engine attained to forty-five millions.

"In 1828 public attention had now been attracted to the improvements which Captain Grose had introduced into his engine at Wheal Towan. The duty of this engine, in the month of April this year, equalled eighty-seven millions.

"This again gave rise to suspicions of error in the returns. This engine was accordingly subjected to a trial (as Stray Park engine had been in 1815), which was superintended and conducted by many of the principal mine agents, engineers, and pitmen of other mines.

"The quantity of coal consumed in 1835, compared with the quantity that would have been consumed by the same engines in the same time, had they remained unimproved from the year 1814, shows that the saving to the county amounts to 100,000 tons of coal, or 80,000l. sterling per annum."[94]

Lean seems to have calculated on a bushel of coal as 94 lbs. In 1798, when Trevithick was about to give increased pressure of steam to the Cornish engines, his friend Davies Gilbert reported the average duty of the Watt engine in Cornwall to be seventeen millions.

In August, 1811, the reported duty averaged 15·7 millions. This was the month and year in which Trevithick, after twelve years of working evidences of the reasonableness of his promises of increased power and economy from using high-pressure steam, was allowed to erect his cylindrical boilers for the large pumping engines in Dolcoath Mine.

Has the reader realized that the 45-inch atmospheric Carloose engine, of nearly 100 years before,[95] had in 1775[96] become the Bullan Garden engine of Trevithick, sen., which was improved and re-erected by Trevithick, jun., in 1799,[97] when the name was again changed, this time to Shammal, because it was linked to another engine, no other than the Watt 63-inch double engine? This Shammal 45-inch took steam from the globular boiler, using a pole air-pump[98] and a Watt condenser, though retaining the beam with the arched head and chain connection; and again in 1811 took still more highly expansive steam from the cylindrical boilers with a new beam and parallel motion, enabling it in 1814 to beat its rival, the Watt Dolcoath great double engine.[99] The old 63-inch Gons, under the name of Dolcoath Stray Park engine, with Trevithick's improvements, did sixty-seven per cent. more work than the Watt 63-inch with an equal quantity of coal.

This startling fact was disbelieved by the advocates of low-pressure steam, and as the visible change in the Dolcoath engine from Newcomen to Watt, and from Watt to Trevithick, had been gradual and not very striking, and the public were careless of principles, the one most puffed was most thought of; but the money saved was tangible, and in 1815 a special trial was made, which lasted two days, to discover if it was really true that Trevithick's appliances could so increase the duty of the engine. The 63-inch cylinder, then called Stray Park engine, was selected; the result proved that the large saving reported from Trevithick's boilers and expansive working during the last three or four years, was an incontrovertible fact.

The high-pressure steam was also given to the defeated Watt 63-inch double engine; yet this newest of the three engines was the first to be condemned, and her place was taken in 1816 by an engine of 76 inches in diameter, which Trevithick promised should, with his high steam and new expansive gear, do the work of the Watt 63-inch and the old 45-inch put together; which was more than fulfilled by its doing forty millions, and, as Lean says, "was the first instance of such duty having been performed by an engine of that simple construction."

In 1819 the new 76-inch engine which had been erected by the mine engineers, Jeffrie[100] and Gribble, who had long been employed by Trevithick in Dolcoath, was the best in the county, doing forty-eight millions, nearly three times the duty as given by Mr. Gilbert for the Watt engine in 1798. In 1827 Trevithick's pupil, Captain Samuel Grose, erected his Wheal Towan engine, which performed a duty of eighty-seven millions, some of the working drawings of which were made by the writer. In 1835 the principle laid down by Trevithick had become so general in the county as to cause a saving to the Cornish mines, in coal alone, of 80,000l. yearly. In addition to this, the increased power of the engine lessened the first cost by at least one-half.

The national importance of such weighty facts calls for further corroborative proof, for we can scarcely believe that two atmospheric low-pressure steam-engines, made before the time of Watt, could be altered so as to perform more work, and at a less cost than the Watt engine, by an ingenious supply of higher steam pressure from Trevithick's boilers, together with the Watt air-pump and condenser. The following words from Watt are descriptive of his practice, though contrary to his patent claim:—

"At a very early period, while experimenting at Kinneil, he had formed the idea of working steam expansively, and altered his model from time to time with that object. Boulton had taken up and continued the experiments at Soho, believing the principle to be sound, and that great economy would attend its adoption.

"The early engines were accordingly made so that the steam might be cut off before the piston had made its full stroke, and expand within the cylinder, the heat outside it being maintained by the expedient of the steam-case. But it was shortly found that this method of working was beyond the capacity of the average enginemen of that day, and it was consequently given up for a time.

"'We used to send out,' said Watt to Robert Hart, 'a cylinder of double the size wanted, and cut off the steam at half-stroke.'

"This was a great saving of steam, so long as the valves remained as at first; but when our men left her to the charge of the person who was to keep her, he began to make, or try to make, improvements, often by giving more steam. The engine did more work while the steam lasted, but the boiler could not keep up the demand. Then complaints came of want of steam, and we had to send a man down to see what was wrong.

"This was so expensive, that we resolved to give up the expansion of the steam until we could get men that could work it, as a few tons of coal per year was less expensive than having the work stopped. In some of the mines a few hours' stoppage was a serious matter, as it would cost the proprietor as much as 70l. per hour."[101]

Pole expresses the same view, intimating that Watt only used steam of 1 or 2 lbs. pressure to the inch.

"In Watt's engine, as is well known, the pressure of steam in the boiler very little exceeded the pressure of the atmosphere. He recommended that when the engine was underloaded, this excess should be equal to about 1 inch of mercury; and when full loaded, ought not to exceed 2 inches; adding, 'It is never advisable to work with a strong steam when it can be avoided, as it increases the leakages of the boiler and joints of the steam-case, and answers no good end.'[102]

"Mr. Watt's engines with such boilers" (which will not retain steam of more than 3-1/6; lbs. per square inch above the atmosphere) "cannot be made to exert a competent power to drain deep mines, unless the supply of steam to the cylinder is continued until the piston has run through more than half its course.[103]

"In 1801-2 Captain Trevithick erected a high-pressure engine of small size at Marazion, which was worked by steam of at least 30 lbs. on the square inch above atmospheric pressure. In 1804, as Mr. Farey admits,[104] the same gentleman introduced his celebrated and valuable wrought-iron cylindrical boilers,[105] now universally used in this county.

"To these, everyone at all acquainted with the Cornish improvements ascribes a great part of the saving we have obtained. This will farther appear from an extract from a valuable work edited by John Taylor, Esq., F.R.S.[106]

"The monthly consumption of coal in Dolcoath Mine was, in 1811, 6912 bushels; in 1812, 4752 bushels.[107] The alteration in the boilers was the introduction of Captain Trevithick's cylindrical boilers in the place of the common waggon boilers, which had until then been there in use.

"Mr. Woolf, as Mr. Farey states, came to reside in Cornwall about the year 1813, and his 'first engines for pumping water from mines were set up by him in 1814.'"[108]

The foregoing was read at the Philosophical Society in 1831, to refute erroneous statements on the Watt and Trevithick engines. My friend Mr. Henwood had at that time made official experiments in conjunction with Mr. John Rennie on the detail, working, and duty of high-pressure steam Cornish engines, the Watt low-pressure steam principle having been wholly given up. Rees's 'Cyclopædia'[109] also bears the following similar testimony to date of the increased duty:—

"Trevithick's high-pressure engine was erected in Wales in 1804 to ascertain its powers to raise water. The duty was seventeen millions and a half pounds raised one foot high for each bushel of coals.

"The high-pressure steam-engines require a greater quantity of coals, in proportion to the force exerted, than the engine of Mr. Watt, and consequently are not worked with advantage in a situation where coals are dear.

"From the reports of the engines now working in the mines of Cornwall, which, with the exception of a few of Woolf's engines, are all on Mr. Watt's principle, and most of them constructed by Messrs. Boulton and Watt, taking the average of nine engines—bad, good, and indifferent together—they were found in August, 1811, to raise only thirteen millions and a half. But when it was known by the engine keepers that their engines were under examination, they took so much pains to improve the effects, that by gradual increase the engines in 1815 lifted twenty-one millions and a half, taking the average of thirty-three engines. In 1816, Stray Park, a 63-inch cylinder, 7 feet 9 inches stroke, single-acting, being one of the three engines on the vast Dolcoath Mine; its performance in four different months was thirty-one, thirty-one and a quarter, twenty-eight, and twenty-eight and a half millions."

This statement reveals a source of error in estimating the relative values of the Watt and the Trevithick engine; that of the latter was the Welsh locomotive, compared in duty with the large Watt pumping engine, pointed out in Trevithick's letter[110] of that time, as an unfair comparison; the small high-pressure puffer, in 1804, is admitted to have done seventeen and a half millions of duty with a bushel of coal of 84 lbs., while in Rees' calculation of the engines, he gives Watt 94 lbs. of coal to a bushel; and having stated that the Watt pumping engines in Cornwall, in 1811, averaged but thirteen and a half millions of duty, draws the false conclusion that the high-pressure cannot compete with the low-pressure where coals are dear; yet he agrees with other writers that the great increase in the duty of the Cornish pumping engines commenced from 1811 (when Trevithick first gave them his high-pressure steam); and states that in 1816 the Stray Park 63-inch cylinder single-acting engine,[111] being one of three then working in Dolcoath, did thirty-one millions.

The 'Encyclopædia Britannica' on the question of duty states:[112]—

"The duty of the best of Smeaton's engines was, in 1772, 9,450,000 foot pounds per cwt. of coal. On the expiration of Watt's patent, about the year 1800, the highest duty of his engines amounted to twenty millions, or more than double the former duty, which may represent the economical value of the improvement effected by Watt under his various patents.

"The reported duty of Cornish pumping engines, by the consumption of 94 lbs. of coals, rose from an average of nineteen millions and a half, and a maximum of twenty-six millions in 1813, to an average of sixty millions and a maximum of ninety-six millions in 1843. It is necessary to bear in mind the distinction between the duty of a bushel of coal and 112 lbs."

Here, also, are the same general facts as to the duty of the Watt engine, and the marked and rapid increase of duty dating from Trevithick's Dolcoath engines in 1811; but the confusion and even contradictions in the statements prove how little the subject was understood.

"A rough draft, prepared by Mr. Edmonds on Trevithick's return from America, dated 1828, for an application to Parliament for remuneration to Trevithick, says, 'That this kingdom is indebted to your petitioner for some of the most important improvements that have been made in the steam-engine.

"'That the duty performed by Messrs. Boulton and Watt's improved steam-engines in 1798, as appears by a statement made by Davies Gilbert, Esq., and other gentlemen associated for that purpose, averaged only fourteen millions and a half (pounds of water lifted 1 foot high by 1 bushel of coal), although a chosen engine of theirs under the most favourable circumstances lifted twenty-seven millions, which was the greatest duty ever performed till your petitioner's improvements were adopted, since which the greatest duty ever performed has been sixty-seven millions, being much more than double the former duty. That, prior to the invention of your petitioner's boiler, the most striking defect observable in every steam-engine was in the form of the boiler, which in shape resembled a tilted waggon, the fire being applied under it, and the whole being surrounded with mason work. That such shaped boilers were incapable of supporting steam of a high pressure or temperature, and did not admit so much of the water to the action of the fire as your petitioner's boiler does, and were also in other respects attended with many disadvantages. That your petitioner's invention consists principally in introducing the fire into the midst of the boiler, and in making the boiler of a cylindrical form, which is the form best adapted for sustaining the pressure of high steam.

"'That the following very important advantages are derived from this your petitioner's invention. This boiler does not require half of the materials, nor does it occupy half the space required for any other boiler. No mason work is necessary to encircle the boiler.'"

"'That, had it not been for this your petitioner's invention, those late vast improvements which have been made in the use of steam could not have taken place, inasmuch as none of the old boilers could have withstood a pressure of above 6 lbs. to the inch beyond the atmosphere, much less a pressure of 60 lbs. to the inch, and is capable of standing a pressure of above 150 lbs. to the inch.'"

Trevithick's retrospect views of 1828 are supported by the letter of the late Michael Williams, M.P., the most experienced of Cornish mine workers, but belonging to the eastern district that had been for many years the users of the Watt engines in Cornwall.

"In reference to his great improvements in the steam-engine, I have a more particular recollection, and can confidently affirm that he was the first to introduce the high-pressure principle of working, thus establishing a way to the present high state of efficiency of the steam-engine, and forming a new era in the history of steam power. To the use of high-pressure steam, in conjunction with the cylindrical boilers, also invented by Mr. Trevithick, I have no hesitation in saying that the greatly-increased duty of our Cornish pumping engines, since the time of Watt, is mainly owing; and when it is recollected that the working power now attained amounts to double or treble that of the old Boulton and Watt engine, it will be at once seen that it is impossible to overestimate the benefit conferred, either directly or indirectly, by the late Mr. Trevithick on the mines of this county. I have often expressed my opinion that he was at the same time the greatest and the worst-used man in the county."[113]