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had carried into practice six years before is likely, although Switzer appears to consider that they invented the whole. In the history of arts and sciences there have been many cases of apparent coincidence of inventions, of which, the theory of fluxions, bringing into opposition the great names of Newton and Leibnitz, forms the most illustrious instance.

“The way of leathering the piston,” says Desaguliers, “ was found by accident about 1713; having then screwed a

large broad piece of leather to the piston, which turned up “ the sides of the cylinder two or three inches; in working, “ it wore through, and cut that piece from the other; which,

falling flat on the piston, wrought with its edge to the cylinder, and, having been in a long time, was worn very

narrow; which being taken out, they had the happy dis“covery whereby they found, that a bridle-rein, or even a “ soft thick piece of rope or match going round, would make " the piston air and water-tight.”*

Probably, also, the further packing of the piston by the ingenious method of a stratum of water resting on its plate, was discovered by accident. Its use led directly to a further invention of great importance, and even some elegance :—“One thing is very remarkable ; as they at first were

working, they were surprised to see the engine go several “strokes, and very quick together, when after a search they “ found a hole in the piston, which let the cold water in to “ condense the steam in the inside of the cylinder, whereas “ before they had always done it on the outside.” † And hence followed the substitution of the rose-head, to inject a shower of cold water through the interior of the cylinder before each descent of the piston, instead of the application of cold from without; in the first engine in which the injection was introduced into the cylinder, the water appears to have spurted straight up from the end of the injectionpipe. To obtain regularity of the injection, “ they used to “ work with a buoy in the cylinder inclosed in a pipe, which

buoy rose when the steam was strong, and opened the in“jection, and made a stroke; thereby they were capable of only giving six, eight, or ten strokes in a minute, till a boy, “ Humphry Potter, who attended the engine, added (what he “ called scoggan) a catch that the beam always opened, and “ then it would go fifteen or sixteen strokes in a minute. “ But this being perplexed with catches and strings, Mr. “ Henry Beighton, in an engine he had built at Newcastle

+

Desaguliers, vol. ii. p. 533,

# Ibid,

on-Tyne in 1718, took them all away, the beam itself “ simply supplying all much better.”*

Thus, then, by many successive stages had at last been formed a machine in which steam,—to use the figure of speech imputed to Sir Samuel Moreland,—had been reduced to weight, measure, and balance; but which could scarcely yet be said with truth to conduct itself very peaceably, or “like “ the best horses," under the various burthens it was intended to bear. For, although it certainly contrived to do a good deal of work, yet it did it in a fashion which was provokingly clumsy, imperfect, and irregular; it would not always move when ordered to do so, nor stop when its progress became dangerous ; in the hands of those unaccustomed to attend, to feed, to clean, to water, and to exercise it, it would astonish the beholders by snorting wildly, rearing badly, and kicking viciously; it would break even its harness of chains, notwithstanding the “bridles” and “martingales” by which it was curbed; or again, when urged to go at a gallop and exhibit its best racing pace, it would sometimes take a fancy to spite its jockey, move even more sluggishly, work more feebly, and perhaps settle the unprofitable struggle by coming at last to a dead halt.

" It is now brought to very great perfection,” writes Dr. Desaguliers, who would fain have had the credit of improving it beyond all the devices imagined by Lord Worcester, Savery, Newcomen, Cawley, and any others who might have had a hand in the Great Machine; “I shall show," quoth he, " that Captain Savery's method is not unuseful in many

cases, especially when it is changed into the very simple engine that I have reduced it to, which I shall also de“scribe.” Yet this very perfect and simple engine was apt to have all the faults we have enumerated above: its original cost, also, was not small, and its appetite for fuel was voracious. This last might indeed be called its favourite weakness ; for each time that the piston was raised, the cylinder had to be filled with steam, and was therefore heated to an equal degree; while, each time that the steam was condensed in order that the piston might fall, and a stroke be made, the cylinder was cooled down in proportion, and fresh heat, or in other words, more fuel, was wasted in recovering the steamheat proper for the next rise of the piston. This consideration, although of comparatively small consequence in collieries, “where the power of the fire is made from the refuse “ of the coals, which would not otherwise be sold,” was practically sufficient to exclude the use of the engine from any application to manufacturing purposes, in localities remote from a cheap supply of coal. Such being the state of the Fire-Engine at the middle of the last century, it is not surprising that although many persons had become observant of its performances, few were much enamoured of them; that its real utility was neither very great nor widely extended; that its economy was in most cases questionable; and that numbers of mines and collieries were left undrained of the floods which had inundated them, because the proprietors would not risk the doubtful remedy involved in the purchase of one of those machines.

* Desaguliers, as above.

The names of Amontons and Dalesme, which have sometimes been included in the history of the steam-engine at the epoch of Savery and Papin, we need scarcely do more than barely mention. The “Fire-wheel of the former, of date 1699, of which an elaborate description, with engravings, is given in the · Mémoires de l'Académie des Sciences' for that year, and also in Leupold's Theatrum Machinarum,' 1724, (Tab. 53, fig. 2), is a complicated apparatus, depending for its action more on the expansion of heated air than on steam, And of M. Dalesme's project, which bears the date of 1705, the only record that remains appears to be the following, contained in the Hist. de l'Académie des Sciences' for that

year, and quoted by Prony :-“M. Dalesme laid before the Society

“ some ideas which it was thought might prove useful, and “ be deserving of the outlay requisite for experiments on a “ large scale. His notion is, that the force of the steam which “ rises from boiling water might be employed as a moving “power : he has shown by a machine in which that force “ alone made water spout to a great height, how powerful it " is.” M. Prony suggests that M. Dalesme's model might still be found to exist in the collection of machines belonging to the Academy; but it seems never to have made its appearance again. The effect described might evidently have been produced by something not more deserving the name of a machine than the hollow ball and tube of De Caus.

The improvements of Smeaton on Newcomen’s, or the atmospheric engine, (as it was called from the pressure of the atmosphere on the piston being the moving power in the downward stroke), are the last to which we are here called on to allude before entering on the consideration of those of Watt. In getting engines erected, Smeaton was so much baffled and annoyed by the irregularity and insufficiency of their work, arising often from the bad proportions of their parts, that he constructed a small experimental engine, not above four horses' power, from which he deduced a valuable table of the proportions of the parts and of their relative performance; the experiments are said to have been made about the year 1765, although Smeaton did not proceed to build large engines in accordance with the results obtained, till nine years afterwards; soon after which he designed several, some of them of more than a hundred horse power, in which it was admitted that there was a considerable saving of fuel,-equal in some cases to one-third of the previous consumption. But those were not in existence at the period of Watt's life to which we must now attend ; and even the table we have spoken of was not published by its author, but was found after his death among his papers, now in the possession of the Royal Society.

CHAPTER XIII.

DR. ROEBUCK HIS HISTORY - CARRON IRON-WORKS BORROWSTONESS

INTRODUCTION TO MR, WATT PROGRESS OF THE NEW STEAM-ENGINES TESTUDO BOILER DIFFICULTIES WITII CYLINDER AND PISTON PLATECONDENSER CIRCULAR STEAM-ENGINE OR STEAM-WHEEL - - DR. ROEBUCK'S EMBARRASSMENTS - MR. WATT'S LAND-SURVEYING AND CIVILENGINEERING -HIS VISIT TO SOHO INTRODUCTION TO DR. SMALL RENEWED EXPERIMENTS PROPOSALS OF PARTNERSHIP WITH MR. BOULTON PATENT OF 1769.

FROM the narratives of both Dr. Black and Dr. Robison, it is apparent that, next to the inventor himself, the person at first most deeply interested in the mechanical and commercial success of the invention, the origin of which has now been so fully detailed, was Dr. Roebuck, an ingenious and enterprising man, whose ultimate want of success in life ill rewarded his fondness for practical science, and his energetic exercise of very considerable talents and industry. It seems indeed a singular fatality, that even his early connection with the greatest invention of his age, full of future profit as it promised to be, and narrowly as we now see that it failed to realise that hope to him, was not only of no ultimate service to his own fortunes, but had nearly cut short the progress of the invention itself; which was long submerged, and wellnigh altogether lost, in the financial wreck in which his affairs became involved.

For the best account of the life and pursuits of the gentleman who was thus destined to become the temporary though unsuccessful associate of Mr. Watt in his important scheme, the public are indebted to the pen of the late venerable Professor Jardine, of Glasgow College. From a biographical notice which he communicated to the Royal Society of Edinburgh, and which is published in their Transactions,* we find

* Trans. R. S. E.,' iv. p. 65, 1796.

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