a Mylne,* a Herschell,† a Deluc, a Ramsden,§ a Robison,|| a Murdock, a Rennie, a Cum

preparatory to the Trigonometrical Survey, and of other papers connected therewith, in the Transactions of the Royal Society, from 1777 to 1790. He bore testimony to the advantages and originality of Mr. Watt's inventions, before the Committee of the House of Commons, in 1775.-TR.

* Mr. Robert Mylne, the architect of Blackfriars Bridge, a structure of deserved celebrity, both for its elegance and the art employed in its construction, also gave evidence on the same occasion, as he did afterwards in the trials in the Court of Common Pleas in 1792 and 1796. He was one of the original Members of the Society of Civil Engineers, was extensively employed in that profession, and directed the Water-works of the New River Company. At his hospitable board at New River Head, Mr. Boulton and Mr. Watt were welcome guests, and the cares of law and business were forgotten in his cheerful society and that of his delightful family. See an excellent life of him in Chalmers' Biographical Dictionary, vol. XXII. ed. 1815.-TR.

+ Of the great astronomer, Dr., afterwards Sir William Herschell, it would be superfluous for us to speak. The voice of posterity has confirmed the admiration and fame awarded him by his contemporaries.-TR.

J. A. de Luc, Reader to Queen Charlotte, a distinguished Genevese philosopher, and author of several works on geology and meteorology. Mr. Watt, on his visits to the metropolis, was in the habit of passing some days at Windsor with these two celebrated men, with whom he lived on terms of the greatest intimacy.-Tr.

§ Jesse Ramsden, the well-known optician and mathematical instrument maker. A man of strong and original genius, with whom Mr. Watt often discoursed on the subjects of his first pursuits.-TR.

|| Dr. John Robison, Professor of Natural Philosophy in the University of Edinburgh, an eminent mathematician, and one of the most scientific mechanical philosophers of the last or any other age. We have already given an early instance of his regard for and attachment to Mr. Watt. It continued through life, and was warmly felt and reciprocated. Upon the occasion of the last trial in the Common Pleas, although suffering under an acute disorder, he hastened to town to give his evidence upon the invention of the separate condenser, which had been confided to him at the time it was made. To show that we have not exaggerated Dr. Robison's merits as a

ming,* a More,† a Southern, eagerly hastened to sustain, before the Judges, the rights of persecuted genius. Perhaps, also, it were proper to add, as a singular feature in the history of the human mind, that some of the barristers,-(I would here have the prudence to beg it to be observed, that I am speaking only of the barristers of a neighbouring country,)—that barristers, to whom malice is wont to ascribe a luxuriant superfluity of words, reproached Watt, against whom a formidable array of them had been retained, with having invented nothing but ideas. This, I may just mention, brought upon them, in presence of the Bench, this apostrophe of Mr. Rous :-" Go, gentlemen, and philosopher, we subjoin the following testimony of the most competent witness. Mr. Watt, in one of his private letters in our possession, dated 7th February 1805, thus writes-" It was with great concern that I learnt, the other day, the death of my worthy friend Professor Robison. He was a man of the clearest head and the most science of anybody I have known, and his friendship to me ended only with his life, after having continued nearly half a century."-TR.

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* Mr. Alexander Cumming, F.R.S., an ingenious mathematician and mechanician, the author of " Elements of Clock and Watch-work adapted to Practice," a "Dissertation on the Influence of Gravitation, considered as a Mechanic Power," and a treatise on "The Destructive Effects of the Conical Broad Wheels of Carriages, with the Improving Effects of Cylindrical Wheels of the same breadth, as they regard the Roads, the labour of Cattle, &c." This was a subject on which he bestowed much ingenuity, and which made a great sensation at the time. He also constructed a magnificent organ for the Earl of Bute.-TR.

+ Mr. Samuel More, many years Secretary to the Society of Arts in the Adelphi, a good mechanician, and a gentleman well skilled in the history of all inventions relative to the arts. Of the other gentlemen named in the text, we shall have occasion to speak hereafter. They formed but a portion of the men of science and engineers who came forward to give their evidence on the occasion in question.—TR.

F

approach this intangible substance, as you are pleased to call it, this pretended abstract idea; -you will be crushed like flies, and leave no trace of your existence !"*

* In the Proceedings in Error in the cause Boulton and Watt v. Hornblower and Maberly, Mr. Gaselee argued the writ for the plaintiffs in error, and Mr. Holroyd for the defendants. This was in Michaelmas term 1798; and in Hilary term 1799, it was directed by the Court to be again argued, "not," as Lord Kenyon observed, "because it was not extremely well argued the last term," but because it involved some points of great novelty, nicety, and importance to the law. This was accordingly done by Mr. Serjeant Le Blanc for the plaintiffs in error, and by Mr. Rous for the defendants, when the Court expressed a unanimous and clear opinion, vindicating and establishing the rights of the patentees. Lord Kenyon was Chief Justice; the other Judges were Ashurst, Grose, and Lawrence.

The arguments of the Judges were printed at great length, along with those in the cause Boulton and Watt v. Bull; Mr. Rous' speech appeared in a separate pamphlet, and, as the opening of it indicates and overthrows the principal argument insisted on by the counsel for the opposite parties, and is, besides, most forcibly and justly expressed, we make no apology for citing it here.

"When I state to the Court, that a very large sum to the individual will depend on the issue of this cause; when I suggest that, in my humble opinion, no patent can stand, if the reasoning on which this is impeached shall be adopted by the Court; I only mean to claim the patient attention of your Lordships, and to offer an apology for myself, if I should deviate, in a case of much novelty, from the ordinary course of legal argument. Can it be seriously contended that the invention of Mr. Watt, which, during the space of nearly thirty years, has been admired by all Europe as the greatest practical advance ever made in the arts, is a mere abstract discovery in science? Can that which, with a single bushel of coals, will raise a foot high thirty millions of pounds weight, or six thousand hogsheads of water; which has brought into subjection to man, and submitted to his use, a power more than double the force of gunpowder; which has taught a beam, moving with this mighty force, to act as the pendulum of a clock, and keep pace with other clocks through the day; can these operations be performed by a mere abstract idea, neither tangible nor vendible? If these gentlemen were to approach this intangible substance, as they are pleased to call

The persecutions which a man of feeling encounters, where the strictest justice entitled him to expect unanimous testimonies of gratitude, seldom fail to dishearten him, and to sour his temper. Watt's naturally happy disposition was not proof against such severe trials. Seven long years of litigation had excited in him a feeling of indignation, which occasionally vented itself in strong expressions; "We have been so beset by plagiaries," writes he to his friend Dr. Black, “that if I had not a very good memory of my doing it, their impudent assertions would lead me to doubt whether I was the author of any improvements on the steam-engine; and the ill-will of those we have most essentially served, whether such improvements have not been highly prejudicial to the commonwealth."

Watt, though keenly irritated, was not discouraged. His engines were at first, like Newcomen's, only simple pumps, mere instruments of exhaustion. In a few years, he converted them into agents applicable to all purposes, and of an unlimited power. His first approximation to this end, was the formation of the double engine.

To understand the principle on which it acts, let me refer to the modified engine,* of which I have already spoken. (See p. 66.) The cylinder is closed; the external air gains no admission into

it, with the same ignorance of what it is, with which they discourse upon it, they would probably be crushed like flies, and leave no trace of their existence !"-TR.

* Mr. Watt's Single Engine.-Tr.

it; it is the pressure of the steam, and not that of the atmosphere, which makes the piston descend; it is simply by a counterpoise that the ascending movement is brought about; for, at the time when this movement takes place, the steam being allowed to circulate freely between the top and the bottom of the cylinder, presses upon the piston equally in both opposite directions. It is thus evident to all, that the modified engine, like Newcomen's, has no real power but during the downward stroke of the piston.

A very slight change will alter this, and furnish us with the double engine. In the engine known by this appellation, as in that which I have called the modified engine, the steam of the boiler, at the will of the engineer, is readily admitted above the piston, and impels it without any obstruction, since, at the same moment, the lower chamber of the cylinder is in communication with the condenser. This movement once completed, and a particular cock being opened, the steam issuing from the boiler can only enter the cylinder below the piston, which it raises up; the upper steam which had produced the descending movement, then finds its way into the condenser, where it is liquefied, and with which it has, in its turn, an uninterrupted communication. Turning the cock in the contrary direction, restores all the parts to their original position, as soon as the piston is at the top of its ascent. In this way, the same effects may be repeated any number of times. The moving-power, as you see, is here exclu