was adopted, and a less expensive method of applying the envelope of steam was used. Other kinds of regulators were invented, and the whole mechanism of the engine was gradually improved, and these improvements have been progressive for the last twenty-one years. Some of them W. has secured by other patents, but many of the most essential he has left free, and by means of them Newcomen's engines have been improved to his loss. "It will now, it is hoped, appear to the candid that W. has not wilfully concealed his invention by a false specification, but has set forth the nature of the same, and the means of performing it. He has told what he had invented; and it could not have been expected that he should have described mechanism already known to all practitioners, or not then invented. "W.'s invention is merely a contrivance to prevent cooling the cylinder, and to make the vacuum more perfect by condensing the steam in a vessel distinct from the cylinder itself; this is the nature of the invention. The means of keeping the cylinder warm,—the substitution of the powers of steam for those of the atmosphere, of grease, &c., in place of water to keep the piston tight, and the drawing out the air, &c., by means of pumps, are merely aids in performing the principal object. This ought to be kept in view in judging of the specification; also that W. supposed it to be addressed to mechanics and philosophers, and not to the ignorant.” CHAPTER VIII. DR. BLACK'S AND PROFESSOR ROBISON'S ACCOUNT OF MR. WATT'S INTRODUCTION TO WITH regard to the model of Newcomen's engine belonging to the College of Glasgow, and which has attained so great a celebrity by the results which it was instrumental in producing, we find two entries in the records of that University: the first is as follows: "University meeting, 25th June, 1760. Mr. Anderson is allowed to lay out a sum, not exceeding two pounds sterling, to recover the steam-engine from Mr. Sisson, instrumentmaker at London.” Mr. John Anderson in 1757 succeeded Dr. Dick as Professor of Natural Philosophy in the College. The next entry concerning the model, in the same records, appears to be this:-"University meeting, 10th June, 1766. An account was given in by Mr. James Watt for repairing and altering the steam-engine, with copper pipes and cisterns, amounting to 57. 11s. The said machine being the property of the College, and having been in such a situation that it did not answer the end for which it was made, the Principal is appointed to grant a precept for payment of the said account, which is to be stated upon the fund for buying instruments to the College." This, it will be remembered, was after the idea of the separate condenser had "occurred," which was "early in 1765;" and by the repairs and alterations of the "copper pipes and cisterns" of the machine, its fault of not answering the end for which it was made, had in all probability been effectually corrected. That interesting little model, as altered by the hand of Watt, and preserved in all safety and honour within the precincts of its ancient birth-place, had been appropriately placed beside the noble statue of the Engineer, in the Hunterian Museum. But on revisiting the College of Glasgow in January, 1854, we found that it had been placed among the apparatus attached to the Natural Philosophy Lecture-room, where, it was alleged, it had dwelt nearly a century ago. None of the different accounts which thus remain to us of the date of this, Mr. Watt's greatest invention, fix the precise day on which, to use Dr. Black's happy expression, "this capital improvement flashed on his mind at once, and filled it with rapture.” According to Robison's recollection, thirty-one years afterwards, it was somewhere about 1765. Dr. Black, writing after the same interval of time, states it as having been "in the beginning of the year 1765." Mr. Watt himself, in his notes on Robison, says early in 1765;" and the nearest approximation we can make, from other documentary evidence, to any more precise date, is, that it must have been previous to the 29th of April in that year, as on that day Mr. Watt writes to his friend Dr. Lind, "I have now almost a certainty of the facturum of the fire-engine, having determined the following particulars: the quantity of steam produced; the ultimatum of the lever engine; the quantity of steam destroyed by the cold of its cylinder; the quantity destroyed in mine: and if there is not some devil in the hedge, mine ought to raise water to 44 feet with the same quantity of steam that theirs does to 32, (supposing my cylinder as thick as theirs,) which I think I can demonstrate. I can now make a cylinder of 2 feet diameter and 3 feet high only a 40th of an inch thick, and strong enough to resist the atmosphere; sed tace. In short, I can think of nothing else but this machine. I hope to have the decisive trial before I see you. Write me to-morrow what you are about, and if any part of what you have to tell me concerns the fire-engine.” INTRODUCTION TO DR. ROEBUCK. 79 "His mind," says Dr. Black, "became now very much employed in contriving the machinery by which this improvement might be reduced to practice; and he soon planned it to such a degree that he thought he was ready to make an experiment on a large scale. But here he was stopped by the want of funds; and he found it necessary to associate himself with some person who had money and spirit for such an undertaking, and to participate with him the advantages which might be derived from this invention. He addressed himself to the late Dr. Roebuck, whose spirit for enterprise and improvement in arts was very well known, and the Doctor accordingly received with zeal the opportunity offered to him. A small engine was soon built in one of the offices of Kinneil House, near Borrowstoness, where various trials were made, and some difficulties surmounted, so as to give satisfaction. "I must add that I was as much upon a footing of intimate friendship with Dr. Roebuck as with Mr. Watt. The Doctor, too, had no small degree of mechanical knowledge and ingenuity; and was well qualified to perceive and value the talents of Mr. Watt. He had also much experience in the use of common steam-engines, which he employed in working his colliery. He was withal ardent and sanguine in the pursuit of his undertakings, and was therefore a fortunate associate for Mr. Watt. Mr. Watt was a valetudinarian, more or less, ever since I knew him; and his mind was liable to be too much depressed by little cross accidents, or by the necessity of a greater expense than he had foreseen; whereas the Doctor was undaunted on such occasions, and roused Mr. Watt to disregard expense, and to double his exertions, until the difficulty was overcome. But Mr. Watt was the sole inventor of the capital improvement and contrivance above mentioned. I remember very well that it cost me several reasonings and conversations to inform the Doctor fully of the nature of steam, of the great quantity of heat, and, consequently, of fuel necessary to produce it, and of the importance, therefore, of preventing the waste of it.” "I was very unfortunate," says Robison, "in two visits I made to Glasgow during that summer; Mr. Watt being from home, once at Greenock, seeing his father, who was ill, and the other time on a survey for a canal. When I came to town for the winter, I found that Mr. Watt was again from home, and that he was deeply engaged with his engine. His situation in life made it imprudent to engage in great expenses, and he was obliged to look out for an associate. Most fortunately there was in the neighbourhood such a person as he wished,-Dr. Roebuck, a gentleman of very uncommon knowledge in all the branches of civil engineering familiarly acquainted with the steam-engine, of which he employed several in his collieries, and deeply interested in this improvement. He was also well accustomed to great enterprises, of an undaunted spirit, not scared by difficulties, nor a niggard of expense. Such a man was indispensably necessary to one of Mr. Watt's character;-modest, timid, easily frightened by rubs and misgivings, and too apt to despond I do not know who pointed him out to Mr. Watt. He was well acquainted with Mr. Watt's talents, and admired them. I believe the connection was very soon formed. Dr. Black and all Mr. Watt's friends were At this time I had not happy at seeing so fair a commencement. the pleasure of being known to Dr. Roebuck." *** "I believe that Dr. Black was the chief means of forming the connection between Mr. Watt and Dr. Roebuck; and I recollect most distinctly his saying to me, that Watt would have some difficulty in managing Dr. Roebuck, who at that time had not become a complete convert to the doctrine of latent heat. Accordingly, it was so; and Mr. Watt was obliged to yield for some time to the Doctor's confidence in his own great experience. The Doctor thought to produce the condensation, with sufficient rapidity and accuracy, by a very extensive surface; and Mr. Watt knew that it also required a great quantity of water, or other matter, to receive the emerging heat. I know that these differences of opinion retarded the completion of the engine. "But Dr. Roebuck had too much judgment not to see the |