JAMES WATT was born at Greenock, Scotland, in the year 1736. At the age of sixteen he was apprenticed to an optician, so called, a person wh..—" byturns a cutler and a whitesmith, a repairer of fiddles, and a tuner of spinets"—tendered his humble ingenuity in any heterogeneous offices for which it might be required. With him Watt remained but two years, and then to London, where he obtained employment from a regular mathematical instrument-maker. His health, however, becoming impaired, he remained in London little longer than twelve months, and returning to his native town commenced business on his own account, both there and at Glasgow, at which latter place he was desirous to settle. After experiencing some difficulties, this object was at length effected, and he obtained, through the management of some friends, the appointment of mathematical instrument-maker to the University of Glasgow, and a room was assigned to him in which he could carry on his work. Here it was that his mind became first engaged upon the subject of the steam-engine ; and we quote his own words in describing the even; which has since become so interesting.
"My attention," he writes, "was first directed in 1769 to the subject of steam-engines, by Dr. Robison, then a student in the University of Glasgow, and nearly of my own age. Robison at that time threw out the idea of applying the power of the steam-engine to the moving of wheel-carriages, and to other purposes; but the scheme was not matured, and was soon abandoned on his going abroad.
" In 1761 or 1762 I made some experiments on the force of steam in a Papin's Digester, and formed a species of steam-engine, by fixing upon it a syringe, one-third of an inch in diameter, with a solid piston, and furnished also with a cock to admit the steam from the digester, or shut it off at pleasure, as well es to open a communication from the inside of the syringe to the open air, by which the steam contained in the syringe might escape. When the com munication between the cylinder and digester was opened, the steam entered the syringe, and by its action upon the piston, raised a considerable weight (fifteen pounds,) with which it was loaded. When this was raised as high as was thought proper, the communication with the digester was shut, and that with the atmosphere opened ; the steam then made its escape, and the weight descended. The operations were repeated ; and though in this experiment the sock was turned by hand, it was easy to see how it could be done by the machine itself, and make it work with perfect regularity. But I soon relinquished
the idea of constructing an engine upon this principle, from being sensible it would be liable to some of the objections against Savery's engine ; namely, from the danger of bursting the boiler, and the difficulty of making the joints tight ; and also that a great part of the power of steam would be lost, because no vacuum was formed to assist the descent of the piston." The experiments thus commenced were stopped by other avocations connected with his business, and his attention became necessarily diverted from the itirther prosecution of the inquiry for a period of many months. In the year 1763-4 the model of a steam-engine belonging to the natural-philosophy class was placed in his hands to repair, and his mind once more recurred to the neglected subject. Whilst engaged upon this little model, he remarked the prodigious loss of steam from the condensation caused by the cold surface of the cylinder, and also the great quantity of heat which is contained in a very minute quantity of water, when in the form of elastic steam. When a quantity of water is heated several degrees above the boiling point in a close digester, if • hole be opened the steam rushes out with great violence, and in three or four seconds the heat of the remaining water is reduced to the mere boiling point. The steam thus wasted would, under condensation, yield but a few drops of water, and yet these carry off with them the whole excess of heat from the water in the digester. Mr. Watt at once saw that to economise the heat thus wasted became a matter of the first importance. The cylinder of his little apparatus could be heated in one instant to such a temperature, that it could not be touched by the hand ; but before a vacuum could be made, it required to be cooled by the injection water, and was then to be heated again by the re-entrance of the steam. This could not happen unless the heat was abstracted from the steam, which must occasion the condensation and waste of a considerable portion. Two points of inquiry were at once raised : what was the exact portion of steam thus wasted, and what material could be substituted for that of the expe rimental cylinder, which would transmit the heat more slowly.