WATT, JAMES, mechanician, engineer, and man of science, famous as the improver, and almost the inventor of the steam-engine, was born at Greenock, in Scotland, Jan. 19, 1736. His father was a blockmaker and general merchant at Greenock, was long a member of the council of that burgh, and for. a time a magistrate. Two members of James Watt's family—his grandfather and his uncle—had had some local reputation for scientific or engineering ability. The former was a teacher of mathematics, surveying, and navigation at Crawfordsdyke, near Greenock; the latter practiced as a land-surveyor and engineer with great success at Ayr. The grandfather, Thomas Watt, had been brought early in life to Lanarkshire from the neighborhood of Aberdeen, where his family had previously lived. The father of Thomas Watt, the great-grandfather of James, is said to have farmed a little property of his own in Aberdeenshire, and to have been killed while fighting on the side of the Covenanters against the marquis of Montrose.
James Watt was very weakly as a child, and being unable to go to school with regu larity, he became, to a great extent, his own instructor. What schooling he did get, he got in the schools of his native town. He early manifested a turn for mathematics and calculations, and a great interest in machines, and accordingly—his father's business,' for which lie had been destined, having greatly declined—he was, at the age of 18, sent to London. to learn the trade of a mathematical instrument maker. III-health compelled him In return home about a year after: but he had made good use of his opportunities in London; and on his health improving, he resolved to set up as a mathematical instru ment maker in Glasgow. The incorporation of ha mmermen of that city put difficulties in his way; but the authorities of the university took him by the hand, appointed him mathematical instrument maker to the university, and gave him the use of premises within their precincts. He occupied these premises from 1757 to 1763. They seem to have been badly situated for his business, for which, moreover, at that time there was but little room in Glasgow; and Watt during those years was scarcely able, to make a living. In 1763 he got a place of business in the town, and after that he did somewhat better; still, lie had to eke out his income by making or mending fiddles (which lie was able to do, though he had no car for music), or doing any mechanical job which came in his way; and no work requiring ingenuity or the application of scientific knowledge seems to have come amiss to him. At length, in 1767, he fell upon a new and a more lucrative occupation. In that year he was employed to make the surveys and prepare the estimates for a canal projected to unite the Forth and the Clyde. This work could not be carried out at the time, because It failed to obtain the sanction of parliament; but Watt had now made a beginning as a civil engineer, and henceforth he got a good deal of employment in this capacity. He made surveys for various canals, for the improve ment of the harbors of Ayr, Port-Glasgow, and Greenock, and for the deepening of the Forth, the Clyde, and other rivers. One of the tasks committed to him was to decide whether a projected canal between time firth of Clyde and the Western ocean should be made by way of Crinau or of Tubed; and the last—also the greatest—undertaking of this kind on which he was employed was a survey for a canal between fort William and Inverness; a work which has since been executed on a greater scale by Telford. In his surveys, he made use of a new micrometer, and of a machine, also of his own invention; for drawing in perspective—the latter of which appears to have been for several years about this time one of his sources of income. The reports which he drew up in the capacity of engineer are said to have been remarkable for perspicuity and accuracy.
Living in the college at Glasgow, in constant intercourse with the professors of the university, with access to books; and with much unemployed time ou his hands—hav ing, too, a great love of knowledge, and a lively interest in novelties— Watt had been a diligent student of science, and experimenter in the application of science to the arts. As early as 1759 his attention had been directed to the capabilities of
steam as a motive-force by Mr. Robison (q.v.), afterward professor of natural philos ophy in tho university of Edinburgh, who was then a student in Glasgow. It had occurred to Mr. Robison that steam-pressure might be used to propel wheeled-carriages; but it does not appear that either Watt or he attempted to carry out this idea. In 1761 or 1762, however, Watt made a series of experiments on the force of steam, using a Papin's digester. These do not seem to have led to any results; and it was not till the winter of 1763-64 that lie began the investigations which ended in his improvement of the steam-engine. During that winter model of the Newcomen engine, kept for the use of the natural philosophy class in the college, was sent to him to be put in repair. Watt quickly found out what was wrong with the model, and easily put i It into order. But in doing this he became greatly impressed with the defects of the machine, and with the importance of getting rid of them. The Newcomer engine (see STEAM-ENGINE) was still but little used and only for pumping- water out of mines. It was a cumbersome machine, and it required so much fuel that expense of working it had restricted, and must always have restricted its use. was not a steam-engine at all. It was worked by means of the atmospheric pressure ; steam being only used in producing by its condensation,, a vacuum in a cylinder, into which—the vacuum made--a piston was depressed by the pressure i of the air. The steam issuing from a boiler was admitted into the cylinder until It filled it, when the supply was cut off by a self-acting cock; and then the steam was condensed in the cylinder. by means of a jet of water. The water so greatly cooled the cylinder that the greater part of the steam at each stroke of the piston was wasted in heating its walls; and on the other hand, much of the injected water was heated to the boiling-point., and gave off steam which resisted the descent of the piston. Watt found that about four-fifths of the steam, and' consequently of the fuel, was wasted; and he asw that to make time machine work economically two apparently incompatible con ditions must be obtained—first, that the walls of the cylinder constantly be of the Mile temperature as the steam which came in contact with d mem; and second, that the injected water must never be heated up to 100', the po m iling-pot in vacuo. He now. experimented upon the conducting power of substances, and made trial of a cylinder made of wood steeped in oil; but with this cylinder, though it cooled less rapidly than a metallic one, there was still far too much waste 'of steam. Constantly, from the end of 1763, occupied with the subjecto f steam, lie at length, early in 1765, hit upon the expedient which solved all his difliculti'es—t le separate condenser, an air. exhausted vessel, into which the steam should admitted from the cylinder and there once p condensed, The separate condenser at one prevented the loss of steam in the cylinder which had arisen in the process of condensation; and there was no difficulty in keeping it cool, so as to prevent the undue heating of the injection-water. lie had now got a perfectly economical engine on principle, but he did not rest content with this--he resolved to make steam his motive-power. Closing the cylinder at both top and bottom, and connecting the piston with the beam, to which it was to communicate motion, by a piston-rod passing through a stuffing-box, he admitted the steam by suitable valves alternately above and below the piston, to push it downward and upward in turn; and this done, his invention was substantially complete. He had at last made a real steam capable of being worked with a comparatively small expenditure of fuel, and of yielding any desired amount of power. Comparing his invention with the atmospheric engine of Newcoinen, it must be admitted that it is not without justice that the popular voice has awarded him the name of inventor of the steam-engine.