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412 W A T A T present the best known of his numerous writings. It was most effective in its clay ; in ours Christianity would hardly be attacked or defended by the arms employed by either disputant. Undismayed by the displeasure of the court, or perhaps hoping to overcome it, Watson continued to exert his pen with vigour, and in general to good purpose, denouncing the slave trade, advocating the union with Ireland, and offering financial suggestions to Pitt, who seems to have frequently consulted him. In 1798 his Address to the People of Great Britain, enforcing resistance to French arms and French principles, ran through fourteen editions, but estranged him from many old friends, who accused him, probably with injustice, of aiming to make his peace with the Government. In 1807 the advent of a Whig ministry almost brought the coveted preferment within reach. Had Dr Markham died a few months sooner Watson would have been archbishop of York. Such a disappointment might palliate the querulous strain of his conversation and published references to himself, though it could not render it dignified or decorous. De Quincey, however, who knew the bishop personally in his latter years, while severely criticizing his complaints, allows that his temper had not been soured by disappoint ment. " His lordship was a joyous, jovial, and cordial host." He died on July 2, 1816, having occupied his latter years in the composition and revision of an autobio graphy, which, with all its egotism and partiality, is a valuable work, and the chief authority for his life. As an advocate of liberal principles in church and state, Watson stands almost alone among the prelates of his day ; and it cannot be said that his longing for preferment, violent and unbecoming as it was, seduced him into mean actions or unworthy compliances. His character is high enough to make it cause for regret that it should stand no higher, as it easily might if he had possessed a nicer sense of dignity and had not measured success so exclu sively by the attainment of wealth and station. Hard-headed and pushing, he yet had an intellectual conscience ; the two main ele ments of his character stood in each other s way : he failed as a courtier, and did not leave a wholly unblemished reputation as a patriot. As a bishop he neither was nor endeavoured to be anything ; as an ecclesiastical statesman it was his misfortune to have been born fifty years too soon. His massive but unoriginal intellect is justly characterized by De Quincey as "robust and commonplace." (R. G.) WATT, JAMES (1736-1819), the inventor of the modern condensing steam-engine, was born at Greenock on the 19th of January 1736. His father was a small merchant there, who lost his trade and fortune by unsuc cessful speculation, and James was early thrown on his own resources. Having a taste for mechanics he made his way to London, at the age of nineteen, to learn the business of a philosophical-instrument maker, and became apprenticed to one Morgan, in whose service he remained for twelve months. From a child he had been extremely delicate, and the hard work and frugal living of his London pupilage taxed his strength so severely that he was forced at the end of a year to seek rest at home, not, however, until he had gained a fair knowledge of the trade and become handy in the use of tools. Before going to London he had made acquaintance with some of the professors in Glasgow college, and on his return to Scotland in 1756 he sought them out and obtained work in repairing astrono mical instruments. JHe next tried to establish himself as an instrument maker in Glasgow, but the city guilds would not recognize a craftsman who had not served the full term of common apprenticeship, and Watt was forbidden to open shop in the burgh. The college, how ever, took him under its protection, and in 1757 he was established in its precincts with the title of mathematical- instrument maker to the university. Before many months Black, the discoverer of latent heat, then lecturer on chemistry, and Ilobison, then a student, afterwards professor of natural philosophy, became his intimate friends, and with them he often discussed the possibility of improving the steam-engine, of which at that time Newcomen s was the most advanced type. The engine was then applied only to pumping water, chiefly in the drainage of mines ; and it was so clumsy and wasteful of fuel as to be but little used. Some early experiments of Watt in 1761 or 1762 led to no positive result, but in 1764 his attention was seriously drawn to the matter by having a model of Newcomen s engine, which formed part of the college collection of scientific apparatus, given him to repair. Having put the model in order, he was at once struck with its enormous consumption of steam, and set himself to examine the cause of this and to find a remedy. In Newcomen s engine the cylinder stood vertically under one end of the main lever or " beam " and was open at the top. Steam, at a pressure scarcely greater than that of the atmosphere, was admitted to the under side ; this allowed the piston to be pulled up by a counterpoise at the other end of the beam. Communication with the boiler was then shut off, and the steam in the cylinder was condensed by injecting a jet of cold water from a cistern above. The pressure of the air on the top of the piston then drove it down, raising the counterpoise and doing work. The injection water and condensed steam which had gathered in the cylinder were drained out by a pipe leading down into a well. Watt at once noticed that the alternate heating and cooling of the cylinder in Newcomen s engine made it work with tedious slowness and excessive consumption of steam. When steam was admitted at the beginning of each stroke, it found the metal of the cylinder and piston chilled by contact with the condensed steam and cold injection water of the previous stroke, and it was not until much steam had been condensed in heating the chilled surfaces that the cylinder was able to fill and the piston to rise. His first attempt at a remedy was to use for the material of the cylinder a substance that would take in and give out heat slowly. Wood was tried, but it made matters only a little better, and did not promise to be durable. Watt observed that the evil was intensified whenever, for the sake of making a good vacuum under the piston, a specially large quantity of injection water was supplied. He then entered on a scientific examination of the pro perties of steam, studying by experiment the relation of its density and pressure to the temperature, and concluded that two conditions were essential to the economic use of steam in a condensing steam-engine. One was that the temperature of the condensed steam should be as low as possible, 100 F. or lower, otherwise the vacuum would not be good ; the other was, to quote his own words, " that the cylinder should be always as hot as the steam which entered it." In Newcomen s engine these two con ditions were incompatible, and it was not for some months that Watt saw a means of reconciling them. Early in 1765, while walking on a Sunday afternoon in Glasgow Green, the idea flashed upon him that, if the steam were condensed in a vessel distinct from the cylinder, it would be practicable to make the temperature of condensation low, and still keep the cylinder hot. Let this separate vessel be kept cold, either by injecting cold water or by letting it stream over the outside, and let a vacuum be maintained in the vessel. Then, whenever communication was made between it and the cylinder, steam would pass over from the cylinder and be condensed ; the pressure in the cylinder would be as low as the pressure in the con denser, but the temperature of the metal of the cylinder would remain high, since no injection water need touch it.

Without delay Watt put this idea to the test, and found