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WATT, JAMES (1736-1819)
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See also:WATT, See also: Steam, at a pressure scarcely greater than that of the See also:atmosphere, was admitted to the under See also:side; this allowed the See also:piston to be pulled up by a counterpoise at the other end of the beam. Communication with the See also:boiler was then shut off, and the steam in the cylinder was condensed by injecting a See also:jet of See also:cold water from a cistern above. The pressure of the See also: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 See also:pipe leading down into a well. Watt at once noticed that the alternate See also: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 See also: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 See also:attempt at a remedy was to use for the material of the cylinder a substance that would take in and give out heat slowly. See also: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 See also:sake of making a See also:good vacuum under the piston, a specially large quantity of injection water was supplied. He then entered on a scientific examination of the properties of steam, studying by experiment the relation of its See also: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 See also:low as possible, too° F. or See also: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 conditions were incompatible, and it was not for some months that Watt saw a means of reconciling them. Early in 1765, while walking on a See also:Sunday afternoon in Glasgow See also:Green, the See also:idea flashed upon him that, if the steam were condensed in a See also:vessel distinct from the cylinder, it would be practicable to make the temperature of condensation low, and still keep the cylinder hot. Let this See also: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, whenevercommunication 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 See also:condenser, but the temperature of the metal of the cylinder would remain high, since no injection water need See also:touch it. Without delay Watt put this idea to the test, and found that the separate See also:con-denser did See also:act as he had anticipated. To maintain the vacuum in it he added another new See also:organ, namely, the air-See also:pump, the See also:function of which is to remove the condensed steam and water of injection along with any air that gathers in the condenser. To further his See also:object of keeping the cylinder as hot as the steam that entered it, Watt supplemented his See also:great invention of the separate condenser by several less notable but still import-See also:ant improvements. In Newcomen's engine a layer of water over the piston had been used to keep it steam-tight; Watt substituted a tighter packing lubricated by oil. In Newcomen's engine the upper end of the cylinder was open to the air; Watt covered it in, leading the piston-See also:rod through a steam-tight stuffing See also:box in the See also:cover, and allowed steam instead of air to See also:press on the top of the piston. In Newcomen's engine the cylinder had no clothing to reduce loss of heat by See also:radiation and See also:conduction from its See also:outer See also:surface; Watt not only cased it in non-conducting material, such as wood, but introduced a steam-jacket, or layer of steam, between the cylinder proper and an outer See also:shell. All these features were specified in his first patent (see STEAM-ENGINE), which, however, was not obtained till January 1769, nearly four years after the inventions it covers had been made. In the See also:interval Watt had been striving to demonstrate the merits of his engine by trial on a large See also:scale. His earliest experiments See also:left him in See also:debt, and, finding that his own means were quite insufficient to allow him to continue them, he agreed that Dr John See also:Roebuck, founder of the Carron ironworks, should take two-thirds of the profits of the invention in See also:consideration of his bearing the cost. An engine was then erected at Kinneil, near See also:Linlithgow, where Roebuck lived, and this gave Watt the opportunity of facing many difficulties in details of construction. But the experiments made slow progress, for Roebuck's affairs became embarrassed, and Watt's attention was engaged by other work. He had taken to See also:surveying, and was fast gaining reputation as a See also:civil engineer. In 1767 he was employed to make a survey for a Forth and See also:Clyde See also:canal—a See also:scheme which failed to secure See also:parliamentary See also:sanction. This was followed during the next six years by surveys for a canal at Monkland, for another through the valley of Strathmore from See also:Perth to See also:Forfar, and for others along the lines afterwards followed by the Crinan and Caledonian canals. He prepared plans for the harbours of See also:Ayr, See also:Port-Glasgow and Greenock, for deepening the Clyde, and for See also:building a See also:bridge over it at See also: By this time the inventor had abandoned his civil engineering work and had settled in Birmingham, where the manufacture of steam-engines was begun by the See also:firm of Boulton & Watt. The See also:partnership was a singularly happy one. Boulton had the good sense to leave the work of inventing to Watt, in whose See also:genius he had the fullest faith; on the other See also:hand, his substantial means, his enterprise, See also:resolution and business capacity supplied what was wanting to bring the invention to commercial success. During the next ten years we find Watt assiduously engaged in developing and introducing the engine. Its first and for a time its only application was in pumping; it was at once put to this use in the mines of See also:Cornwall, where Watt was now frequently engaged in superintending the erection of engines. Further inventions were required to See also:fit it for other uses, and these followed in See also:quick See also:succession. Watt's second steam-engine patent is dated 1781. It describes five different methods of converting the reciprocating See also:motion of the piston into motion of rotation, so as to adapt the engine for See also:driving See also:ordinary machinery. The simplest way of doing this, and the means now universally followed, is by a See also:crank and See also:fly-See also:wheel; this had occurred to Watt, but had meanwhile been patented by another, and hence he devised the " See also:sun and See also:planet wheels " and other See also:equivalent contrivances. A third patent, in 1782, contained two new inventions of the first importance. Up to this time the engine had been single-acting; Watt now made it See also:double-acting; that is to say, both ends of the cylinder, instead of only one, were alternately put in communication with the boiler and the condenser. Up to this time also the steam had been admitted from the boiler throughout the whole stroke of the piston; Watt now introduced the See also:system of expansive working, in which the See also:admission See also:valve is closed after a portion only of the stroke is performed, and the steam enclosed in the cylinder is then allowed to expand during the See also:remainder of the stroke, doing additional work upon the piston without making any further demand upon the boiler until the next stroke requires a fresh admission of steam. He calculated that, as the piston advanced after admission had ceased, the pressure of the steam in the cylinder would fall in the same proportion as its See also:volume increased —a See also:law which, although not strictly true, does See also:accord very closely with the actual behaviour of steam expanding in the cylinder of an engine. Recognizing that this would cause a See also:gradual reduction of the force with which the piston pulled or pushed against the beam, Watt devised a number of contrivances for equalizing the effort throughout the stroke. He found, however, that the inertia of the pump-rods in his mine engines, and the fly-wheel in his rotative engines, served to. compensate for the inequality of thrust sufficiently to make these contrivances unnecessary. His See also:fourth patent, taken out in 1784, describes the well-known " parallel motion," an arrangement of links by which the top of the piston-rod is connected to the beam so that it may either pull or push, and is at the same time guided to move in a sensibly straight See also:line. " I have started a new See also:hare," he writes to Boulton in See also:June of that year; " I have got a glimpse of a method of causing a piston-rod to move up and down perpendicularly by only fixing it to a piece of See also:iron upon the beam, without chains or perpendicular guides or untowardly frictions, See also:arch-heads, or other pieces of clumsiness. I think it a very probable thing to succeed, and one of the most ingenious simple pieces of mechanism I have contrived." A still later invention was the throttle-valve and centrifugal See also:governor, by which the See also:speed of rotative engines was automatic-ally controlled. One more See also:item in the See also:list of Watt's contributions to the development of the steam-engine is too important to be passed without mention: the See also:indicator, which draws a See also:diagram of the relation of the steam's pressure to its volume as the stroke proceeds, was first used by Boulton & Watt to measure the work done by their engines, and so to give a basis on which the charges levied from their customers were adjusted. It would be difficult to exaggerate the part which this simple little instrument has played in the See also:evolution of the steam-engine. The eminently philosophic notion of an indicator diagram is fundamental in the theory of See also:thermodynamics; the instrument itself is to the steam engineer what the See also:stethoscope is to the physician, and more, for with it he not only diagnoses the ailments of a faulty machine, whether in one or another of its See also:organs, but gauges its See also:power in See also:health. The commercial success of the engine was not See also:long in beingestablished. By 1783 all but one of the IQewcomen pumping-engines in Cornwall had been displaced by Watt's. The mines were then far from thriving; many were even on the point of being abandoned through the difficulty of dealing with large volumes of water; and Watt's invention, which allowed' this to be done at a moderate cost, meant for many of them a new See also:lease of See also:life. His engine used no more than a fourth of the fuel that had formerly been needed to do the same work,, and the Soho firm usually claimed by way of See also:royalty a sum equivalent to one-third of the saving—a sum which must have been nearly equal to the cost of the fuel actually consumed. See also:Rival manufacturers came forward, amongst whom See also:Edward See also:Bull and See also:Jonathan See also:Carter Hornblower are the most conspicuous names. They varied the See also:form of the engine, but they could not avoid infringing Watt's patent by the use of a separate condenser. When See also:action was taken against them on that ground, they retaliated by disputing the validity of the fundamental patent of 1769. In the See also:case of Boulton es' Watt v. Bull the See also:court was divided on this point, but in an action against Hornblower the patent was definitely affirmed to be valid by a unanimous finding of the Court of See also: It is remarkable that Watt, notwithstanding the fact that his own invention of expansive working must have opened his eyes to the See also:advantage of high-pressure steam, declined to admit it into his practice. He persisted in the use of pressures that were little if at all above that of the atmosphere. His rivals in Cornwall were not so squeamish. See also:Richard Trevithick ventured as far as 12o lb on the square See also:inch, and a curious See also:episode in the history of the steam-engine is an attempt which Boulton & Watt made to have an act of parliament passed forbidding the use of high pressure on the ground that the lives of the public were endangered. The third and only other respect in which a great improvement has been effected is in the introduction of See also:compound expansion. Here, too, one cannot but regret to find the Soho firm hostile,' though the See also:necessity of defending their monopoly makes their action natural enough. Hoei~blower had in fact stumbled on the invention of the compound engine, but as his machine employed Watt's condenser it was suppressed, to be revived after some years by See also:Arthur Woolf (1766-1837). In one of his See also:patents (1784) Watt describes a steam See also:locomotive, but he never prosecuted this, and when See also: His last work was the invention of See also:machines for copying See also:sculpture
' Another narrative of the utmost interest was written by Watt in 1814 in the form of a footnote to Robison's See also:article " Steam-Engine," from the fourth edition of the See also:Encyclopaedia Britannica, which Watt revised before it was reprinted in the collected edition of Robison's works. See Robison's Mechanical Philosophy, vol. ii.
—one for making reduced copies, another for taking facsimiles by means of a See also:light stiff See also:frame, which carried a pointer over the surface of the work while a revolving See also:tool fixed to the frame alongside of the pointer cut a corresponding surface on a suit-able See also:block. We find him in See also:correspondence with See also:Sir See also:Francis See also:Chantrey about this machine not many months before his See also:death, and presenting copies of busts to his friends as the work " of a See also:young artist just entering on his eighty-third year." His life drew to a tranquil See also:close, and the end came at Heathfield on the 19th of See also:August 1819. His remains were interred in the neighbouring See also:parish See also: See also:Writing to Joseph See also:Priestley in See also:April 1783, with reference to some of Priestley's experiments, he suggests the theory that " water is composed of dephlogisticated air and phlogiston deprived of part of their latent or elementary heat." It is difficult to determine the exact meaning attached to these antiquated terms, and to say how far Watt's See also:suggestion anticipated the See also:fuller See also:discovery of See also:Cavendish. Watt's views were communicated to the Royal Society in 1783, Cavendish's experiments in 1784, and both are printed in the same volume of the Philosophical Transactions. The early and See also:middle part of Watt's life was a long struggle with poor health: severe headache prostrated him for days at a time; but as he See also:grew old his constitution seems to have become more robust. His disposition was despondent and shrinking; he speaks of himself, but evidently with unfair severity, as " indolent tc excess." " I am not enterprising," he writes; " I would rather See also:face a loaded See also:cannon than See also:settle an See also:account or make a bargain; in See also:short, I find myself out of my See also:sphere when I have anything to do with mankind." Hi. was a man of warm friendships, and has left a See also:personal memorial of the greatest interest in his numerous letters. They are full of sagacity and insight: his own achievements are told with a shrewd but extremely modest estimate of their value, and in a See also:style of remarkable terseness and lucidity, lightened here and there by a touch of dry See also:humour. In his old age Watt is described by his contemporaries as a man richly stored with the most various knowledge, full of See also:anecdote, See also:familiar with most modern See also:languages and their literature, a great talker. See also:Scott speaks of " the alert, See also:kind, benevolent old man, his talents and See also:fancy overflowing on every subject, with his attention alive to every one's question, his See also:information at every one's command." See J. P. Muirhead, Origin and Progress of the Mechanical Inventions of James Watt (3 vols., 1854; vols. I. and ii. contain a memoir and Watt's letters; vol. iii. gives a reprint of his patent specifications and other papers); Muirhead, Life of Watt (1858); See also:Smiles, Lives of Boulton and Walt; See also:Williamson, Memorials of the Lineage, &c., of James Watt, published by the Watt See also:Club (Greenock, 1856) ; Correspondence of the See also:late James Watt on his Discovery of the Theory of the Composition of Water, edited by Muirhead (1846); See also:Cowper, " On the Inventions of James Watt and his See also:Models preserved at Handsworth and See also:South See also:Kensington," Proc. Inst. Mech. Eng. (1883) ; article " Watt " in the Encyclopaedia Britannica (6th edition, 1823), by James Watt, junior; Robison, Mechanical Philosophy, vol. ii. (1822) (letters and notes by Watt on the History of the Steam-Engine). (J. A. Additional information and CommentsThere are no comments yet for this article.
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