414 W A T W A T from their customers were adjusted. It would be difficult to ex aggerate the part which this simple little instrument has played in the evolution of the steam-engine. The eminently philosophic notion of an indicator diagram is fundamental in the theory of thermodynamics ; the instrument itself is to the steam-engineer what the 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 organs, but gauges its power in health. The commercial success of the engine was not long in being established. By 1783 all but one of the Newcomen 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 lease of 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 royalty a sum equivalent to one-third of the saving a sum which must have been neai ly equal to the cost of the fuel actually consumed. Rival manufacturers came forward, amongst whom Bull and Hornblower are the most conspicuous names. They varied the form of the engine, but they could not avoid in fringing Watt s patent by the use of a separate condenser. When action was taken against them on that ground, they retaliated by disputing the validity of the fundamental patent of 1769. In the case of Boulton and Watt v. Bull the court was divided on this point, but in an action against Hornblower the patent was definitely affirmed to be valid by a unanimous finding oif the Court of King s Bench. This was in 1799, only a year before the monopoly ex pired, but the decision enabled the firm to claim a large sum as arrears of patent dues. In connexion with these trials Watt him self, as well as his early friends Black and Robison, drew up narratives of the invention of the steam-engine, which are of much interest to the student of its history. 1 Before Watt s time the steam-engine was exclusively a steam- pump, slow-working, cumbrous, and excessively wasteful of fuel. His first patent made it quick in working, powerful, and efficient, but still only as a steam-pump. His later inventions adapted it to drive machinery of all kinds, and left it virtually what it is to day, save in three respects. In respect of mechanical arrangement the modern engine differs from Watt s chiefly in this, that the beam, an indispensable feature in the early pumping-engines, and one which held its place long after the need for it had vanished, has gradually given way to more direct modes of connecting the piston with the crank. Another difference is in the modern use of high-pressure steam. It is remarkable that Watt, notwithstanding the fact that his own invention of expansive working must have opened his eyes to the 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. Trevithick ventured as far as 120 E6 on the square inch, and a curious episode in the history of the steam-engine is an attempt which Boulton and 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 compound expansion. Here, too, one cannot but regret to find the Soho firm hostile, though the necessity of defending their monopoly makes their action natural enough. Hornblower 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 Woolf. In one of his patents (1784) Watt describes a steam-locomotive, but he never prosecuted this, and when Murdoch, his chief assistant (famous as the inventor of gas-light ing), made experiments on the same lines, Watt gave him little encouragement. The notion then was to use a steam-carriage on ordinary roads ; its use on railways had not yet been thought of. When that idea took form later in the last years of Watt s life, the old man refused to smile upon his offspring ; it is even said that Watt put a clause in the lease of his house that no steam-carriage should on any pretext be allowed to approach it. On the expiry in 1800 of the Act by which the patent of 17G9 had been extended, Watt gave up his share in the business of engine-building to his sons, James, who carried it on along with a son of Boulton for many years, and Gregory, who died in 1804. The remainder of his life was quietly spent at Heathfield Hall, 2 his house near 1 Another narrative of the utmost interest was written by Watt in 1814 in the form of a footnote to Robison s article "Steam-Engine," from the fourth edition of the Encyclopedia Britannica, which Watt revised before it was reprinted in the collected edition of Robison s works. See Robison s Mechanical Philosophy, vol. ii. 2 His workroom at Heathfield (now in the possession of Mr Birmingham, where he devoted his time, with scarcely an interruption, to mechanical pursuits. His last work was the invention of machines for copying sculpture, one for making reduced copies, another for taking facsimiles by means of a light stiff frame, which carried a pointer over the surface of the work while a revolving tool fixed to the frame alongside of the pointer cut a corresponding surface on a suitable block. We find him in correspondence with Chantrey about this machine not many months before his death, and presenting copies of busts to his friends as the work " of a young artist just entering on his eighty-third year." His life drew to a tranquil close, and the end came at Heathfield on the 19th of August 1819. His remains were interred in the neighbouring parish church of Handsworth. Watt was twice married, first in 1763 to his cousin Miss Miller, who died ten years later. Of four children born of the marriage, two died in infancy; another was James, who succeeded his father in business ; the fourth was a daughter who lived to maturity, but died early, leaving two children. His second wife, Miss Macgregor, whom he married before settling in Birmingham in 1775, survived him ; but her two children, Gregory and a daughter, died young. Some of Watt s minor inventions have been already noticed. Another, which has proved of great practical value, was the letter- copying press, for copying manuscript by using a glutinous ink and pressing the written page against a moistened sheet of thin paper. He patented this in 1780, describing both a roller press, the use of which he seems to have preferred in copying his own corre spondence, and also the form of screw press now found in every merchant s office. In the domain of pure science Watt claims recognition not only as having had ideas greatly in advance of his age regarding what is now called energy, but as a discoverer of the composition of water. Writing to Priestley in 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 suggestion anticipated the fuller discovery of Cavendish. Watt s views were communicated to the Eoyal Society in 1783, Cavendish s experiments in 1784, and both are printed in the same volume of the Philosophical Transactions. The early and 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 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 to excess." " I am not enterprising," he writes ; " I would rather face a loaded cannon than settle an account or make a bargain ; in short, I find myself out of my sphere when I have anything to do with mankind." He was a man of warm friendships, and has left a personal memorial of the greatest interest in his numerous letters to Dr Small and others. 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 style of remarkable terseness and lucidity, lightened here and there by a touch of dry humour. In his old age Watt is described by his contemporaries as a man richly stored with the most various knowledge, full of anecdote, familiar with most modern languages and their literature, a great talker. Scott speaks of "the alert, kind, benevolent old man, his talents and fancy overflowing on every subject, with his attention alive to every one s question, his information at every one s com mand." See J. P. Mulrhead, 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.liii. gives a reprint of his patent specifications and other papers) ; Mulrhead, Life of Watt, 1858 ; Smiles, Lives of BouUon and Watt ; Williamson, Memorials of the Linea/je, &c., of James Watt, published by the Watt Club, Greenock, 185G; Corre spondence of the late James Watt on his Discovery of the Theory of the Composition of Water, edited by Muirhead, 184(i ; Cowpcr, " On the Inventions of James Watt and his Models preserved at TIamlsworth and South Kensington," Proc. Inst. Mech. Eng., 1883; article "Watt" in the Encyctopxdia Britannica, Cth 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. E.) WATTEAU, ANTOINE (1684-1721), French painter, was born at Valenciennes in 1684. Thrown on his own resources at an early age, the boy went moneyless and Tangye) has been preserved full of his tools and models of his inven tions. These are described, along with other Watt relics now at South Kensington, in an interesting paper by Mr E. A. Cowper, Proc. Inst,
Mech. Enrj., Nov. 1883.