the true conclusion to be drawn from Priestley's experiment, and in a letter to that philosopher, dated 26th April 1783, expressed himself as follows:-"Let us consider what obviously happens in the case of the deflagration of the inflammable and dephlogisticated air. These two kinds of air unite with violence, they become red hot, and, upon cooling, totally disappear. When the vessel is cooled, a quantity of water is found in it equal to the weight of the air employed. This water is then the only remaining product of the process; and water, light, and heat, are all the products. Are we not then authorised to conclude that water is composed of dephlogisticated air and phlogiston, deprived of their latent or elementary heat; that dephlogisticated or pure air is composed of water deprived of its phlogiston, and united to elementary heat and light; that the latter are contained in it in a latent state, so as not to be sensible to the thermometer or to the eye; and if light be only a modification of heat, or a circumstance attending it, or a component part of the inflammable air, then pure or dephlogisticated air is composed of water deprived of its phlogiston and united to elementary heat?"

of

This document the first known assertion in writing of the fact that water is a composition of oxygen and hydrogen (dephlogisticated and phlogisticated air) was communicated by Dr Priestley to various scientific men in London, and a copy it was sent to Sir Joseph Banks, president of the Royal Society, to be read at a meeting of that body. Circumstances prevented the paper from being read, and in all probability it lay, with the other papers of the Society, in the hands of the secretary, Sir Charles Blagden. Nearly nine months passed, when, on the 15th of January 1784, a paper, communicated by the celebrated Mr Cavendish, was read before the Society. In this paper the experiment of burning oxygen and hydrogen in a close vessel is described; and the conclusion stated, that in the process the two gases were converted into water. Later in the same year, a paper of the great French chemist Lavoisier was published, parts of which had been read before the Academy of Sciences in November and December 1783; and in this paper the same conclusion of the composition of water from oxygen and hydrogen is explicitly stated. On the publication of these conflicting claims, a controversy naturally arose as to who was the real discoverer of the new truth-the rival claimants being Mr Cavendish and M. Lavoisier. Mr Cavendish stated that he had made the experiment of burning the two gases so early as 1781, and that he had mentioned it verbally to Dr Priestley; he does not say, however, whether, at the time of mentioning it to Dr Priestley, he had come to the grand conclusion, nor does he state at what time he first came to that conclusion. So far, therefore, this evidence, admitted to its full extent, only amounts to a declaration that Mr Cavendish early repeated Mr Warltire's experiment. The only indication given by Mr Cavendish as to

the precise time at which he formed the important conclusion capable of being drawn from the experiment, is contained in a further statement, that " a friend of his, in the summer of 1783, gave some account of his experiments to M. Lavoisier, as well as of the conclusion drawn from them, that dephlogisticated air is only water deprived of its phlogiston." The person here alluded to as having told Lavoisier of the discovery made by Cavendish is Sir Charles Blagden, already named as the secretary of the Royal Society, and who was a very intimate friend of Mr Cavendish. Sir Charles corroborates Mr Cavendish's statement, and distinctly avers that he communicated the grand conclusion to Lavoisier in the summer of 1783. Lavoisier, on the other hand, assumes the conclusion as his own, and states that Sir Charles Blagden's communication consisted in a mere intimation to him, while engaged in his experiments, that Mr Cavendish had already performed similar ones, and as the result "had obtained from the burning of inflammable air a very sensible quantity of water." Sir Charles Blagden and Lavoisier, therefore, flatly contradict each other: Lavoisier stating that, in the summer of 1783, he was engaged in experiments which led to the momentous conclusion; Sir Charles declaring that, in that summer, he announced the conclusion to Lavoisier, as having already been drawn by Mr Cavendish. Admitting, as most favourable to the claims of Mr Cavendish, Sir Charles Blagden's statement, this would amount only to a proof that Mr Cavendish had arrived at the conclusion previous to the summer of 1783. Were this true, it would establish the precedency of Mr Cavendish over Lavoisier in respect of the discovery. The question would still remain, however, between Mr Cavendish and Mr Watt. Mr Watt, we have already seen, had expressed the conclusion on paper as early as the 26th of April 1783; the question now would be, on the most favourable terms to Mr Cavendish, at what time previous to the summer of 1783 he had arrived at the conclusion. On this point Sir Charles Blagden's statement is less distinct. "During the spring of 1783," he says, "Mr Cavendish showed us that he had necessarily deduced from his experiments the conclusion that oxygen is nothing else than water deprived of its phlogiston. About the same time the news reached Birmingham, that Mr Watt of Birmingham had been led by some observations to a similar conclusion." Here it may be necessary to remind our readers, that Mr Watt's letter containing the announcement of the conclusion must in all probability have been put into the hands of Sir Charles Blagden at the time it was intended to be read before the Society.

Clearly the whole weight of the evidence goes to prove, that whatever may have been the merits of Mr Cavendish and M. Lavoisier, and the degree of originality in their inquiries with regard to the point at issue, Mr Watt stands before them both, as having been the first person who expressed in writing his

belief that water was a compound of two gases. It may also be mentioned, that Mr Watt, although he took no public part in the controversy, never renounced his claim to be considered the original author of the discovery, for the honour of which Cavendish and Lavoisier were contending.

Mr Watt, in a visit to Paris in 1786, undertaken for the purpose of inspecting the waterworks at Marly, met, among other Frenchmen of scientific celebrity, the chemist Berthollet, who had just discovered the valuable bleaching properties of chlorine. This discovery he communicated to Mr Watt, through whose means, accordingly, the process of bleaching by chlorine was introduced into this country; his father-in-law, Mr Macgregor, being the first to apply it on a large scale. Another subject in which Mr Watt took much interest, was the administration of the various gases for medical purposes. In short, besides his distinction as an engineer and inventor, Mr Watt sustained, by the universality of his acquirements, the general character of a British man of science.

MR WATT'S RETIREMENT FROM BUSINESS-HIS DEATH-
PERSONAL HABITS AND CHARACTER.

Mr Watt's various patents expired in the year 1800. In that year, therefore, he withdrew entirely from business, leaving his share in the Soho establishment to his sons, James and Gregory; the latter of whom, his son by the second marriage, was cut off in 1804, at the early age of twenty-seven, after giving evidence of very great literary and scientific talent. Mr Watt survived this event about fifteen years-years spent in ease and retirement, and in the enjoyment of that genial social intercourse for which he always exhibited so great a relish. The activity of his mind during this retirement will be illustrated by the following anecdote, related by M. Arago :-"A water company in Glasgow had established, on the right bank of the river Clyde, great buildings and powerful machines, for the purpose of conveying water into every house in the town. When the works were completed, it was discovered that, on the other side of the river, there was a spring, or rather a kind of natural filter, which abundantly supplied water of a very superior quality. To remove the works was now inexpedient; but a question arose as to the practicability of drawing the water from wells on the left bank, by means of the pumping-engines then existing on the right bank, and through a main-pipe to be carried by some means across the river. In this emergency Watt was consulted; and he was ready with a solution of the difficulty. Pointing to a lobster on the table, he showed in what manner a mechanist might, with iron, construct a jointed tube which would be endowed with all the mobility of the tail of the crustacea. He accordingly proposed a complete jointed conduit-pipe, capable of bending and applying itself to all the inflections, present and

future, of the bed of a great river-in fact, a lobster-tail of iron, two feet in diameter, and a thousand feet in length. He soon after furnished plans in detail, and drawings; and the design was executed for the Glasgow Water-Company with the most complete success."

The last years of the life of the great engineer present few incidents worthy of notice. His health, which was extremely delicate in his youth, and liable to be affected by violent headaches, to which he was subject, improved as age advanced, and his decline was calm and happy. "He preserved," says Lord Jeffrey, "up almost to the last moment of his existence, not only the full command of his extraordinary intellect, but all the alacrity of spirit and the social gaiety which had illuminated his happiest days. His friends in this part of the country never saw him more full of intellectual vigour and colloquial animationnever more delightful or more instructive, than in his last visit to Scotland in the autumn of 1817. Indeed it was after that time that he applied himself, with all the ardour of early life, to the invention of a machine for mechanically copying all sorts of sculpture and statuary—and distributed among his friends some of its earliest performances, as the productions of a young artist just entering on his eighty-third year."

Watt died at Heathfield, in Staffordshire, on the 25th of August 1819, in his eighty-fourth year; and was buried in the parish-church of Handsworth, where a monument to his memory, with a marble statue by Chantrey, was erected by his son, Mr James Watt. A second statue, by the same artist, was presented by his son to the college of Glasgow. Greenock, as the birthplace of Watt, has likewise a statue of her most illustrious son; and, not to mention others, the finest production of Chantrey's chisel is the colossal one of Watt in Westminster Abbey, bearing an inscription from the pen of Lord Brougham.

The task of describing the general demeanour of Watt, and of summing up his character, has happily been performed by one able to do it justice—his friend Lord Jeffrey.

"Independently of his great attainments in mechanics, Mr Watt was an extraordinary, and in many respects a wonderful man. Perhaps no individual in his age possessed so much and such varied and exact information-had read so much, or remembered what he had read so accurately and well. He had infinite quickness of apprehension, a prodigious memory, and a certain rectifying and methodising power of understanding, which extracted something precious out of all that was presented to it. His stores of miscellaneous knowledge were immense, and yet less astonishing than the command he had at all times over them. It seemed as if every subject that was casually started in conversation with him, had been that which he had been last occupied in studying and exhausting; such was the copiousness, the precision, and the admirable clearness of the information which

he poured out upon it without effort or hesitation. Nor was this promptitude and compass of knowledge confined in any degree to the studies connected with his ordinary pursuits. That he should have been minutely and extensively skilled in chemistry and the arts, and in most of the branches of physical science, might, perhaps, have been conjectured; but it could not have been inferred from his usual occupations, and probably is not generally known, that he was curiously learned in many branches of antiquity, metaphysics, medicine, and etymology, and perfectly at home in all the details of architecture, music, and law. He was well acquainted, too, with most of the modern languages, and familiar with their most recent literature. Nor was it at all extraordinary to hear the great mechanician and engineer detailing and expounding, for hours together, the metaphysical theories of the German logicians, or criticising the measures or the matter of the German poetry.

"His astonishing memory was aided, no doubt, in a great measure, by a still higher and rarer faculty-by his power of digesting and arranging in its proper place all the information he received, and of casting aside and rejecting, as it were instinctively, whatever was worthless or immaterial. Every conception that was suggested to his mind seemed instantly to take its place among its other rich furniture, and to be condensed into the smallest and most convenient form. He never appeared, therefore, to be at all incumbered or perplexed with the verbiage of the dull books he perused, or the idle talk to which he listened; but to have at once extracted, by a kind of intellectual alchemy, all that was worthy of attention, and to have reduced it for his own use to its true value, and to its simplest form. And thus it often happened that a great deal more was learned from his brief and vigorous account of the theories and arguments of tedious writers, than an ordinary student could ever have derived from the most faithful study of the originals-and that errors and absurdities became manifest from the mere clearness and plainness of his statement of them, which might have deluded and perplexed most of his hearers without that invaluable assistance.

66 It is needless to say that, with those vast resources, his conversation was at all times rich and instructive in no ordinary degree; but it was, if possible, still more pleasing than wise, and had all the charms of familiarity, with all the substantial treasures of knowledge. No man could be more social in his spirit, less assuming or fastidious in his manners, or more kind and indulgent towards all who approached him. He rather liked to talk, at least in his later years; but though he took a considerable share of the conversation, he rarely suggested the topics on which it was to turn, but readily and quietly took up whatever was presented by those around him, and astonished the idle and barren propounders of an ordinary theme by the treasures which he drew from the mine they had unconsciously opened. He