derful engine are everywhere visible. Steam navigation, railway travelling, automatic factory labour, steam printing, mining, and hundreds of other arts, have been brought to their present state only by means of Watt's discoveries. In its adaptation to mills and factories, steam is doubtless more costly than waterpower; but, being independent of situation or seasons, it is in general circumstances preferable. Its placid steadiness, and the ease with which it may be managed, are also great recommendations in its favour. As a motive power in the arts, steam takes the lead of all others, and, viewing it as an economiser of labour, it must assuredly be pronounced the stay of Britain—the saviour of the country from universal ruin.

The steam-power at present employed in Great Britain and Ireland is equal to about 8,000,000 of men's power, or 1,600,000 horse-power. It is calculated that a horse requires eight times the quantity of soil for producing food that a human being does; if, therefore, horse-power were made to supersede steam-power, additional food for 1,600,000 horses would require to be raised, which would be equal to the food of 12,800,000 men.

It is in consequence of the improved mechanical arrangements, and employment of inanimate forces in Great Britain, that that comparatively small country is enabled to manufacture goods cheaper, and with greater profit, than can be done by the largest and most populous countries in which mechanism is imperfect, and labour performed exclusively by living agents.

The profits of manufactures so produced spread their beneficial influence over the whole mass of society, every one being less or more benefited. Thus, almost all the luxuries and comforts of life, all the refinements of social existence, may be traced to the use of tools and machinery. Machinery is the result of mechanical skill, and mechanical skill is the result of experience and a long course of investigation into the working of principles in nature, which are hidden from the inattentive observer. Much of the present mechanical improvement is also owing to the pressure of necessities, or wants, which have always a tendency to stimulate the dormant powers of man. What are to be the ultimate limits and advantages of mechanical discoveries no one can foresee. The investigation of natural forces is yet far from being finished. Every day discloses some new scientific truth, which is forthwith impressed into the service of mankind, and tends to diminish the sum of human drudgery and suffering. In this manner, therefore, are we usefully taught that the study of nature forms a never-failing source of intellectual enjoyment, and that "KNOWLEDGE IS POWER."

MISCELLANEOUS INVENTIONS OF WATT-HIS CONCERN WITH THE DISCOVERY OF THE COMPOSITION OF WATER.

Although it is with the steam-engine that Watt's name is immortally associated, his inventive genius was displayed in various

contrivances totally unconnected with it. Residing in Birmingham, in the receipt of an ample income from the establishment of which he was a partner-left at liberty, by the superintendence which Mr Boulton exercised over the commercial part of the business, to devote his time to his own proper department, that of invention—and interrupted only by the calls which his lawsuits against those who pirated his machines made upon his patienceWatt was able to maintain an acquaintance with all that was taking place in the scientific world, and to take an interest in all kinds of researches and experiments. Accordingly, besides being the author of the machine now, with some modifications, used in all writers' offices for copying letters; of the plan also in common use for heating buildings by steam; and of an instrument capable yet of being brought to great perfection for multiplying copies of busts and pieces of sculpture; all of which inventions he was led to make by the interest which he took in the arts in general, Mr Watt is now ascertained, by very good evidence, to have been connected in a more direct and intimate manner than perhaps any one else, with that grand discovery of modern chemistry-the composition of water. As it is only of late years that the connexion of Mr Watt with this discovery has been sufficiently investigated, a short account of it, drawn up from the statements of Lord Brougham and M. Arago, who have had the principal share in proving Watt's claims, will not be out of place.

Air and water were, until about the middle of last century, regarded as simple bodies, or, according to the ancient language, elements. It was at length shown, however, by various inquirers, the principal of whom were Black, Cavendish, and Priestley, that air was not a simple substance, but a compound of two gases. Still no one thought that the same thing might be true of water; and water continued to pass for a simple body after the compound nature of atmospheric air was demonstrated. In the year 1781, however, Mr Warltire, a chemist, observed that when an electric spark was passed through a mixture of hydrogen gas (then called inflammable or phlogisticated air) and common atmospheric air, a deposit of dew took place on the sides of the vessel, which dew was found to be water. The same result occurred when the vessel contained a mixture of hydrogen gas (phlogisticated air) and oxygen (dephlogisticated air). Priestley, in 1782-3, repeated Warltire's experiment, but discovered the additional important circumstance, that the weight of the water deposited on the sides of the vessel in which the detonation of the oxygen and hydrogen took place was precisely equal to the joint weight of the two gases. This result Priestley communicated to his friend Mr Watt, as well as to the Royal Society, in a paper dated the 21st of April 1783. Mr Watt, who had long been interested in the subject, and who had for sometime entertained the idea that possibly air was but a modification of water or steam, instantly seized

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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?"

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 сору of 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