ter, as well as his high character, will repel the supposition that he was influenced by any private feeling, we shall call to his support the testimony of another witness."

The illustrious chemist, Baron Berzelius,* a living professor of the science which he adorns, has borne a still stronger testimony to the claims of Mr. Watt-stronger only, however, in so far as that, while he has expressed it as his clear conviction that Mr. Watt arrived at his conclusions eight months earlier than Cavendish,Cavendish could scarcely have been ignorant of those conclusions when he wrote his paper on air. On the ground, however, that different chemists of the Phlogistic school attached different meanings to the word phlogiston, M. Berzelius has blamed M. Arago for substituting the term hydrogen for phlogiston, and he goes on expressly to say, that if we translate the quotation from Mr. Watt's paper into the language of the Antiphlogistic Chemistry, Mr. Watt's conclusion is indisputable. Now, this criticism would have been just, if M. Arago had merely guessed at the meaning which Watt affixed to his own terms; but the question is not what meaning, or what varieties of meaning did the phlogistic writers attach to the term phlogiston? It is what meaning did Mr. Watt attach to it when he wrote his paper? Mr. Watt himself tells us this in language which cannot be mistaken,f and we have already shewn that Cavendish himself understood Mr. Watt as attaching this meaning to the terms which he employed.

It would be a work of supererogation to muster in detail the long list of authorities which might be added to those we have adduced. Our limits indeed would not permit us; but as it has been asserted by one of Cavendish's advocates, that Mr. Watt did not in his lifetime put forward a distinct claim to the discovery of the theory of the composition of water; and by another, that Cavendish was "universally regarded, and has continued to be regarded as the sole author of this great discovery," it is necessary to reply briefly to these allegations. The published correspondence of Mr. Watt is an answer to the first, and we have no doubt that our readers will ask no farther information with respect to the second, than is contained in the following statement by Mr. Muirhead.

"Nicholson," says he, "in his preface to the translation of Fourcroy, published in 1788, says: 'Mr. Watt has therefore a claim to the merit of a discoverer with regard to the composition of water, and has the advantage of priority in the discovery of its decomposition.' The

* Berzelius," Jahres-Bericht über die Fortschritte der Physischen Wissenschaften." -II. Heft, pp. 43-51. Tübingen, 1841.

+ Mr. Muirhead has adduced eight distinct passages from Mr. Watt's writings to prove this. Vol. i. p. 14,

same statement is repeated in his chemical Dictionary, in 1795; although in both places Mr. Cavendish also is called a discoverer. In the excellent article on Water, in the third edition of the Encyclopædia Britannica, published in 1797, it is distinctly said- With respect to Mr. Watt, we think it appears that he was the first person who formed the true theory.' In the translation of the fifth edition of Fourcroy, published with numerous valuable notes, by the late Dr. John Thomson of Edinburgh, the very learned translator has supplied the undue omission of his author;- It is but justice,' he says, 'to add that the same inference had been made by Mr. Watt, and communicated by him in a letter to Dr. Priestley, dated April 26, 1783. See Phil, Trans. Vol. lxxiv. p. 330. Lord Brougham, writing in the Edinburgh Review in 1803, ably stated, for the first time, the opinion to which his early studies had led him, and which the additional inquiries of nearly half a century have so materially confirmed, viz. that some ingenious men, particularly Mr. Watt, reasoning from all these facts, 'concluded that this fluid is a compound of the two airs, deprived, by their union, of a considerable portion of their latent heat; the quantity, viz, which is necessary for maintaining the elastic state.' In Dr. Thomas Thomson's Chemistry, 1804, 1807, and Murray's Chemistry, 1806, 1819, while the independence of Mr. Cavendish is maintained, the priority is assigned to Mr. Watt. Dr. Dalton, in his New System of Chemical Philosophy,' in 1810, says, that the composition and decomposition of water were ascertained; the former by Watt and Cavendish, and the latter by Lavoisier and Meusnier.' In his history of the Royal Society also, published in 1812, Dr. Thomas Thomson says, after having mentioned Cavendish's paper, Mr Watt had previously drawn the same conclusion from the experiments of Dr. Priestley and Mr. Warltire.'

6

"All of these statements excepting the last were made during the life of Cavendish, who died in 1810; and the whole of them were made in the lifetime of Watt, who died, as is well-known, in 1819 and also in that of Blagden, who died in the following year."*

When such reckless assertions as that which we have been combating are brought to the support of a failing cause, and when anonymous writers scatter their insinuations in order to weaken the argument of their opponents, or to strengthen their own, controversy must become personal, and discreditable to science. We have ever thought that it is only a scientific man that can judge aright in a scientific controversy, and that it is only an original inquirer who has anticipated others in discovery, and been himself anticipated, who can deal justly and tenderly with those great questions which involve the reputation of a philosopher, and affect the glory of his country. Such a man has a personal interest in the honest adjudication of scientific disputes.

To these authorities given by Mr. Muirhead, we may add that of Dr. Ure in the Art. WATER of his Dictionary of Chemistry. Lond. 1821. Both Mr. Watt and Cavendish receive from him their due meed of praise.

The case which he tries may be his own. His devotion to the science which he cultivates will consecrate its judgment-seat and hallow its responses; and in the truth and purity of its history, he will seek to embalm his verdict. An alien in the republic of letters cannot administer its laws. A pleader without its vernacular tongue cannot cross-question its witnesses. Hence do we exclude ourselves and all our anonymous craft from the bench of judicial science, and we call upon the Faradays, the Berzeliuses, the Liebigs, and the Dumas to eject us and occupy our place.

We have been led into these observations, by observing that the personalities in this controversy are already thickening into a cloud which must burst upon some devoted head: The friends of Mr. Watt in England have shown no desire to trench upon the just rights of Cavendish, or to cast a suspicion upon his character. Dr. Black, Dr. Robison, Dr. Henry, have all given him, what others have considered his due, the credit of making Mr. Watt's hypothesis a great physical truth. They have acknowledged the priority of his experiments to the full extent that it has been proved, without abating their conviction of the priority of Mr. Watt's conclusions. Had this priority been admitted, Cavendish's reputation would have experienced no defalcation from its amount-no eclipse of its brightness. But rejected as it has been with contumely, and with allegations unfounded, and reproachful, feelings of reprisal have been excited, and the good name of Cavendish and Sir Charles Blagden have been subjected to an ordeal which may either purify or destroy them.

In referring to the friends of Mr. Watt in England, we, of course, mean to exclude M. Arago, who has introduced into his Eloge very severe allusions to the persons who he supposed had been parties to the extraordinary errors of date, which marked the memoirs both of Watt and Cavendish. As the functionary of a great European Institute, M. Arago was called upon as a duty to write an Eloge of one of its members, and was therefore entitled to take a bolder and a stronger position than might have been justifiable by a private friend. We are of opinion that the language which he used upon that subject was too strong, and the suspicion too grave; but the prolonged discussion of the subject has brought out facts which do not contradict M. Arago's reprehensions, but which must make every friend of science dread the possibility that there may have been corruption in her councils, and treason in her camp.

The theory of the composition of water which Mr. Watt communicated to the Royal Society in 1783, has been characterized by Mr. Harcourt as "an erroneous speculation," and his views previous to the publication of Cavendish's paper, as "vague and wavering to a degree scarcely comprehensible to those who have not studied the ideas prevalent at that period of chemical his

tory," while an anonymous writer in still bolder phrase styles the same theory unprofitable and worthless! If there be any foundation for these charges and still more, if they be true, why disturb the serenity of science by any discussion respecting their priority? Let Mr. Watt enjoy his claim to be their author, and his friends will be satisfied with the concession. They can have no anxiety about the truth or worth of a theory which the members of the Royal Society received with high approbation, and which Black, and Robison, and Henry, and Berzelius, and Dumas have accepted as a great chemical truth-which Cavendish has in express terms stated to be the same as his own, with only an apparent difference, and which living chemists of high name, Professor Graham, of University College, for example, have shown to be exactly similar to those entertained by the most distinguished philosophers of the present day.

The friends of Mr. Watt have not thus dealt with the labours of Mr. Cavendish. We have admitted the originality and the value of Mr. Cavendish's experiments; we have regretted the severity of Mr. Arago's judgment, while we have expressed our dread lest it should be sound. We would willingly have avoided any public reference to it, but as M. Arago has pronounced it anewas M. Dumas has adopted it implicitly, and as the whole question is now submitted to the decision of the living chemists of Europe, and to the stern award of posterity, we must not shrink from the inquiry, however tender be the ground, and however hazardous its disclosures. We are therefore constrained to address the following sunimary to the jury of our readers.

Before April 1781, Macquer, Priestley, and Warltire, observed the remarkable fact, that pure water was deposited on the sides of a glass vessel in which a mixture of common and inflammable air was burned, or was fired by the electric spark. In July 1781, Cavendish, who was cognizant of their experiments, repeated them, and obtained the same result, and mentioned this result to Priestley. If the experiment involved the theory, then Cavendish was anticipated in the discovery by the three chemists whom we have named. If the experiment did not involve the theory, and if Cavendish drew from it in 1781, the conclusion that water was a compound body, he neither mentioned this conclusion to Priestley, nor to any of his friends, but kept it locked up in his own mind till the Spring of 1783, (if we admit the vague testimony of Blagden) when he communicated the longkept secret to him and to his particular friends in the Royal Society, that water was composed of the two exploded gases. But as not one of these friends came forward in their lifetime, when the question was agitated, to confirm the statement of Blagden, we must hold that statement to be inadmissible evidence. Supposing, however, that they had all borne the same

*

general testimony, a conversation said to have taken place in Spring by one of the listeners, might have become the end of Spring, or the beginning of Summer with others. Nay, the evidence of Cavendish's particular friends might have placed the conversation posterior to the date of Mr. Watt's paper! But independently of this view of the subject, conversations, and still more conversations with particular friends, cannot be received as fixing the date of a discovery under any circumstances, and still less when the opposite claims rest upon written or printed testimony. The 15th of January 1784, is therefore the true date of Cavendish's conclusions, and this would receive great support from the testimony of Lavoisier, that Blagden did not, as he insists in Crell's Journal, communicate to him any of the conclusions of Cavendish in June 1783. But Watt's theory is proved by written testimony to have been known to Priestley in 1782. It was communicated in writing to Dr. Black in December 1782, alluded to in February 1783, in Winter, not in Spring; and was sent to the Royal Society on the 26th of April 1783, in the Spring, and from Blagden's vague language, about the same time" when he first learned the conclusions of Cavendish.

In this collision of claims, Cavendish never publicly asserted his priority to Watt; but he had a friend in Dr. Blagden, who was able and willing to promote the interests, we shall not say the views, of his patron. Mr. Cavendish was a person of great and deserved influence in the Royal Society. Elected in 1760, he had been a Fellow for twenty-four years. He had received the Copley Medal in 1766 for his Experiments on Air. He had frequently sat in its council; and his great wealth and high rank, combined with his talents and character, gave him a voice of authority in all its proceedings. No sooner was Watt's paper received than a change is contemplated in the Secretaryship of the Society. Dr. Maty, the Secretary in 1783, who, as we have seen, considered Watt as the true inventor of the theory of the composition of water, resigns in the spring of 1784, and is succeeded by Dr. Blagden, who thought otherwise. In the performance of his principal duty, viz., in superintending the printing of the Phi losophical Transactions, the new Secretary commits, or allows to be committed, two gross errors of date, both of which are favourable to his patron, and unfavourable to Mr. Watt. Had these dates been correctly given; had Dr. Blagden not inserted two interpolations in Cavendish's memoir; and had he neither conversed with Lavoisier, nor corresponded with Crell;-or, to take another alternative, had Dr. Maty continued Secretary to the

* In 1785 and 1786, when the little dispute, as Blagden calls it, was agitating, it would have been easy to have obtained the testimony of Cavendish's particular friends to the correctness of his historical statement in Crell's Journal, ́