« PoprzedniaDalej »
duced no change in the sentiments of M. Arago, and did not even induce him to “retract the suspicions” of Cavendish's honesty, which he had, without sufficient evidence, impugned. He repeats, on the contrary, in the presence of the Academy of Sciences, his conviction that Watt had anticipated Cavendish in the discovery of the composition of water, and promising a more extended refutation of Mr. Harcourt's arguments, he contents himself with replying to two of the principal objections which he had adduced. M. Arago had attributed to Priestley the capital observation, dated April 1783, that the weight of the water de posited on the sides of a close vessel after the detonation of the oxygen and hydrogen which it contained, was equal to the sum of the weights of the two gases. Mr. Harcourt, on the contrary, asserts positively that this statement“ has not only no real foundation, but is contradicted by the repeated assertions of Priestley himself, who constantly maintained that in no experiment made with care had he ever found
the weight of the fluid produced equal to the sum of the gases."* In reply to this assertion M. Arago adduces the assertion of Priestley himself, that “he always found, as nearly as he could judge, the weight of the decomposed air in the moisture acquired by the paper. The balance of Priestley,” continues M. Arago, “ was, according to Mr. Harcourt, not sufficiently sensible. Have I pretended that the experiment of the Birmingham chemist did not require to be repeated ? I have always found, declares Priestley, “ as nearly as I could judge, the weight of the decomposed air in the moisture acquired by the paper!” The more perfect weighing of Cavendish will never efface these words.
With respect to the uncertainties, or, if you choose, the tergiversations, which we find in the works of Priestley seven years later than his Memoir of 1783, M. Arago asks, " In writing the history of a discovery, of which the most recent date is 1784, could I search for the claims of competitors in the Memoirs of 1786 and 1788 ?"
In translating a passage of Watt's Memoir, M. Arago had substituted for the words dephlogisticated air and phlogiston the modern terms of oxygen and hydrogen. In the opinion of Mr. Harcourt this was an unpardonable error. M. Arago replies, in a single word, that Cavendish had himself used the ancient language; and he exhibited to the Academy an autograph letter of Priestley to Lavoisier, dated 10th July, 1782, a letter anterior to the Memoir under discussion, in which the celebrated chemist of Birmingham thus expresses himself, “I gave Dr. Franklin an account of some experiments which I made with inflammable
* Mr. Harcouri's Address, p. 3.
† Phil. Trans., vol. lxxiii., P. 427.
air, which he probably [may] have shown you, that seem to prove that it is the same thing that has been called phlogiston."*
To the verbal communication thus made by M. Arago to the Academy, the celebrated chemist, M. Dumas, added, that after having examined with attention the reasoning of his colleague, and after having, at Aston Hall, the residence of Mr. Watt, carefully studied the correspondence of that illustrious engineer, hè adopts completely, and in all its parts, the history which M. Arago has written of the Discovery of the Composition of Water “My opinions on this point,” says M. Dumas, " are so fixed that I am desirous of seeing my declaration inserted in the Comptes Rendus of this sitting !”+
To these distinct assertions and manly declarations, made by philosophers of the highest name, and uninfluenced either by personal or national feeling, the scientific world cannot fail to give the greatest consideration. No member of the Academy ventured to challenge them, and no chemist either in the old or the new world, with the exception of Mr. Harcourt, has yet called them in question. In a postscript which accompanies his address Mr. Harcourt has resumed the discussion in the hope of " furnishing M. Arago with such evidence as can no longer leave any doubt upon his mind,” by establishing these three positions, 1st, That Cavendish's experiments of 1781 involved the notion (the theory of Watt,) and substantially established the fact of the composition of water; 2d, That Priestley's experiment of 1783 added nothing to that of Cavendish ; and, 3d, That while the views of Cavendish were 'precise and philosophical, those of Priestley and Watt were vague and wavering. In support, or in illustration of these views, Mr. Harcourt has lithographed the original memoranda of Cavendish's experiments on the composition of water, which, as Mr. Harcourt informs us, “are numbered and indexed, as well as written in Mr. Cavendish's own hand," and after freeing himself from the charge of ascribing to M. Arago a wilful misrepresentation of the words of Watt when he replaced the terms dephlogisticated air by oxygen, and phlogiston by hydro gen, he states that he “ does not despair of convincing both M. Arago and M. Dumas that there are still more cogent proofs of the inexpedience of this substitution, and that in 1783, Watt and Priestley were almost as little acquainted with the distinctive properties of the gas which we call hydrogen as they were with the word.”
* The above is an abstract of the communication made by M. Arago himself, in presenting to the Academy of Sciences a copy of Mr. Muirhead's Translation of his Eloge of Watt. See the Comptes Rendus, 20 Jan. 1840, p. 109-1 il.
† Ibid. p. 111.
When the Eloge of Watt was read to the Academy of Sciences in 1834, Lord Brongham, his personal friend and admirer, happened to be present. Anxious to do justice to his memory," he collected,” says M. Arago, " valuable documents, and studied afresh the historical question to which I have assigned so large a space, with all that superiority of discernment which is habitual to him, and that acuteness, in some degree judicial, which might have been expected from one who was Lord Chancellor of Great Britain. I owe it to a considerate kindness, of which I feel the full value, that I am enabled to make known the results, hitherto unpublished, of the labour of my illustrious fellow-member.” The communication by Lord Brougham, to which M. Arago here refers, is entitled “ Historical Note on the Discovery of the Theory of the Composition of Water," and is printed as an appendix, with notes by Mr. James Watt, in M. Arago's Eloge. It contains a masterly discussion of the relative merits of the contendo ing claimants, and cannot fail to be regarded as a strong corroboration of the views of M. Arago. Among other propositions, Lord Brougham considers it as established--that there is no evidence of any person having reduced the theory of the composition of water to writing so early as Mr. Watt-that his statement of the theory is even more distinct in April and November 1783 than Mr. Cavendish's was in 1784—that there is neither proof nor assertion that Mr. Cavendish's theory was communicated to Dr. Priestley before Mr. Watt stated his in 1783, still less of Mr. Watt having heard of it-that Mr. Watt's theory was well known among the members of the Royal Society some months before Mr, Cavendish's statement appears to have been reduced into writing, and eight months before it was presented to the Society, and that no proof exists of any one having drawn the conclusion so early as Mr. Watt is proved to have done.
The historical note of Lord Brougham was not noticed by Mr. Harcourt either in his Address or in his postscript to it; but circumstances now occurred by which his Lordship has been drawn into the controversy. Having had occasion to write the lives of Watt and Cavendish in his " Lives of the Men of Letters and Science, who flourished in the time of George III.,” Lord Brougham reprinted his historical note as an appendix to his Life of Watt. In an additional note he refers to Mr. Harcourt's Address and Postscript, and after disclaiming all intention to “ cast the slightest doubt upon Mr. Cavendish's perfect good faith in the whole affair," he adds, that “ having read the full publication, with fac-similes, Mr. Harcourt has clearly proved one thing, and it is really of some importance. He has made it appear that in all Mr. Cavendisl’s diaries and notes of his experiments, not ani intimation occurs of the composition of water having been inferVOL. VI. NO, XII.
red by him from these experiments earlier than Mr. Watt's paper of spring 1783." *
In consequence of these observations, Mr. Harcourt has addressed a letter to Lord Broughamt containing some severe strictures on his Historical Note, and on his Lives of Watt and Cavendish. In this pamphlet, which is written with great spirit and ability, the author continues to deny to Mr. Watt any merit in reference to the composition of water, reiterating his expectation that M. Arago will yet" rectify the inadvertence into which he has fallen, and concludes with the following remonstrance, addressed to Lord Brougham :
“ What friend of yours, my dear Lord, but must regret to see a great man trifling with his own reputation, by thus confidently dealing with subjects of which he betrays so defective a knowledge ? I sincerely lament, for my own part, that having once been honoured by your regard, and having always respected your talents, it should have fallen to me to presume in this manner to rectify your misapprehensions. I declined to enter into controversy with you, partly for old acquaintance' sake, and partly because I thought you on this question less responsible than the official writer of France. But you would do battle with and
your weapons were none of the fairest ; for instead of replying to my arguments, you did me the injustice without provocation, to compare the abilities and character of the obscurest lover of science in England with those of one of its most eminent cultivators in France. I know not that I shall even now have convinced you that the meanest of our philosophical chemists, in his own art, and in a just cause, may be more than a match for the most learned judge of Patents, or even for the ablest member of the “ Institut,” whose studies have lain in another direction.”+
At this stage of the controversy, at which the temperature of feeling seems to be rapidly increasing, we are anxious to strip it of all collateral topics, and to leave the minds of our readers in such a state as to yield only to the influence of undoubted facts and unimpassioned argument. While one party denies to Mr. Watt all merit whatever as the suggester, the promoter, or the anticipator of the discovery of the composition of water, and have even thrown out hints of his ignorance of the subject, and of the bad faith of his friends, the other party is accused of having transferred the whole merit of the discovery to Mr. Watt, and
* Lives, &c., vol. i. p. 401. In his life of Cavendish, Lord Brougham has shortly referred to the controversy, and he has added other notes to the Lives of Black, Watt, and Cavendish, in which he blames Cuvier for overlooking Watt's claims, and animadverts with severity upon the “ very strange attack made on both M. Arago and himself in the Quarterly Review,” [December 1845.]—See vol. i., p. 436, and vol. ii., pp. 507,511.
+ London and Edin. Phil. Mag., 1846. # Letter, pp. 85, 86.
of having charged Cavendish and his friends with using unfair, and even fraudulent means to stifle the claims of Watt, and establish those of Cavendish. We do not say that M. Arago and M. Dumas have done this, but Mr. Harcourt distinctly charges them with it in the following passage of his address : “ The secretary of the Academy (M. Arago) has not confined himself to taking from Cavendish the honour of his discoveries, but has cast a cloud of suspicion on his veracity and good faith. He has, in fact, imputed to him the claiming discoveries and conclusions which he borrowed from others, of inducing the Secretary of the Royal Society to aid in the fraud, and even causing the very printers of the Transactions to antedate the presentation copies of his papers.”—P. 7. Mr. Harcourt, in his letter to Lord Brougham, reprints this very passage, as giving“ no more than the plain meaning of M. Arago's clever sarcasms, and he describes M. Arago as “proceeding to fix the charge on Cavendish and his fellow-conspirators.". After having read this passage, and those views which have been taken of his attack upon Cavendish, and having also carefully perused Mr. Harcourt's advocacy of Cavendish's claims, and the lithographed memoranda upon which it rests, M. Arago comes boldly forward in the Institute, and avers before the world his adherence to his former opinions, while M. Dumas gratuitously advances to the combat, and “ adopts completely, and in all its parts, M. Arago's history of the discovery of the composition of water," and desires that this his declaration shall be recorded in the periodical organ of the Institute of France.
Now, as M. Arago has for ten years continued to take the same strong and unfavourable view of the conduct of Cavendish and Blagden, and as Mr. Harcourt has, in his very last letter, regarded him as taking such a view, how does it happen that, throughout the whole of the controversy, he speaks of M. Arago in such flattering terms, while he uses such strong language towards Lord Brougham, and that he describes M. Arago's attack upon Cavendish, even when implicitly adopted by Dumas, as an "inadvertence into which he has fallen." This marked respect of persons, this excessive civility shewn to a foreign antagonist, and withheld from a friend, this want of moral courage to denounce what he avows to be worthy of denunciation, is a feature in this controversy which we have never found in any other, and which will not be without its influence in moulding the ultimate decision of the public. Knowing, as we do, the high character of Mr. Harcourt, and the true nobility of his nature, we can only ascribe it to his great admiration of the talents of his opponent; and admiring, as we do, the talents of M. Arago, and his entire disinterestedness in the advocacy of Mr. Watt's claims, we rejoice