gave some account of these new experiments, and of the opinions founded upon them. They replied that they had already heard something of these experiments; and, particularly, that Dr. Priestley had repeated them. They did not doubt that in such manner a considerable quantity of water might be obtained; but they felt convinced that it did not come near to the weight of the two species of air employed; on which account it was not to be regarded as water formed or produced out of the two kinds of air, but was already contained in, and united with the airs, and deposited in their combustion. This opinion was held by Mr. Lavoisier, as well as by the rest of the gentlemen who conferred on the subject; but, as the experiment itself appeared to them very remarkable in all points of view, they unanimously requested Mr. Lavoisier, who possessed all the necessary preparations, (‘Vorrichtungen,') to repeat the experiment on a somewhat larger scale, as early as possible. This desire he complied with on the 24th June, 1783, (as he relates in the latest volume of the Paris Memoirs.) From Mr. Lavoisier's own account of the experiment, it sufficiently appears, that at that period he had not yet formed the opinion, that water was composed of dephlogisticated and inflammable airs; for he expected that a sort of acid would be produced by their union. In general Mr. Lavoisier cannot be convicted of having advanced any thing contrary to truth; but it can still less be denied that he concealed a part of the truth. For he should have acknowledged that I had, some days before, apprized him of Mr. Cavendish's experiments; instead of which, the expression 'il nous apprit,' gives rise to the idea that I had not informed him earlier than that very day. In like manner Mr. Lavoisier has passed over a very remarkable circumstance, namely, that the experiment was made in consequence of what I had in'formed him of. He should likewise have stated in his publication, . not only that Mr. Cavendish had obtained 'une quantité d'eau très sensible,' but that the water was equal to the weight of the two airs added together. Moreover, he should have added, that I had made him acquainted with Messrs. Cavendish and Watt's BLAGDEN'S LETTER TO CRELL. 277 conclusions; namely, that water, and not an acid or any other substance, ('Wesen,') arose from the combustion of the inflammable and dephlogisticated airs. But those conclusions opened the way to Mr. Lavoisier's present theory, which perfectly agrees with that of Mr. Cavendish, only that Mr. Lavoisier accommodates it to his old theory, which banishes phlogiston. Mr. Monge's experiments, (of which Mr. Lavoisier speaks as if made about the same time,) were really not made until pretty long, I believe at least two months, later than Mr. Lavoisier's own, and were undertaken on receiving information of them. The course of all this history will clearly convince you, that Mr. Lavoisier, (instead of being led to the discovery, by following up the experiments which he and Mr. Bucquet had commenced in 1777,) was induced to institute again such experiments, solely by the account he received from me, and of our English experiments; and that he really discovered nothing but what had before been pointed out to him to have been previously made out, and demonstrated in England." Now, before examining the history which this letter gives of the discovery, it is to be observed that it professes to have been written in order to give the best account of the dispute about the first discoverer. And from the relations in which Blagden stood to Cavendish, and the obligations he owed him, he cannot be suspected of under-stating any claims which he might have been able to establish for that gentleman to the possession of so great an honour. Bearing this in mind, and taking the statement as we find it, an extraordinary fact which meets us at the outset is, that it does not contain any distinct allegation of Cavendish having been the first discoverer; although it does positively assert that he was prior to Lavoisier, and appears to aim at having it understood that he was prior also to Mr. Watt. Even the time at which Cavendish is reported to have communicated to his friends of the Royal Society his experiments and their results, and "showed that out of them he must draw the conclusion," is only noted in the most general way, as "in the Spring of 1783." But we know that Mr. Watt's conclusions, on the other hand, were actually formed, reduced to writing, (which Cavendish's confessedly were not,) and known to many members of the Royal Society, also "in the Spring of 1783;" and Blagden, though he was well aware of all these circumstances, and professes to give "the best account," and was naturally desirous of gaining the credit of the priority for his patron, does not even state that Cavendish's verbal communication preceded his knowledge of Mr. Watt's written conclusions. CHAPTER XXII. ARGUMENTS OF THE ADVOCATES OF CAVENDISH-THEIR GROUNDLESSNESS-PRIORITY OF WATT MAINTAINED DURING HIS LIFETIME-OPINIONS OF PHILOSOPHERS SINCE HIS DEATH-DR. HENRY-SIR HUMPHRY DAVY-LORD BROUGHAM-ARAGO-DUMAS -BERZELIUS-SIR DAVID BREWSTER LORD JEFFREY-LIEBIG-MR. WATT'S SCRUPULOUS SENSE OF JUSTICE-HIS ACQUAINTANCE WITH CAVENDISH-FESTIVITIES OF THE ROYAL SOCIETY. BESIDES employing the argument arising from the reputation of Mr. Cavendish, which does not really affect the question of priority in the discovery, if established by other evidence, the advocates of Cavendish have made three principal assertions with the view of impugning M. Arago's accuracy. They have said, first, that Priestley "constantly maintained" that he had never found the weight of the water, produced in his experiment, equal to that of the gases exploded; secondly, that an undue licence had been used, in substituting the term hydrogen for phlogiston, as used by Mr. Watt; and thirdly, that the conclusions of Cavendish, which were first stated to the Royal Society in his paper read on the 15th of January, 1784, must be supposed to have been included, or involved, in his experiments made in 1781. The first of these assertions might well be termed by M. Arago “inconceivable,” when it is remembered that in Priestley's own paper he says,"In order to judge more accurately of the quantity of water so deposited, and to compare it with the weight of the air decomposed, I carefully weighed a piece of filtering paper, and then having wiped with it all the inside of the glass vessel in which the air had been decomposed, weighed it again; and I always found, as near as I could judge, the weight of the decomposed air in the moisture acquired by the paper. In the very first pages of Mr. Watt's paper "on the Constituent Parts of Water," in describing Dr. Priestley's experiment, it is said,"The moisture adhering to the glass after these deflagrations, being wiped off, or sucked up by a small piece of sponge paper, first carefully weighed, was found to be exactly, or very nearly, equal in weight to the airs employed." And,-"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."† So in Mr. Watt's Correspondence, "he finds on the side of the vessel a quantity of water equal in weight to the air employed." ‡ And again, "No residuum, except a small quantity of water equal to their weight."§ So also, "you will find the water, equal in weight to the air,) adhering to the sides of the vessel." The circumstance of the equality of weight was indeed one of the facts on which Mr. Watt repeatedly states that he founded his deductions; and, as will presently be seen, it is of great importance in more points of view than one. The substitution of the term hydrogen for phlogiston, had been so amply explained by M. Arago, in the note on that subject which accompanied Lord Brougham's Historical Note,¶ that it might have been supposed no fair objection could have been raised to it by any one; even by the most injudicious and ill-informed partisan of Mr. Cavendish. M. Arago was also at the pains to produce a letter from Dr. Priestley to M. Lavoisier, dated 10th July, 1782, in which he says he has made "some experiments * 'Phil. Trans.,' 1783, p. 427. + 'Phil. Trans.,' 1784, pp. 332, 333. Mr. Watt to Mr. Gilbert Hamilton, 26 March, 1783. § The same to the same, 22 April, 1783. T'Eloge of Watt,' p. 167. |