September 4, 1890] 



NATURE 



453 



concluded from the conditions under which he had worked that 

 the weight of the water formed could not be other than equal to 

 that of the two gases which had formed it. The experiment was 

 made in the presence of several men of science, among whom 

 was Blagden, a member of the Royal Society of London, who on 

 this occasion recalled the observations of Cavendish {^qui rappda 

 a ictte occasion les observations de Cavendish)." 



On the following day Lavoisier published his results. The 

 following is the official minute of the communication taken from 

 the register of the sittings of the Academic des Sciences : — 



Meeting of Wednesday, June 25, 1783. 



MM. Lavoisier and De Laplace announced that they had lately 

 repeated the combustion of Combustible Air with Dephlogisticated 

 Air ; they worked with about 60 pints of the airs, and the com- 

 bustion was made in a closed vessel: the result was very pure 

 water. 



. The cautious scribe who penned that minute did not commit 

 himself too far. M. Berthelot, however, regards it as the first 

 certain date of publication, established by authentic documents, 

 in the history of the discovery of the composition of water; "a 

 discovery," he adds, "which, on account of its importance, has 

 excited the keenest discussion." 



You will search in vain through the laboratory journals, as given 

 by M. Berthelot, for any indications either of experiments or 

 reflections which would enable you to trace the course of thought 

 by which Lavoisier was guided to the truth. There is absolutely 

 nothing on the subject until in the eighth volume (25 mars, 

 1783, aufevrier 1784), and on p. 63 we come to the experiment 

 of June 24, and we read : — " In presence of Messieurs 

 Blagden, of [name illegible], de Laplace, Van- 

 dermonde, de Fourcroy, Meusnier, and Legendre, 

 we have combined in a bell -jar dephlogisticated 

 air and inflammable air drawn from iron by means 

 of sulphuric acid, &c. ...The amount of water 

 may be estimated at 3 drachms: the amount 

 which should have been obtained was i ounce 

 I drachm and 12 grains. Thus we must suppose 

 that there was a loss of two-thirds of the amount 

 of the air or that there has been a loss of 

 weight." 



And this is the experiment which, according to M. Berthelot, 

 enabled Lavoisier to conclude that " the weight of the water formed 

 could not be other than equal to that of the tzvo gases which had 

 formed it " I It is on this single experiment, hurriedly and im- 

 perfectly done, that Lavoisier's claim to the discovery of the 

 compound nature of water is based ! M. Berthelot objects to 

 the assumption that it was hurriedly done. He says, on p. 114 : 

 " Lavoisier caused a new apparatus to be made, with a couple of 

 lubes and two reservoirs for the gases, an arrangement which 

 would require a certain amount of time to put together ; this 

 circumstance proves that it could not have been an improvised 

 trial." To what extent it was improvised will be seen im- 

 mediately. 



Now although the laboratory journals do not in this case 

 "inform us of Lavoisier's methods, and of the direction of his 

 mind, . . . the successive steps in the evolution of his private 

 thought," we have other means of ascertaining how he arrived 

 at his knowledge. The method was simplicity itself : he was told 

 of the fact, and his informant 7vas none other than Cavendish's 

 assistant, Blagden. 



Cavendish's memoir was published in 1784. Before it was 

 struck off its author caused the following addition to be made : 

 " During the last summer also a friend of mine gave some ac- 

 count of them [the experiments] to M. Lavoisier, as well as 

 of the conclusion drawn from them, that dephlogisticated air 

 is only water deprived of phlogiston ; but at that time so far 

 was M. Lavoisier from thinking any such opinion warranted 

 that, till he was prevailed upon to repeat the experiment him- 

 self, he found some difficulty in believing that nearly the whole 

 of the two airs could be converted into water." This addition, 

 as I have had the opportunity of verifying by an inspection of 

 the original MSS. in the archives of the Royal Society, was 

 made in the handwriting of Cavendish's assistant and amanu- 

 ensis, Blagden. 



When Lavoisier's memoir appeared, it was found to contain 

 the following reference to this circumstance : — " It was on the 

 24th June that M. de Laplace and I made this experiment in 

 presence of MM. le Roi, Vandermonde, and several other 



NO. 1088, VOL. 42] 



Academicians, and of Mr. Blagden, the present Secretary of the 

 Royal Society of London. The latter informed us {ce dernier nous 

 apprit) that Mr. Cavendish had already tried, in London, to burn 

 inflammable air in closed vessels, and that he had obtained a 

 very sensible quantity of water." 



This reference was so partial, and its meaning so ambiguous, 

 that Blagden addressed the following letter to Crell to be pub- 

 lished in his Chemische Annalen (Crell's Annalen, 1786, vol. i. 

 p. 58). 



It is so direct and conclusive that I offer no apology for giving 

 it almost entire : — ^ 



" I can certainly give you the best account of the little dispu'e 

 about the first discoverer of the artificial generation of water, as 

 I was the principal instrument through which the first news of 

 the discovery that had been already made was communicated 

 to Mr. Lavoisier. The following is a short statement of the 

 history : — 



" In the spring of 1783, Mr. Cavendish communicated to me, 

 and other members of the Royal Society, his particular friends, 

 the result of some experiments with which he had for a long time 

 been occupied. He showed us that out of them he must draw 

 the conclusion that dephlogisticated air was nothing else than 

 water deprived of its phlogiston ; and, vice versd, that water was 

 dephlogisticated air united with phlogiston. About the same 

 time the news was brought to London that Mr. Watt, of 

 Birmingham, had been induced by some observations to form a 

 similar opinion. Soon after this I went to Paris, and in the 

 company of Mr. Lavoisier and of some other members of the 

 Royal Academy of Sciences I gave some account of these new 

 experiments and of the opinions founded upon them. They 

 replied that they had already heard something of these experi- 

 ments, 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 pos- 

 sessed all the necessary preparations, to repeat the experiment, 

 on a somewhat larger scale, as early as possible. This desire 

 he complied with on June 24, 1783 (as he relates in the latest 

 volume of the Paris memoirs). From Mr. Lavoisier's own 

 account of his experiment, it sufficiently appears that at that 

 period he had not yet formed the opinion that water was com- 

 posed 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 anything 

 contrary to truth ; but it can still less be denied that he con- 

 cealed a part of the truth ; for he should have acknowledged 

 that I had, some days before, apprised 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 informed him of. He 

 should likewise have stated in his publication not only that Mr. 

 Cavendish had obtained ' une quantite d'eau tres 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 conclusions — 

 namely, that water, and not an acid, or any other substance, 

 arose from the combustion of the inflammable and dephlogisti- 

 cated 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. . . . 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." 



' Mr. Muirhead's translation. VideVfMi, "Correspondence," "Composi- 

 tion of Water," p. 71. 



