43 



made a single experiment on the subject after February 1783. Why 

 then the date of May in that year? I know not, unless because Watt 

 claimed to have made the discovery in April 1783, and Lavoisier 

 claimed to have made it in June 1783 ; and therefore by the argument 

 fromkindness and country, which sometimes gains an ascendence over the 

 imagination and belief even of the wisest and most virtuous minds. 

 Cavendish inust have made his decisive experiment in the intermediate 

 month of 3Iay. There can be no doubt however that had these lec- 

 tures been printed during the life of their author, he would have taken 

 more pains, before he had published them, to ascertain the facts. Nor 

 ought it to be omitted, that in other parts of the volume the discovery 

 of the composition of water is assigned to its rightful owner, and that 



he saw Mr. Watt, were directly contrary to this opinion. [Mr. Watt himself 

 withdrew the communication.] Dr. Priestley's experiments e-vcited the attention 

 of the Honouralle Mr. H. Cavendish, and recalled to his mind his own observation 

 of the moisture in the vessels in which he had exploded these two airs. [There is 

 no foundation for this statement.] These experiments had been begun in the 

 summer of 1781, and were continued from time to time, along with those by 

 which he had discovered the composition of the nitrous acid. He immediately 

 set about repeating the explosion of dephlogisticated and inflammable airs by the 

 electrical sparks ; and in May 1783, he found that when six parts by weight of 

 pure dephlogisticated air were exploded with one of inflammable air, they dis- 

 appeared entirely, and that the result was, a quantity of pure water, equal in 

 weight to the airs employed. The utmost care had been taken to free the airs 

 made use of, by making them pass through the dry muriat of lime. [These were 

 the experiments of the French chemists.] The vessel burst in several of his 

 experiments, because, in the instant of explosion, the vapour of the produced wa- 

 ter was expanded by the heat extracted from the airs. Much of this heat, to be 

 sure, ivas expended in giving these the vaporous form, or supplying it with latent 

 heat. But the vessel was instantaneously heated, shewing that the heat contained 

 in the two airs more than siifficedfor this purpose. These experiments were 

 published in the Philosophical Transactions for 1784. [No such observations 

 were made by Cavendish or published in the Transactions.] 



" Such curious experiments, and so interesting a result, could not remain a 

 secret, had such a thing been intended. But there was no such intention. 

 Mr. Blagden, Secretary of the Royal Society, went to Paris in June 1783, 

 and communicated these experiments of Mr. Cavendish to M. Lavoisier, and 

 his associates, De la Place, Meusnier, Mongez, &c., knowing that they were 

 much interested in the result, which was so intimately connected with the new 

 theory which M. Lavoisier was then establishing. 



" Accordinglj", M. Lavoisier, who saw the immense consequence of this dis- 

 covery to his theory, immediately set about repeating the experiments of com- 

 posing water by the combination of the two airs; and in September 1783, 

 with the assistance of M. Meusnier, effected the composition in a way that 

 admitted no doubt." 



