268 Dr. Thomson* s Answer to the Review of the [April, 



stance. I am still pursuing the inquiry, and 1 shall not fail 

 immediately to comnuniicate to the Society such results as may 

 appear worthy of their attention." 



There can be no doubt, from all that appears in this paper, 

 that in the month of January, 1809, Davy was of opinion that 

 muriatic acid is composed of oxygen and a combustible basis. 

 The experiments of Gay-Lussac and Thenard were read to the 

 Institute on the 27th of February, 1809. An abstract of them 

 was published in the second volume of the Memoires d'Arcueil 

 during the summer of 1809. Gay-Lussac and Thenard showed 

 that muriatic acid cannot be obtained from chlorine except by 

 means of hydrogen, or some substance containing it. They 

 conclude their experiments in the following manner : 



'* Le gaz muriatique. oxigene n'est pas, en effet, decompose 

 par le charbon, et on pourroit, d'apres ce fait et ceux qui sent 

 rapportcs dans ce Memoire, supposer que ce gaz est un corps 

 simple. Les phenomenes qu'il presente s'expliquent assez bien 

 dans cette hypothcse ; nous ne chercherons point cependantala 

 defendre ; parce qu'il nous semble qu'ils s'expliquent encore 

 mieux en regardant I'acide muriatique oxigene comme un corps 

 compose." — (Mem. d'Arcueil, ii. 357.) 



How was it possible after reading these two papers to avoid 

 saying that the first great addition to our knowledge of chlorine 

 was made by Gay-Lussac and Thenard ? Davy attempted to 

 decompose muriatic acid, but did not succeed. The French 

 chemists showed that oxygen could not be extracted from chlo- 

 rine by any method whatever, and they state in explicit terms 

 that it might be considered as a simple body. 



Davy's next paper, entitled ** Researches on the Oxymuriatic 

 Acid, its Nature, and Combinations," was read on the r2th of 

 July, 1810. In.|;he introduction to this paper he gives an histo- 

 rical detail oi what had been done respecting the oxymuriatic 

 acid, mentions the paper of Gay-Lussac and Thenard as already 

 published, and states the curious nature of the experiments con- 

 tained in it. It' is clear then to a demonstration, that the expe-; 

 fiments of these gentlemen were generally known before Davy 

 suggested his opinion that chlorine is a simple body. This is all 

 ^at I state in my System, and I never so much as dreamed that 

 any person either would or could call the accuracy of the state- 

 ment in question. 



Davy, in the paper just mentioned, and in another read to the 

 Royal Society on the loth November, 1810, details the experi- 

 ments which he had made to see whether chlorine gas could be 

 decomposed, shows that they were all unsuccessful, and that 

 we have no evidence whatever that it is a compound. Hence 

 be deduces that, in the present state of our knowledge, we must 

 consider it as an undecompounded substance. Ihe present 

 theory then, respecting chlorine and muriatic acid, is owing to the 



