266 Dr. Thomson^s Amwer to the Review of the [April, 



Gilbert, in his appendix to the Count's paper, in which he gives 

 an historical detail of all that had been previously done on the 

 subject, never alludes to Davy's paper. He must, therefore, 

 have been unacquainted with it in February, 1816. 



8. In p. 142, the Reviewer ridicules me for stating that a 

 volume of chlorine is equivalent to an atom, while half a volume 

 of oxygen is equivalent to an atom. These inconsistencies, it 

 seems, I should have avoided had I followed Davy. I nmst 

 bear the ridicule as well as I can, because I am satisfied that 

 my statement is true, and that it is of importance. 



9. The Reviewer has pointed out an arithmetical error in my 

 section on fiuorine ; and asks how I could have allowed it to 

 remain uncorrected in two editions of my System. The reason 

 was simply that I did not suspect its existence. In my fifth 

 edition 1 had deduced tlie atomic weights of bodies as nearly as 

 I could from the experiments of others. I had formed the 

 resolution of investigating the subject with all the precision of 

 which I was capable by experiments of my own. Hence in the 

 sixth edition I naturally allowed every thing which I had not yet 

 verified by experiment to remain unaltered. This was the 

 reason why the section on fluorine was printed verbatim from 

 the fifth edition. 



The readers of the Ajiuah of Philosophy are aware of the assi- 

 duity with which I have prosecuted this mvestigation. I have 

 now determined the atomic weights of all the simple bodies, 

 except about 15. Fluoric acid has occupied my attention as 

 well as the others ; but my experiments on it are not yet ready 

 for publication. I may, however, state here, that at present J 

 am inchned to consider fluor spar as a compound of 



Lime , 3*5 



Acid 1-25 



Hence the atomic weight of the acid seems to be 1*25. It 

 may be a compound of one atom of oxygen and one atom of an 

 unknown combustible, whose atomic weight is 0*25, or double 

 that of hydrogen. If we suppose it a compound of equal 

 volumes of fluorine and hydrogen, then the atom of fluorine will 

 weigh exactly as much as the atom of oxygen. This is rather 

 against the probability of the existence of fluorine. 



10. In p. 144 of the Review, the writer thinks proper to dis- 

 pute the accuracy of my experiments on hydrocarbonic oxide, 

 though it is evident that he has never repeated them. I have 

 prepared this gas at least a dozen of times ; have exhibited its 

 properties to my students ; and it has been repeatedly examined 

 and analyzed by my pupils. 



1 1. In the same page, the Reviewer denies that I ascertained 

 in 1810 that chloric ether is a compound of defiant gas and 

 chlorine. I refer the reader to ray paper on the subject printed 

 in the first volume of the Wernerian 1 ransactions, p. 516. Hs 



