On the Expansion of Gases. 295 



"J'ai pense\ Monsieur, d'apres l'obligeance que vous m'avez 

 temoign6e que vous interpr6teriez favorablement le sentiment qui 

 a dicte ces observations. 



" J'ai l'honneur d'etre, Monsieur, avec une parfaite consi- 

 deration, 



" Votre tres-humble et tres-obeissant serviteur, 



H Gay-Lussac." 



I return my best acknowledgments to M. Gay-Lussac for this 

 obliging correction of an error. He has not been mistaken in 

 supposing that such criticism would be most acceptable to me. I 

 was milled, by inconsiderately supposing an analogy between 

 the mixture of gases with one another, and their mixture with 

 vapour, which does not exist. I shall take the first opportunity of 

 re-calculating the table for finding the specific gravity of any 

 mixture of air and aqueous vapour by the correct formula. 



I must not let this occasion pass of likewise acknowledging 

 a mistake into which I have fallen with regard to M. Gay-Lussac, 

 in the thirty-sixth number of this Journal, by ascribing to him a 

 critique in the Annates de Chimie, which wanted the usual dis- 

 tinctive initials of the two editors of that work. This error has 

 been already corrected by M. Arago, in no very philosophic 

 mood. The article in which this correction is conveyed, I should 

 have been in no danger of mistaking, even without the A. sub- 

 scribed. Nobody, who has had the advantage of any acquaintance 

 with M. Gay-Lussac, or his works, could, for a moment, suppose 

 that he would substitute personal abuse for argument, and wilful 

 perversions for criticism. 



J. F. D. 



