16 Mr. Ivory's Rcpli) to Professor Airj-. 



sance des terns pour I'annee 1826. A' cette occasion, j'ai relu ce 

 ■Memoire et un autre qui en est le developpement [Annales de 

 Physique et de Chimie, tome xxiii. page 337) ; et j'avoue que 

 je n'y ai rien trouve d'inexact. Mr. Ivory en comparant la 

 forniule (6) de mon Memoire k une equation qu'il a trouvee 

 d'une autre maniere, pense qu'elles sont differentes I'une de 

 I'autre, et que c'est la mienne qui est en defaut. J'attendrai 

 qu'il fasse voir en quoi le raisonnement qui m'a conduit k cette 

 formule seroit erronne ou incomplet ; et jusques-la je persis- 

 terai a croire qu'elle exprime la variation de temperature qui 

 accompagne une tres petite compression ou dilatation de I'air, 

 iquand sa quantite de chaleur propre reste la meme, ainsi qu'on 

 le suppose dans le phenomene du son, a cause de la rapidite 

 des vibrations du fluide ; ou bien encore, comme cela a lieu 

 lorsque I'air est comprime dans un vase ferme dont la matiere 

 n'absorbe pas sensibleraent la chaleur. 



Paris, le 19 Mai 1827- PoiSSON. 



III. ^ Letter to Professor Airy, zm reply to his Bemarhs on 

 some Passages in a Paper by Mr. Ivory. By J. Ivory, 

 Esq. M.A. F.B.S. 



To the Editors of the Philosophical Magazine a?id Annals. 



1. Gentlemen, 

 HAVE to beg the favour of you to insert in your next 

 publication the following short letter occasioned by Pro- 

 fessor Airy's remarks in your last. 



To G. B. yliry, Esq. A.M., Lncasian Professor of Mathema- 

 tics in the University of Cambridge. 

 Sir, 

 I have examined the note in your paper in the Phil. Trans. 

 1826, but I confess, without seeing much reason to alter my 

 opinion. In my paper to which the note refers, I limited my 

 investigation to homogeneous fluids, expressly setting aside 

 those of variable density as matter for future discussion. Your 

 paper is confined to the case of variable density, and your re- 

 ference to a law restricted to homogeneous fluids appears in- 

 considerate and misplaced, and looks as if you had gone out 

 of your way to find fault with what I had written. I do not 

 conceive that Science could in any respect be bettered by the 

 note, and ultimately it will be found that no advantage ha^ 

 resulted from it. You barely assert an opinion without con- 

 descending to allege any reason on which it is founded, and 

 I am not aware that such a procedure is very unaptly charac- 

 terized 



