418 Prof. Clausius on the Conduction of Heat by Gases. 



I must, however, observe that Jochinann's paper does not come 

 up to my expectations, inasmuch as I nowhere find in it strict 

 proofs, but ouly opinions which arc generally entertained, or are 

 based upon analogies, and from which, in my judgment, no 

 safe conclusions can be drawn. I intend, in the first place, to 

 discuss a point which has been raised by Jochmann (and upon 

 which great stress has been laid in other quarters also) as con- 

 clusive against this hypothesis, namely the conduction of heat by 

 gases, and reserve to myself to return to other points at a future 

 time. I will, however, at once remark that I consider the rest 

 of Joehmann's objections as equally without foundation. 



heat, after the appearance of Kronig's memoir, I mentioned that, according 

 to a communication I had received, the idea of the motion of the molecules 

 of gaseous bodies had already been pronounced by Joule, and that Joule, 

 again, had mentioned Herapath as having preceded himself. Somewhat 

 later P. Du Bois Reymond pointed out that Dan. Bernoulli had expressed, 

 and to a certain point worked out, the same view in his Hydrodynamica. 

 Quite recently my attention has been called to a book edited by Prevost 

 {Deux Traites de Physique Mecanique, publies par Pierre Prevost, Geneve 

 et Paris, 1818), which contains two memoirs — one by G. L. Le Sage, 

 edited after his death by Prevost, and one by Prevost himself, in which 

 Le Sage's views are worked out further. In these memoirs, likewise, the 

 idea is put forth and discussed, that the molecules of gases are in a state 

 of progressive motion ; and although they contain much, in reference to the 

 way in which this motion is produced and sustained, greatly at variance with 

 my own views, the manner in which the expansive force of gases is explained 

 by means of it is essentially the same. 



Le Sage quotes a series of authors who, previously to himself, had enter- 

 tained similar ideas. At page 126 his words are :— " On trouve des ves- 

 tiges de cette opinion sur la nature de l'air, et merae de quelques autres 

 fluides, dans divers auteurs qui m'ont precede : Lucrece, livre ii. vers 111— 

 140. Gassendi, dans la l re section de sa Physique, au milieu du 8 e cha- 

 pitre du 4 e livre, et au commencement du 4 e chapitre du 6 e livre. Boyle, 

 dans ses Nouvelles experiences physico-mecaniques sur la force elastique de 

 l'air et sur ses effets, ainsi que dans son Traite sur la Jluidite et la durete. 

 Parent, dans VHistoire de VAcademie des Sciences de Paris, pour 1708, 

 a la suite des "Variations observees dans la regie Mariotte sur la dilatation 

 de l'air." Phoromie de Herman, liv. ii. chap. 6. Dan. Bernoulli, dans la 

 10 e section de son Hydrodynamique. Enfin Dan. et Jean Bernoulli, dans 

 une des pieces qui ont eu part au prix de l'Acad. des Sc. de Paris, en 1746." 



It is scarcely needful for me to remark that I knew nothing of these 

 earlier attempts at explaining the gaseous condition of bodies when I wrote 

 my own memoir ; otherwise I should not have neglected to mention them 

 along with those of Kronig and Joule. Amid the large number of authors 

 who are now quoted with reference to this subject (a number which might 

 perhaps be still increased — some of whom, however, I venture to think, 

 although I have not read the passages referred to in the earlier ones, ex- 

 pressed themselves very likely somewhat vaguely), it would be difficult to 

 indicate with any certainty the one to whom the first suggestion of this 

 hypothesis is to be ascribed, and all we can do is to determine how much 

 each one has contributed to develope the vague idea into an admissible 

 physical theory. 



