M. Achiile Cazin on Internal Work in Gases. 201 



than/> 2 ; hence it may happen that the quantity of heat created 

 in this part during the expansion increases with the volume 

 of reservoir B. We may prove that it is so by the following 

 reasoning. 



The gas of the second part absorbed the work of expansion 

 of the first part, and transmitted to the third a less quantity of 

 work, which served for the compression ; the velocities acquired 

 by the molecules of this second part correspond to the difference. 

 In each pair of experiments the work absorbed remains the same, 

 but the velocities change; when they diminish, the work trans- 

 mitted increases, and with it the quantity of heat which it causes 

 to appear. 



The creation of this heat is evidently opposed to the depres- 

 sion, and the greater it is the smaller the depression ; this is 

 what occurred in our experiments. 



When I shall attempt subsequently to give a complete expla- 

 nation of the phenomena observed, I shall examine all the causes 

 which may intervene ; and we shall then see whether to the cause 

 of depression which has just been noted no other cause is joined. 

 Some new observations will have prepared for this research. 



The experiments mentioned in this paragraph teach us, again, 

 that with a glass reservoir the abscissa of the point A = is 

 greater, and the maximum of h smaller, than with a zinc reser- 

 voir; whence it follows that the curve does not rise so quickly 

 with the first reservoir as with the second. We shall find the 

 explanation of this in the calorific action of the sides. 



If the sides were impermeable to heat, the curve of the ^s 

 ought to remain below the axis of the abscissse, unless it be ad- 

 mitted that a gaseous mass in which some exchanges of motion 

 and heat take place, without any external positive or negative 

 work, can of itself create heat and become spontaneously heated. 

 This supposition being very improbable, we must have recourse, 

 to the thermal action of the sides. 



The sides of the reservoir A are cooled during the expansion , 

 they then give up heat to the gaseous mass. On the contrary, 

 the sides of reservoir B are heated ; they withdraw heat from 

 the gas. The quantities of heat respectively yielded and with- 

 drawn are not equal. If they were equal, the effect would be 

 the same as if the sides were impermeable. Since there is a 

 maximum of h, it is because a certain quantity of heat has been 

 supplied finally from without. Let us see how this can have taken 

 place. The fall of temperature in A is greater than the rise in 

 B; but, on the other hand, the surface of the reservoir A is 

 smaller than the other. Assuming the same emissive power fo 

 the sides of both, we cannot foresee in what direction the in- 

 quality will take place. Let us suppose that the heat given up 



Phil. Mag. S. 4. Vol. 40. No. 266. Sept. 1870. P 



