248 On the Cooling of Liquids in Vessels 



It is generally recognized (I might say that it is 

 proved) that the intensity of the action of calorific or 

 frigorific rays is inversely proportional to the squares of 

 the distances from the body from which they proceed ; 

 now, if this relation is constant, since the effect produced 

 by these rays in a given time must necessarily be in pro- 

 portion to the intensity of their action, it is evident 

 that at the point of contact (if, indeed, there can be an 

 actual contact between two bodies) the rapidity of the 

 calorific action between two particles of different tem- 

 peratures, and which are in contact, must be infinite. 



But the time necessary to establish an equality of 

 temperature throughout the entire masses of two bodies 

 in contact, which are of sensible size and of different 

 temperatures, will depend not only on the size of the 

 bodies and on the extent of the surfaces by which they 

 are in contact, but also, and above all, on the greater or 

 less rapidity with which is propagated among the parti- 

 cles of the bodies that peculiar motion of those particles 

 which constitutes their temperature. 



I will observe here, in passing, that if in the commu- 

 nication of heat between two bodies in contact, it were 

 only a question of the transfer from one to the other of 

 the excess of a fluid as rare and as elastic as caloric is 

 supposed to be, one would expect, it seems to me, an 

 action as instantaneous as the discharge of a Leyden jar. 



It cannot be said, in objection, that the warm body 

 does not offer avenues enough for the escape of the 

 caloric, for it is proved that the pores of all bodies, 

 even of the most solid, are so considerable in compari- 

 son with the space occupied by the particles of those 

 bodies, that a fluid as rare as caloric is supposed to be 

 would be able to move about therein with great free- 



