and the Mode of its Communication. 1 1 1 



points inversely, the intensity of the rays from the 

 internal surface of the smaller sphere must be to the 

 intensity of the rays from the internal surface of the 

 larger sphere as 4 to i, at the common centre of those 

 spheres. 



Now, as the time of the cooling of the hot body will 

 depend on the quantity of frigorific rays which arrive at 

 its surface, and on the intensity of their action, and as 

 the intensity of the rays from the internal surface of the 

 sphere at its centre is diminished in the same propor- 

 tion as the surface of the sphere is augmented when its 

 diameter is increased, it follows that a hot body placed 

 in the centre of a hollow sphere at any given constant 

 temperature below that of the hot body, will be cooled 

 in the same time, or with the same celerity, whatever 

 may be the size of the sphere. 



If this conclusion be well founded (and I see no rea- 

 son to suspect that it is not so), it will follow, from the 

 principles assumed, that the hot body will be cooled in 

 the same time, in whatever part of the hollow sphere it 

 be situated. And as the cooling of the body is not 

 affected, that is to say, accelerated or retarded, either by 

 the greater or smaller size of the enclosed space in 

 which it is confined, or by its situation in that confined 

 space, so it cannot be in any manner affected either 

 by the form of that hollow space or by the presence of 

 a greater or less number of other solid bodies ; provided 

 always, that all these surrounding bodies be at the same 

 constant temperature. 



If, however, any of these surrounding bodies, the 

 temperature of which is liable to be sensibly changed 

 during the experiment by the calorific rays emitted by 

 the hot body, be placed very near that body, the cooling 



