1 1 2 Inquiry concerning the Nature of Heat, 



of that hot body will be retarded, the rays from this 

 neighbouring body, so heated, being less frigorific than 

 those from other bodies at a greater distance, which it 

 intercepts. 



The results of all my experiments on the cooling 

 of bodies tended uniformly to confirm the above con- 

 clusions. 



Admitting that the cooling of a hot body is effected 

 solely by the rays which proceed from colder bodies, 

 and that these rays, like those of light, are reflected, 

 refracted, and concentrated, according to certain known 

 laws, by the polished surfaces of mirrors and lenses, it 

 might perhaps be imagined that the cooling of a hot 

 body might be accelerated or retarded by giving it 

 some peculiar form ; or by placing near it, and in cer- 

 tain positions with respect to it, two or more highly 

 polished reflecting mirrors. 



As these conjectures, if well founded, might lead to 

 experiments from the results of which the truth or false- 

 hood of the hypothesis in question might be demon- 

 strated, it is of much importance that this matter should 

 be thoroughly investigated. I shall therefore beg the 

 indulgence of the Society while I endeavour to examine 

 it with that careful attention which it appears to me to 

 deserve. 



When different solid substances, heated to the same 

 degree of temperature, are exposed in the air to cool, 

 those among them which appear to the touch to be the 

 hottest are not those which cool the fastest, or which 

 send off calorific rays through the air in the greatest 

 abundance. 



As polished metals reflect a great part of the rays 

 from other bodies which arrive at their surfaces, and as 



