184 ON THE RADIATION OF CALORIC. 



and it also prevents any of the rays from HI reaching the 

 mirror AB. This is compensated for, because all such rays, 

 as MCL or NCK, from MDEN which pass through C, 

 and fall on KL, are by it reflected in parallel lines to AB, and 

 by the second mirror are concentrated at T. But when the 

 cold body is introduced at C, it intercepts the whole of these 

 rays, and therefore great cold is produced. This explanation 

 of the apparent reflection of cold is precisely the same with 

 that given by Mr Davenport ; but, from his having attempted 

 to express it without using diagrams, his statement is not easi- 

 ly understood. 



In this paper, therefore, the part which is absolutely new, 

 is that which relates to the sensibility of different surfaces to 

 the impressions either of heat or cold. I hope, however, that 

 I have succeeded in making the other parts more easily un- 

 derstood than former writers have done. This explanation of 

 these facts on the theory of all bodies always radiating calo- 

 ric in proportion to their temperatures, appears to me to fur- 

 nish a decisive confirmation of that theory, as it shows, that 

 the circumstances which have been supposed to be the strong- 

 est objections against it, are in fact necessary consequences 

 from it. 



Fig. 4. 



