96 Inquiry concerning the Nature of Heat, 



was less intensely cold, and where its temperature could 

 be sensibly raised by the calorific rays from the hot body, 

 the cooling of the hot body was retarded by a nearer 

 approach of that cold surface. 



From the results of these experiments we may safely 

 conclude that, if the hot body, instead of being a conical 

 vessel covered up on all sides except its flat bottom, 

 had been a globe, and if this hot globe had been sus- 

 pended in the centre of another larger thin hollow sphere 

 (this last being, at the beginning of the experiment, at 

 the same temperature as the air and walls of the room), 

 the vicinity of the surface of this hollow globe to the 

 surface of the hot body would have retarded the cooling 

 of the hot body in the same manner as the cooling of 

 the conical vessel No. 5 was retarded in the foregoing 

 experiments ; and if, instead of inclosing the hot body 

 in the centre of a single hollow sphere of any given 

 thickness, it were placed in the common centre of a 

 number of much thinner concentric spheres, of different 

 diameters, the time of cooling would be still more re- 

 tarded. 



By tracing the various operations which would take 

 place in the cooling of the hot body in this imaginary 

 experiment, we shall become acquainted with the nature 

 of those which actually take place when the cooling of a 

 hot body is prolonged by means of warm clothing. 



From the results of several of the foregoing experi- 

 ments we may conclude that, supposing the thin con- 

 centric hollow spheres in which the hot body is confined 

 to be made of metal, the cooling will be slower if the sur- 

 faces of these spheres are polished than if they are unpol- 

 ished or blackened ; and hence we might very naturally 

 be led to suspect (what is probably true in fact) that the 



