136 Experimental Investigations 



above the temperature of the medium. Now, I found, 

 by observation, that the polished vessel A employed 

 39 minutes and 30 seconds to pass over that interval 

 of cooling, while the blackened vessel B employed only 

 11 minutes. These times are in the proportion of 

 10,000 to 5810. By one of my experiments, made last 

 year, I found that the times employed in passing through 

 the same interval of cooling in the open air by a clean 

 polished metallic vessel, and another of the same form 

 and capacity, but blackened without, were as 10,000 to 



5 6 54- 



Reflecting on the consequences which ought to result 

 from the radiations of bodies, on the supposition that 

 the temperatures of bodies are always changing by 

 means of these radiations, I was led to the following 

 conclusion : If the intensity of the action of the rays 

 which proceed from a body be universally as the 

 squares of the distances of bodies inversely, which is 

 extremely probable, a hot body exposed to cool in a 

 close place, or surrounded on all sides by walls, ought 

 to cool with the same celerity, or in the same time, 

 whatever may be the magnitude of this enclosure, pro- 

 vided the temperature of the sides or walls be at a 

 constant given temperature; and the results of the 

 experiment here described, in which the hot body was en- 

 closed in a vessel of a few inches diameter, compared with 

 those of several experiments made last year, in which 

 the heated bodies were exposed to cool between the walls 

 of a large chamber, appear to confirm this conclusion. 



As to the effect produced by the air in cooling a 

 heated body exposed to cool in a close place filled with 

 that fluid, I have reason to believe that it is much less 

 considerable than has been supposed. 



