92 Inquiry concerning the Nature of Heat, 



wards in their turns ; and under these circumstances 

 it might reasonably be expected that as much heat as 

 possible would be communicated immediately to the air 

 by the hot body, and that the heat so communicated 

 would of course accelerate the cooling of that vessel. 



It was in fact cooled in a shorter time than the other, 

 No. 5, which was suspended in a vertical position ; but 

 the difference of the times of cooling was very small ; 

 which indicates, if I am not mistaken, that a compara- 

 tively small quantity of the heat a hot body loses 

 when it is cooled in air is communicated to that fluid, 

 much the greater part of it being sent off through the 

 air, to a distance, in calorific rays. 



The vessel No. 5 was found to cool through the 

 standard interval of 10 degrees in 38-^ minutes; and 

 No. 6, which was in a reclined position, in 37^ min- 

 utes. 



It will no doubt be remarked that the vessel No. 5 

 cooled somewhat faster in this experiment than it had 

 done in the two preceding experiments (No. 29 and 

 No. 30), when it stood over a pewter platter which (at 

 the beginning of the experiment at least) was at the 

 same temperature as' the air of the room. 



The calorific rays from the bottom of the vessel heat- 

 ing the platter in some small degree, and still more, 

 perhaps, the upper surface of the perforated sheet of 

 paper which covered it, the frigorific rays from these 

 bodies were, on that account, somewhat less powerful 

 in lowering the temperature of the neighbouring hot 

 body ; and the time of its cooling was consequently a 

 little prolonged. 



In one of the preceding experiments it cooled through 

 the given interval in 39^- minutes, and in the other in 



