514 M. Regnault on the Specific Heat of Simple Bodies, 



selenium had been alone ; and we still neglect the heat which 

 our complex system has lost by radiation in the oven from the 

 61st minute, at which it began to exceed the temperature of the 

 oven, to the 73rd minute, at which it reached its maximum tem- 

 perature. 



It cannot be admitted that at the moment at which the ther- 

 mometer indicates its maximum temperature, the molecular 

 transformation is complete, and that the calorific source ceases 

 to act ; for from the 73rd to the 78th minute the rapidity of the 

 cooling increased, which proves that a disengagement of heat 

 constantly decreasing was opposed to the normal cooling of the 

 system. If we assume that the heating cause had ceased at the 

 78th minute, and that from this time the cooling took place 

 proportionally to the excess of the temperature of the system 

 above the surrounding medium, we could then calculate approx- 

 imatively the temperature which the system has lost by radiation 

 from the 61st minute to the 73rd. The loss of temperature 

 during each minute from the 72nd to the 78th would have been 

 at least 8°*2 if the body had not disengaged any heat. But the 

 variation of temperature was — 



Comparing these coolings with that of 8°'2, which would have 



been the normal cooling, we see that there ought to have been 



disengaged — 



From 72' to 73' a quantity of heat which would have raised 

 the thermometer, if it had not been compensated for by ^ 

 the cooling 8*2 



From 73' to 74' a quantity which would have raised the 

 thermometer to 



From 74' to 75' „ 



From 75' to 76' 



From 76^ to 77' 



From 77' to 78' „ „ 



Number of degrees by which the temperature would have 

 been increased up to the 78th minute, if there had been 



no cooling by radiation 27*8 



We may now assume, supposing that the loss of heat by 



radiation was, during the ascending period of the thermometer, 



equal to that observed during the descending period, for equal 



81 

 6-3 

 4-2 

 10 

 0-0 



