129 
and the Mode of its Communication. 
If we might suppose that the temperatures of bodies are 
changed, not by the rays they emit , but by those they receive 
from other neighbouring bodies, this fact might easily be ex- 
plained ; but, without stopping to form any hypothesis for the 
explanation of these appearances, I shall proceed in my account 
of the various attempts I have made to elucidate, by new expe- 
riments, those parts of this interesting subject which still ap- 
peared to be enveloped in obscurity. 
As the cooling of hot bodies is so much accelerated by covering 
their surfaces with such substances as emit calorific rays in great 
abundance, or with such as are much affected by the frigorific 
rays of the colder bodies by which they are surrounded, it seems 
to be highly probable, that a comparatively small part of the 
heat, which a body so cooled actually loses, is acquired by the 
air; a much greater proportion of it passing off through that 
transparent fluid, under the form of calorific rays, without af- 
fecting its temperature. 
If this supposition should turn out to be well founded, the 
knowledge of the fact would enable us to explain several inte- 
resting phenomena, and particularly that most curious process 
by means of which living animals preserve an equal temperature, 
notwithstanding the vast quantities of heat that are continually 
generated in the lungs, and notwithstanding the great variations 
which take place in the temperature of the air in which they 
live. 
It is evident, that the greater the power is which an animal 
possesses of throwing off heat from the surface of his body, inde- 
pendently of that which the surrounding air takes off, the less 
will his temperature be affected by the occasional changes of 
mdccciv. S 
