Animals pojfefs of producing Cold. 48 3 
ium of fire, the ufe of the air in inflammation, and the diftinc- 
tion of bodies into combuftible and incombuftible. 
From the firft dawnings of philofophy it muft have been 
perceived, that moft animals have a higher temperature than 
the medium in which they live ; and that a conftant fucceffion 
of frelh air is neceflary to the fupport of animal life. The 
caufes of thefe phenomena have afforded matter for much fpe- 
culation in ancient as well as modern times : but the difcovery 
that animals have, in certain circumftances, the power of 
keeping themfelves at a lower temperature than the furfounding 
medium, was referved for the induftry of the prefent age. 
This difcovery feems originally to have arifen from obferva- 
tions on the heat of the human body in warm climates. It 
was mentioned by Governor ellis in 1758 ; it was taught by 
Dr. cullen before the year 1765 ; and at length it was com- 
pletely eftablifhed by the experiments of Dr. fordyce in 
heated rooms, which were laid before the Society in 1774. 
In the courfe of thefe experiments the dodtor remained in a 
moift air heated to 1 30° for the fpace of fifteen minutes, during 
which time the thermometer under his tongue flood at 1 oo°. 
his pulfe made 139 beats in a minute, his refpiration was but 
little affedted, and ftreams of water ran down over his 
whole body, proceeding from the condenfation of vapour, as 
evidently appeared from a fimilar condenfation on the fide of a 
Florentine flalk that had been filled with water at 1 oo°. 
He found, however, that he could bear a much greater 
degree of heat when the air was dry. In this fituation, he 
frequently fupported, naked, for a confiderable time, without 
much inconvenience, the heat of 260°, his body preferving 
very nearly its proper temperature, being never railed more 
than 2 0 above the natural ftandard. 
Various 
