and the Mode of its Communication. 119 
again to move towards the opposite side ; which, by the bye, 
shows that ice emits a greater quantity of frigorific rays than a 
bright metallic surface, at the same temperature. 
Having frequently observed, on presenting my hand to one 
of the balls of the thermoscope, that the instrument was greatly 
affected by the calorific rays which proceeded from it, apparently 
much more so than it would have been by a much hotter body, 
of the same quantity of surface, but of a different kind of sub- 
stance, placed at the same distance, I was extremely curious to 
find out, whether animal substances do not emit calorific (and 
consequently frigorific) rays much more copiously than other 
substances ; and whether living animal bodies do not emit them 
in greater abundance than dead animal matter. 
The first experiment I made, with a view to the investigation 
of this particular point, was as simple as its result was striking 
and conclusive. 
Exper. No. 21. Having procured a piece of gold-beater’s skin, 
(which, as is well known, is one of the membranes that line 
the larger intestines in cattle, and is exceedingly thin,) I moist- 
ened it with water ; and, applying it, while moist, to the flat 
circular end of one of my horizontal cylindrical vessels, it re- 
mained firmly attached to the surface of the metal, when it 
became dry. I now filled this vessel, and another, of equal dimen- 
sions, the end of which was not covered, with hot water, (at the 
temperature of 180 0 ,) and presented them both, at the same 
moment, to the two balls of the thermoscope, and at the same 
distance. 
The bubble of spirit of wine was immediately driven out of 
its place, to a great distance ; and did not return to its former 
station, till after the vessel whose end was covered with gold- 
