THEORY OF RADIATION. 195 



of innumerable points, than from such as are 

 smooth and highly polished ? 



Connected with this subject, is another fact 

 that has never been explained, and which may 

 appear at variance with the above theory of 

 radiation, until duly considered. It has been 

 ascertained by Leslie and other experimenters, 

 that the reflecting power of bodies is inversely as 

 their radiating power ; and that their power of 

 absorbing caloric is proportional to their radiating 

 power. 



It was discovered by Newton, that the surfaces 

 of glass and polished marble are covered over by 

 an invisible and repulsive medium, which pre- 

 vents their actual contact, even when pressed 

 together with great force. It is doubtless owing 

 to this elastic and repulsive aether, which adheres 

 to polished metals by a still stronger attraction, 

 that when water is poured upon them, it glides 

 over, without wetting or touching them ; and 

 that steel needles are enabled to float on the 

 surface of water, notwithstanding their greater 

 specific gravity. It is this thermo-electric aether 

 which prevents polished metals from absorbing 

 caloric, and causes it to rebound from their sur- 

 faces by reflection ; while light bodies, and metals 

 that are rough or uneven, which contain less of 

 the repulsive medium over their surfaces, absorb 

 more, and reflect less caloric. 



