162 COUNT RUMFORD. 



The more rapid chilling of the glass bottle was due, in 

 like manner, to the fact that glass possesses a greater 

 radiative power than tin. 



He next applies himself with energy, zeal, and 

 tenacity to prove that there are frigorific rays which 

 act in all respects like calorific rays, and which enjoy 

 an individuality quite as assured as that of the latter. 

 He pictures his frigorific rays as produced by vibrations 

 of a special kind. In Pictet's celebrated experiment 

 of conjugate mirrors, and in many other experiments, 

 chilling by a cold body showed itself to be so exactly 

 analogous to heating by a warm one, that Eumford 

 never could shake from his mind the notion of rays of 

 cold. The fall of the thermometer in one focus when a 

 lump of ice was placed in the other, was in his view 

 caused by a positive emission of cold rays from the ice, 

 and not by its absorption of the heat radiated against it 

 by the thermometer. These frigorific rays, he says, 

 were suspected by Bacon. Their existence was actually 

 established by the academicians of Florence, but these 

 learned gentlemen were so ' blinded by their prejudices 

 respecting the nature of heat, that they did not believe 

 the report of their own eyes.' 



Kumford indulges in various untenable speculations 

 and erroneous notions regarding the part played by 

 clothing, by the blackness of the negro's skin, and by 

 the oiled surface of the Hottentot. We are, he con- 

 tends, kept, warm by our clothing, not so much by con- 

 fining our heat as by keeping off the frigorific rays 

 which tend to cool us. He reverts to the respective 

 cases of a black and a white man, and describes an ex- 

 periment which elucidates his views. He covered two of 

 his vessels with goldbeater's skin, and painted one of 

 them black with Indian ink, leaving the other of its 

 natural white colour. Filling both vessels with hot 



