COUNT RUMFORD. 163 



perirnent 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 

 water, he left them to cool in the air of a large, quiet 

 room. The vessel covered with the black skin repre- 

 sented a negro, the other vessel a white man ; and the re- 

 sult was that while the black required only 23 minutes 

 to cool, the white man required 28 minutes. The prac- 

 tical issue of the experiment is thus stated : " All I will 

 venture to say on the subject is, that were I called to 

 inhabit a very hot country, nothing should prevent me 

 from making the experiment of blackening my skin, or 

 at least of wearing a black shirt, in the shade, and espe- 

 cially at night, in order to find out if, by those means, I 

 could not contrive to make myself more comfortable." 



There was at times a headstrong element, if I may 

 use the term, in Eumford's scientific reasoning. He 

 here overlooks the fact that in a former experiment he 

 found scarcely an appreciable difference between white 

 and black as regards their powers of cooling. He also 

 forgets the possible influence of a second coating, which 

 his former experiments had revealed. As regards the 

 negro and the white man, Kumford's first experiment 

 illustrated the case more correctly than his subsequent 

 ones. There are, moreover, transparent substances 

 which, used as varnishes, would not have impaired the 

 whiteness of the goldbeater's skin, but which would have 

 hastened the cooling even more than the Indian ink. 



Those who are acquainted with Sir John Leslie's 

 experiments on radiant heat will not fail to notice that 

 he and Rumford travelled over common ground. With 

 a view of setting this matter right Rumford wrote a 

 paper entitled " Historical Review of Experiments on 

 the Subject of Heat," in which he shows that his experi- 



