and the Mode of its Communication. 79 



skin, I painted one of them black, with Indian ink; 

 and, filling them both with boiling-hot water, I exposed 

 them to cool, in the manner already often described, in 

 the air of a quiet room. 



No. 4, which was blackened, cooled through the stand- 

 ard interval of 10 degrees in 23 1- minutes; while the 

 other, No. 3, which was not blackened, took up 28 

 minutes in cooling through the same interval. 



In a former experiment (No. 25), the instrument 

 No. 4, covered with gold-beater's skin, but not black- 

 ened, had taken up 27! minutes in cooling through 

 the given interval, as we have before seen. 



The results of these experiments do not stand in 

 need of illustration ; and I shall leave to physicans and 

 physiologists to determine what advantages may be 

 derived from a knowledge of the facts they establish, 

 in taking measures for the preservation of the health of 

 Europeans who quit their native climate to inhabit hot 

 countries. 



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 especially at night ; in order to find out if, 

 by those means, I could not contrive to make myself 

 more comfortable. 



Several of the savage tribes which inhabit very cold 

 countries besmear their skins with oil, which gives 

 them a shining appearance. The rays of light are re- 

 flected copiously from the surface of their bodies. May 

 not the frigorific rays, which arrive at the surface of 

 their skin, be also reflected by the highly polished sur- 

 face of the oil with which it is covered ? 



