BODY HEAT 57 



The answer is really not a good one at all, for we can 

 only afford to expose the face because the rest of the 

 body is warmly clothed. Clothes regulate heat loss by 

 diminishing it, whereas the natural regulation of heat 

 loss by the skin is chiefly in the direction of increasing 

 it. Civilized man trusts to the former method to enable 

 him to resist cold, and to the latter to help him to 

 withstand heat. 



Clothes should be so constructed as to lessen radiation 

 and conduction without interfering any more than can 

 be helped with evaporation. They will thus be of the 

 maximum utility in cold, and of the least inconvenience 

 in heat. The material of the clothes should therefore 

 be a bad conductor of heat. Count Eumford made 

 some interesting experiments* on the conducting power 

 of different materials, which are instructive from this 

 point of view. He placed a thermometer with its bulb 

 in a glass globe, the space between the thermometer 

 and the globe being filled with the material to be tested. 

 The instrument was heated to the temperature of boiling 

 water, and then plunged into a freezing mixture, and 

 the time taken for it to cool down to 35 F. noted. 

 The results were as follows : 



When surrounded with Seconds. 



Twisted silk ... ... ... 917 



Fine lint ... ... ... 1,032 



Cotton-wool ... ... ... 1,046 



Sheep's wool ... ... ... 1,118 



Eider-down ... ... ... 1,305 



Hare's fur ... ... ... 1,312 



* Phil. Trans., Eoy. Soc., 1792, Ixxxii. 48. 



