PTAKMIGAN SHOOTING. 101 



ness : at that season, when they perceive any person, 

 they remain quiet upon the snow, to avoid being 

 seen ; and are often betrayed by their very white- 

 ness, which surpasses that of the snow. 



The plumage of the ptarmigan not only becomes 

 of this snow white in winter, but much thicker, 

 closer, and more downy ; thus proving the beautiful 

 economy of nature : for as colour is well known to 

 influence the rate by which bodies acquire, reflect, 

 or part with heat; and as white is the colour w r hich 

 most readily and perfectly reflects it, and which most 

 difficultly parts with it, so a body clothed with that 

 colour shall retain heat longest, and, therefore, be 

 better fitted - to exist in the coldest latitudes. It is 

 the limited expenditure of vital heat, therefore, 

 in the ptarmigan, that is supposed to influence its 

 choice of situation. Mr. Daniel thus scientifically 

 puts an example : " If two animals, one of a black 

 colour and the other white, be placed in a higher 

 temperature than that of their own body, the heat 

 will enter the one that is black with the greatest 

 rapidity, and elevate its temperature considerably 

 above the other. But when these animals are placed 

 in a situation, the temperature of which is consider- 

 ably lower than their own, the black animal will give 

 out its heat by radiation to every surrounding object 

 colder than itself, and speedily have its temperature 

 reduced ; while the white animal will part with its 

 heat by radiation at a much slow r er rate." 



