84 THE PTARMIGAN. 



opposite change. The whitening seems always to be 

 the result of a diminished action in the hair or feather, 

 which may be produced either by heat or cold, or 

 natural decay. Thus we find that the children of 

 peasants have the points and upper parts of the hair 

 bleached almost white by the sun, while the roots are 

 brown : those alpine animals turn white in winter ; 

 and men and other animals become grey with age. It 

 seems that the bleaching process takes place in the 

 hair itself, and has no connexion with a temporary 

 change of colour in the skin, as the rete mucosum ; for 

 we often find that the same summer sun which darkens 

 the skins of those who are much exposed to it, bleaches 

 and whitens the hair upon the hands and eye-brows. 

 Thus it remains doubtful, whether the action of the 

 sun in summer, even by drying the hair and feathers 

 of those beasts and birds which turn white in the 

 winter, may not assist in producing the change of 

 colour. That these are material causes for all those 

 changes, we may rest assured ; and that these have 

 some connexion with chemical action, is highly pro- 

 bable; but we must be careful not to confound the 

 chemical action of living bodies with that chemistry 

 of dead matter which alone we can study in the 

 laboratory. 



The common residences of the ptarmigans are in 

 the most elevated parts of the mountains, where they 

 hide themselves in crevices, and often in holes in the 

 snow, which, till the temperature rises as high as that at 

 which snow begins to melt, are both warm and dry ; so 

 that a ptarmigan at the top of Ben Nevis has really a 

 more comfortable winter abode than a pheasant in one 



