CLOTHING OF ANIMALS. 19 



The rate at which bodies cool is greatly influenced by 

 their colour. The surface which reflects heat most readily, 

 suff'ers it to escape but slowly by radiation. Reflection 

 takes place most readily in objects of a white colour, and 

 from such, consequently, heat will radiate with difficulty. If 

 we suppose two animals, the one of a black colour, and the 

 other white, 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 con- 

 siderably above the other. These differences are observ- 

 able in wearing black and hght coloured clothes during a 

 hot day. When, on the other Iiand, these animals are 

 placed in a situation, the temperature of which is consider- 



thological Dictionary, article Common Gull, says, — " We have had this 

 species alive for some years, and observed, that when it had attained its full 

 mature plumage, in the second year, the head and neck is pure white during 

 the summer ; but, like the herring gull, these parts become streaked, and 

 spotted with brown, in aiitumn, which is continued all the winter ; and in 

 the spring become again pure white." When speaking of the herring gull, 

 he says, — " This gull is now living, and in high health, being thirteen years 

 old. It begms moulting about the middle of August, when it annually as- 

 sumes the mottled head and neck ; and about the middle of February, the 

 partial spring moulting commences, the mottled feathers are discharged, and 

 succeeded by pure white." A herring gull, at present six years <ild, in the 

 garden at Canonmills, of my esteemed friend Mr P. Neill, has, for the last 

 three years, regularly acquired the mottled plumage of the head and neck, 

 in the month of August. It did not acquu-e the pure white head and neck 

 in spring and summer, before the third year. Captain Sabine, in his valuable 

 Memoir on the Birds of Greenland, Linn. Trans, vol, xii. pT 544, when de- 

 scribing the changes of plumage which the Larus glaucus exhibits, adds,— 

 " In winter, the mature bird has the head and neck mottled with brown, as 

 is usual with all the white-headed gulls." In a specimen of L. marinvs, 

 shot in winter, I observed on the head, and chiefly in front of the eyes, a 

 few black hairs, which were formed from the produced ends of the shafts. 



n O 



