80 Retrospective Criticism* 



act and react upon each other. Cold is the exciting cause of 

 a process, the object and result of which is to enable the 

 creature to resist cold. And how is this effected ? It is well 

 known that substances of a black or any dark colour absorb 

 heat more rapidly, and are more perfect conductors of it, than 

 the same substance would be if white, or of any light colour. 

 In other words, the former both receive and part with it 

 quicker. Let us now consider the circumstances of the case. 

 The animal is placed in an atmosphere of a temperature in- 

 finitely lower than that of its own body ; and the grand object 

 is, to keep in the internal vital heat as much as possible. By 

 the law just mentioned, a coat of black fur would carry it off 

 from the system, and dissipate it by radiation into the cold 

 atmosphere much more speedily than a white one ; while the 

 latter would retain it the longest and most effectually. This, 

 therefore, is wisely and kindly given. Besides this change of 

 colour, the whole clothing becomes much longer in winter*, 

 and is thickened by the addition of a coat of short wool con- 

 cealed among the hair or fur of animals, and one of down 

 among the feathers of birds ; and these substances being, in- 

 dependent of their whiteness, the best non-conductors of heat, 

 the best possible provision is made for resisting the extreme 

 rigours of an arctic winter. This under coat, also, is produced 

 earlier or later, and is more or less dense, according to the 

 setting in of the frost, and the severity of the season f , and 

 falls off in spring as the cold departs. The whole arrange- 

 ment is one of those innumerable instances of adaptation which 

 point so clearly to the Great Author of all things, and make 

 the devotion and feelings of every one who studies and appre- 

 ciates them as he ought, purer and stronger. Let this, which 

 ought to be the grand end and aim of every student in the 

 boundless and enchanting field of natural science, never be 

 lost sight of by the young enquirer. 



It will not be out of place here, to hint that a similar pro- 

 vision for the protection of vegetable life is given in snow, 

 whose white colour and soft light texture make it the best 

 possible non-conductor that, under the circumstances, could 

 be provided, and the most effectual agent for preventing the 

 escape of heat from the surface of the earth. Plants de- 

 fended by this warm and fleecy mantle cannot be subjected 



* Hence horses, &c, that lie out through the winter have a long and 

 shaggy coat'; while those that are kept in a warm stable, especially if clothed, 

 retain the short and sleek dress of summer. 



-J- On this account the furs taken by the arctic hunters after the setting 

 in of the frost are the thickest and the most valuable. The very best are 

 those of the severest winters. 



