130 POLAR COUNTRIES. 



while the days are short, and the few hours of 

 mid- day sun would only rouse the energies of vege- 

 tation for a little, to be destroyed by the rigour 

 of the long night. But though the light and heat 

 are thus, at those times, in those places, excluded 

 from contact with the earth, and action upon its 

 vegetable productions, they are not lost. The 

 white surface sends them upward to warm the air ; 

 and as there is little evaporation there, and little 

 vapour in the sky to absorb the heat, the atmo- 

 sphere maintains a far more comfortable tempera- 

 ture than one would be led to suppose. Thus in 

 every place, and at every season, there is some- 

 thing in nature to compensate man for what the 

 inhabitants of other countries regard as his priva- 

 tions. 



Heat is still more wonderful than even light, 

 wonderful as that is, and abundant as are the in- 

 formation and the pleasure which we derive from 

 it. Like light, we never can find heat alone ; for 

 PS light is only perceived when something lightens 

 or is lightened ; so we become conscious of the 

 existence of heat only when something heats or is 

 heated. Thus, as we never can by any process in 

 nature, or any experiment that we can perform 

 artificially, obtain any knowledge either of light 

 or of heat as a distinct substance, or even as a ma- 

 terial and measurable part of any substance, we 

 cannot know any thing further of either than as a 

 property of those substances in which we perceive 

 its effects. To speak of the properties either of 

 light or heat, is an absurdity, because we know 

 light and heat themselves only as properties ; and 

 therefore all their countless variations are varia- 

 tions only in degree ; and as no property can be 



