90 TERRESTRIAL ADAPTATIONS. 



the habit of considering them as symptoms of the 

 power of winter to interrupt that state of the 

 elements in which they are subservient to life. 

 Yet, even in this form, they are not without their 

 uses.* " Snow and ice are bad conductors of 

 cold ; and when the ground is covered with 

 snow, or the surface of the soil or of water is 

 frozen, the roots or bulbs of plants beneath are 

 protected by the congealed water from the in- 

 fluence of the atmosphere, the temperature 

 of which, in northern winters, is usually very 

 much below the freezing point ; and this water 

 becomes the first nourishment of the plant in 

 early spring. The expansion of water during its 

 congelation, at which time its volume increases 

 one-twelfth, and its contraction in bulk during a 

 thaw, tend to pulverize the soil, to separate its 

 parts from each other, and to make it more 

 permeable to the influence of the air." In con- 

 sequence of the same slowness in the conduction 

 of heat which snow thus possesses, the arctic 

 traveller finds his bed of snow of no intolerable 

 coldness ; the Esquimaux is sheltered from the 

 inclemency of the season in his snow hut, and 

 travels rapidly and agreeably over the frozen 

 surface of the sea. The uses of those arrange- 

 ments, which at first appear productive only of 

 pain and inconvenience, are well suited to give 



* Loudon, 1214. 



