DECEMBER 249 



so long as the air is dry. I have heard 

 Kennan, the Siberian traveller, say that he 

 had worked comfortably on a calm, dry day 

 when the temperature was sixty degrees 

 below zero. The very first thing that hap- 

 pens as the air begins to get cold is that the 

 moisture settles out of it in the graceful, 

 delicate form of snow, leaving the air dry, 

 pure, and exhilarating. And, with all its 

 other blessings, snow is white. Fluffy and 

 transparent as each crystal is, it could be 

 nothing else. For the light that enters it 

 is reflected from so many surfaces that it is 

 sure to come back whole, as it went in, and 

 whole light means white light. 



THE WHITENESS OF SNOW 



Black snow would be dangerous; so 

 would red or yellow. These are "warm- 

 ing-up colors," and they change the sun's 

 rays to heat. Such snow would soon melt 

 again and prove a very poor protection. 

 But white snow throws back the sunlight in 

 just the form in which it receives it, con- 

 verting none of it into heat, and thus the 



