IMPORTANCE OF SNOW. 211 



bottom of valleys or other positions where it is sheltered botli 

 from wind and sun.* 



The e-eneral effect of the forest in cold climates is to assimilate 

 the winter state of the ground to that of wooded regions under 

 softer skies ; and it is a circmnstance well worth noting, that in 

 Southern Europe, where iJ^ature has denied to the earth a warm 

 winter-garment of flocculent snow, she has, by one of those com- 

 pensations in which her empire is so rich, clothed the hillsides 

 with umbrella and other pines, ilexes, cork-oaks, bays, and other 

 trees of persistent foliage, whose evergreen leaves afford to the 

 soil a protection analogous to that which it derives from snow in 

 more northern climates. 



The water imbibed by the soil in winter sinks until it meets a 



* As the loss of snow by evaporation has been probably exaggerated by pop- 

 ular opinion, an observation or two on the subject may not be amiss in this 

 place. It is true that in the open grounds, in clear weather and with a dry at- 

 mosphere, snow and ice are evaporated with great rapidity even when the ther- 

 mometer is much below the freezing-point ; and Darwin informs us that the 

 snow on the summit of Aconcagua, 22,400 feet high, and of course in a tem- 

 perature of perpetual frost, is sometimes carried off by evaporation. The sur- 

 face of the snow in our woods, however, does not indicate much loss in this 

 way. Very small deposits of snow-flakes remain unevaporated in the forest, 

 for many days after snow which fell at the same time in the cleared field has 

 disappeared without either a thaw to melt it or a wind powerful enough to 

 drift it away. Even when bared of their leaves, the trees of a wood obstruct, 

 in an important degree, both the direct action of the sun's rays on the snow 

 and the movement of drying and thawing winds. 



Dr. Piper {Trees of Ainerica, p. 48) records the following observations : " A 

 body of snow, one foot in depth and sixteen feet square, was protected from 

 the wind by a tight board fence about five feet high, while another body of 

 snow, much more sheltered from the sun than the first, six feet in depth, and 

 about sixteen feet square, was fully exposed to the wind. When the thaw 

 came on, which lasted about a fortnight, the larger body of snow was entirely 

 dissolved in less than a week, while the smaller body was not wholly gone at 

 the end of the second week. 



" Equal quantities of snow were placed in vessels of the same kind and ca- 

 pacity, the temperature of the air being seventy degrees. In the one case, a 

 constant current of air was kept passing over the open vessel, while the other 

 was protected by a cover. The snow in the first was dissolved in sixteen min- 

 utes, while the latter had a small unthawed proportion remaining at the end 

 of eighty-five minutes." 



The snow in the woods is protected in the same way, though not literally to 

 the same extent, as by the fence in one of these cases and the cover in the 

 other. 



