IMPORTAKOE OF SNOW. 209 



The snow in contact witli the earth now begins to melt, with 

 greater or less rapidity, according to the relative temperature of 

 the earth and the air, while the water resulting from its dissolu- 

 tion is imbibed by the vegetable mould, and carried off by infil- 

 tration so fast that both the snow and the layers of leaves in 

 contact with it often seem comparatively dry, when, in fact, the 

 under surface of the former is in a state of perpetual thaw. No 

 doubt a certain proportion of the snow is given off to the atmos- 

 phere by direct evaporation; but in the woods, the protection 

 against the sun by even leafless trees prevents much loss in this 

 way, and besides, the snow receives much moisture from the air 

 by absorption and condensation. Yery little water runs off in 

 the winter by superficial watercourses, except in rare cases of 

 sudden thaw, and there can be no question that much the greater 

 part of the snow deposited in the forest is slowly melted and ab- 

 sorbed by the earth. 



the snow, therefore, the previously frozen ground had been thawed and raised 

 to seven degrees above the freezing-point. — Williams's Vermont, i., p. 74. 



Boussingault's observations are important. Employing three thermometers, 

 one with the bulb an inch below the surface of powdery snow ; one on the 

 surface of the ground beneath the snow, then four inches deep ; and one in 

 the open air, forty feet above the ground, on the north side of a building, he 

 found, at 5 p.m., the first thermometer at — 1.5° Centigrade, the second at 0°, 

 and the third at +2.5° ; at 7 a.m., the next morning, the first stood at — 12\ 

 the second at — 3.5°, and the third at — 3° ; at 5.30 the same evening No. 1 

 stood at — 1.4°, No. 2 at 0°, and No. 3 at +3°. Other experiments were tried, 

 and though the temperature was aif ected by the radiation, which varied with 

 the hour of the day and the state of the sky, the upper surface of the snow 

 was uniformly colder than the lower, or than the open air. 



According to the Report of the Department of Agriculture for May and 

 June, 1873, Mr. C. G. Prindle, of Vermont, in the preceding winter, found, 

 for four successive days, the temperature immediately above the snow at 13° 

 below zero ; beneath the snow, which was but four inches deep, at 19° above 

 zero ; and under a drift two feet deep, at 27° above. 



On the borders and in the glades of the American forest, violets and other 

 small plants begin to vegetate as soon as the snow has thawed the soil around 

 their roots, and they are not unfrequently found in full flower under two or 

 three feet of snow. — American Naturalist, May, 1869, pp. 155, 156. 



In very cold weather, when the ground is covered with light snow, flocks 

 of the grouse of the Eastern States often plunge into the snow about sunset, 

 and pass the night in this warm shelter. If the weather moderates before 

 morning, a frozen crust is sometimes formed on the surface too strong to be 

 broken by the birds, which consequently perish. 



