210 IMPOETANCE OF SNOW. 



The immense importance of the forest, as a reservoii' of thia 

 stock of moisture, becomes apparent, when we consider that a 

 large proportion of the summer rain either flows into the valleys 

 and the rivers, because it falls faster than the ground can imbibe 

 it ; or, if absorbed by the warm superficial strata, is evaporated 

 from them without sinking deep enough to reach wells and 

 springs, which, of course, depend much on winter rains and snows 

 for their entire supply. This observation, though specially true 

 of cleared and cultivated grounds, is not wholly inapphcable to 

 the forest, particularly when, as is too often the case in Europe, 

 the underwood and the decaying leaves are removed. 



The quantity of snow that falls in extensive forests, far from 

 the open country, has seldom been ascertained by direct observa- 

 tion, because there are few meteorological stations in or near the 

 forest. According to Thompson,* the proportion of water which 

 falls in snow, in the Northern States, does not exceed one-fifth of 

 the total precipitation, but the moisture derived from it is doubt- 

 less considerably increased by the atmospheric vapor absorbed by 

 it, or condensed and frozen on its surface. I think I can say 

 from experience — and I am confirmed in this opinion by the tes- 

 timony of competent observers whose attention has been directed 

 specially to the point — ^that though much snow is intercepted by 

 the trees, and the quantity on the ground in the woods is conse- 

 quently less than in open land in the first part of the winter, yet 

 most of what reaches the ground at that season remains under the 

 protection of the wood until melted, and, as it occasionally re- 

 ceives new supphes, the depth of snow in the forest in the latter 

 haK of winter is considerably greater than in the cleared fields. 

 Measurements in a snowy region in 'New England, in the month 

 of February, gave a mean of 38 inches in the open ground and 

 44 inches in the woods, but the actual difference between the 

 quantity of snow in the woods and that in open ground, in the 

 latter part of winter, is greater than these measurements would 

 seem to indicate. In the woods, the snow, which remains con- 

 stant, is consoHdated by pressure, while in the open ground, being 

 blown off or thawed several times in the course of the winter, it 

 seldom becomes as densely packed as in the woods, except in the 



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* Thompson's Vermont, Appendix, p. 8. 



