1395. Snow is of great use to the vegetable kingdom. Were we to judge from appearance only, we might imagine, that, so far from being useful to the earth, the cold humidity of snow would be detrimental to vegetation: but the experience of all ages asserts the contrary. Snow, particularly in those northern regions where the ground is covered with it for several months, fructifies the earth, by guarding the corn or other vegetables from the intenser cold of the air, and especially from the cold piercing winds. It has been a vulgar opinion, very generally received, that snow fertilises the land on which it falls more than rain, in consequence of the nitrous salts which it is supposed to acquire by freezing: but it appears from the experiments of Margraaf, in the year 1731, that the chemical difference between rain and snow-water is exceedingly small; that the latter contains a somewhat less proportion of earth than the former; but neither of them contains either earth, or any kind of salt, in any quantity which can be sensibly efficacious in promoting vegetation. The peculiar agency of snow as a fertiliser, in preference to rain, may be ascribed to its furnishing a covering to the roots of vegetables, by which they are guarded from the influence of the atmospherical cold, and the internal heat of the earth is prevented from escaping. Different vegetables are able to preserve life under different degrees of cold, but all of them perish when the cold which reaches their roots is extreme. Providence has, therefore, in the coldest climates, provided a covering of snow for the roots of vegetables, by which they are protected from the influence of the atmospherical cold. The snow keeps in the internal heat of the earth, which surrounds the roots of vegetables, and defends them from the cold of the atmosphere.
