This section is from "Scientific American Vol XXXVI. No. 8", by Munn & Co. Also available from Amazon: Scientific American Science Desk Reference.
Snow is often called the "poor man's manure;" and if it is true that it has any manurial value, the farmer's prospects for the next season are certainly flattering. The body of snow upon the ground in all the Northern and Middle States is very great, and millions of acres of land are covered by it as with a blanket of the whitest wool. It is probable that seldom, perhaps never, has so wide an area of our country been covered as during this month of January, 1877. The question whether snow is capable of affording to lands any of the elements of fertility is one often asked; and in reply, the Boston Journal of Chemistry says that it probably is. The atmosphere holds ammonia and some other nitrogenous products, which are without doubt brought to the soil by snowflakes as well as by rain drops. Experiments both here and abroad would seem to prove the truth of this conclusion.
Rains are not only valuable for the moisture which they supply, but for what they bring to us from the atmosphere. During a thunderstorm nitric acid is produced in considerable quantities; and dissolved in the rain drops to a high degree of attenuation, its effects upon soils are highly salutary, as the nitrogen permeates the entire soil.
 
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