174 The Ottawa Naturalist. [December 



Another phase of the subject is the fertiUzing value of rain 

 and snow. This is a matter that has received attention during 

 the past two years at the Experimental Farm laboratories. A 

 sample from every rainfall and snowfall is analysed and the 

 nitrogen compounds determined. The atmosphere contains 

 many gases in addition to those two which make up its general 

 composition, oxygen and nitrogen. The combustion of fuel, 

 the oxidation of food in animals, produce gases which find a 

 natural home in the atmosphere. From such sources, and also, 

 no doubt, to some extent from electric discharge, the air receives 

 gaseous nitrogen compounds. The air also contains much dust 

 and in the neighbourhood of cities a considerable quantitv of soot. 

 The rain and the snow falling through the atmosphei^e dissolves 

 these gases and washes out the dust and soot and thus bring 

 not inconsiderable amounts of fertilizing material to the soil. The 

 nitrogen compounds are chieflv ammonia, ammonium salts and 

 nitrates. All these are valuable agriculturally, because they fur- 

 nish available plant food. During the winter of 1 906-07 ,85.5 inches 

 of snow fell and this was found to possess nitrogen compounds 

 equivalent to 1 lb. (approximately) nitrogen per acre. Similarly, 

 analyses of last season's rain show that it furnished 3.5 lbs. 

 (approximately) of combined nitrogen per acre. As nitrogen 

 suitable for plant food is worth in a fertilizer about 1 7 cents per lb. 

 we find that the rain and snow together furnish, in the neighbour- 

 hood of Ottawa, about 75 cents worth of plant food per acre. 



The soot and dust present in what appears to us the whitest 

 snow is readily made evident bv collecting some snow imimediatelv 

 after a fall and allowing it to melt in a clear glass jar as the 

 snow liquifies the soot will be seen clinging to the sides of the 

 vessel and there will probably be also a deposit at the bottom 

 of the jar. 



Snow benefits the farmer and frviit grower in other ways 

 besides fertilizing the land. Thus it lies as a blanket protecting 

 the roots of our fruit trees against excessive cold. 



How Rain and Snow Affect the Health of the World. 



The filtering of the atmosphere, the washing of the atmos- 

 X^here by the rain and snow, have already been referred to; 

 they purify and cleanse the air of both gaseous and solid impurities 

 and further, no doubt, rid it of many microbes. The large 

 amount of absorbent and filtering surface presented by the flakes 

 of snow as they fall perform this useful function to a 

 wonderful degree. In a very large measure the exhilarat- 

 ing character, the crispness, the claritv of our winter air is due 

 to this action of the snow. ' V^. Ui T A i ^ 



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