[shutt-dorrance] nitrogen COMPOUNDS IN RAIN AND SNOW 71 



reason for this, as already remarked, is the greater effectiveness of the 

 snow as a filter for the solid particles of the air. The percentage of 

 nitrogen as nitrates is the same for both rain and snow, but the per- 

 centage as free ammonia in the snow (48%) is lower than in the rain 

 (53%). The snow is not influenced to the same degree by atmospheric 

 conditions as rain, its nitrogen content remains fairly constant through- 

 out the winter months and from year to year. 



In Table V the amount and proportions of nitrogen furnished 

 by rain and snow are given. The proportion of the total nitrogen 

 furnished by the snow for the first and last years of the decade is 

 above the average; this is explained by the fact that during those 

 years the snow fall was very high — that for the first year is the highest 

 recorded, that for the last year stands second. The results taken 

 generally indicate that approximately 83% of the total nitrogen is 

 furnished by the rain, 17% by the snow. 



During the ten years, 65-826 pounds of nitrogen per acre were 

 furnished to the soil, of these 34 06 pounds were in the form of free 

 ammonia, 10 136 pounds in the form of albuminoid ammonia and 

 21 -630 as nitrates and nitrites. If we assume the availability of this 

 nitrogen as equal to that in the more soluble nitrogenous fertilizers, 

 we deduce that the land has received per acre during the decade an 

 amount equivalent to that in an application of 440 pounds of nitrate 

 of soda. This nitrogen at a conservative estimate is worth 20 cents 

 per pound and consequently the nitrogen supplied by the rain and 

 snow annually is roughly $1.30 per acre. 



This enquiry while furnishing evidence of the value of rain and 

 snow as hygienic factors in cleansing the atmosphere has contributed 

 materially to our knowledge regarding the importance of the precipita- 

 tion as a source of available nitrogenous crop food. 



