64 THE ROYAL SOCIETY OF CANADA 



as well as that of the rain, through the atmosphere must be of con- 

 siderable hygienic importance. That there may be other features of 

 scientific and hygienic interest is admitted, but they are not here 

 discussed. 



Agricultural Importance of the Investigation. 



The agricultural significance of this study will be apparent from 

 the fact that of the three essential fertilizing elements, nitrogen, 

 potash and phosphoric acid, the first named is the most important. 

 Nitrogen, under ordinary conditions of farming and in the larger 

 number of instances involving the consideration of virgin areas, be- 

 comes the limiting factor of fertility, or, in other words, the element 

 most essential to productiveness. Further, it is the element most 

 easily lost from the soil, especially under irrational or injudicious 

 methods of farming. And lastly, it is the most costly of all the fer- 

 tilizing elements when recourse must be had to increasing its store 

 from commercial fertilizers. 



The results obtained during the ten year investigational period 

 (1908-1917) have given an average of 6-583 lbs. of nitrogen as fur- 

 nished annually per acre. They further show that under normal 

 conditions the largest amounts of this nitrogen are usually supplied 

 during the months of April and May. Since the greater part of this 

 nitrogen is present in the forms of free ammonia and nitrates, com- 

 pounds which are practically immediately available for crop use, the 

 rain becomes a direct fertilizer at a most opportune time. 



The Collection of the Sample. 



The analytical work was carried out at the Chemical Labor- 

 atories, Central Experimental Farm, Ottawa. The farm, com- 

 prising between four and five hundred acres, is situated on the out- 

 skirts of Ottawa in a south-westerly direction. Ottawa is essentially a 

 residential city, the absence of factory smoke-stacks being quite 

 marked, and therefore the air should not be seriously contaminated. 

 There is a single railroad line about one-quarter of a mile north-east 

 of the laboratory, but the trafifiic is not heavy and engine smoke 

 therefrom cannot materially contaminate the atmosphere. The 

 ground on three sides of the laboratory is given to grass, trees and 

 shrubbery, that on the fourth or northern side is used for experimental 

 work with grains and hence is under growth or snow except for a few 

 months in the spring. We have, however, to remark that north 

 of the city, just across the Ottawa river, is the plant of the E. B. 

 Eddy Company, manufacturers of matches and fibre products. 

 Fumes from their sulphite mill are very much in evidence at times 



