1907] Rain and Snow. 171 



quantities of water for its maintenance. Oiar crop yields depend 

 not only on tlic amount of plant food in the soil, on a proper 

 texture of the soil, but also on certain climatic conditions, 

 prominent among which, and one might say of first importance, 

 is an adequate supply of available moistvire. 



We are all aware, no doubt, that the footl taken from the soil 

 by plants is absorbed by the yoimg rootlets in the form of a very 

 dilute solution. This dilute food solution non-elaborated sap 

 passes up through the tissues of the stem or trunk and reaches 

 the leaves where chemical changes (metaboli.sm) takes place, 

 elaborated sap is formed and the excess of water, after the 

 deposition, as it might be termed, of mineral and nitrogenous 

 matter, passes ofif as vapour through the stomata of the leaves. 

 In this way enormous amounts of soil moisture are required for 

 our crops. For ever\- 1 lb. of dry matter stored tip in the plant, 

 at least 300 lbs. of water pass through its tissue and escape into 

 the atmosphere, Thus, a crop of Indian corn requires, per acre, 

 during its season of growth more than 1,000 tons of water. This 

 must be supplied, in addition to that lost b)' evaporation from 

 the surface of the soil, if a maximum crop is to be obtained. 

 By certain methods of cultivation, soil moisture mav be con- 

 served for crop use, and thus protect our crops against seasons 

 of drought. Indeed we now know how to keep over large amounts 

 of soil moisture from one season for the next vear's crops. This 

 is practised in the wheat fields of our Northwest by fallowing, 

 fohowed by frequent cultivation the earth mulch so prepared 

 checks surface evaporation. In districts of sparse precipitation, 

 provision for the crop's need is made bv irrigation. This leads 

 us naturally to a consideration of the precipitation in various 

 parts of Canada. In a country or district to be settled the 

 question of the rainfall is a very important one to have some 

 information upon, and in this connection the data that are being 

 obtained and tabulated bv the Meteorological Service of Canada 

 are of inestimable value. The precipitation, as observed for 

 three consecutive years at a few important points across the 

 Dominion, is recorded in the following table. The data are 

 taken from the published records of our Meteorological vSer\-ice. 



Precipitation is measured in inches. One inch of rain means 

 113 tons 601 lbs. of water per acre. Ten inches of snow are 

 considered the equivalent of one inch of rain. The average 

 rainfall at Ottawa for the past 16 years is 25.56 inches, and the 

 average snowfall" for the same period is 90.06 inches. This 

 latter fact means that we have had, per acre, during the winter, 

 approximately 1,000 tons of snow water. 



