U THE SOILS AND CKOPS OF THE FARM. 



scopic power. The quantity of water so absorbed is 

 comparatively small, although in extreme cases it may 

 be as much as five per cent. A thoroughly dried soil 

 will absorb moisture from the air if the latter contains 

 it, but, ordinarily, the soil gives to the air much more 

 moisture by evaporation than it absorbs from it. 

 Even when the soil seems perfectly dry it contains 

 considerable moisture, as may be proV'ed by heating it. 

 In examinations of a large number of samples of the 

 loamy prairie soil at the Illinois Agricultural Experi- 

 ment Station, during times of unusual drouth, the 

 surf ace .soil, to the depth of six inches, was found to 

 contain less than ten per cent of water, in only a few 

 samples; in but a single sample was as little as eight 

 per cent of water found. The soil at greater depths 

 contained more than the surface soil in each sample 

 examined. 



When rain falls in time of drouth, the surface soil 

 becomes saturated. As the rain continues the depth 

 of saturation increases until rock, impervious clay or 

 hard-pan is reached, or the water in excess of what 

 the soil can hold passes down into the sandy or 

 gravelly sub -soil, or through underground drains. As 

 the water goes down, carrying with it carbonic acid 

 and oxygen, it helps decompose the materials of the 

 soil, making the potash, phosphoric acid, lime, etc., 

 soluble and suitable for the use of plants. Some of 

 this dissolved mineral matter is carried down by the 

 water. In time of heavy rains there is a loss of plant 

 food through drains or in the open sub-soil. 



After the rain ceases, evaporation commences, with 

 greater or less rapidity, depending on the temperature 

 and dryness of the atmosphere. As the surface be- 



