70 THE SOILS AND CEOPS OF THE FARM. 



liosses from Drainage. — The great benefits 

 from underground drainage are accompanied with 

 some loss. There is, sometimes, a considerable loss 

 of nitrogen in the drainage water. It is possible that, 

 if the water level is reduced to the depth of several 

 feet, the surface soil may be dryer during drouth, 

 as the soil cannot draw water up by capillary power 

 from a great depth. Usually, however, a well drained 

 soil has rather more than less mcjisture in it during dry 

 weather, than an undrained one. It is possible that 

 drainage of large areas may have some effect on the 

 climate, possibly affecting slightly the rainfall. 

 Wherever done with ordinary discretion, it may be 

 safely affirmed that tile drainage will do much more 

 good than harm. 



Irrigation. — Where the rainfall is insufficient or 

 comes at long intervals irrigation is necessary for 

 profitable farming. The practice is very ancient. 

 Perhaps it was first introduced along the valley of the 

 Nile. In England the practice is most common in the 

 case of low-lying grass lands, often called "water 

 meadows," on which water is kept for a considerable 

 time in winter. In this country irrigation is practiced 

 with remarkable success in what is termed the "arid 

 region," and on the plains of California. The water 

 from rivers or large streams is carried along hillsides 

 by canals and ditches and from these distributed over 

 the land, sometimes by means of elaborate systems of 

 shallow ditches. In some parts of the country great 

 supplies of water are obtained from artesian wells. 

 As yet, however, the regions in which irrigation is 

 practiced, while actually large, are relatively but a 

 very small fraction of the country, and the methods 



