Objects of Irrigation 93 



passes over and leaches through, enough of potash, 

 phosphoric acid, and other ingredients of plant -food, 

 to hold the strength of the soil up to a uniformly high 

 standard, even when constant cropping is practiced. 





Fig. 19. Heavy growth of grass on the Craigeutinny meadows, 

 Edinburgh, Scotland. 



A third object in irrigation, in certain classes of 

 cases, is primarily to change the texture of the soil. 

 When soils are very sandy and open, having so small 

 a water capacity that not enough is retained for the 

 growth of most crops, then the leading of the water of 

 a turbid stream over such lands results in the deposition 

 of silt to such an extent as, in the course of time, to 



