6o 4 



POPULAR SCIENCE MONTHLY. 



partial, or entire crop failures are to be looked for. The regular- 

 ity of production, of course, results from command of the water 

 supply as such ; the high production has usually been ascribed 



First * Foot Second 

 Depth of Soil Column - 



largely to the plant food brought to the land by the stream 

 waters used in irrigation, whether in the form of suspended mud 

 or in actual solution. Especially has the never-failing fertility 



