30 



GENERAL INTRODUCTION 



TABLE X 

 POWER REQUIRED TO THRESH A BUSHEL OF GRAIN 



TABLE XI 

 POWER REQUIRED FOR GRINDING 



Irrigation. Water is a necessity for the growth of every crop. 

 In the Western States, the rainfall is, as a rule, insufficient to sup- 

 port even a scant growth of vegetation, but in the Central and 

 Eastern States the average rainfall during the growing season is 

 ordinarily considered sufficient. However, in the latter sections 

 of the country hardly a year passes without some particular 

 section being badly in need of rain. 



As rains, to be beneficial, must come at such times and in such 

 amounts as will properly moisten the soil and produce growth, a 

 check in this supply of soil moisture at any stage of the growth 

 affects both the quality and quantity of the yield and may greatly 

 reduce the profits of the grower. The real test of the necessity of 

 irrigation is not the total annual rainfall, but the monthly, and, 



