FOREST INFLUENCES. 43 



to the rise of temperature furnishes impetus to previously 

 existing horizontal currents, and by 10 o'clock in the morn- 

 ing the hot wind is fully developed. Hundreds of miles of 

 hot dry earth contribute to maintain and feed the current, 

 and, gathering strength as the sun mounts higher, the hot 

 wind sweeps over the defenceless prairie. Neither hills 

 nor forests rise in its path to break its power or dispute its 

 sway, and, with no enemy save the tardy rain-cloud, the 

 fetid blast sucks out the life-sap of the growing grain. It 

 will be readily seen, then, that each of the States Kansas, 

 Nebraska, and North and South Dakota develops its own 

 hot winds and cannot charge them to the account of its 

 neighbors." 



The local origin of these winds at once suggests the desira- 

 bility of frequent windbreaks on the prairie farms, as offer- 

 ing the most practical way of breaking them up. Irrigation 

 of large areas will also undoubtedly do much to prevent 

 them. 



