CHAPTER II 



WORK OF THE WIND 



The conditions essential for the effective work of the wind are 

 aridity and a scarcity of vegetation. Since such conditions prevail 

 over more than one fifth of the land surface of the world, the work 

 accomplished by this agent is of great importance. 



Wind and Sand 



Wind without Sand. — Wind is much less effective without sand 

 than with it, but is nevertheless important. In semiarid regions 

 and in those which are suffering from a long period of drought, 

 cultivated fields may be excavated disastrously. In Wisconsin 

 there are extensive regions of light lands which almost every year 

 suffer from the drifting action of the wind. In these regions winds dry 

 up the soil and sometimes sweep away the crops of grain, even after 

 they are four inches high, uncovering the roots by the removal of one 

 to three inches of surface soil. (King.) During the drought of 1894 in 

 Nebraska, the finely pulverized soil of the cultivated fields was blown 

 out over extensive areas to a depth of two or more inches and was piled 

 up in small dunes near fences and buildings. Blow-outs, as the pits 

 excavated by the wind are called, are often the indirect result of the 

 close grazing of a light soil, or are developed in land which is covered 

 with a sparse vegetation. Blow-outs may be excavated to a depth 

 often feet or more, and at certain seasons of the year may be occupied 

 by temporary lakes. The work of the wind in removing loose sand 

 is termed deflation. 



Besides these more important effects of the wind, rocks are dis- 

 lodged from cliffs by its force, as in the Orkney and Shetland Islands, 

 where it is common to find pieces of flagstone or slate weighing several 

 pounds, which have been detached from the precipices and blown 

 upon the moors above during high gales. (A. Geikie.) Trees are 

 blown down ; water is thrown into waves ; and birds, insects, and 

 seeds are carried about. 



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