MOVEMENTS OF THE ATMOSPHERE 



51 



The following table by Mohn {6y:i3i) gives the range in 

 velocities and also the corresponding pressure. The values are 

 somewhat different from those in the table by Hann. 



Type of wind 



Calm .... 



Light 



Moderate . 

 Fresh .... 

 Strong. . . 

 Storm .... 

 Hurricane 



Velocity in 



meters 

 per second 



o 

 o. 



4 



7 



II 



17 



to o 

 to 4 

 to 7 

 to II 

 to 17 

 to 28 



above 28 



Pressure in kilo- 

 grams per 

 square meter 



o 

 o 

 I 

 5 

 15 

 34 



to o 

 15 to I 

 87 to 5 

 96 to 15 

 27 to 34 

 35 to 95 

 above 95 



15 



.87 

 .96 

 .27 

 •35 



•4 

 •4 



EOLATION OR MECHANICAL WORK OF THE 

 ATMOSPHERE. 



The mechanical work of the wind is expressed by the term eola- 

 tion, which is the process of the earth sculpture by wind, the scour- 

 ing by wind-driven sand, dust, and other substances, and the 

 transportation and deposition of rock material by wind. It may be 

 summarized as wind erosion or corrasion, as wind transportation or 

 deflation, and as colian sedimentation. The last will be especially 

 dealt with in Chapter XIII. 



