RELATION OF WIND TO TOPOGRAPHY 



555 



dew fall. But at 9 o'clock, although the force of wind had not in- 

 creased much, the sand was moving briskly and the shifting continued 

 through the day. 



The sand separator was kept at the same distance from shore as 

 on day I, but the ground was so slightly sloping as to be almost hori- 

 zontal. The day was warm and the sand quite dry. From 2 to 3 

 o'clock the separator was in action, and subsequent analysis gave the 

 following result: 



PERCENTAGE 



Diameter in mm. 



Floor A. — 0.02-0.5 

 o . 05-0 . I 

 O.I -0.2 

 0.2 

 0-3 

 0-5 



OF DIFFERENT GRADES 



-0-3 

 -0-5 

 -I 

 -2 



Floor 



B. — 0.02-0.05 

 o . 05-0 . I 

 0.1 -0.2 

 0.2 -0.3 

 0-3 -0.5 

 0.5 -I 

 Floor C. — 0.02-0.05 

 o . 05-0 . I 

 0.1 -0.2 

 0.2 -0.3 



0-3 -0-5 

 0.5 -I 

 D. — 0.02-0.05 

 o . 05-0 . I 

 0.1 -0.2 

 0.2 -0.3 



0-3 -0-5 

 Floor E. — 0.02-0.05 

 o . 05-0 . I 

 0.1 -0.2 

 0.2 -0.3 



Floor 



Per Cent. 



trace 



6.4 

 10.2 



41.3 



28.4 



9.6 



3-5 

 0.6 



1-7 



26.5 

 47.8 



14. 1 



6.6 



5-1 



10. 



23-4 



41 .2 

 6.7 

 3-6 



16.3 



34-7 

 28.5 



12. 1 

 8.4 



32-5 

 34-1 

 16.8 



S-4 

 1 .2 



0-3 -o-S 



A wind with a velocity of 22.4 m. per second was thus able to lift 

 medium sand at least 8 cm. and coarse sand 4-6 cm. The coarsest 

 grains at all raised above the surface had a diameter of i mm. 



x\s for the distance to which the wind was able to transport colored 

 grains I found grains 4.3 m. away from the original place of exposure 

 after 15 minutes, while grains of 0.2 mm. diameter were carried at 



