554 



PEHR OLSSON-SEFFER 



separator had received a quantity of grains on each floor. Mechanical 

 analysis of these grains showed that on the lowest floor A, on a level 

 with the surrounding ground where the greatest quantity of sand 

 had collected, many different grades were represented. This is self- 

 evident as the grains here had only rolled and not been lifted by the 

 wind; at least not higher than 2 cm., in which case they were inter- 

 cepted by the next higher floor B. The wind was gusty, but the force 

 of the separate gusts was comparatively uniform, and the intervals of 

 wind of lesser velocity, brief and somewhat regular in length. 



PERCENTAGE OF DIFFERENT GRADES 

 Diameter in mm. 



Floor A. — 0.02-0.05 



O 

 O 

 O 

 o 

 o 

 I 

 Floor B. — o 

 o 

 o 

 o 



•OS 

 .1 



Floor C 



Floor D 

 Floor E 



05-0. 



1 -o. 



2 -o. 



3 -o- 

 5 -I 



-2 



02-'0 . 

 05-0. 

 1-0.2 

 2-0.3 



0-3 -0-5 

 — o , 02-0 . 05 

 o . 05-0 . I 

 O.I -0.2 

 0.2 -0.3 



0-3 -0-5 

 — 0.02-0.05 

 o . 05-0 . I 

 O.I -0.2 

 — o . 02-0 . 05 

 o . 05-0 . I 

 O.I -0.2 



Per Cent. 



trace 

 2.2 



13-1 

 56.2 



21.5 

 5-6 

 1-4 

 0.8 



S-2 

 42.9 



44-S 



6.6 



12 .3 



16.6 



58.4 

 10.7 



2.0 

 37-4 

 56.7 



5-9 

 72.5 

 26.3 



1 .2 



The coarsest material with certainty lifted by a wind of a velocity 

 of 12.8 m. per second was, as indicated by the above table, medium 

 sand, and the greatest height to which this sand was lifted, 4-6 cm. 



During the same period of time the colored sand samples exposed 

 to the wind were distributed as follows: 



Fine sand . 

 Medium sand 

 Coarse sand 



12 m. 

 12 



7-5 



II. During morning hours the drifting was insignificant as the 

 surface of the ground was still somewhat moist with the abundant 



