DISCUSSION OF DATA 



739 



same process, differing only in this, that in drifting and blowing the 

 material is not lifted far from the ground or from the bottom. In silt- 

 ing and dusting the transported load is raised high up in the water or 

 in the air, and there is less opportunity for elements of extremely differ- 

 ent sizes to be swept along and become mingled with the sizes normal to 

 the deposits of each prevailing current. From averages of the analyses 

 in the two groups of the two transporting media it appears that the chief 

 ingredient in drifted materials has higher percentage than in silt, and 

 that in blown materials it has a higher percentage than in dust. At the 

 same time drifted material has in most cases a greater range of grades 

 than silt, and blown material has a greater range than dust. In silt as 

 well as in dust the admixtures of the first order have higher percentages 

 than in either drift or blown material. This difference is greatest in the 

 wind deposits. Another difference is that in silt and dust the admixtures 

 are almost always more symmetrically arranged on either side of the 

 maximum than they are in blown or drifted material. 



In drift this distribution is often extremely unsymmetrical. This 

 irregularity in sorting of sediments carried in the lowest strata of each 

 medium is due to a greater variation in velocities in the lower part of 

 the medium than at greater heights. 



Table showing Averages of Quantities in the Grades for Deposits resulting 

 from each Mode of Deposition in Water and Wind Sediments 





Coarse admixtures. 



Maxi- 

 mum. 



Fine admixtures. 



Materials averaged. 



6 



5 



4 



3 



2 



1 



1 



2 



3 



4 



5 



6 



7 



Drift (78 samples) 



Blown materials ( 73 



samples). 

 Silt (53 samples) 



Dust (74 samples) 



.1 



.1 



1.0 



.3 

 .1 



1.7 



2 



.9 



2 



2.1 

 1.2 

 1.7 



.7 



6.0 

 4.0 

 6.4 



4.8 



15.2 

 17.2 

 19.3 

 23.0 



43.2 

 59.2 

 38.3 

 46.3 



16.6 

 13.5 

 20 9 

 20.3 



7.8 

 3.2 

 7.5 

 3.4 



2.8 

 .8 



2.5 

 .2 



1.8 

 .1 



.7 



.8 

 .1 



.2 



.1 



Another observation that seems pertinent is that in drift and blown 

 sand the coarse admixtures are in excess of the fine, while in silt and 

 dust there is apparently an excess in the fine admixtures. The excess of 

 the coarse admixtures in drift and blown sand is probably due to "roll- 

 ing," as explained elsewhere, in connection with the discussion of secon- 

 dary maxima. The excess of the fine admixtures in silt and dust may be 

 caused by flocculation. These differences do not appear so clearly in the 

 general averages. It is believed that the mingling of a number of acci- 



