DISCUSSION OF DATA 



737 



grades in blown material. The average position of the cnlmination, or 

 the highest point of this secondary maximum, is in the fourth grade of 

 coarse admixtures for water drift and in the third grade for blown ma- 

 terial. In other words, 



4. When a transporting medium is supplied with sufficiently heterogeneous 

 material it will tend to carry and to deposit more of two certain sizes of 

 material than of any other sizes. The principal deposit it makes will consist of 

 materials it can momentarily lift. With this it will leave an excess of another 

 considerably coarser ingredient which it can roll, smaller in quantity. This 

 makes what we may call a secondary maximum. For water deposits, the 

 secondary maximum will consist of elements having a diameter about sixteen 

 times the diameter of the elements in the chief ingredient. For wind deposits, 

 the secondary maximum will consist of elements having a diameter about eight 

 times that of the elements in the chief ingredient. In atmospheric sediments 

 the quantities present in the secondary maxima usually average greater than in 

 aqueous sediments, presumably because there is apt to be a greater supply of 

 smaller clastic elements than of larger. 



The facts on which the above inferences are based are not as full as 

 would be desirable, but they are believed to be sufficient to sustain the 

 statements made. It is believed that the relatively smaller distance 

 between the secondary and primary maxima in blo^\ai sand than in 

 drifted and washed sand will prove to be a diagnostic feature in the 

 identification of blown sand which otherwise may resemble washed sand. 



In the following table 23 samples of what appear to be true cases illus- 

 trating the operation of this law in sedimentation in water are averaged. 

 All maxima believed to consist of the principal material laid down by 

 the drifting current are averaged in one grade and the admixtures are 

 then averaged in successive order for each grade. These averages are of 

 the samples numbered 10, 11, 12, 13, 17, 18, 26, 35, 36, 37, 60, 69, 82, 

 86, 87, 89, 93, 96, 97, 100, 102, 103, 104. Of atmospheric sediments 

 having secondary maxima clearly produced under similar conditions 

 there are only seven: numbers 192, 194, 195, 196, 197, 211, and 218.. In 

 the table these are averaged in the same manner as the water sediments. 



Table showing the Position and Height of the secondary Maximum in Water 



and Wind Deposits 





Coarse admixtures. 



Maxi- 

 mum. 



Fine admixtures. 





7 



6 



5 



' 



3 



- 



1 



1 



'•^ 



3 



4 



5 



Water deposits. . . . 

 Wind deposits 



.2 



1.1 



3.8 

 .3 



5.3 

 10.0 



5.2 

 19.5 



11.0 



12.8 



17.5 

 17.4 



40.0 

 33.7 



11.3 



5.3 



3.4 



.6 



.7 



2 



.1 











