742 



J. A. TDDEX- 



rOMPOSlTIOX OF CLASTIC SEDIMENTS 



Difference in the quantity of the chief ingredient. — The difference is 

 likewise evident from the variations in the percentages of the quantities 

 contained in the chief ingredient. In the water deposits the percentages 

 of the maxiniiun range from 18.5 to 94.0 per cent, while in wind deposits 

 there is a range from 25.1 to 9T.0 per cent. These figures are not diag- 

 nostic. Bnt if we arrange the maximum percentages of water deposits 

 in groups, each ranging between limits of 10 units of per cent, we find 

 evidence of the two different modes of sorting, one (drifting) resulting 

 in producing maxima containing about 10 per cent of the sample and 

 another mode (washing) sorting the sediments until about 65 or TO per 

 cent wiU be of one and the same grade. The two groups evidently over- 

 lap, as we would expect. Drifting under some conditions produces de- 

 posits which are better sorted than the least thoroughly sorted deposits 

 produced by washing, as stated before. 



TaMe showing Variations in the Percentages contained in the Maxima of all 



Sediments examined 



Limits of Kroups in per 

 cent 



11-20 



21-30 



31-40 



41-50 



51 -co 



61-70 



71-80 



81-f»0 



91-100 







Xumbers of water 

 sediments 



Xumbers of wind 

 sediments 



3 



28 

 3 



49 



18 



34 

 53 



22 

 32 



23 

 23 



14 



14 



5 

 3 



4 

 2 



The slightly greater frequency in water deposits of maxima containing 

 from 61 to TO per cent than of maxima containing from 51 to 60 per 

 cent is caused by the samples of washed materials. Xo similar grouping 

 is indicated for the wind sediments, where perfection of sorting in the 

 coarser deposits is effected only by the processes analogous to driftiag 

 and silting. 



Difference as to average number of grades. — Again, the less effective 

 sorting power of water, except in case of washing, is evident when we 

 examine the number of grades containing any certain minimum per- 

 centage of the whole sample. The difference is evident, whatever quan- 

 tity be taken as a minimum, as appears from the following: 



