296 



THE REGOLITH 



into chips and flakes of notable sizes. Particles much coarser 

 than those above enumerated occur, but their actual number is 

 comparatively small, though their comparative bulk may be 

 considerable. 



Work of a like nature, but done under somewhat different 

 conditions, by Dr. Milton "Whitney, showed the residues from 

 the Trenton limestones near Hagerstown, Maryland, to contain 

 on an average some 45 7o of finely comminuted material, the 

 individual particles of which vary in size between .005 and 

 .0001 millimetre in diameter, and which may appropriately 

 be termed clay. As Dr. Whitney has calculated, there are 

 approximately 22,000,000,000 grains of sand and clay in each 

 gramme of such a sub-soil, presenting in every cubic foot not 

 less than 158,000 square feet of surface to the action of water 

 and air, as well as to the roots of growing plants. 



The results of mechanical analyses of (I and II) residues from 

 the Trenton limestone, (III) Triassic sandstone, (IV) gabbro, 

 and (V) gneiss are presented in tabular form beiow.^ 





Mechanical Analysis of 



Eesidual Deposits 







Diameter 















OF 



CONTBNTIONAL KaMES 



I 



II 



III 



IV 



Y 



Particles 















MM. 



















0/ 



/o 



% 



% 



% 



/o 



2-1 



Fine gravel 



0.64 



0.17 



0.00 



0.00 



0.19 



1-.5 



Coarse sand 



0.32 



0.00 



0.23 



1.60 



1.80 



.6-.25 



Medium sand 



0.72 



0.15 



1.29 



3.49 



3.12 



.25-.1 



Fine sand 



0.62 



0.25 



4.03 



6.24 



6.96 



.1-.06 



Very fine sand 



4.03 



2.34 



11.57 



11.74 



8.76 



.06-.01 



Silt 



36.02 



19.04 



38.97 



32.60 



34.92 



.01..005 



Fine silt 



14.99 



20.88 



8.84 



10.77 



12.14 



.005-.0001 



Clay 



Total mineral matter .... 



41.24 



61.77 



32.70 



26.62 



28.82 





98.48 



94.60 



97.63 



92.96 



96.71 





Organic matter, water, and loss 



1.52 



5.40 



2.37 



7.04 



3.29 





100.00 



100.00 



100.00 



100.00 



100.00 



Many of the products of weathering of siliceous crystalline 

 and calcareous rocks are of economic importance as soils, clays, 

 and iron ores, as elsewhere noted. The kaolin beds of northern 



^ Bull. No. 21, Maryland Agr. Exp. Station, 1893. 



