250 WARREN J. MEAD 
ments than any of the others, and any deviation from the best ratio 
will consequently produce greater discrepancies in calcium and 
silicon than in the elements which are more evenly distributed among 
the three sedimentary rocks. For this reason it is probable that the 
best point les somewhere between the lime and silica lines. By 
referring to Table III it is seen that the shales contain more iron 
than either of the other classes of sediments, and hence a point above 
the iron line would indicate an excess of iron in the sediments and a 
point below it a deficiency. As we know that iron is segregated to 
a large extent in iron formations and ores, a deficiency is more prob- 
able than an excess, and the point evidently hes below the iron line. 
This throws it inside of the area bounded by the calcium, silica, iron, 
and potassa lines. A point at the center of this area gives a ratio 
of 82 parts shale, 12 parts sandstone, and 6 parts limestone, con- 
sidering only such a part of the masses as is made up of the “derived.” 
elements. 
From Table II it is seen that the “derived” elements of the shales 
make up only 91.34 per cent. of the mass, of the sandstone only 
95.30 per cent., and of limestone only 60.49 percent. It is evident, 
then, that in the above ratio 82 represents only 91.34 per cent. of 
the total mass of the shales, 12 represents only 95.30 per cent. of the 
total mass of the sandstone, and 6 represents only 60.49 per cent. 
of the total mass of the limestone. If these figures are recalculated 
to take into account the entire mass of the sediments, we have as a 
ratio of shales, sandstone, and limestone, in even numbers, 80:11:09, 
respectively. 
The relative abundance, then, of the three classes of sediments, 
as determined in the present investigation on the basis of average 
composition of crystalline rocks, is 80 parts shale, 11 parts sandstone, 
and g parts limestone. 
The same process of solution was applied to a series of five average 
analyses of crystalline rocks, ranging from acid to basic, and the 
same predominance of shale was observed in each case, ranging 
from 79 per cent. for acid rocks to 88 per cent. for the basic end of 
the series. This would seem to indicate that the redistribution of 
any crystalline rock results in a large predominance of shale in the 
t Wright, Tables of Igneous Rocks, after Rosenbusch’s classification. 
