254 WARREN J. MEAD 
In the following table are listed the discrepancies arising under Van 
Hise’s ratio of 65:30:5 and the differences encountered in the present 
investigation. 
TABLE VII 
COMPARISON OF THE TWO RATIOS 
Diff. under Ratio of Diff. under Ratio of 
65:30:5 80:11:90 
SIO pamantneen sti caietere +3.2470 +2.04 
As Ob acter ie mcnaisrseniuete — 3.6800 =670 
Tle irepenctersacten- tape tspepecoaences =f. l490 (6) 510s) 
CHO a Gen wre omen tis (no discrepancy) +2.41 
Mig @Eirtest serpents: — 2.2025 ih as) 
INais Oleic toe ctotsr spares ane — 2.4985 SOSA 
IRAO RoHS aaa s 66 —0.2925 +0.10 
The differences are less for the ratio of 80:11:9 than for 65:30:5. 
Van Hise’s choice of ratio was influenced by estimates of observed 
thickness and relative proportions, and not alone by analyses. 
Another estimate of the relative importance of the three classes of 
sedimentary rocks is one made by Clarke.t In attempting to ascer- 
tain the average composition of the lithosphere, he estimates it to be 
made up of 95 per cent. of igneous rock, with 5 per cent. of sediments, 
and he assigns 4.0 per cent. to be shales, 0.75 per cent. to the sand- 
stones, and 0.25 per cent. to the limestones. This is equivalent to 
a ratio of shales to sandstone to limestone of 80:15:5, which accords 
rather well with the results of the present discussion. Clarke obtained 
his results by assigning all the free quartz of the average crystalline 
rock to the production of sandstone and half of the calcium of the 
average crystalline rock to the formation of limestone. The figure 
for free quartz was obtained from petrographical descriptions of about 
700 igneous rocks. 
The results of the present investigation are also roughly in accord 
with the results obtained from measurement of materials carried by 
rivers, but so many factors enter into such comparison that it will not 
be discussed here. 
It is hardly to be expected that the relative abundance of the 
principal sedimentaries determined from field observations should 
t F, W. Clarke, “The Statistical Method in Chemical Geology,” Proceedings of 
the American Philosophical Society, Vol. XLV (1906), p. 21. 
