1) CES MY RH ike 
where the number of analyses is limited. The other constituents 
cannot differ much in relative amounts in sediments and in igneous 
rocks. Van Hise! has pointed out, and explained, certain discrep- 
ancies when the analyses of the sediments are compared with those 
of the igneous rocks, but for the present purpose these may be 
overlooked. However, in view of the possible divergence of the 
compositions of sediments used from the true mean, it may be 
worth while to make a similar calculation using the composition 
of the igneous rocks, instead of that of the surface rocks, as above 
estimated. It is probable that this composition of the igneous 
rocks is more accurate than that of the sediments which was intro- 
duced in calculating the composition of the surface rocks, and, 
except for the soda, fairly accordant results might be expected, 
although as pointed out above, the surface rocks must differ 
from igneous rocks not only in bulk composition but also as 
to compounds present, and a comparison of the composition of 
drainage waters with that of the igneous rocks is, therefore, highly 
artificial. The results of such a comparison of the mean composi- 
tion of river waters with that of the average composition of igneous 
rocks, are as follows: 
Vv VI VII VIII. 
cues sean Igneous Rocks Solubilities aes 
CaQe css 48.34 4.81 10.05 100.00 
INGAO) 6:5 oan c 14.61 3.41 4.28 42.5 
INGRO)S cis boc oo 9-55 3.89 2.46 24.5 
KG Oe eac teen 3.09 2.95 I.05 10.4 
SiO ieee 19.70 59.99 0.33 QR 
RIOR aie 4.65 21.34 0.22 2.0 
Comparing the figures of columns VII and VIII with the corre- 
sponding figures of columns III and IV, the expected relations are 
seen, substantial agreement except for soda which shows, in column 
VII and VIII, decidedly smaller relative solubility. This must 
necessarily be the case, since the river waters actually derive their 
soda largely from the already depleted sediments, and if, as here 
done, their content be compared with that of the unleached igneous 
«¢C. R. Van Hise, ‘Treatise on Metamorphism,” Monograph XLVII, U.S. Geol. 
Surv. (1904), chap, xi. 
