SOLUBILITIES OF CHEMICAL CONSTITUENTS OF ROCKS 115 
The composition of the Mississippi River water, so far as the 
abundant oxides are concerned and with the soda and potassa 
calculated according to Clarke’s' ratio, is given in IX, calculated to 
100 from Dole and Stabler’s analysis. Clarke’s? average composi- 
tion of sediments is assumed to represent the composition of the 
Mississippi basin. The resulting relative solubilities appear in 
columns XI and XII: 
Ix x XI ("22 ary 
Mississippi River | Average Sediments Solubilities | Ce 
CaOiae t= one 51.05 5-42 9.6 | 100.0 
INaEORGr. fers 16.45 10 518) Te 152.8 
VI OT srcrue 15.86 2.52 Ons 65.5 
IA) tions Geshe 3.44 2.80 ne 125 
SHOR Bao eee E252 58.51 214 | 2.2 
IRA Pep itesinraets 0.68 18.69 .036 | 0.4 
Compared with the figures of column VIII, there is a striking 
increase in the solubility of soda and magnesia. In other words, 
these two constituents are notably abundant in Mississippi water 
as compared with the amounts in the rocks, if these latter are accu- 
rately represented by the analyses used. If they are too low in 
the estimate used, the solubilities would come nearer the mean 
values. Potassa and silica are in fair accord with the mean, while 
the sesquioxides are low. On the whole, however, the agreement 
is surprisingly close in view of the fact that a single river basin is 
concerned, even though it be of a rather generalized type. 
Another case, representing quite different conditions, is afforded 
by the Ottawa River, draining an area of crystalline rocks. The 
composition of the dissolved salts, as given by Daly’ and recalcu- 
lated to 100 per cent of abundant oxides, is shown in column XIII. 
Clarke’s! estimate of the mean composition of the lithosphere 
is taken to represent the composition of the Ottawa’s drainage 
-basin, column XIV, although the assumption is recognized as a 
rather sweeping one. 
VOD Gits. p=: Op. cit., Pp: 13. 
3R. A. Daly, “First Calcareous Fossils and the Evolution of Limestones,” Bz//. 
Geol. Soc. Am., XX (1909), 158. 
4“The Data of Geochemistry,” U. S. Geol. Surv. Bull., No. 330, p. 31. 
