SOLUBILITIES OF CHEMICAL CONSTITUENTS OF ROCKS 117 
taking the values for the Mississippi and the Ottawa in the ratio 
of three to one, is given in column XVIII. 
XVII XVIII 
CaO eae cee ae 100.0 100.0 
Na OR acsers cic 95.6 124.2 
Mig OMA AAs etn: 8 ome 5Onn 
RAO er Meee eat 12/50 T2e7 
Oba eaonene cea 4.5 34 
REO catia ye et tate 1.9 TT st 
Representing roughly the relative areas of crystalline and 
sedimentary rocks, the figures in column XVIII must be com- 
pared with those of IV. 
The same groups appear in column XVIII, but owing to the 
high figure obtained for soda in the Mississippi water this con- 
stituent has changed places with lime as most soluble, while, for a 
similar reason, magnesia gives an abnormally high figure. Never- 
theless, when the nature of the data used is considered, the agree- 
ment between these special cases and the general case is as close 
as could be expected. 
What widely different relative solubilities may prevail in an 
individual case, which does not approximate to the general con- 
ditions, is shown by the waters of the Cache a la Poudre of Colo- 
rado, as analyzed by Headden' when compared with the average of 
four granites, from Pike’s Peak Region, analyzed by Hillebrand,’ 
which may be taken as fairly representing the stream basin. 
XIX XX XXI XXII 
Cache Ala Poudre | Pike's Peak Solubilities es 
Care. So: Brae 0.74 42.05 100.0 
INGO ae 2 21.48 2a10 6.91 16.4 
MISO Geis eh: Tae 0.07 103.14 244.4 
KOM ie bette 4.89 5-92 0.84 2.0 
SIO sa.5 62 2: 34.64 74.90 0.49 1.0 
RE ORE Riva dies 0.65 14.48 0.05 o.1 
A mere glance at the two analyses (XIX and XX) shows a 
notably high content of lime and magnesia in the water as com- 
t foc. cit. 
2E. B. Mathews, “Granite Rocks of the Pike’s Peak Quadrangle,” Journal of 
Geology, VIII, 237. 
