116 CS. SM VAR Seis 
The resultant relative solubilities are given in columns XV and 
XII XIV XV XVI. 
Ottawa River Average Crust Solubilities ees 
CaAOse seas B57) iD 4.82 770 100. 
INGADs cbieséoc 9.73 3.28 2.96 38.5 
WEOL eon osaac T2157 3.98 3.16 40.1 
KUO) ee ae 3.02 2.96 I.02 13.4 
SiOs aes 31.07 2 59.79 53 6.9 
REO ena nnine 5-59 21.25 .26 3.4 
These figures approach most closely to those derived from 
comparison of the mean river water with the average igneous 
rocks, and differ most widely from those derived from the Mississippi 
River and average sediments. 
The most striking variation is in the soda, which, instead of 
being close to lime in solubility, falls below, but close to, magnesia, 
thus changing the solubility groups. It is interesting to note 
that this order of relative solubility is the same as the order of 
percentage loss for each constituent for a group of nine crystalline 
rocks, as given by Van Hise.’ 
It would seem to be a necessary inference that, on the average, 
the silicates of the alkaline earths and sodium are more readily 
decomposed than those of potassium, aluminum and iron. 
Without placing too much dependence upon either case, it 
seems safe to conclude that the figures for the Ottawa River roughly 
represent the relative solubilities for crystalline regions, while 
those for the Mississippi roughly represent the relative solubilities 
for sedimentary regions. 
It is rather surprising to find the relative solubilities of soda 
and magnesia greater in sediments than in crystallines. While 
this may be due in part to the presence of more soluble compounds 
the essential reason probably is afforded by the rule elsewhere 
pointed out that, as a constituent decreases in absolute quantity 
in the rocks, its relative solubility increases. 
The average of the solubilities derived from the Mississippi 
and the Ottawa is given in column XVII and the weighted mean, 
1 Op. cit., p. 516. 
