SOLUBILITIES OF CHEMICAL CONSTITUENTS OF ROCKS 119 
of the absence of such knowledge, it seems fair to infer that the 
minute quantities of metals that have sometimes been determined 
in rocks of mining districts have, because of their small quantities, 
higher relative solubilities than the other constituents of the rocks 
and thus take the first step, and perhaps a long one, toward their 
final concentration, when they go into solution in ground waters. 
The same doubtless applies to the rarer gangue materials as well. 
One further special case may be added, particularly because it 
affords positive data as a basis of calculation, which were lacking 
in all the preceding cases. Reference is made to Headden’s* 
experiments upon the solution of feldspar in carbonated water. 
The powdered feldspar was treated with successive portions of 
distilled water for 48 hours, agitation being effected by a current 
of air containing a little carbon dioxide. Nearly 35 gallons of 
water were used, evaporated to dryness, and the residue analyzed. 
The results appear in column XXIII, the composition of the feldspar 
in XXIV, and the relative solubilities in columns XXV and XXVI. 
XXIII ) xiv XXV _XXVI 
Feldspar Solution Feldspar Solubilities es 
CAO sed 14.43 0.314 45.95 100.0 
Na.O 7.39 2.728 2.70 5.9 
IMISOS. 5 sce 22 1.08 0.029 By 824: 80.8 
BOO. i... : 15-45 THE Oe ase 2.9 
‘Sil O);a toa 57.41 65.760 0.87 1.9 
REOr ee oes fs) ee 1g. 291 On22 0.5 
The agreement with the Cache a la Poudre figure is not as close 
as might be expected, the magnesia here occupying second place 
instead of first. 
The relative solution concentration of magnesia, is less pro- 
nounced, for if all the figures be multiplied by five, while it gives 
high results for potassa, silica, and sesquioxides, the magnesia 
becomes only 404 as compared with 1,222. Still, the abnormally 
high relative solubility for constituents in small quantity is again 
illustrated. On the other hand, potassa shows no reduction of 
relative solubility as compared with soda, silica and sesquioxides, 
~Op. Git... Pp. 181. 
