J. LeConte—Mineral Vein Formation. 427 
. and forming sulphuric acid. In a word the phenomena are 
re very similar to those at Sulphur Bank, except that here 
the up-coming solfataric waters are less abundant and perhaps. 
less rich in metallic. sulphides. This, however, can only be 
determined with a certainty by deep explorations. 
Comparison +of Steamboat Springs with Sulphur Bank.—A 
comparison of the phenomena at these two places is interesting. 
The surface phenomena, it is seen, are very different: in fact in 
complete contrast. At Steamboat Springs the whole country 
tock is covered 20 to 30 feet deep and completely concealed by 
a hard crust of deposited silica; at Sulphur Bank, on the con- 
trary, there is no crust but only a soft chalky residue from the 
acid decomposition of surface rock—a residual silica from whic 
At the California Geysers—so-called—we find also solfataric 
action with its invariable accompaniment of acid decomposition 
idue, but the freight of 
ited. In true geysers like those of : 
land, the super-heated waters contain usually only alkaline car- 
_ bonates, and therefore carry in solution and deposit only silica~ 
