154 The American Geologist. March, 1896 
might be cited, however, of the vein in the Reveredge district 
which lost its gold on the passage from granite to limestone, 
but in other localities of the presence of rich gold bearing 
veins in limestone. In regard to the occurrence of gold ores 
on the western slope of the Sierras the writer sometime si net- 
expressed views* which are in accord with the observations 
recorded in this paper, namely, "The character of the min- 
eral deposits depends partly on the nature of the chemical 
action, the material subject to that action, and partly on the 
complex chemical conditions in the crushed zone or fissu im- 
penetrated by the mineral bearing solutions." It is a fact of 
general application that certain districts in eastern California 
are characterized by gold, others by silver, without any 
marked dependence, except in the case of galena, on the 
character of the rocks in those districts, that is, gold and silver 
deposits do not generally occur indiscriminately side by side. 
This would imply a much greater dependence on the nature 
of the chemical action than upon the physical conditions 
existing or the precipitating power of the walls upon the 
mineral bearing solutions. 
A number of the gold mines in the granite have reached a 
depth of 700 feet without becoming poorer, while those of 
Bodie have been opened to 1,200 feet. It is only in the latter 
that the veins have been found to give out, becoming weaker 
below the 500 foot level. 
The occurrence of gold in galena is rather remarkable, as 
well as that of its dissemination in the granite northeast of 
Mojave. 
It is probable that the gold deposits of eastern California, 
with the exception of Bodie. are of the same age as those of 
the rest of the state, posterior to the upheaval terminating the 
•Jurassic. 
Mr. Lingrenf expresses the following view in regard to the 
formation of the gold quartz veins of California. " Replace- 
ment proper of the minerals of the country rock along the 
fissure by quartz I have never been able to observe, and cases 
supposed to be of such nature have always proved to be (\ue 
to the shattering of the country rock and the rilling of it 
*En<j\ and Mining Jour., vol. lv, p. 200. 
fBulJ. Geol. Soc. Am., vol. vi, p. -22U. 
