_— 
SOURCE AND DISTRIBUTION OF THE GOLD. 
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surpass all other regions in the world in metallic wealth; for hundreds of 
years they have been supplying the world with a large part of its silver, and 
no inconsiderable proportion of its gold. The richness of the Peruvian mines 
long saice became proverbial, and the word “ bonanza” is now familiar to all 
from its association with the mines on the Comstock Lode and others of the 
Far West. These regions have been the seat of the most intense volcanic 
activity during Tertiary times, and in all probability in previous geological 
epochs. It is hardly possible, therefore, in view of all the facts, not to 
admit that there is likely to be some genetic connection between the mani- 
festations of igneous forces and the impregnation of the rocks with the 
precious metals and metalliferous ores. 
Quite a number of theories relating to the geological epochs at which the 
various metals have made their appearance, or been introduced into the 
formations where we now find them, have been put forth by chemists and 
geologists. Gold has been specially favored in this respect. No theoretical 
views regarding this metal have been so widely promulgated and generally 
accepted as those of Murchison. According to this eminent authority, gold 
in paying quantities is exclusively confined to the Palxozoic rocks, into 
which, however, it was introduced at a very late geological epoch. It was 
also a favorite dictum of this geologist that auriferous quartz veins are a 
superficial phenomenon, and that mines of this metal would not hold in 
depth as persistently as those of other metals. The discoveries of the Cali- 
fornia Survey in regard to the age of the gold-bearing formations of that 
State have entirely refuted the (until 1864) generally accepted theory of the 
exclusively Paleozoic age of rocks of this kind, although this fact was not 
admitted by Murchison in his latest publications.* The great depth to 
which some gold mines have been wrought, with profit, both in California 
and Australia, in connection with many other facts observed in various parts 
of the world, justifies us in asserting that auriferous quartz veins are as per- 
sistent, on the average, as those worked for the other metals. That the 
_ impregnation of the rock with gold took place at a comparatively recent 
geological epoch, at least in certain prominent and important mining regions, 
cannot be denied. These are regions of former intense volcanic activity, and 
the period to which that belongs is unquestionably Tertiary. In regard te 
mining districts where gold and other metals and metalliferous ores have 
been found in considerable quantity, and where there have been no striking 
* See ante, p. 34; also Siluria, 4th Edition (1867), p. 469. 
