onal dodecahedrons), may have misled the Georgia prospectors.
Many
notices have from time to time appeared, both in local newspapers and
in scientific journals, of the occurrence of diamonds in California.
After making due allowance for errors and unfounded rumors, the fact of
such occurrence in certain localities is well established ; but the
number and size of the diamonds found have not been such as to render
the search for them profitable. The fact of their discovery is highly
interesting, and some of the specimens possess both elegance and value
; but as a rule they are small and rare. The mode of their occurrence
seems to be in all cases that they are imbedded in the auriferous
gravels, and thence washed out in the search for gold. These
gold-bearing gravels of California present two types of distribution :
first, as loose material in the valleys and bars of the modern streams,
and, second, as great accumulations of gravel occupying the valleys of
much larger ancient streams, and now covered with masses of lava or
compact volcanic tufa. The sides of the Sierra Nevada are trenched with
cross-valleys running down into the great, troughlike valley of
California, which lies between the Sierras on the east and the Coast
Range on the west. Along this great depression, the drainage from the
mountains on both sides finds its way to the sea through the Sacramento
and San Joaquin rivers, the former flowing from the north and the
latter from the south into the Bay of San Francisco, where a break in
the Coast Range, at Golden Gate, allows a passage between the ocean and
the bay. In the northern part of the State, where the streams from the
Sierras run down to the Sacramento, this remarkable system of "buried
river gravels" is found. In and before the tertiary period of geology
these streams had worn valleys on the slopes of the Sierras, and made
extensive deposits of gravel, by the erosion of the mountain-sides.
Then came a period, or a succession of volcanic disturbances and
outflows, which made the great "lava-beds" of northern California and
Oregon. In many cases the lavas flowed down and filled up the
river-beds from side to side, covering the gravel deposits, and in some
instances hardening and compacting them. The rivers have since then
worn down a new series of channels between these hard lava-streams,
