The
top gravel of the channel which passes through Columbia Hill, Nevada
County, has in several instances been successfully washed. This is
especially remarkable on account of the great depth of this deposit,
which, from the explorations on Badger Hill and Grizzly Hill, is
inferred to be from six hundred to six hundred and twenty feet deep.
Gold, in the Grass-Roots.—Not
unfrequently a fine lamina gold is found in the grass-roots. This last
mentioned circumstance is in no way localized, the same fact having
been noted in other countries. Mawe called attention to the existence
of gold in the grass-roots on Mount San Antonio,* in Brazil; and Walsh
states that gold was first discovered in the deposits between San Jose
and San Joao, Brazil, by Paulistas, who, pulling tufts of grass, "
found numerous particles of gold entangled in the roots." f
Pay Gravel sometimes high above Bed-Rock. —
At the Polar Star Mine, Indiana Hill, Placer County, the best pay was
found from six to eighty feet above bedrock. At diggings near Forest
Hill, Placer County, the gravel twenty to sixty feet above the bed-rock
has yielded profits. At Bath a stratum one hundred feet above bedrock
was drifted profitably and the top dirt hydraulicked subsequently.
Pay Gravel generally near Bed-Rock.—But
experience has proved that, as an almost universal rule, the top
gravel of deep alluvions is not rich enough to warrant large
investments of capital. Also that the " pay " is obtained, not
from.the washings of the entire bank, but chiefly from that stratum or
those strata which are in most cases within eight or ten feet of the
bed-rock. Where this is of slate upturned on its edges the gold
frequently permeates it one or two feet X
* Mawe's Travels, p. 264. t Walsh's " Notices of Brazil," 1S28-20, vol. ii. p. 122.
X See
Murchison's " Siluria," p. 456, and " Russia and the Ural Mountains,"
vol. i. p. 487 ; also " Gold-Fields and Mineral Districts of Victoria,"
pp. 86, 106.
