and have been well rewarded for their labor.
Millions of dollars have been taken from this lead, and its richness,
even in portions longest worked, is yet undiminished. These tunnels
have cost from $20,000 to $100,000 each, and interest in the claims
they enter sell readily at from $1,000 to $20,000, in proportion to the
amount of ground within them remaining untouched, and the facilities
which exist for working it. Many of these claims will yet afford from
five to ten or more years' profitable labor to their owners, before the
lead itself within them is exhausted. As in some of them quartz veins
and poorer paying gravel have been found, many of them may be valuable
to work from the top down as hydraulic claims."

This idea that the blue lead occupies the bed of an antediluvian river
is however not universally accepted. Mr. B. P. Avery, who has written
numerous newspaper articles upon the mineral deposits, asserts that the
"blue lead," as it is called, is not a "lead" but an extensive stratum
which is many miles wide, and is found all the way from the foot hills
to the summit of the Sierra Nevada. In reply to this, it is said that
while a bluish stratum of clay similar to that of the blue lead is
found over a wide district, that it is evidently different in origin
from the blue lead itself, which is confined to a narrow bed, and
marked by the signs found in all the other ancient river beds of the
state.

The Sierra Butte Quartz Mining Company has some of the best auriferous
quartz lodes in the state. One lode called the Cliff Ledge, is
twenty-five feet wide; and another called the Aerial Ledge, is about
three feet wide. In the Cliff Ledge, the paying rock averages about six
feet in thickness next the foot wall. The average yield is eighteen
dollars per ton. The quartz is bluish white in color, and very hard
when first taken from the lode, but on exposure to the air it slowly
crumbles into sand.

_Yuba and Butte._--West of Sierra county, and drained by the same
streams, is Yuba, which reaches to the Sacramento River, lying half in
the mountains and half in the plains, the mining district being in the
former half. The principal mining towns are Camptonville, Timbuctoo,
Foster's Bar, Texas Bar and Long's Bar. In 1859 there were nine
quartz-mills in the county, three at Brown's valley, and one each at
Camptonville, Dobbin's Ranch, Dry Creek, Honcut, Indiana Creek and
Robbin's Creek. The assessor in 1860 reported only two