estimated
at 10,000 dollars in value; and I may here remark that the Americans
do not calculate the outcome of their crushings as we do in ounces,
pennyweights, and grains, but they reckon the intrinsic commercial
value of the gold, &c, per ton in dollars.) The east vein alluded
to has been worked for a length of over 2,800 feet to a depth of 1,236
feet for an average width of 15 inches, the angle of underlay west
being 31 degrees. There were other mines at work, such as the
Centennial and others, all paying very well, whilst others were idle on
account of heavy underground water. All the lodes thereabouts were
highly charged with sulphurets, chiefly of iron, copper, and lead;
arsenic, zinc, and antimony being more of a rarity than in our mines.
In the neighboring mining district of Nevada City, the municipal centre
of the county, nearly all the quartz lodes occur in the granite, which
forms the country rock principally, except on the south-eastern side of
the Bear's Creek Valley; and, of the mines inspected, the New
Providence forms a very good example of how auriferous quartz lodes in
pure granite country may occur with a regularity and permanency that
should be instructive to miners engaged in a like country. This
company's lode underlays a little north of east at an average angle of
38 degrees, and it was, at my time of visit, worked 800 feet in depth,
having, moreover, been traced by several companies and worked for one
mile and a half in length, with an average width of 6 feet. The hanging
wall has a very peculiar appearance, by exhibiting strongly marked and
clean polished striations, presumably the result of intense friction;
but there is in this case no corresponding foot wall, as the main
bodies of ore run into the underlaying country rock, where they split
into numerous veins, decreasing gradually in size, but are still
gold-bearing for a distance of over 60 feet from the main back. It has
been found the rule here and elsewhere in the State that, when these,
lodes assume an eastern underlay, the "makes" of quartz, stone, or ore
dip north; and, if the lodes underlay west, the opposite dip of such
"makes," &c, obtains. South of the main shaft (New Providence
Company), in the 600-foot level, no less than three of these makes of
ore occur, and, as they are accompanied by a soft "selvage," or
"flucan," at the hanging wall, it is a very remarkable circumstance
that, in these makes of ore of a lense-like form, concentric
laminations occur, which correspond thoroughly with the outer lines of
each block, and these laminations are strongly indicated by bands of
very rich sulphurets (they yield by chlorination after concentration
from 60 to 100 dollars per ton). This ore resembles that of the St.
Arnaud mines, and also of that strong block of nearly pure pyrites at
the 600 and 700-foot levels of the Lazarus Company, Bendigo. In this
Nevada district the upper portions of the quartz lodes, embedded in
softer country than deeper down, were very rich in free gold; but
gradually harder country appeared with greater depth, and a very
decided modification was manifested, for the quartz depreciated
gradually in value in proportion to the greater prevalence of the
incoming denser wall rock. An opinion prevailed then that these "ledges" as
they are termed in California, would ultimately become quite barren of
gold; but shortly afterwards all this was disproved to everyone's
satisfaction, because, at greater depths, as rich auriferous sulphuret
lodes have been found in as hard wall rocks below the water-level as
where such were of a kinder character, as the miners would say. The
fact of the matter was simply this: that, with greater depth in a
harder country, the free gold at the shallower levels became associSJed
with sulphurets, which latter prevented the old methods for gold
extraction to be as successful as they had been during the treatment of
the ore with free gold only, occurring at the higher levels. It may also
