Dodgeville chronicle. [volume] (Dodgeville, Wis.) 1862-current, 1871-07-28
MINING DEPARTMENT.

| Odicnd unlo STONE. III loio"iHS eniS
line north, | find that every bed of
rock, from the surface to the azoic, or
Granite rocks below, rises to the sur
face, and becomes inssturn the surface
rock, then thins out, and is seen no mole.
l find the different divisions of rock
constituting the strata of the lead dis
trict above the Azoic, namely the Ga
lena and blue lime stones, the upper
sand stone, lower magnetism lime stone,
and the Potsdam sand stone, uniformly
in their places, as described in our last
report by Prof Whitney, and vary ng
but little in their thickness or general
character from his descriptions.
| In looking over the map, and noting
the exact position of the mining ground
along this line, we can hardly avoid the
conclusion that the depth of our min
ing operations has been influenced to a
great extent, if not fully, by the depth
of the water from the surface at these
different localities. There is great
uniformity in the depth of our best
mines in all these places-that is, in
their depth from the surface; but
great dissimilarity in their depth in the
strata. In the southern part of the
lead district, where we have $50 to 800
feet of Galena lime stone, mining ope-
rations are confined. to that formation,
and mostly from the middle portion up
wards But further north, where that
formation becomes thinner, the mines
are worked in the lower portion and
still further north, where there is but
thin layer Of this rock, we find the de-
posts of ore, as we'll as the assures, en-
bracing the two formations. We have
several instances of this in the mines of
! Mineral Point, also at the Linden
mines, and the mines at Grow Branch.
In each of these places mines that were
productive in the Galena lime stone,
continued to be productive into and
through the blue lime stone.
If we look along this course, from
the State line south to the north side
of the lead district, we see very dis
tinctly that while mining operations
have been carried on at about certain
depth from the surface, governed most
Iy by the depth at which water becomes
an obstacle, they are nevertheless rap
idly gaining downward in the strata,
| from the fact that there is a gradual
rise of the beds ofrock toward the north.
For instance, if we mark the position
in the rock where the mines are work
ed at Platteyille, and follow it back on
the map to Hazel Green, New Dig
gings, and Shullsburg, we shall find
that it will be from 50 to 100 feet be-
low where these mines are worked. Or
if we take the blue lime stone, that po-
sition in the strata in which some OF
the best mines Of Mineral Point, Lin
den, Mifflin and Highland are found,
and follow it back on the map to Platte
vile, we shall find it will be over 100
feet below where the mines there are
worked and if we continue to follow
It back until we reach the mines OF
Haz Green, New Diggings and Shulls
Bur, VII be from $50 to 20j feet below
| Now it is a question Of great inter
,,st. whether or not the mines at Platte
vile, and the central part of the lead
district, and the mines at Hazel Green
md the southern part of the lead dis
trict, are likely to be productive if
followed down to the positions in the
strata known to be good mineral bear
:ng rock where it has been reached Ill
the northern mines. If this should
prove to be true, it will give us ON an
average through the lead district, not
less than $50 feet of what is known to
be good mineral bearing rock beneath
where most of our mines have been
| worked. This mineral strata alone, to
say nothing of what is below it, will
furnish grounds for mining operations
more than three times in vertical thick
ness, the average depth of what we
have mined; and is consequently capa-
bic, under proper mining operations, OF
furnishing for century an average
Weld not less than our mines have fur
nished in the past. But this question
is vet an unsettled one, and the evil
dences on both sides should be careful
:ly examined.
If it can be shown that these depos-
it's Of ore are mere surface deposits,
produced, as some teach, by surface or
atmospheric agencies, then the proba-
bilities are that our mineral reso lrces
are exhausted, ard it will be waste of
time and money to look for deposits be-
low them, where these agencies cannot
reach. Let us examine the evidences on
this point first, for if this view can be
established, we need 60 no farther.
In looking over the surface geology
of the mining region, it is apparent to
every one, that large portion of what
was once the surface has been removed
by denudatier, under the same influence,
or by the same causes that are now at
work, that is, rain, frost and the like,
Prof. Whitney says not less that $50
or 400 feet, A large portion of this
must have been the Niagara limestone,
for we find the out-layers of this for
tmation now ON the highest points of land
| Now in order to have correct ideas
of the relation Of these ore deposits to
surface or atmospheric agencies, it is
important that we put back on our map,
and consequently on the surface of the
lleaa district, this 35e or 400 feet of
rock, which is in reality the original
surface. Now let us see what We have,
and how these deposits look. They are
separated from the surface and surface
agencies nv at least 400 feet of solid