Evening star., 1917-11-04

throwing the iron-mixed earth high
into the air.
I stood a while on the edge of the
Biwabic mine and watched the steam
shovels working. This mine is in the
form of great cut like that-of Guile
bra. 1t is now more than 200 feet
deep. Starting from the grass roots
there are gray strata of clay and rock.
running down perhaps forty feet Be
low comes a deposit of rich reddish
brown earth, SO soft that it could be
easily dug with a pick. This is the
iron-bearing formation, which is being
cut of in layers about thirty feet thick.
or of the depth to which steam shovel
can work. II you will consider the ore
body as great loaf Of brown bread,
and each Of the layers slice, you Will
get some idea of how the steam shovels
are mining and dropping the ore Into
the cars. In some places they have
cut through the main body and are
getting out the ore. which, as have de-
scribed it. branches into the roots OF
the iron-crowned tooth. The work 1s
iron is saved and waste is as carefully
guarded against as in the steel furnaces
and mills to which the iron is taken.
Another pit is the Dean mine. This is
a beautiful oval which makes me think
of one of the diamond pipes of South
Africa 1t Is twelve hundred feet long.
six hundred feet wide and hundred
and twenty feet deep. Its walls for
fifty feet down are earth and rock, and
below that to the arena it is rich red
ore. That mine covers about thirteen
acres or as much space as the Great
Pyramid of Ghizeh. You could drop
two Colosseums like that at Rome in
side 1t and they would just about fill
the space.
The Shenango pit is like the famed
Kimberly diamond mine. save that the
latter is almost half mile deep. where
as the depth of the Shenango is only
few hundred feet. 1t is almost round
and the bottom is marked with a great
coil of railroad tracks. In all of these
mines the cars move in and out. and
there are terraces and tracks so ar
ranged that the ore is hauled by easy
grades to the surface. There are scores
Of steam shovels. which have an eff
cheney as great as those of the Panama
canal They each take two tons at
bite. and one will fill a fifty-ton car in
less than FIVE minutes. In that time it
loads burden as great as one hundred
horses could haul on wagon. The
newest of the shovels weighs 290 tons.
1t cuts to a depth of sixty feet and has
a swing or swath Of 420 feet.
In addition to this open-ptt work out
under the sky. a great deal of mining
Is carried on underground. The open
pit work can be done only during the
eight months of the open season, but
the underground mining goes on also
throughout the winter. It is restricted
to the deposits which are SO deep that
it costs too much to strip off the heavy
earth which lies oyer them. In such
mining. shaft is sunk at the edge and
the miners cut out of the iron forma-
tion huge chambers. sending the ore up
to the surface. They begin at the top
and support the roof or the first layer
Of chambers by timbering and leaving
pillars Of ore. When they have work
ed from one side of the deposit to the
other they lay a floor of heavy logs.
and the earth above Is allowed to cave
in.t This floor then forms the roof for
a second series Of chambers which they
cut out below. The ore is piled up at
the surface. and is loaded upon the
cars by steam shovels when the winter
is over.
The underground mines have miles Of
tunnels. They have great pumps which
are kept going day and night They are
lighted by electricity and the machin-
cry is moved by the same power.
Everything is carried on after cost ef-
ficiency methods. and great care is
taken as to the prevention of waste.
About one-third Of the output of the
Lake Superior region now comes from
these underground mfnes.
I'D A ~ rAnOENTE,P