The true northerner. [volume] (Paw Paw, Mich.) 1855-1920, 1891-03-18

rises one foot in fifty feet for 3, 1872 feet
The American great cutting is fifty-two
feet deep, about 200 feet wide at its
broadcast part, and rises one foot i'm fifty
feet for 2.533 feet An inclined track
was laid for fiat cars to haul out the tun-
mel soil. In September 1890, two steam
shovels began work on each side of the
river Each shovel was attended by a
locomotive and train of fiat cars Hun
dreds OF men are employed day and
night When the tunnel proper was
commenced scarcely more than two lay
ers of the soil had been removed The
tunnel company grew inpatient and on
Monday, Feb 9, 1891, took the Canadian
work from the contractors. over 500
men are employed. As the tunnel will
not be opened for traffic until after the
approaches are completed the work on
the cutting is being rushed.
Mr.. Alfred +. Beach, an American
engineer, designed and used shield in
the Broadway tunnel, New York City,
in 1868. Since then similar shields have
been used in Chicago, Buffalo, Hudson
River, London, and other tunnels. This
eXcavating shield may be compared TO a
cylinder with no head. 1t is circle of
steel plates. Inside these plates are
braces, doors, and aids for the workmen.
In the front end are kniie-edgcs to pene-
trate the soil. In the rear portion Of the
shield, around the main walls, are hy-
draulic jacks, each supplied with valve,
so that its action may be independent of
Others. The material of the tunnel
walls, masonry, or east iron, is built i'm
the rear of the shield. Pressure is ap-
piled to the hydraulic rams, and thus the
SHE'D is pushed ahead the length of the
jacks pistons. The soil is pushed into
the front of the shield, and the men re-
move 1t by loading il upon cars, which
are pushed out TO the tramways, on
which they are drawn by mules, or
horses, TO the entrance of the tunnel,
where they are hoisted TO the regular
fiat cars and taken to the dumping
ground While the men are removing
the soil in front the men in the rear are
busy erecting the walls Of the tunnel.
In case OF iron plates. revolving crane
lifts the plate by means OF a counter
balance weight TO the desired position,
where IL is bolted to the other plates.
When the section of the tunnel is com
pleted, and the pistons Of the rams have
been drawn back, the air is applied again,
and the jacks pushed forward for an
other section of the tunnel to be put I'm.
By this arrangement the workmen are
always protected from danger above,
around or below. The air pressure
keeps the water back in front, and the
comp etcd tunnel protects the rear.
Two shields were used In the StaClair
aunn !. Each weighed eighty tons.
r. hey were brought in sections to the
north bank OF the cutting. where they
were erected Then came the problem OF
placing the shields in position. Wooden
tracks were laid, huge ropes were placed
around each shield, and they were grad
ually lowered by men. In eighty min.
ntes they were in place at the proposed
mouth of the tunnel. Each shield wa:
1G feet long, and had an outside diameter
OF 2iL feet The steel plates were
inch thick. Each shield had twenty-foul
hydraulic rams at equal distances apart
Each ram had a stroke OF feet and
diameter OF inches. Each
time the pistons were showed ahead the