The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1897-06-28

the tunnel forced through these loose
and treacnerous materials, had to pass
at one place within five feet CT the bed
of the river above. One of the difficult
conditions was the enormous size of
this great iron pipe, 81 feet in outside
diameter, six feet larger than the great
tunnel under the St. Clair river, south
of lake Huron, which was constructed
in much the same manner.
We need not delay with description
of the ordinary approach work, which
may be seen in almosttany of our large
cities or towns. The work under the
river is a circular iron tunnel formed
of rings, each one consisting of II cast
iron pieces 21s feet wide. These ring
pieces are all tightly .bolted together
and each ring bolted to the adjoining
rings. and all the minute openings in
the joints filed by cumming into them
as a ship carpenter calks his blanks.
fine iron filings, chemically prepared so
as to make cement. This prevents
the water from forcing its way into
the tunnel when built. Then these
rings, which have ribs projecting into
the tunnel, are all filed up solid with
concrete made Of fine stones. sand and
portland cement mixed together with
wafer. so that the rings and the whole
pipe are at last nearly IL feet thick
of solid iron and concrete. Then on
this concrete surface are set beauti-
full glazed tiles, or thin bricks, five
eighths of an inch thick
In the bottom or near it. as the cross
section shows, was built an arched sub
way II feet wide and 81 feet high, in
which the water pipes are laid. On the
top of this arch the roadway FOR We
hicles is made, is feet wide. with side
walks on each side a little over three
feet IL width. The entire underground
work is lighted with three rows, one in
the center. on top and one on either
side. of SO candle power lights ttWice
the power Of the ordinary incandescent
electric lights). placed alternately
about ten feet apart in the length of
the tunnel.
There are four shafts leading from
the open air above into the tunnel.
They are also lined with glazed tile.
Two of these are As feet in inside di-
ameter, and are provided with spiral
staircases for people who wish to reach
that part of the city above the shafts.
Now, how was the work done-this
deep part, through these bad mater
ials2
TWO MAMMOTH SHAFTS.
The level of the tunnel had first to be
reached from the banks of the river,
and here were sunk two shafts. Two
others were also sunk farther away for
the same purpose. Each shaft was IS
feet in diametersoutside. It's thickness
was five feet; two shells of iron filed
with concrete. Near the lower edge of
the shafts a hole was made through
these shells about % feet in diameter.
This great shaft, or caisson as 1t is
called, was built on the land and put
together where it was 10 sink, and as
it sank; then the dirt was dug away
from the inside, and little by little, by
its own weight or by extra weights
put upon it, this great hulk, with a
cutting edge feeling and forcing its
way down. gradually sank through the
ground until the bottom rested in the
was to be placed. Then these 10 feet
were filed with concrete, and there
was let down from the top to the bot
tom of the shaft and put right oPpo-
site the 29-foot hole left in the casing.
the great tool OF the work. a shield"
fitted out by human ingenuity, TO cut
it's way through horizontally under
the river toward the next shaft on the
other side. This shield was of such
great weig'ht-250 tons; a fair load for
about IS of our freight cars-that it
could scarcely be handled by any ap-
pliance and lowered into the caisson
to the depth of 80 feet. So the plan was
hit upon of pumping the caisson full
of water, and making the shield water
tight like a boat, and floating it down.
gradually pumping out the water until
the shield rested on the bottom. near
where it was to be set up and put to
work. This shield is wonderful con-
trivance which it has taken many
years and many minds TO perfect, but
most of its design was the work of Mr..