Omaha daily bee., 1897-06-27

and the methods Of overcoming them, and
evolve 1t, from a mass of mud and water
and other treacherous materials of that
great alluvial valley into a beautiful, light
ana comfortable passageway for human be-
ings. With two or three profles, sections,
pictures and brief descriptions the work
may be clearly understood by any one, The
prohle or longitudinal section shows the
work completed exactly as 1t would look
II we could, with a huge cleaver, cut it
straight open from end to end. lust as n
piece OF timber looks cut through in the
middle lengthwise in the sawmill. The
cross section shows it as it would look If
we cut 1t square across from the surface of
me water to the bottom of the tunnel and
look the mud and water away from one
ehd and thus brought to the eye all the
strata or material and the end of the cut
on tunnel with the water above it and the
Doats and ships moving therein.
The reader will understand that in n
lehgth OF $500 feet, nearly a mile and a
quarter, a depth of eighty feet, if shown by
a natural or true scale, could hardly be
seen by the eye. In fact, the entire depth,
from the surface Of high water to the bot.
tom of the tunnel would be less than one-
eishth OF an inch. The engineer, therefore.
uistorts or eXaggerates his vertical scale so
as TO bring the work to the eye. The profile
Is distorted In this case ten times for thls
pulpose, lt therefore shows the grades a
great zeal sleeper than they really are. The
hgures' however, show them to be only about
one loot descent or ascent in thirty-hye
feet. w.
The length OF the open approach. the part
tnat was built by cut and cover" that is,
where the work was done by digging a
trench and then lining it and covering n
over again, the distance Of tunneling. the
level stetch under the river. the depths of
the shafts and the various kinds of material
are an stated on the profile and section and
need only be referred to by the reader as
Ike upEprlntinn nnuV frpnaaIg ;,.n H. -
features which comprise those peculiar and
quite unusual difficulties so successfully and
safely surmounted.
DIFFICULTIES OF CONSTRUCTION.
FIRST, the difficulties. The ground through
winch most of the work was driven was
loose, porous and saturated under the pres
sure or the great weight OF water above,
Whlch at times OF high tide was ~forty-six
Ieet deep, The materials were sand, CLAW.
gravel, mud, vegetable mold, peat and what
not. Then in places the regular stiff London
clay with occasionally beds of open scanned
limestone, all saturated or the seams filled
with water, which turned many Of the finer
and softer materials into veritable quick
sands. The top Of the tunnel, forced through
these loose and treacherous materials. had
TO pass at one place within five feet Of the
bed of the river above. One of the difficult
conditions was the enormous size of this
great iron pipe, twentySeven feet in out
NN'N HlA AN1N ia AlhI III ElNdk
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 almost any of our large cities or towns.
The work under the river is a circular iron
tunnel formed Of rings. each one consisting
Of fourteen cast iron pieces two and a half
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 filled by jamming into them,
as a ship carpenter calks his planks, fine
iron Filings. chemically prepared so as to
make a 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 filled up
solid with concrete made OF fine stones, sand
and portland cement mixed together with
water. so that the rings and the whole pipe
are at last nearly one and one-half feet thick
of solid iron and concrete. Then on this con-
crete surface are set beautiful glazed tiles,
or thin bricks, fve-eighths OF an inch thick.
In the bottom or near It, as the cross Sec
tion shows, was built an arched subway
twelve feet wide and five and one-half feet
high. in which the water pipes are laid. On
the top Of this arch the roadway for vehicles
Is made, sixteen feet wide, with sidewalks
on each side a little over three feet in width.
The entire underground work is lighted with
three rows, one In the center, on top and one
on either side, OF thir.y-two candle power
lights Twice the power OF the ordinary In
candescent electric Light, placed alternately