The evening telegraph. [volume] (Philadelphia [Pa.]) 1864-1918, 1871-05-17
ANOTHER BIG TUNNEL.

The United States and Canada TO be United
by n Tunnel Over Eight Thousand Feet
I'm Length under the Detroit River.
From the Iron Age.
The building of the great subnuvial tunnel
under the Detroit river, the completion OF which
is now assured by the practical consolidation OF
the Michigan Central and Great Western Rail.
roads, will be the greatest engineering work OF
its kind ever projected In this country IL not IN
the world. The lake tunnel at Chicago, though
of considerable length, is of small capacity and
will bear no comparison with that to be built at
Detroit, while those carried under the river at
the former city, though of good size, are so short
as to be in all respects inferior to the present
undertaking as engineering works. In the
MAGNITUDE OF THE PLAN
Of its construction, in the capacity 1t will have
under water, and in the amount of business
which will pass through it, the Detroit tunnel
will certainly have no rival upon this continent
until the long contemplated scheme of uniting
New York with the New Jersey shore by tun-
mel under the Hudson is carried into effect.
The plan finally adopted by the tunnel COM
pany for the construction of the great work is
substantially the same as that prepared some
months since by Mr.. Chesbrough, of Chicago.
The length from the Detroit to the Canada pOr-
tai will be S568 feet. 1t will be built in two
separate parts, with view TO diminishing the
amount of excavation necessary, and lessening
the liability to accident, and also for the impor
tant consideration that, If an accident should
occur in one half the other would still be avail
tunnels will be cylindrical in form, and will be
fifty feet apart.
THE INTERIOR DIAMETER
of each is 1S15 feet, and at all points under the
river the shell of masonry will tbe two feet in
thickness. The excavation will be made through
a stratum of hard clay, and it is not intended
that it should at any point come within less than
20 feet of the surface of the bed. Whenever it
is found that the distance is less than this ave-
rage, clay will be filed in to q sufficient depth
to avoid the possibility of cccident. In addition
to the main tunnels a small drainage tunnel,
with an interior diameter of five feet, will be
built considerably below the main lines and mid
way between them. This will be first con-
structed, in order to drain the main tunnels
while the work progresses, well as after
ward and also TO fully develop the character Of
the soil at the commencement of the work. The
grade of the transit tunnels is one in fifty at each
end with 1000 feet of level line under the river.
The estimates for excavation and masonry are as
follows:-
cubic Yards.
Excavation in open cutting g.............2O0 2O0, 900
Excavation in tunnels 233, 600
Brick masonry exclusive of drainage tun-
Stone masonry 3,1OO
The entire cost of the tunnel and approaches,
including a permanent double track of steel
rails, right of way at the ends, ETC., will amount
| to So, $50, 600.
The enterprise is one of great magnitude and
| Importance, and its completion will mark the
| beginning of new era in American railroad
| engineering.