The Elk County advocate. [volume] (Ridgway, Pa.) 1868-1883, 1875-02-18
TUNNELING THE HUDSON.

The Engineers Plan for Overcoming OBJ
stncles--Compresscd Air Put TO n New
and Valuable Use.
The recent soundings of the North
river on the proposed line of the Hudson
Tunnel Railroad Company, and the tests
made to ascertain the material through
which it will be necessary to work, great
ly encourage Mr.. Haskin, the originator
of the scheme and president of the COM
pany. The bed of the river is composed
of deposits of river mud, mixed with
gravel, forming a compound which is
known as silt. This deposit forms q
stratum varying from fifty to seventy
feet in depth, and is, Mr.. Haskin thinks,
sufficiently cohesive to hold together
without caving while the tunnel is in pro-
cess of construction. But, nevertheless,
all precautions will be taken to prevent
any break--first, by following the exca-
vation closely with heavy circular brick
lining, 80 that at no time will the roof
of the tunnel be without substantial
support of solid masonry, except for the
four or five feet where the diggers are
actively at work; and, secondly, by sus-
tanning this space of four or five feet by
volume of compressed air enclosed i'll
the tunnel, and affording a pressure of
from twenty to thirty pounds per square
inch, according to the necessities of the
situation. Utilizing compressed air i'll
its application to tunneling is original
with Mr.. Haskin, and he claims that the
saving in expense will be enormous.
The old plan-the one on which the
Thames tunnel in London was con-
structed-was to have heavy, strong
framework and lining exactly fitting the
excavation, which was pushed forward
by screwiacks at the very instant that
the removal of the earth in front of it
allowed it to advance. All this neces-
STATED elaborate and intricate machinery,
which could only be worked at immense
cost, and also greatly disconnected the
workmen. Consequently the Thames
tunnel cost over $1,000 ineal foot,
while the estimated cost of the Hudson
river tunnel is only fraction of that
sum. The method of applying the force
of compressed air is also Mr.. Haskin' S
device.
After the tunnel has been excavated,
arched and finished for one hundred
feet, the opening will be closed again at
the shore end by filling it with bank
of earth, through the length of which
will run an iron tunnel about five feet in
diameter. This iron tunnel will have at
each end a strong, close-ftting door, all
tight. Through this tunnel will pass
pipes for the conducting of the com
pressed air to the pocketed tunnel, and
also return pipes through which the ma
terial excavated will be forced by the
compressed air to the surface of the eartl
above. The iron tunnel will also atfort
ingress and egress to the workmen EN-
ployed, and also passage for the bricks
and mortar needed for the permanen
arch. OF course this stoppage, or air
lock, is only temporary, to be removed
on the completion of the tunnel The
brick arch, or rather lining, for it com
pletely envelops the tunnel, will average
three feet in thickness, varying accord
ing to the distance from the roof of thi
tunnel to the bed of the river, whicl
distance is sometimes fifty feet, an(
never less than twenty-five feet. Th,
line of the tunnel runs through laye
of silt or clayey mud its whole length
except at one point about three hundre,
feet from the New York shore, where i
strikes a sand bank. There extra pre-
cautions will be taken, either by con
strllcting caisson over the weak portion
and pumping the water out of it, or els
by using for little while machin
similar to that invented by Sir M. I
Brunei for the Thames tunnel. A littl
knob of rock is also found near NeN
York.
The dimensions of the tunnel will b
81 feet in height by 26 feet in width
sufficient to accommodate double tracl
railroad, and the length from shore t.
shore will be about 5000 feet. in addi
ton the approaches will on each end b
about half a mile long, the one in Jerse
City comingto to the surface somewhere o
Fifteenth street, while the one in Nc'
York will terminate about twenty fee
underground in the vicinity of Washing
ton square. On the New York shore tn
tunnel will pass under the space betwee
Piers 80 and 81.