Mineral Point tribune. (Mineral Point, Wis.) 1869-1938, 1907-02-21

From a personal letter to the Tribune
publisher, dated Richmond Hill, Long
Island, Feb. 18th, by nephew, w. B.
Bennett, recently of Mineral Point and
graduate of our state university, is
excepted the following, believing it
will be of interest to all who care to
familarize themselves with great en-
gineering projects, and especially local
schoolmates and chums Of the writer:
81 am engaged on q great piece of
engineering work here. You have no
doubt read some of the extent of the
project by which the Pennsylvania r. R,
is TO have a terminal station in New
York and run it's trains onto Manhattan
Island At present all railroads from
the west, except those that come down
the Hudson, have only ferry connection
with New York from the Jersey side.
From your geography you will re-
member that Hudson River, or North
River as it is called just before it enters
New York Bay. separates New Jersey
from the Empire state at this point
New York City proper is an island be-
tween North and East Rivers, and is cut
Off from the main land on the north by
the Harlem River which joins the two
above mentioned streams. Across East
River lies Long Island stretching to the
east and little northward for a length
Of some 1870 miles and having an aver
age width of perhaps 20 miles.
''The Pennsylvania tunnels are to
connect Weehawken in Jersey City with
Long Island City. Entering the ground
on the west side Of Bergen Hill they
bore through rock to the west banks of
North River, then through the Hudson
River silt to Manhattan Island. Across
the Manhattan the course is through
solio rock, for the most part a species
known as New York gneise.
1.-The depth of the tunnels across the
island of Manhattan is from 70 to 50 fl.
below the surface, descending in grade
toward East River. Near the west
bank of East River the tunnels emerge
from rock and enter quicksand. In this
and other varying materials the tracks
are to be carried to the Long Island side
in four single track circular tubes of
cast iron and steel, with an inner lining
of REINFORCED concrete. This same
tube construction is used through the
Hudson River silt. while in the rock
tunnels the pore is just blasted through
the rock an two pair of twin tunnels
finished up with the arched concrete
lining.
"The most interesting and difficult
part of the work is the putting of the
tubes through under East River. 1t is
in tube 'B of these tunnels that my
duties lie. Near the bank of East Riv-
err on the Manhattan side shaft was
sunk for each of the two pairs of tubes
to the grade of the tunnels. AT this
level, still in rock, the excavation was
started eastward until a sufficient bore
had been dug out to permit of the erec-
ton of the tunnel shields. These CON
sist of a steel cylinder of heavy con-
struction about % feet inches in dia-
meter and about 20 feet long. The adj
vancing end has around its perimeter a
cutting edge for cutting its path through
the surrounding material Near the
center of the shield, longitudinally, is a
compartment formed by two partitions
or diaphragms placed perpendicular to
the axis of the shield. By doors and
fastenings in these partitions the finish
ed tunnel behind can be sealed against
danger from the front. Around the per-
imeter of this central compartment are
located twenty-seven 17-tJn hydraulic
jacks used for pushing the shield AHEAD.
THE tunnel. as built following the
advance of the shield, consists of cir
cular cast iron or steel tube, rs the ma
teral being passed through may require.
This tube is built in 2i2 #. sections
called rings. Each ring consists of IL
circular segments and key. These
segmcnts. or plates as we usually call
them are Hanged on all -four sides to
permit of being firmly bolted plate to
plate and ring to ring. The rings are
twenty three feet in diameter out to
out and the Aarges have Il depth of II
inches while the main web Of the tube
is inches thick.
when power is applied to the afore-
mentioned jacks of the tunnel shield they
but. aEaut he aauge Of tho last cree