The Cecil Whig. [volume] (Elkton, Md.) 1841-current, 1884-04-26
THE NEW Il. 4 o.
Some Grand Engineering. Work
Great Progress Made.

\ correspondent Of the Baltimore SIM,
thus describes the work of the new b.
e O. railroad at the Susquehanna:
The most interesting work on the
road and that involving the greatest en-
gineering skill is the bridge of a mile
and quarter in length over the Susque-
hanna river at iiavre de Grace. The
railroad skirts the hillside north of the
| town until it comes to Cooley's Point.
high hluil on Franklin Iopper's land.
! Here there is a stone quarry, and but
little additional support will be needed
for the shore end of the bridge OF the
| llarford's side. Watson's Island or Gar
ret'S as it is now called. lies near the
middle OF the stream, forming q good
resting place for two piers of the mas
sive structure. The water varies in
depth from eleven to forty-one feet, bat
the difficulty of making the bridge lies
in the mass OF mud, from so to 60 feet
deep, in the bed of the river. The con-
tract for building the five immense piers
upon which the bridge will rest has been
undertaken by Gen. William Ssoy Smith
4 oou, of Chicago. Two piers will be
or the west and three on the east side Of
the Island The work Of excavating the
mud III order to reach a solid foundation
will be by means of pneumatic caissons
similar to those used in building the
Brooklyn bridge. The largest cajsson
will be IS by 40 feet in size. They are
made of yellow pine timbers, from u to
is inches square, strongly bolted to-
gether. The caisson is merely large
wooden diving-hell, consisting of an air
chamber 81 feet high, in which the men
work. The wallis are two feet thick and
the interior is carefully caulked, making
the chamber air and water-tight. They
are built on shore, launched and towed
20 the place where the pier is to be built.
4 co -ering OF s. feet of heavy timbeIs
above the air-chamberS supports the ma
sonry OF the bridge. An iron hue 3,
! feet square extends from the air-cham-
Der through the intervening timbers to
the open air. The opening in this,
through which the men descend, is also
air-tight. The water is forced out of the
air-chamber by compressed air by means
ranged trap-door permits the wol kmen
to descend without letting the compress.
. ed air out. The men are assisted in get
tin- out the mud by a stream of water.
forced against the mud through a pipe
. The liquid mud will be pumped off into
the river. The caisson will be lighed by
f electricity. While the men are at work
in the mud, concrete is poured into a
crib work on top, and as the mud is
taken out the mass of wood, iron and
stone slowly sinks through the mud I'm.
til it rests on the solid granite bottom
The concrete extends to the mud line
and before it reaches it the mason-work
is commenced all of it being thus built
above water. When the caisson reaches
the granite bottom the air-chamber i.
filled with concrete, and there is then a
solid mass of wood, stone and iron tt
support the masonry.
On the Cecil county side, it is said, a
) shelving rock will be encountered, which
will have to be blasted until a level foun
dation is secured. This is regarded as
great feat of engineering skill Mr.
Charles Sooy Smith has charge of the
work of constructing the caissons anG
piers. One Of the caissons is in place OIL
the Hartford side and one on the Ceci
side of the Island.
The building of the bridge gives EN-.
rloyment to an army of mechanics anG
laborcrs, and is boon to Iavre de
Grace. AS the work progresses more
men will be employed, and by the mid
die of next summer 100 men will prob
ably be at work on the bridge.