The Indianapolis journal. [volume] (Indianapolis [Ind.]) 1867-1904, 1883-05-23


OF Henry Worthington, Sinclair Tousey and
George Opdyke, had approved the plans,
Congress passed an act authorizing the con-
struction of the bridge. The elder Roebling
made the initial surveys While standing
on a strlng-pece of the pier next to Fulton
Ferry slip in 1869, fixing a location for the
Brooklyn tower, ferry-bOat in entering the
slip drove the tenders against the pier so as
to crush the engineers foot. He was firm
believer in hydropathy and on going to bed
he put his injured foot beneath faucet of
running cold water and allowed it to remain
there until over-chilled. He died sixteen
days later from lockjaw Not a stroke OF
work had there been done on the bridge.
The plans were most general in character,
the details not having been considered They
have been matured by Mr.. Roeblings son,
and executed by his assistants, c. c. Martin,
Colonel w, H. Paine, Francis Collingwood,
George W. McNulty and S. r. Probasco. and
by E. f. Harrington, master mechanic Many
new problems in bridge architecture have
been solved in erecting this bridge.
THE cAIssoN WORK.
The work of construction began on Jan. 3,
1870. The greatest difficulty was to secure
firm foundations for the towers To build
these foundations below the level of the bed
of the river was work of great magnitude.
Wooden caissons were used to support the
towers of the bridge. A caisson is merely a
greaS box bottom turned up. The Brooklyn
CARSON was fifteen feet thick on the top, of
large, solid yellow pine timbers, and the
sides were nine feet thick and nine feet high.
The measurement across the box from
edge to edge was 102x16S feet.
1t was divided into six commandments
which were connected by means of doors.
This great box was made water-tight and
then anchored on the spot on which the
tower was to stand. The caisson was pro-
tected from the river by coffer-dam of
piles and sheeting. The work of building
the tower On the caisson was at once begun
and continued until enough weight was on top
of it to keep it on the river bottom. There
were large wrought-iron tubes or shafts in
the roof OF the caiSson through which earth
and stones excavated on the inside could be
taken ont, and there was all air-lock for per-
sons to enter the caisson.
When it was sunk on the river bottom the
water was forced out of the caisson by COM
pressed air, and men could go in and work.
one pound OF air pressure equals two feet OF
tide water, so tor every two feet the caisson
was lowered, one pound had to be added to
the air pressure inside. Gauges in the en-
gineroom above indicated the heighto OF the
TIDE and the pressure of air The highest
pressure attained in the caissOn was thirty
TOUR pounds to the square inch, in addition
TO atmospheric pressure. At that pressure
man could not whistle and candle blown
out would Immediately ignite again. Fresh
water springs appeared, Beneath this Gals
son blasting and excavation went on for
months, when a depth of forty We feet
was reached, and the caisson was then
settled on rocky foundation. The inside
was then filled with broken stone and
concrete until the whole thing was
solid mass; and then the work of erecting the
tower went on rapidly.
Greater difficulty NUaS anooupforad tl,o
New York side, and the caisson was made
stronger and bigger, and had to be sunk to a
depth OF seventy-eight feet. Even at that
depth solid rock was not discovered But
Jagged points of rock stuck up here and
there, amid bed of quicksand The points
of the ledge which appeared only under one
end of the caisson were leveled off and the
quicksand was confined within wall of con-
CRETE the whole area of the eaisson was filled
with the same material, after which the
tower was erected and finished like the one
in Brooklyn.
There were many interesting incidents in
the work of building the foundations The
pressure of the compressed air would some
Tunes tilt up caiSson and portion of the air
would escape, throwing up a large column of
water fifty to sixty feet high On Sunday
morning a neglectful Waterman caused a
blowout which covered the adjoining build
lngs and shipping with a coat of mud and
injured two or three persons. Under ex-
IRENE pressure some of the workmen became
subject to certain physical arrangements
which have received the name of caisson
disease The Brooklyn caiSson caught fire
several times, and twice had to be flooded
with water. In December, 1870 a careless
laborer placed lighted candle on a shelf in
close proximity to the oakum caulking OF a
timber joint, which ignited. and under the
pressure the fire made its way into the tim
Der and out of sight. As the pressure was
oil tttu ord, Aoy, /. /
in the caisson, and it was some time before
the lire was discovered. Colonel Roebling
was summoned, and he entered the caisson
at o'clock P NJ. and did not leave it until 5
A. NJ. Overwork and anxiety in addition to
the many hours in the compressed air. had
its effect, and he was partially paralyzed be-
fore he reached home. This was the beginning
of the disease that has so long Frustrated
him.
The towers, built of granite brought
from Maine are 276 feet 9 inches
above high-water mark The Brooklyn
tower reached its full height in May 1875.
and its New York mate in July, 1876. The
New York tower above the top of the caisson
weighs $4,000 tons. The firmness of the
foundation is shown in the fact that the
tower has not settled two inches. At
height of l19 feet there are two arched open-
ings in each tower, through which will pass
the streams of travel On the top of the
tower are saddle-plates, huge iron castings,
on which rest the weight of the cables
The cables are fastened in anchorages $50
feet distant from the towers. The anchor
ages are built of stone, and are 129 by 1l9
feet at the base and 80 feet high. Over the
top of them run the roadways Embedded
in the two anchorages are huge plates of iron
weighing twenty-three tons each, to which
are fastened iron bars formed into chains, at
the end of which are the cables that hold nm
the suspended part of the bridge There are
vaults in the anchorages, where the cables
join the anchor chains, and they can be in
spected at any time by the engineers. The
remaining stone work OF the bridge consists
of granite approaches which are lofty via
Sands street. and it is OIL feet long to the
anchorage. The grade is two feet nine inches
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