Washington standard. [volume] (Olympia, Wash. Territory) 1860-1921, 1901-07-19
VOLUME XLI.---NUMBER 35.
UNDER THE WATER.
PERiLS AND DISCOMFORTS OF
WORKING IN RIVER BED.

Laying Foundation that Has to Go Many Feet
Below the Bottom to Reach Hard Pan-A
Caisson Descrbed-now Workmen Go Down
in Them-lts Ventilation and General Opera
tion-The Caisson Disease Pay in Proper.
ton to the Danger.
Going down in a coal mine gives
one strange sensations. A descent in
a diving bell is an experience. Work
in a tunnel presents features peculiar
to themselves. But the men who
work in caissons in great engineering
undertakings, such as laying the foun-
dations for the piers of the Brooklyn
bridge or the East River bridge, that
is now being constructed, can tell of
novel sensations that in some respects
discount the experiences of divers and
all other workers in the depths.
A caisson is merely a hollow box of
iron or wood, open at the bottom, sunk
where piers are to be placed. The
largest caisson yet sunk was for the
tower Of the Brooklyn bridge on the
New York eide. At the bottom it was
172 feet long and l02 feet wide. with
an air chamber 81 feet high, the roof
p feet thick and the sides carried up
81 feet from the bottom line. 1t was
built Of timber, lined with boiler iron,
and bolted together. When complet-
ed it weighed 1927 tons, and there
we're 10000 tons OF masonry laid with
in it. A description of this caisson
answers in general way for all struc-
lures of the kind. There were two
double-air locks extending into the
air chamber, in which were steam
pipes to keep up an even temperature
in winter. Two shafts passed up
through the we'll holes in the mason.
ry, with an elevator in one, and two
spiral stairways in the other. Below
the lowest edge of the caisson extend
ed two water-shafts, each q feet in
diameter, in which dredges and scoops
grappled the stones and soil, raised
their loads to cars above, which con-
veyed the refuse away. At the same
time sand and fine dirt were blown
away by air pressure through 40 or
more pipes in various parts of the
structure. The interior was illumi-
mated by gas, and constant communi.
cation was kept up by telegraph with
the workmen inside. There were four
shafts, each two feet in diameter, for
the introduction of material for the
concrete with which the whole interior
was to be filed. The caisson was
sunk 78 feet below mean tide. The
earliest caissons for such purposes
were used in England in 1880 in
laying the foundations of the West
minister bridge over the Thames.
The work now going on in laying
the foundations for the towers of the
East River bridge is typical. Each OF
the piers will carry load Of $4,000
tons, and to secure stable foundation
it was found necessary to 60 down in
some places 95 feet below the water,
through sand, loose rock and hard.pan
to the solid rock. In order to force
the large caissons to the bottom, the
top was built full Of masonry to weight
it.
After the caiss0ns were sunk the
water was forced out by powerful en-
gines forcing the air in. Steel shafts
run up through the caissons to above
the surface OF the water. These
shafts terminate in air.tight rooms,
called sir-locks. There is an air-tight
door in the shaft opening into the air.
lock, and an air-tight outside door in
the air-lock leading 10 the open air.
In entering the caisson the workman
opens the outside door, enters the air
lock and closes the door before open
ing the door in the shaft, for il. both
doors we're opened simultaneously the
air in the caisson would escape and
the water would rush into the caisson
from below and drown the workmen
like rats in box.
The caissons are necessarily very
strongly built, and are made air and
water-tight by calking the seams with
oakum and pitch. Caissons are built
on shore and launched the same as
ships. The space below the deck or
roof is called the working chamber.
1t is about seven feet high. The lower
edge is provided with heavy iron
plates extending a couple Of feet be-
low the timbers and forming . cutting
edge.
Writing in Harper's Weekly, F. w.
Skinner, c. E., describes descent into
a caisson of the East River bridge.
"The visitor was questioned if he
was quite well and his heart perfectly
sound. If so, he removed his outer
clothing, donned hip.boots, rubber
coat and slouch hat, and accompanied
by one OF the engineer corps, climbed
up short ladder and entered the cir
cular cage of passenger elevator that
was protected by strong wire-netting,
and was lowered so feet through q
steel cylinder, like smokestack. Ar.
rived at the bottom, the party crawled
into q circular chamber in which 20
men could stand, and its massive steel
door was pushed tight against thick
rubber cushion on the side Of the steel