The Bloomfield times. [volume] (New Bloomfield, Pa.) 1867-187?, 1872-04-09
The East River Bridge.
A Wonderful Undertaking.

XTERY few persons comprehend what
wonderful undertaking is the build
ing of bridge over the Eas .iver to con-
meet the cities of New York and Brooklyn.
Last week while in New York we visited
the foot of Roosevelt street where the caisson
for the bridge to rest upon is being built.
The following description from recent
visitor will be found interesting:
"Twelve air pumps were at work forcing
air into the depths below, while two sand
pumps were throwing out large streams of
sand. Under charge of one of the engin-
GERS, a party were just starting to descend
into the depths below. Two shafts afford
access to the interior of the caisson, and
down one of these the party descended by
means of a spiral staircase. At the bottom
of each shaft on one side is small oval
opening just large enough to admit the
body of q man, and closed by an iron door,
This affords entrance to small circular
chamber about eight feet in length and six
feet in diameter, called, the clock" At
the bottom of the lock on the opposite side
from the entrance is a similar opening,
into the caisson, which gives access to its
interior.
The pressure of air in the caisson is
thirty pounds to the square inch, or double
the ordinary atmosphere pressure. Once
in the lock and the entrance closed, it be-
comes necessary to have an equal amount
of pressure, before the door into the caisson
can be opened. To this end air is forced
into the lock until the right pressure is
reached. 1t is here that the most unpleas-
ant part of the journey is experienced, as
the constantly increasing pressure acts
upon the tympanum of the ear, and would
rupture it, if it were not counteracted by
closing the nostrils, and initiating the cheeks
to their fullest extent thus creating an an
tificial pressure upon the inside of the ear.
This has to be done every few seconds, and
even then the sensation is sometimes pain
full. Tho air rushes into the narrow cham
Der with a noise like the kissing Of steam.
Four or five minutes were needed to obtain
the required pressure, when the air was
turned off and the lower door opened. De-
scending short ladder, the party found
themselves standing upon narrow plank
walk in one of the chambers of the caisson,
and seventy feet below the level of the
water in the river. This great depth being
required to get to solid base, below the
quick sand. la l. H tff
Onoa inaida mn dieoo,uF,,k ;a
from the compressed atmosphere. The in
terror is divided into six chambers by mas
siye partitions Of wood and iron, with pas
sages through them into each chamber In
all directions are laid narrow plank walks
for the convenience of wheeling the sand
which forms the bed of the river to the dis
charge pipes. The chambers are about
eight feet in height and lined throughout
with thin plating of iron. This is to
guard against the woodwork catching fire.
Such an act happened to the Brooklyn Gals
son, and very nearly destroyed it,
The chambers are well lighted with gas,
but are dim with clouds of mist. In that
compressed atmosphere a foot BURNER gives
as much light as a four-foot burner would
in ordinary air, 1t would naturally be sup
posed that in so confined space, there
would be liability Of the air becoming inn
pure, but such is not the case. An analysis
of the air in the excavation was made a
short time ago, and it was found to con
taina very small per centage of carbonic
acid gas. A couple of pigeons were kept in
a chamber nearly two weeks, and seemed
TO experience no discomfort. The sand ex-
cayated is forced out through the pipes by
the simple pressure of the air. The pipes
are about four inches in diameter, and oper-
ate upon the principle Of a syphon. The
sand is wheeled from the different cham
bers to the pipes, and there shoveled
around them. The flow can be shut of at
any time by means Of a stop-cock worked
by means Of huge wrench.