The New York herald., 1870-02-27
A COLOSSAL CAISSON.
Brooklyn Tower-A Great Working Cham
ber''-Its Size, Construction and Cost.

process OF construction and hope to complete in
about three weeks time, colossal caisson, designed
TO form porIion OF the foundation on the Brooklyn
shore OF the East river bridge, ana upon which the
tower on that side will rest. 1t is work OF such
magnitude, and combining so much that Is
novel when contrasted with similar struc-
lures, that 1t claims no small degree of
attention from the engineering world. This
caisson VIII be snnk in the old cast slip OF the Fulton
ferry, the preparatory labor Of dredging which by
machines for its reception was commenced ON Mon
day January 3, this year, and has since Deea vgor-
0usly continued.
DESCRIPTION OF THE CAIs3oN.
caiss0n Is really o chest, and when applied to
bridge building the term suggests wooden box
or frame Of strong ana massive tmbels,
intended for laying tho foundations OF a
bridge In such situations where the ordinary
Golfer dam cannot be used. In the present instance
there being no rock foundation OF suitable nature
on the Brooklyn shore for the employment OF the
dam, this casson viii form part OF the foundation
of the tower ITSELF The system adopted In its con-
structon involves besides the usual ones, the prn
cple Of the pneumatic pile, which, IN the
majority OF instances IS tubular cylinder OF
large dimensions forced down by atmospheric
pressure; yet In this case, however. the
atmospheric pressure viii be assisted BY the
continual excavation or the earth, rocks and
sharp-edged bouldeA beneath the mass OF the Gals
son. In fact, there is also something in the con.
structlon or this apparatus partakng OF the principle
of the diving bell. The caisson properly, or the
enormous chamber within which
THE WORK or EXCAVATION
will be carried Is rectangular in shape. iss feet
long loa feet wide outside and Is feet high from the
lower edges. The sides are wedge shaped IN sec.
tlon the lower edge being eighth inches, aud the
upper eighth feet three thick The roof which
rests on these sides il five feet in thickness which
leaves--the dimensions OF roof and sides beng al.
lowed fora working chamber OF 1855 feet by ninety
eight feet in ground area ana nine feet IN height.
The whole n constructed Of yellow pine tmbefs,
twelve inches square the seams % oI which are payed
water. while between the outside layers OF
timber ,. she snsatning n1ayn. o. 1n TN between
through AS the sharp lower edges are intendes to
facilitate the sinking Of the caisson they made
Is Of OAK, ana 70 this il bolted cast iron shoe,
eight inches wide and oval on It's face. being three
inches thick IN me cenLre Around snis shoe is
above on b0tn sides OF the chamber wall.
the whole being strengthened by heavy interior
angie irons. Especial pains has been taken to pre-
vent the corners the bottom from spreading under
the great pressure TO which they Will De subjected
serted knee OF hard wood extending twenty feet
each way. The tinlbers OF the casson all bolted
together vertically horizontally and diagOnaiy with
two to seven feet. These Dots are, on an average,
eighteen inches-none more than two feet eight
inches-aparL throughout the whole structure, and
the heads and nuts are made airtght by rubber
washers.
As this huge work is sunk In It's desired position,
sixty feet below low tide marx, whicn Will be the
same the depth OF the rivers channel additional
courses OF timber Will be lald on the top
TO the height OF fifteen feet four inches aud filed In
with concrete, and then when the whole mass has
become nxed IN its fnal resting place the tower VIII
be built on the solid foundation thus obtained
n
the carss0n--thc TWO outside ones are the excava-
ting shafts, rectangular in shape and SIX feet six
supply shafts, circular In form, f0rty.three
inches In diameter, through which the workmen
are the two shafts, also circular, twenty. one
inches tn diameter. The shafts are made In every
particular with reference to both convenience and
safety Through the air shafts large air pumps will
continually force air into the caiss0n, expeIng the
water, and thus enabling the wOrKmen to de-
scend and work upon tue bottom OF the river.
Tne earth excavatcd WIN be deposited around tho
excavatng shafts, when dredging machine VIII
it the material aud annp y INTO @ sGows; AZ tue ex
ing purposes. Tue following figures wlIl
The magnitude aud Importance or this work.
Length OF caisson 1913 feet; Width 102 feet; negnt
concrete, CO s 30 ss ncnes: lumber IA caisson
900 feet: seght OF caIss0n, $500 TO 200 tons;
wrought iron tised IN noltA angle IRON and plates,
$4,000 feet
The caisson was commenced about the rrst Of
November last, aud sheud no detention occur II will
be ready for launching between the l7th and 20tn
Of Maren. The process that WIN bc adopted 70
send this huge structure into the water will
be both novel ana interesting. One hnn-
dred and ninety-6ve men have been daily
employed upon 1t, ana when 1t s delivered to the
Bridge Company at the slip designed Tor It's reccp-
ton II viii have cost $400 000
Thus an idea can be formed OF what has already
been accomplished to span the East river with
colossal and handsome bridge that Will connect
Brooklyn TO TINS city, making ia the union the
greatest metropolis In the world