The sun., 1897-09-05

NOW THE EAST RIVER BRIDGI
BUILDERS ToIL UNDER WATER.
In nm Air Pressure or Twenty Pounds to tba
Square Hnch They shovel Up the sandy Rives
Bottom. MIX Ht Into Mud. and Force nt Ip
Thrnnnh n Elnn q e nn,n neh In thn ni-..


! Bottom. MIX It Into sIud. and Force nt Up
Through Pipe to ne Dumped late tho River.
Ono Of tho most interesting pieces OF work
which Is now being carried In this city ls the
sinking OF the big caisson which will form the
| foundation for ono log Of the tower for the now
East River Bridge at tho foot OF Delaney street.
| The fridge. when 1t is complete. will reach from
| Delaney street. in this city. to Williamsburg.
and will be tho biggest suspension bridge in
! the world.
| The caisson which is now being sunk to bed
rock lies at tho northeast cornor OF tho old De-
lancy street pier, with its outer end about oven
| with tho end of tho pier, 1t is great oblong
box OF timber, divided into two parts by n hort
ZontRl partition feet thick. Underneath this
partition is tho working chamber 2 feet in
| depth. and above the partition another chamber
of about the same Depth which is now filed
! with cement concrete and capped with the first
courses OF stone which will eventually form the
bridge foundation.
This concrete and stono have sunk the cnisson
deep down into tho mud and sand of the river
bottom, and the earth is taken out from
| underneath II by men who labor away below the
river bed in the working chamber. moro and
more stoncwork will be built above to force the
caisson down and TO complete the structure.
Tho caisson is sovcnty-six feet long and sixty
feet wide, and It's bottom edge is now about
thirty feet below the high water mark and
perhaps twelve feet into tho river bottom. All
about ii as II lies appliances for carrying on
tho work Of sinking 1t. and of building up the
stonework upon it as il goes down. On the pier
near two of its corners stand derricks.
each with It's steam boilers and
engine. and outside Of it, in the slip.
near its other corners, are two other derricka
each standing upon clusters of piles sunk in the
slip. On the pier are other engines working air
compressors and concrete mixers. and usually
there is boat or two lying along the outer end
OF the caisson with cut stone aboard.
The courses OF stone work already laid stand
about even with the planking Of the wharf and
high above this and sticking through 1t are half
q dozen mir locks for letting mon and materials in
and out OF the working chamber below Besides
these are lot Of smaller pipes, through which
air and water and electric light wires pass into
the working chamber, and water and mud are
The working chamber has no bottom except
the earth or rock on which the caisson rests,
and il is kept free from the surrounding waters
by being fed with compressed air. At its pres
requires pressure Of about twenty pounds to
the square inch to keep the water out.
sGS FSpSTsT na mafG % ephs o see
how the work OF sinking 1t is carried on. 4
5%9k Sd es
OF the big black iron pipes which rise through
the masonry. The pipe was not unlike a smoke
stack, and il rose perhaps seven feet above tho
masonry. 1t was three feet in diameter. The
workman went ahead and climbed up a ladder
sounded signal to the men inside by striking a
certain number of blows on tho top Of the closed
pipe win hammer. This said to the men In
Presently there. was a sound of some ono
and fastened. then there was kissing Of air.
and after = wait OF several minutes nut door just
OPENED in the TOP Of the pipe from the inside.
The conductor scnped down into this hole. find
will his feet and then his hands. ard in a mo-
mGnt he called to THE Sun man 10 follow him.
the bottom floor. and in the centre Of this
was another trap-door like the one above, only
was close quarters, with three men me in a s.foot
well. but 1t is said that five persons can get into
The conductor now reached up and closed the
door. through which tho visitors had entered.
and } n made it fast: Then he stopped and opened =
the working chamber. 1t came with n Kissing
snd prst stfsnSs rs the &
great and un' omfortablc pressure on the dIuDs
Keep your mouth shut and swallow and
clear the air passages of your head" had been
his Instructions before he entered. and he fol-
dneed by very present belief e. that II he didn't In
pressure the discomfort ceased and the visitor
was quite comfortable by the time the pressure
in the air lock had reached the twenty pounds
to the inch, which made 1t equal to that in the
working chamber below.
1t was pitch dark in the lock: and tho stay
many times much. At the end Of that time
cession res nj the | three men cIam6ered further down.
The shaft below was lit by incandescent electric
shaft ended al the roof of the working chamber.
and from here down the descent was made by
The vas, chamber under the caisson. thirty
feet or more below the tide, was well !it up with
1ulpQred gDnClOnS
ss Ss and FunnnE muudo dfoFof
81 work shovelling away the flow. They worked
point Of its shoyellIng, the end OF a four-inch
pipe. which reached clear down to the earth.
%ssS into bS ho;s nS and S,d 'tss /:
lated to a eqnsdera bic amount this man opened
a valve at the bottom Of the pipe and the e air.
Pf % nf TRe nnd ef the
followed ont until it is shaped under the
| whole caisson. with the centre down perhaps
four or five feet lower than the earth about the
As the casson sinks inch by inch men watch
manner as 10 keep it going always upon q level.
In this way it must be sunk until II reaches 2
When the rock resshea and
isveed led 1f the the work work Of sinking % the oaissop wi
be allied soidiy with eorcrets. Then tho foun-
dation win be complete for by that time the
where 1t is to end, twenty feet above tidewateF.
Before this end is reached the workmen win
| have encountered rocks. boulders, old timbefa,
or perhaps many other obstructione which oan-
not be forced out of the pipes by air pres
mers or blasting into pieces. which oan bo
passed up in buckets through air locks pro-
vided for this purpose. There are six of those
working air locks and II is through these that
| the cement concrete will be passed down with
| which the working chamber will finally be flled.
At the present .depth men arc able to do an
ordinary days work Of eight hours without diff
| hculty. but as the depth and air pressure in.
crease they work in shorter and shorter shifts
| and get higher pay.
The process OF getting out of the caiason was
the reverse Of that OF getting in Tho visitors
meath their feet, and then let the air slowly, ,out
Of tho back until its pressure was % only equal 70
and they clambered out into the sunlight.
The second caisson for the New York pter -
| nearly ready TO launch from the yard at North
| Third street. WILLIAMSBURG and one for tho