The sun. [volume] (New York [N.Y.]) 1833-1916, 1894-09-30

century or 80 ago, WAS n good SOLD piece OF
work. II the building Of a new bridge had not
been rendered almost imperative by the United
States law which authorized the Harlem Ship
Canal and at the same time required that all
the bridges across the Harlem River should
have "a feet In the clear under them at mean
high water the old bridge would have been put
In repair and made to servo for a long time yet.
Sooner or later, however, 1t would have had to
70, to make room for one OF adequate size to
carry the rapidly increasing traffic over that part
of the Harlem. Even over the temporary
bridge OF to-day 5000 vehicles pass daily.
Ono Of the most interesting parts OF a bridge
Is its foundations, and the foundations which
wero put under the old Harlem bridge are OF
particular interest. One can see them now, bare
and staring from the waters. Where the draw
ives pivoted stands a circle of eleven big iron
pipes. with another one In the centre OF the ring.
At either side. where tho ends Of tho draw
rested, are rows of these iron tubes, Eve in O row
on each side.
Those iron tube foundations have a place In
the history Of engineering. They were the first
pieces OF foundation work to be sunk under the
system so common now. of excluding the water
from inside them by means OF compressed air
and digging the way for them through the
rivers bottom from the inside. That was the
method used n few years afterward by Mr..
Roebling, and IL il by this same means that
the foundations for the new bridge will be sunk
to their places. The first of these tubes that
was put down Is the one standing in that centre
ring, nearest to the New York shore.
What u change is marked in great Industries
by the differences in construction between that
old bridge and the one to succeed it! In place OF
the steel of to-day, TINT bri lse was built OF
wrought and cast iron. Thosr foundation tubes
are cast irnns They are six feet in diameter, ard
bv which these sections were boItcd together are
on the inside, and the Outsides OF the sections
were all r turned smooth and to gauge IN the
ntted as an air lock, and, as the tubes were sunk,
these sections were lifted and new, pieces put in
under them. These old tubes go down into the
river bed from ~ to 80 feet beneath the surface
OF the water, and rest, upon hard sand STRAIT
tom with concrete. They have all got to be re
moved, at least to a depth OF 90 feet below low
H. done has not been decided. PROBABLY sls y the 20
vii be blasted out.
on June 81. About that time. too, the con
tractors began building n great ~caisson, with the
sinking Of which the work Of reconstruction has
combs Dam Bridge. and IL was foated into
place about three weeks ago. In preparation for
Works had marked it's place by ranges, and the
contractors had put down piles 10 moor it TO.
piles outside Of where the caissoa was TO 70.
built q working platform upon these, and erected
much more. one NAV see now from The sids az az
the temporary bridge Just below.
cOmpRctly clustered between IL and the New
York shore, is a mass Of uncOuth scOws, floats,
and cannlboats. From the midst OF these rises
building. unenclQsed. and without any roof raft
ers. This frame shows the size and position of tho
foot-thick timbering which encloses its lower
part Is merely n confer dan. To keep out water
the latter the stone and concrete walls which
are eventually to rise from IL. The Caisson it.
sells sell Is h TEis the ana % I y almost 1SS submerged al.
the pier on which tlie end Of the new draw will
rest near the New York side Of the river.
- feet wide. and about as deep rs il is
wide. II is built 81 southern pine thinkers, each
Midway OF its height II has a solid partition,
built OF the same sort OF timbers, which divides
ments. The lower OF these spaces Is where men
VIII work pretty soon digging the way down for
the whole Gaisson 20 sinh 70 4 s~Ie foundation,
The first purpose Of this concrete filling Is 10
sink the cGisson, for It will be very buoyant with
second purpose is 10 receive the stone and con-
crete which will finally rise from il for the pier.
at the right OF the group Of boats about The
caisson a big noat with q house Of corrugated
and reaching from il too, to the
caisson, are hose pipes. This float carries the
pumps Air eomPressors, and electric light plant,
toT, the work OF sinking the eaisson, and the
Ap asaS for furnishing ,hs power % run them.
.iYe derricks Oyerhang the caisson, and several
NJ these are busy every day handling the
material for the eonorsts that 10 being rapidly |
put into the caissOn.
Tons and tons OF beautiful white sparkling
sand and gravel enter into this composition In
the proportion OF barrel Of Portland cement
10 one cubic yard OF gravel and One-half cubic
yard Of sand. The canal boats which hug along
side ths eGlssoR bring the sand and gravel from
the bar at NOrthpOrt, l.. ].
Looking into the ~ungainly Golfer dam that sur
mounts the catssOn one secs four steel pipes.
whose closed tops rise 10 the top Of the en-
,losnre. II Is through these pipes, and the air
IN each OF them. that men will pass in and
OF that dismal under chamber, and through
hem also will be taken out the excaVated mud
Ind sand. When the eXcayators get To good, firm
latton solid enough for any one. The expecta-
ion Is that this will DO reached az about the
lepth that the old iron cylinders were sunk
or nifty feet. When the caisson is
Town deep enough, the whole space where the
men worked within II will be hlled with con
and 1t will be closed forever. The pier
AAt hto Be carried up from l. viii have walls