The record-union., 1897-08-22

There is a plan for each course, show
ing exactly where every stone is to go.
The span of the neys bridge will be
precisely 1000 feet, four and a half
feet more than the span of the older
structure.
1t is just beyond the sugar refneries
on the Brooklyn River bank, at the foot
of North Second street, that the second
caisson for the New York tower (to be
completed and towed across in a month
or so) is being built The contracts for
the caissons on the Brooklyn side
these are to be placed at a point be-
tween North Fifth and North Sixth
street-have not yet been awarded, and
work in any event will not be COM
menced on them until next fall.
Just how long it will take to build
these caissons canont be said The
entire bridge is to be completed about
five years from now, and will cost
$7,000,000. 1t is on the New York
side that there will be the greatest
length of approach and the most ex-
pert engineering needed though the
caiSsons viii have to be sunk deeper
on the Brooklyn side. This first cais-
son meets with rock early, and will be
sunk to the least depth of all. The
pier it is finally to make Will be II feet
in length, 3S feet of masonry below,
and 10 feet of the caiss0n Itself. con-
crete top, and the chamber filled with
concrete, all in one solid, firm col
unln.
Just to the south, where the second
New York caisson is to stand, the rock
shelves off and a depth of nine feet
more will be necessary. The Brooklyn
caissons will go far deeper than this,
one of them very nearly 100 feet be-
low the surface of the river.
Approximately, it takes about three
months to sink a caisson. Hence if the
contracts for those in Brooklyn are
let in the fall and there are not extra
ordinary delays the caisson work should
be completed by early next spring at
the furthest, and the steel work started.
Before the summer is over however,
other parts of the bridge are to be
commenced. It is planned to tear down
for the New York anchorage some
time in August or early in September.
This great pile of masonry is to extend
from Tompkins to Mangin. street and
along Delaney, and viii be 40 feet
square. In this the cables are to be
fastened, the ends of their strands inn
bedded and woven into great steel claps
in a curious fashion. This anchorage
will be on what is called a pile and
grillage foundation that is, piles are
first driven down and timbers put atop
of them, then a heavy flooring of con-
crete laid, and stone masoned upon
that. The pull of the four great ca
bles upon each anchorage viii be,
when the bridge is loaded (and there
are to be two elevated and four trolley
tracks upon it,, something lolze 10000
600 pounds, or 10000 tons.
Compared with the old bridge, the
towers and their settings are interest
ing. The caissons completed will stand
twenty feet above high water. Each
will have four pedestals on its top, ar
ranged in a square. On these pedes-
tails eight colossal steel legs will set,
these legs carrying up the tower which
will arch between the caissons.
Each tower of the old bridge rests
on a single caisson 16S by 102 feet.
They were built in 1872, and since then
there has been little Improvement in
actual caisson working, except in the
speed with which a caisson can be sunk
and better methods for taking out
dirt, sand and rocks from the bottom.
When a rock is met with in a caisson
nowadays it is blasted out with rack
rock" an explosive much resembling
dynamite The chief danger is from
fire Electric lights are now used, but
even with these there is no absolute
safety, for wires may get crossed.
A Troy Polytechnic graduate, Free
man by name, is in charge of the cais-
son work He has been employed in
the construction of several important
bridges in the West, and is an engi-
neer of ability. Lefferts L. Buck is
chief engineer of the entire structure
New York Times.