Watertown republican. [volume] (Watertown, Wis.) 1860-1906, 1876-03-22
A GIANT FIRE-CRACKER.


Visit to He'll Gate and What it Taught
Forty Thousand Pounds of Nitro G1yce-
rine to be Exploded.
From the New York Evening Telegram.
Ten years ago the War Department
directed General John Newton, of the
United States engineer corps, to make
estimates for the removal Of the OBJ
structions in the East river at Hallet's
Point, Familiarity known as "Hell
Gate" Many attempts to remove the
distractions had been previously made,
but had altogether failed in the one great
end-that Of rendering the channel
safe and deep enough to admit the
passage of large vessels. Upon the re-
ceipt of the Generals report the sum
of $34, 900 was raised, partly by sub
scription among our local merchants
and partly by a grant from Congress.
The survey for the work was made in
1869.
The work itself involved the removal
of the Middle Reef, Gridiron, Hen and
Chickens and Negroes Head; virtually
the complete demolition of Hallett's
Point. In September, 1869, the first
machinery was erected and the work of
burrowing into the heart Of the sub
merged rocks progressed slowly but
surely. The unwise delay of Congress
IN appropriating the necessary funds
and the niggardly, paltry allowances
made, hampered the advancement of
the scheme. At last however, it is an
nounced as near completion, by the
bulletin, that the chamber prepared for
the great charge which is to rend the
stony mass to splinters, and make Hell
Gate terror to the past, is as large as
it is required to be. By this explosion
the eastern entrance to the port of New
York will be opened to vessels of twen-
ty-six feet draught. The cost of the
affair In money has been, so far, $780,
600
The work has been under the direc-
ton of General Newton, and deserves
special record in the annals Of Ameri-
can engineering. At the extremity Of
Hallests Point, which is laid bare at
low water, a central shaft was sunk,
and the ledge of rocks into which it de-
scended was surrounded by q Golfer
dam to guard the workings from the
high tides. From the main shaft ten
large headings radiated, like the spokes
of a wheel, running out into the river
bed and under the reefs which it was
necessary to remove. From these
twenty-eight smaller drifts were driven.
The larger shafts, the chief of which was
200 feet long, were named after various
United States officers, as the Grant,
Mcclellan, Meade, &C., galleries, and
were connected atregular distances by
lateral galleries, circular in form and
concentric with the centre of the shaft.
Twenty-Five and one-haf acres were
undermined in this way, and mile
and half Of tunneling made. The
great danger attendant on the work
was, of course, that likely to result
from the caving of the roof rock. To
fully guard against this, soundings were
made all over the work at regular in
tervals of one foot. In ordinary cases
the lead was sunk, but where shale was
met with, the patent sounding instru-
ment was driven through the bed rock
by boring But few short of 10000 of
these measurem ents were required to
establish the necessary knowledge Of
the ground. The best comment on the
correctness of the measure arrived at
Is in the fact that no serious case of
caving In the galleries has occurred
since the work was commenced.
An enormous quantity of blasting
material was used; at first nitro
glycerine, but later an agent composed
of thirty parts of nitro-gIycerine
to seventy of gunpowder. This COM
pound, called vulcan powder, answered
the requirements better than any other,
producing the short, quick blast requir-
ed, to a marvel Explosives, equiva-
lent on the whole to 10000 pounds of
nitro-glycerine, have been consumed
in bringing the work 10 its present state.
To-day the mine is to re-
ceive the final charge; in the
pit or chamber, which is thirty-fve
feet deep and two hundred feet in di-
ameter, 10000 small holes, two and a
half inches in diameter, and from sew
en- to twelve feet deep, are being drilled
in the roof and sides Of the passages
for further blasts, and are to be charged
with the explosive enclosed in iron tubes
In the matter of that explosive the en-
gineers are at present IN doubt. From
among the entire list of blasting mate
rial at their command they desire to Sc
lect that which can be most certainly
relied on for effective work. The
choice has SO far narrowed down to
two, respectively known as Rendrock
and Kieselguhr. The latter is a Ger
man compound, an especial favorite in
the extensive workings of the Prussian
mines. The charges are to be simulta
neously ignited by percussion, with
caps similar in principle to those Of a
gun.
Forty thousand pounds of nitro-gly-
cerine are to form the grand charge.
The discharge of the various blasts is OF
be effected by electricity, and, in order
to avoid the possibility of an irregular
series of explosions, Gen. Newton pro-
poses to connect the mines by means
of an electric wire enclosed in iron
tubing and carried about the entire
workings, communicating directly with
each blast. A hundred and twenty
men are at present employed drilling
the holes for the minor blasts, and
twenty-oneo of them are driven each cay.