Year: 1876

| The great explosion at He'll Gate


now certain to take place during the lat


ter part of September, and contrary T.


reports which have been generally cir
| culated the entire mass of rocks will b,


demolished by one terrific explosion
| The work of tunneling and BORING is nov
ended, and nothing remains undone ex
| cept the preparation and insertion of tn,


cartridges.


| The tunnels radiating from the mair
| shaft, and likewise those crossing them


are all cleared out, leaving the upper


crust of rock supported on one hundred


and seventy-twO piers, each eight feet
| square, but varying in heigth from TWEEN
| ty feet near the shaft to ten or twelve
feet near the outer circumference. In
! the roof of rocks thus formed $500 holes


have been bored in an upward direction,


ranging in depth from three to eleven


feet, with a uniform diameter of three


inches. These holes will be the recepta-


cles of the explosive material, which will


be dynamite where the rock ia hardest


and ordinary vulcan powder where the
perincumbent mass is more friable and
easier to blow to pieces. As the floor of
the tunnel slopes outward from n depth
of thirty two feet to forty feet below low
water, and the depth of water required
for navigation in the neighborhood of
New York is only twenty-six feet at
mean low water, it is plain that after the
explosion and the subsequent dredging
there will be ample room for the largest
ships in the world to reach New York
bay through the waters of the sound
and thus make saving of time on the
voyage to and from Europe.


NitrO-glycerene was for time con-
templated as the most suitable explosive
agent but on mature consideration it
was rejected, not only as being too dan
gerous in the manufacture, but also be-
cause some of the charges are liable to
slip out of the holes prepared for them,
and in such an event nitro O-glycerine
would be liable to explode prematurely.
Dynamite, which is composed of twenty
five per cent. of clay and seventy-fve
per cent. of nitro glycerine, was finally
selected and it is calculated that each
charge will break up twenty cubic yards,
there being in or about seventy thou
sand cubic yards in the entire mass to
be exploded. A bomb-proof chamber
has been prepared for the operators, at a
distance of three hundred feet southeast
of the main shaft and in the direction of
tho Ravenswood road. In this chamber
will be placed at least two hundred gal
vanic batteries of the pattern known as
Groves, and each of these will explode
from seventeen to twenty charges. A
most ingenious scheme has been devised,
by which all these batteries are brought
into action at the same time, and then a
complete circuit will be formed, setting
off the entire $500 charges together, and
utterly destroying the great plateau OF
rock which has made He'll Gate so dan
gerOus to navigatOrs.


General Newton has been unceaSing in
his exertions, and has kept up a constant
series of experiments to insure perfect
success when the great day comes; and
there is no reasonable ground for fear of
any untoward accident occurring The
assistant engineers, who will have practi
cal charge of the operations on the day
of the explosion, will, according to the
popular belief, be placed in position of
great danger; but this is only visionary,
as the utmost foresight has been used to
prevent any harm to the operators.


The engineers are of opinion the only
apparent effect of the explosion will be |
the hurling into the air of a huge col. |
umn of water, with perhaps some bits of
rock, as the assistance of the superincum-
bent water will prevent any except few |
of the smaller masses from being elected |
beyond the surface. As soon as ever the |
explosion is over the work of dredging |
will begin, in order to throw the channel |
open to navigation at the earliest posi-
bic moment.