Perrysburg journal. (Perrysburg, Wood Co., O. [Ohio]) 186?-1965, 1876-09-22
The He'll Gate Explosion.

The work preparatory to the blasting
of the rock at Hallett's Point will soon
be brought to a close. Everything is be-
ing put in readiness for the final tremen-
dous explosion which is to give New
York new doorway to the Atlantic
Ocean, lessening the time between this
city and Europe by twenty-four hours.
The last of September has been fixed
upon by Gen. Newton, the United States
engineer in charge of the work, as the
time when the final explosion is to take
place.
Many suppose that this rock is in the
middle OF the stream, but it is a part of,
and projection from, the shore OF
Long Island, running far out under the
water Being on point around which
the stream makes bend of nearly 90
degrees, 1t causes the current to set so
strongly toward the opposite shore of
Wards Island that wreck is inevitable
to any vessel which attempts to make
the passage when there is not wind
enough to carry her through Persons
living near the point say that two or
three vessels week are often thrown
upon "The Gridiron,n the opposite rock,
and that many of these are so shattered
that they are dismantled and sold for
old lumber. The removal of the great
rocky bar upon the point win give the
current another and more direct course
and greatly deepen the channel
The approach to the excavations is
along the shore, after leaving the Astoria
ferry, and the visitor comes suddenly
upon deep pit, called "shaft," and
guarded by a few posts with boards
nailed across them. Around the mouth
of the pit great heaps of stone give evi-
dence of the amount that has been taken
out, though much of it has been removed
from the place. The whole quantity ex-
cavated from the shaft and the tunnels
has been over 10000 cubic yards. This
stone is hornblende gneiss, metamor-
phic stone of almost the same compost
tion as granite, from which it differs by
layers Of quartz, mica and teldspar. 1t
generally has tendency to cleave along
the planes where the mica exists in the
greatest quantities. The stone is very
hard; harder than granite. For this
reason and on account of the seams in
the rock in some places which admit
the water from above into the tunnels,
the work has been very difficult. The
shaft is S2 feet deep and 100feet in
diameter. On the water side Golfer
dam, in the shape of an irregular penta-
gon, keeps out the water. On the land
side of the shaft are the various build
ings necessary for the carrying on of
the work. There is an engine-house in
which are the great air chambers by
means of which the air was compressed
until it gave the requisite number of
pounds pressure to the square inch, and
was conducted thence in tubes to the
Burleigh drills far below in the tunnels.
Near the building are the shops, engi-
neers' offices, etc. 7
Ten vast portals, looking like the en-
france of great tombs excavated in
open side by side around two
birds of the circumference of the shaft.
rbey are the entrances to ten large tun-
lels and to the network of small tunnels
which undermine the rock Within
water pours down IN streams at certain
POINTS and drips constantly at others,
making necessary the continued use of a !
engine, which stands in the
middle of the Shaft. The tunnels have
'een entirely cleared of pieces of stone
md rubbish, and the plan of excavating
caves the roof supported by 172 piers,
ZACH 8 feet square and varying in height
rom 20 feet near the shaft to 10 or 10
eet near the outer circumference of the
The entire work of boring |
las been completed, and nothing remains I
o be done except the manufacture of |
he explosive material and placing the
harges in the holes prepared for them
n the part of the rock which forms the !
oof 800 holes have been bored in an |
Upward direction, varying in depth from
to IL feet, and all three inches in
iameter. The columns have been
ierced, also, in the same manner from
oor to roof. These holes will receive |
he explosive charges, which will be
ynamite where the rock is hardest, end /
rdlnary vulcan powder where the super
1cumbent mass is more pliable and less
ense in its consistence. The entire roof |
nd the columns will be demolished at
be same instant. ....-
Nitro-glycerine was for time thought
I as the most suitable explosive agent,
ut on Mature consideration it was re-
ected-not as too dangerous, but as in
onvenient to use on account of leakage.
dynamite, which is composed of 25 per
ent. of clay and rs per cent. of nitro
lycerine, was finally selected for blast
lg the more solid portions of the rock.
he charges win be put into cans about
inches in diameter, and varying in
,ngth according to- the depth of the
oles. These cans will be placed in the
oles, and then connected by short wires
18th the long wires which extend to the
A bomb-proof chamber will
e prepared for the operators of the
artery at some distance southeast of the
lain shaft and in the direction of the
avenswood road, In this chamber Wilt
e placed at least 200 Goves galvanie
atteres, and each of them will explode
ON II to 20 charges. An Ingenious
theme has been devised by which all
lese batteries will be brought into ac-
on at the same instant, and thus com
ete circuit will be formed, firing all the
larges together, and utterly destroying
&c great plateau of rock which has
therto obstructed navigation except
# small crafts through He'll Gate chan
IL. sa1a
Gen Newton has kept up a constant
iries of experiments TO insure perfect 4,
Iccess when the great day comes, and
Iere is no reasonable ground for fear of
ny accident. The engineers are of the
oinion that the only apparent effects of !
e explosion will be the hurling into the
r of a huge column of water, with pos
bly, a few pieces of rock, as the resist
ice of the water will be sufficient to
event any only the smaller masses
ON being thrown beyond the surface. !
S soon as the explosion is over the +,
ork of dredging will be begun at once, !.
as to make the channel open for naYi-
ltiOn at the earliest possible time AS
e floors of the tunnels slope outward, /,
ON a depth of thirty-three to forty III
ven feet below low-water mark, and
e depth of water required for naviga- q
on in the neighborhood Of New York 1
only twenty six feet at mean low S
ater, il is plain that after the explosion d
ID the subsequent dredging there will v
aunnla Room for tha IarOaaf ahf,.o L., -