Wood County reporter. [volume] (Grand Rapids [i.e. Wisconsin Rapids], Wis.) 1857-1923, 1876-09-07
The HeII-Gate Explosion.


ing of the rock at Hallett' Point will
he brought to a close in about month.
Everything is being put in readiness for
the final tremendous 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 Sep
TENDER 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 part
OF, and a projection from, the shore of
Long Island, running far out under
the water. Being on point around
which the stream makes a bend of
nearly ninety degrees, it 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 a
week are often thrown upon 1.-The
Gridiron," 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 will 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 a deep pit, called
"shaft,' only guarded by few posts
with boards nailed across them.
Around the mouth Of the pit great
heaps of stone give evidence of the
amount that has been taken out,
though much of it has been removed
from the place. The whole quantity
eXcavated from the shaft and the
tunnels has been over 10000 cubic
yards. This stone is hornblende
gneiss, a metamorphic stone of almost
the same composition as granite, from
which it differs by layers of quartz,
mica and feldspar. 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 i'll some places which admit the
water from above into the tunnels, the
work has been very difficult. The
shaft is thirty-two feet deep and 100
feet in diameter. On the water side
cOtfer-dam in the shape of an irregular
pentagon, keeps the water out. On
the land side of the shaft are the vari-
Gus buildings necessary for carrying
on 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 these buildings are the
shops, engineers offices, etc.
Ten vast portals, looking like the
entrances of great tombs excavated in
mountains, open side by side around
tWo-thirds of the circumference of the
shaft. They are the entrances to ten
large tunnels 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 neces-
sary the continued use of a pumping
engine, which stands in the middle of
the shaft. The tunnels have been en-
tirely cleared Of pieces of stone and
rubbish, and the plan Of excavating
leaves the roof supported by 127 piers,
each eight feet square and varying in
height from twenty feet near the shaft
to ten or twelve feet near the outer
circumference of the excavations. The
entire work Of boring has been COM
pleted, and nothing remains to be
done except the manufacture of the
explosive material and placing the
charges in the holes prepared for them.
In the part of the rock which forms
the roof, $500 holes have been bored
i'll an upward direction, varying in
depth from three to eleven feet, and
all three inches in diameter. The
columns have been pierced also in the
same manner from floor to roof. These
holes will receive the explosive charges,
which will be dynamite where the rock
is hardest, and ordinary vulcan powder
where the superintendent mass is
more pliable and less dense in it's con-
SlStence. The entire roof and the
columns will be demolished at the
same instant.
Nitro-glycerine was for a time
thought of as the most suitable eX-
ploslve agent, but on mature consid-
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