The Toledo chronicle. [volume] (Toledo, Tama County, Iowa) 1873-1924, 1876-09-07


suddenly upon deep pit, called a
"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 a
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 thirty-two feet deep and 100
feet in diameter. On the water side a
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
tn la
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
in an upward direction, varying i'll
depth from three to eleven feet, and
all three inches in diameter. The
columns Lave 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 its con-
| sistence. 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-
plosive agent, but on mature consid-
Grafton it was rejected-not as too
dangerous, but as inconvenient to use
on account of leakage. Dynamite,
which is composed of twenty-five per
cent. of clay and seventy-fve per
cent. Of nitro-glycerine, was finally
selected for blasting the more solid
portions of the rock. The charges
will be put into cans about two and
one-half inches in diameter, and vary
ing in length according to the depth of
| the holes. These cans will be placed
in the holes, and then connected by
short wires with the long wires which
extend to the batteries. A bomb-proof
chamber will be prepared for the OPP
orators of the battery at some distance
| southeast of the main shaft, and in
the direction Of the RavensWoOd road.
In this chamber will be placed at least
200 Groves galvanic batteries, and
each of them will explode from seven
teen IL twenty charges. An ingenious
scheme has been devised by which all
these batteries will be brought into ac-
ton at the same instant, and thus a
complete circuit will be formed, firing
all the charges together, and utterly
destroying the great plateau of rock
which has hitherto obstructed naviga
ton except for small craft through
Hell Gate Channel.
Gen. Newton has kept up constant
series of experiments to insure per-
feet success when the great day comes,
and there is no reasonable ground for
any fear of any accident. The engi-
neers are of the opinion that the only
apparent effects of the explosion will
be the hurting into the air of huge
column of water, with possibly few
pieces of rocks, as the resistance of the
water will prevent any except few
of the smaller masses from being
thrown beyond the surface. AS soon
as the explosion is over, the work of
dredging will be begun at once, so as
to make the channel open to naviga-
ton at the earliest possible time. AS
the floors of the tunnels slope out
ward, from depth of thirty-three to
forty-seven feet below low water mark,
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.-N. Y. Tribune.
| s
The Clothie5' and Halter says that
English silk hats are not imported into
this country to any great extent now,
although so recently as 1871 they were
all the rage in New York. New York
hats are now considered finer than the
English, and are exported and sold to
some extent in England and on the