Worcester daily spy. [volume] (Worcester [Mass.]) 1850-1888, 1871-02-23
amhmnrinc RInstinG.

Notwithstanding the reports to the contrary,
| the work Of removing the distractions OF the
| East river, Hell Gate, is being theoretically
| prosecuted, under the direction of Gen. John
| Newton, United States engineers. For the past
| six months great progress has been made, con-
siderng the obstacles met with, and great en-.
gineering ability is manifest in the mode adopted
to accomplish the end in view. The obstruction
is an extension of the rocky ledge which passes
across the upper end of Manhattan Island, and
which crops out in so many forms Whereabouts,
neCeSsitating SO much blaStingaud hard digging
for the streets and cellars between the park and
the rivers on either side. 1t passes the narrow,
crooked channel of the East river, just above
BlackwelPs Island, causing, by its resistance to
the rushing tide, the swift counter current and
whrling eddies which have always made that
channel so dangerous and have given 1t the e&-
pressive name of He'll Gate. The most danger
Gus portion of this hidden ledge is where Hal
let's Point juts out from the Long Island shore,
reaching, by gradual slope, some 300 feet into
the narrow channel before it attains the depth
of 80 feet beneath low water mark. The cur
rent runs here at the rate of from to Sknots
per hour, and when the tide on some portions OF
the rock has risen to the depth OF but two feet
its force is so great as to sweep strong man IN
stanty off his feet.
1t is this rock against which the engineers d.
rected their first efiorts. They began the work
by sinking Shaft close TO the shore, some go
feet broad, and extending out into the river about
100 feet, semi-eliptcal in form, and shielded on
the water side by a Golfer dam or miniature
levee 10 feet high. This shaft was eXcayated 10
the depth of 80 feet below low water mark. Out
from it, on a level with its bottom, they are now
engaged in working what are termed "tunnel
headings" ten in number, in every direction un-
der the river. These are ten feet in width at
bottom, are arched at the top, and have an aver
age length of 800 feet. Their height Is sixteen
feet nj the junction with the shaft, but running
to a point at the eXtremitles. AT intervals of
fifty feet one beyond another, are these to be ex-
cavated, galleries running entirely around, so as
to cross every one of these tunnel headings.
This will leave but honey-combed shell, the
crust above-as thin as the workmen dare to
leave it-being supported by what may be
termed "pillars," or the portions Of the rock left
standing by the intersection Of the headings
and galleries. The Pillars are to be pierced ut
last by excavations, in the eXtremities of which
the powder for the last grand explosion is to be
placed. All these pillars being connected, they
Will be fired, and what remains of the rock, it is
expected, will be blown into pieces so small that
it will not be difficult to raise and remove them
by large steam dredgeS.
But the object is to leave as little for the final
explosion and subsequent dredging as possible.
1t is far easier to remove all the workmen dare
to by the present working under the rocky roof
The crust which remains above the tunneling is
ten feet thick, but it would be imprudent to
make it thinner, as there is great danger of
opening seams in the rock above, through which
the water would run in and food the works.
Though this work is comprised within SO small
compass, it is really gigantic in its nature, as
the aggregate excavations are about mile and
half IN length, or, accurately, 1856 feet, of
which 3004 are headings, 2275 galleries, and 2677
powder chambers. In allluding to this subject,
the Mercantile Journal Of late date says
"Great difficulty results from the extreme hard
ness of the rock. Some idea of this can be
for fnaIf from fhaf aat hot 20
sink hole one inch and half in diameter one
foot in depth, will blunt from 90 to rs drills of
the best English steel. The drilling for the
shaft was done by steam, but thus far Tor until
within very short time certainly the head
ings have been drilled entirely by hand. 1t is
proposed, however, to introduce compressed air
as power. Partly from the use of this hand
power only, and the necessity in many places
of shallow drilling, and partly from the greater
hardness Of the rock, the forward progress OF
the headings has been much less than was at
tanned in the Mont Gents tunnel. There it
was from one and half to three feet per day
here, as yet, it has only been about eight feet
per month.
For blasting here powder only is used; but
this is Of three times, or more, the ordinary
force. Other explosives have been tried but not
with sufficient success to warrant their adoption.
Too great force in the upper portion of the
rock involves the danger of opening the seams
so as to allow water TO come through; in other
parts no hole is required deep enough to utilize
greater force than that of powder. In the
blasts, thirty or forty charges are fired nearly al
the same time, gong being previously sounded
to give notice to the workmen. Huge timberS,
bound together with iron bands, are hung as
curtains at the opening of each tunnel to pre-.
vent the detached rock from flying into the all
without. So great is the force, however, that
| these ponderons curtains are swung out eight Oh
ten feet" One hundred and seventy-ive mer
are employed on the work, fifty or more working
for eight hours at a time, and resting sixteer
hours. 1t will probably require two years tt
complete this gigantic undertaking.-Ne0 Yorl
| Herald.