New-York tribune. [volume] (New York [N.Y.]) 1866-1924, 1871-06-10
LOCAL MISCELLANY.
CONQUERING HE'LL GATE.

MINING UNDER WHARF.-THE EXTENSIVE OPER-
ATOMS AT HALLETT's PONT-RAPID PRO-
GRESS OF THE WoRK-ITs DAHGERs-oTHER
HARBOR IMPROVEMENTS.
The removal of Halletts Point, the most
dangerous Of the Hell Gate distractions truly ggan
tic work Gen Newton plan oontempates the removal
Of about 10000 cubic yards about 100000 tuns, Of
solid rock The method which the General has adopted
IL remarkable both for it's boldness and simplicity, and
II is believed, has been applied in similar oper
atoms In this country Sufficient progress has been
made TO show that it is only entirely practicable but
safe and economical The whole reef Is to be honey
combed, and the rock removed just coal is taken
from mine. For this purpose a central
shaft about 40 feet in diameter has been
sunk at the waters edge the Long Island shore,
in the middle OF the reef This shaft has been quaed
10 q depth OF feet below low water mark. From
this large open space 10 great tunnels have been started
which will be advanced until the gradually increasing
depth Of water will no longer permit sufficiently thick
roof to be left above Good progress has been made IN
all of these the longest having been driven 1l5 feet The
object get all the material possible so that when
the roof falls in uniform depth OF feet at low water
may be obtained To this end circular tunnels,
oOncentric with the open sLaft will be driven The hrt
Of these has been finished and the second and third are
in progress. When completed the mine viii present the
appearance of a hall Of columns with dome-shaped
roof about Is feet high where it starts from the shaft
forgotten that the object Of the tunnels is
not simply for the purpose Of introducing powder blow
I'D the roof but TO furnish cellar for the roof TO drop
into. 1t much cheaper TO get the rock out now than
to grappe for it after the explosion.
When the excavation has been carried sufficiently FAR
for this purpose charges Of are
10 be introduced into the pillars, the mine filled with
water the pillars shattered and the roof raised and
broken by simultaneous explosion After this II sup
posed that very little viii remain 10 be DONE except to
survey the bottom and make that the Sound steam
boats NAV pass over in safety Mr.. G. Reithemer
the superintendent does not think that piece OF rock
weighing ten tuns will be left any such pieces should
be left Morris & Cummings graphing machines can
easily remove such OF them might impede navigation
or few charges Of nrOgycerne exploded alongside OF
them would break them in pieces. AS 70 the explosion
ITSELF neither Gen. Newton Mr.. Reitheimer thinks
there Will be any difficulty. Mr. Reitheimer has had
some experience in large blasts, having en-
cneered at HoIyhead, England, % discharges Of
from 5000 10 2l,OOO pounds Of powder each,
and displaced at one time 10000 cubic yards OF rock
The charge will be made by electricity and its effect
will be seen lifting up aud breaking up of the water
over the reef There will he danger 10 property on
the shore to the vessels floating near and the water
will smother the noise and prevent conclusion.
1t is estimated that year and half more will he re-
qured to complete the mining force of 200 Cornish
miners is present employed which is divided into
three shifts for the purpose Of working night and day
great quantity Of rock has been already deposited on
The thickness required for the roof is greater
than would be necessary there not so many per-
pendcuar assures in the rock. In some places OAK
wedges oakum and Roman cement as well as engineer
ing skin have literally used to keep out the water
vein Of decOmpOsed mica was struck the Other ddy
and for while the water rushed IN fearuy, but the
leak has been reduced 10 Insignificant proportions
Gen NewtOn's drilling machine has done great deal
Of work Diamond Reef and has now been removed 10
Ceentes Reef Both these reefs are In the channel OF
the East River, between the lower END OF Manhattan
Island Brooklyn The drilling machine Is placed on
large scow, which is built with well 80 feet IN diane
ter in the middle IT, The being firmly anchored
over the reef large dome Is let down 20 the bottom,
through the well The dome proteSSlthe drills which
Of the East River have no tendency 70 upset It, The
drilling machinery rests on four platforms when are
swung over the sipken dome when every thing fixed
for work The machine usually drills holes, OF 10 feet
in depth in from TO is hours time. BY tn, machine.
with the aid OF divers and ntrogyCene Diamond Reef
has broken up that solid rock can no where be
found All that remains TO be done Is the removal OF the
pieces by the graphing machine.