The New York herald., 1874-11-20
Removal of Distractions at
Hallett's Point.
Extraordinary Subterranean
Operations.
How the Interests Of Commerce
Are To Be Subserved.
Six Hundred Thousand Dollars Wanted
for Next Year.

United otases Engineer corps tBreyet Major Gen-
sraD received orders from the War Department
70 make an estimate Tor the removal OF obstruc-
lions a; He'll Gate, TO subserve the wants OF COM
merce. The first thing he did was TO study the
reports OF surveys upon the impediments IN the
navigation OF Hell Gate already made py the
United States Coast Survey. Among these reports
was one from the ADVISORY Council OF the state
Commission Of 1861 IN regard TO the estaollsh-
ment OF pier and bulkhead lines OF the haroor OF
New York. All these reports pointed out very
plainly what the impediments In He'll Gate were,
but they recommended tue removal only OF some
OF the smaller rocks which lie in the channel,
such as
POT ROCK, FRYING PAN, WAYS REEF AND SHELL
DRAKE ROCK,
and small portion OF the reef at Hallett's Point.
There was no mode suggested IN any OF these re-
ports for the removal OF these rocks except under
the general term or "blasting.n Prior TO these
reports there had been an attempt made to
remove Pot Rock, Ways Reef and Frying Pan by
means OF process known as
SURFACE BLASTING,
as first practised in this country by Maillefert.
Tnis surface blasting consisted in simply placing
charges Of gunpowder upon the surface OF the
ROCKS and exploding them. This process was very
successful az Pot Rock within certain limits re-
moving the rock to o aeptn at low water Of about
twenty feet. But II should be noted that the rock
removed within those limits as more or the form
Of a square pillar with moderate base. The
process of removal was rapid, until the reef was
reached at depth OF eighteen or nineteen feet.
Here the process became very slow and costly.
The appropriation being expended nothing iur-
ther was done at this tlme
The merchants Of New York subscribed about
$l4ooo. and Congress appropriated $40 600 Tor the
prosecution or this WORK.
GENERAL NEWTON COMMENCES WORK.
Under the light OF these reports General Newton
became convinced that the scheme OF improve
ments therein recommended was NO: extensive
enough to fulfil the oojects aad that while 1t was
necessary to remove those smaller rocks noted IN
tue early reports 1t was likewise necessary to ex-
tend the scheme by the total removal OF
nALLETT's POINT
md the removal OF what may be called the Middle
Reef which includes Flood Rock, the Grdron,
Hen and Cnickens and Negro Head, embracing an
area OF about six acres The cause OF former
ports being limited in their scneme OF improve
ments to the removal OF the smaller rocks was un.
doubtedly the little development that had been
made mp to that time in the ait or
BLASTING UNDER WATER.
We may state here that the proportion OF the
amount proposed 10 be removed in the smaller
ROCKS would only have been about two per cent OF
the bulk of Halett's Point and Middle Reef. Toe
application Of o superior process to that which
had been In vogue was necessary to accomplish
the great additional result-vz., the removal Of
Halletu's Point ana Middle Reef
There are now
TWO METHODS
for the removal Of rocks under water. One Is q
drn from the surface OF the water. number OF
blast noles are drilled IN the rock, which are then
nlled with explosives and the surface OF the rock
hrar mn ND ha of ffArw 10
raRIng, II the water is deep around the reef, or BY
raising 1t TO the surface by means OF steam grap-
pies or, again, by loading buckets at the bottom
BY means divers. For the purpose OF drilling
Genera Newton invented what IS known as the
STEAM DRILLING SCREW.
This machine consists essentially OF 1oat IN the
form OF scow, wlcD mas wei mole Ia IL OF thirty
two ieet IN diameter The SEQ " IS very strongly
built, and, to protect 1t against collisions whlcn
Is an lnoispensaoie condition OF It's worxisS u pro.
tected by guard or eihang Ike monitor.
The other esse eAtiRl part ol this machine ls dome
oil thirty leet III diameter, formed OF Doier IRON,
properly strengthened. rms dome Is open at the
eter at the top. The OBJECT or the dome when 1t s
on the bottom, is TO furnish fixed and imnova-
BILE framework ior a number OF drills, used % guide
the drills III periorating tue rock. me dome 10
also furnished vita number or movable legs at
its lower circumerence; me operation ao ..
not In use tue legs are trlced up
within the dome, and are so arranged
When the dome Is lowered (whlcn Is done by four
chains, symmetrlcally placed), the moment It ap-
proaeBes contact with the rock, the legs are let
60, supporting the dome in horizontal position.
The OBJECT OF making the dome horlZontal IS TO
make the drill TUBES vertical and thus iaciiitate
the operation OF drilling The dr1l engines are
supported on irame work directly over the well
noe. They raise the drills, which are previously
inserted III tile drnl tubes, and allow them TO IAN
By taeii own weight upon the rock. Durlng the
operation OF driiilng and as the drill tubes are
tive position somewhat by the operation oil the
currents the connection between the drill
means OF : rope or other nexible attachments.
The drill Itself is steel bar, weighing
about 100 or SO pounds, the cutting edge OF which
certain angie with every stroke. The drilling en-.
gines are provided with iced gear TO compensate
WITH the rise and iau o. the tide.
OPERATION OF THE MACHINE.
When not III use the dome IS suspended In the
face being above the water. Tne scow Is fist au.
cnored IN position with Six, sometimes WITH eight
and sometimes with fourteen anchors, depending
upon he strength oil the current, the anchors
weighing from 4,o00 TO 5000 pounds each. The
dome is then let down to the bottom. the legs are
let 20, The drills are introduced into tie drill tubes,
the rope connections are made fast to the drill
gines above and the operation oi drilling COM
mences. Holes ol i've inches IN diameter and rom
ten 10 fourteen eet III depth are drilled within o
period OF tweiye TO nfteen nours. Tne dome is
then raised into the wel Dole py the CHAINS the
drlllug screw Is removed rom 100 to 200 feet from
the blast noies, which are charged with
NITRo-GLYCERiSE
contained in long tin cylinders, which are placed
In the holes by divers, tae wire connection being
then made with the electrical batteries on the
Dcow, and the explosion then occurs. Toe charges
ntrO-glycei Inc III these holes are Uiten as much
as tlty or sixty pounds each. Tne effect or dis
charge OF nineleen holes drilled with the circum-
ference vi the bottom OF the dome Is sunlcient TO
break up the Whole surface, an area OF about 900
square leet, or nearly 100 square yards. OWING TO
The great rregularlty OF the rocks II 10 seldom
necessary or possible TO drill ful battery OF holes
lor every portion o! the dome.
THE SURVEY AT HALLErT's POINT
was commenced on the 25d OF June, 1859, by
Colonel Jonn Mechan tat present o. tue Dock De.
partment IN the city Board OF Public Works.,
nnaer the immediate direction oi General New.
Ton. by the end OF september In that year
lhe machinery tBurleIgns drills, derricks,
&cl were put In operation, ana were
tnen worked oy steam, but since then
comuIesseo ar nas superseded steam IN these
operations as IN the case oil the MI. Cents Tunnel
pnder the Alps in Italy ihe first operation was
tne sinking OF the vertical shaft which, was OF an
area " loo BY $50 feet. From this large snaft
winch reached nearly Iorty feet beneath mean low
water mark, series OF tunnels raaiated out