The Portland daily press., 1872-03-26
THE PR ESS.
TUESDAY MORNING, MARCH go, ,7s.
lFrom the New York Evening Post.
The Hell-Gate Improvements.
MINING UNDER THE soUND-pRoaREss OF
THE woRK-ITs DANGERS AND DIFFIcUL-
TIES.

THE woRK-TTs DANGERS AND DIFFIcUI-
TIES.
The work of removing the distractions at
Hell Gate which was begun about two years
ago, has been vigorously carried forward with
but trifling interruption, and will, it is now
estimated, be completed within a year and
half One hundred and sixty-five thousand
cubic yards of rock were to be removed from
the river, and of this amount at least forty
two thousand cubic yards have already been
taken out. About two hundred and forty
men are now employed in the work, nearly all
Of whom are Cornish miners of 'long expert
ence. A much larger number Were formerly
employed, but the introduction of the dia-
mond drill and the increased use of machin-
cry in all branches of the labor, has permitted
great reduction of the working force. A
hundred of the workmen were discharged last
week.
The immense bed of rock is now perforated
by sixteen tunnels and seven concentric gall
leries, the floor line of which is thirty-two
feet below the level of the river at mean low
tide. 1t was originally designed to make the
channel but twenty-five feet in depth, but
subsequently it was determined to render it
perfectly safe for vessels of the largest draught.
The average height of the tunnels and gal
leries is twenty-five feet and their width six
teen, leaving roof from seven to ten feet
thick supported by numerous pillars. The
length of the extfeme gallery is six hundred
feet, and of the grand tunnel two hundred
and twelve feet and a half There will ulti-
mately be twenty-eight tunnel headings, some
of which will extend three hundred and sew
enty-fve feet.
The work of boring is done wholly by ma
chinery, the laborers serving only to trim and
dress the rock after the rougher work has
been executed and to perform the operations
connected with blasting. OF the six drills
used, two are the diamond-pointed drills and
four Burleigh steel percussion drills. The di-
amond drill is the invention of Rudolphe Le-
schot, a French engineer, and was first used
in the construction of the Mont Gems tunnel,
but is now worked by improved machinery
under American patents. The two used at
Hell Gate were introduced last October, and
have proved so satisfactory that three more
will be added in few weeks. This drill con-
sists of a hollow steel disc an inch and a half
in diameter, the rim of which is studded with
twelve bits of black carbon. Attached to an
iron pipe of the same thickness, it is propelled
by compressed air at pressure of sixty
pounds per square inch, and cuts its way
through the hardest rock with marvellous
rapidity. The motion is rotary and the num-
Der of ofrevOlutions seven hundred and fifty per
minute. Unlike percussion drills, it receives
no wear except from friction, and hence is
constantly in working order, and needs no
sharpening.
Tor ,-fxy-T ho,, hno
tunnelled by this drill in eight hours, through
amass of granite and quartz. By screwing on
additional pieces of pipe it can be propelled in
one direction to an indefinite extent, but for
blasting purposes it is seldom driven further
than fifteen feet. Occasionally, however,
through the Intervention of a new process in
blasting, it is expedient to continue a tunnel
of this character for a long distance, thereby
effecting a great saving OF time. Sand or
clay is then rammed into the bore until it is
nearly full, to act as a recoil block to the
charge, and the rock is blasted section by
section.
All the blasting at He'll Gate is done by nj
tro-glycerine, and has been so carefully man.
| aged that not an accident has yet occurred.
| The nitro-glycerine is made into cartridges
| from eight to fifteen inches in length, about
an inch in diameter, and holding from four to
/ eight ounces. They are coated with glutin-
| Gus composition which effctually protects
them from water. When blast is made, a
| little tube of illuminate is attached to the cart
4 ridge and a spark transmitted to il through \
| wire connecting with an electric battery.
| Through large number of cartridges are of
| ten discharged in succession with great rapid
ity, they are never fired at once, as the vibra-
| ton in this case might seriously jar the stone
roof opening seems for the admission of the
water.
The explosions are of tremendous force,
| shattering the rock into fragments of a size
| convenient for removal. These are piled on
ears drawn by mules, running on iron tracks
4 which are laid in all the tunnels, and convey
| ed to the shaftwhere they are hoisted up by a
steam derrick. The masses already taken out
| form two immense embankments on the riv-
| er front.
| A building near themouth of the shaft con-
tains three large steam boilers and five COM
pressers, the latter furnishing the motive
power for the drills. In working the COM
| pressers lubricating oil is now used instead of
water, thereby avoiding the formation of ice
in the pipes during severe weather. Near by
is powerful steam pump, which drains all
the tunnels comparatively dry through pipes
| radiating from its base.
Before blasting it is necessary to use great
care in aseertaining the line of resistance and
quality of the rock, which is chiefly composed
of granite, quartz and gneiss. The strata
| CuAOAaSC q 6ACdJ variety VI hOWCNCIS
including besides various metallic deposits,
veins of decomposed feldspar that are as soft
as clay. The testing is done with the dia-
mond drill, which in two instances struck
| sand and water after boring twenty-eight and
thirty-tour feet respectively, rendering 1t nee
essary to abandon blasting in that direction,
and to have the bores tightly plugged up. In
opening tunnel heading No 8, section OF
rock was struck so full of seams that the wat
er poured through the roof at the rate of six
| hundred gallons per minute. This was effec-
| tually remsded by constructing a massive
schilt of timber, oakum aud Roman cement,
fourteen feet in length by twelve in width.
The work is carried forward almost con-
stantly night and day, the men being divided
into gangs which relieve each other at regu-
lar intervals. 1t is executed under the super
vision of Major-General John Newton, of the
United States Engineer Corps, who planned
it from the beginning. The Superintendent
In immediate charge 10 G. G. Reitheimer, an
engineer of wide experience in varions coun-
tries who has devoted himself especially to
| work of this kind.
When the rock is at length completely
honeycombed, and nothing remains but the
roof, its supporting pillars and the outer walls
it will be mined with seven thousand pounds
OF nitro-glyeerine, which is equal in explosive
power to seventy thousand pounds of gun
powder. All the charges will be connected
| by wires with an electric battery in the Office
of the Superintendent, when, at the given
signal, it is confidently expected that the
whole vast mass will be blown into atoms,
which will be entirely removed from the bed
ofthe river.
A COLISEUM FULL OF KINGs.-In notic-
ing that Mr.. Gilmore is about to invite Queen
Victoria, to his jubilee next summer, the
New York Times says:
There is no reason why Mr. Gilmore should
restrict his invitations to the exemplary lady
who is the figure-head of the British Empire.
Doubtless he intends to invite all monarchs