Worcester daily spy. [volume] (Worcester [Mass.]) 1850-1888, 1872-03-23

The HeIl-Gate improvements.
The work of removing the distractions of
He'll Gate which was begun about Two wears aro
has been vigorously carried forward with but
tritiing interruption, and will, it is now estima
ted, be completed within year aud half
One hundred and Sixty-6ye 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 meu are now employed in
the work, nearly ali of whom are Cornish miners
Of long experience A much larger number
were formerly employed, but the introduction of
the diamond drill and the increased use Of ma
chinery in all branches of the labor has permit
ted 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 gal
leres, the floor line of which is thirty two feet
below the level of the river a mean low-tide. IL
was originally designed to make the channel
but twenty-five feet in depth, but subsequently
il was determined to render it perfectly safe for
vessels of the largest draught The average
height of the tunnels and galleries is twenty
two feet and their width sixteen, leaving roof
from seven to ten feet thick supported bynumer-
GUS pillars. The length Of the extreme gallery
is six hundred feet, and OF the grand tunnel two
hundred and twelve feet and half. There will
ultimately be twenty-eight tunnel headings,
some of which will extend three hundred and
seventy-iye 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 10 perform the operations connect
ed with blasting. OF the six drills used, two
are the diamoned-pointed drills and four Bur
leigh steel percussion drills. The diamond drill
is the invention of RodOlphe Leschot, a French
engineer, and was first used in the construction
of the Mont Gents tunnel, but is now worked by
improved machinery under American patents
The two used at He'll Gate were introduced last
October, and have proved so satisfactory that
three more will be added in a few weeks.
This drill consists of hollow steel disc an inch
and half in diameter, the rim of which is stud
ded with twelve bits Of black carbon. Attached
to an iron pipe Of the same thickness, it is pro-
PEELED by compressed air at pressure Of sixty
pounds per square inch, and cuts its way
through the hardest rock with marvellous ra-
pidity. The motion is rotary and the number
Of revolutions seven hundred and fifty per min
ute. Unlike percussion drills, it receives no
wear except from friction, and hence is constant
ly in working order, and needs no sharpening.
Forty-lour feet and four inches have been tun-
need by this drill in eight hours, through
mass of granite and quartz. BY ScreWing on
additional pieces of pipe it can be propelled in
one direction 10 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
DlaStlQ1, II Is eNpeulcnJ 10 continue q tun1el OF
this character for a long distance, thereby effect
inc great saving of time. Sand OF clay then
rammed into the bore until it is nearly full, to
act as a recCil block TO the charge, and the rock
is blasted section by section.
All the blasting at Hell Gate is done by nitro.
glycerine, and has been so carefully managed
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 dame
ter, and holding from four to eight ounces. They
are coated with glutinous composition which
eifectually protects them from water. When a
blast is made, little tube OF illuminate is at
tached to the cartridge and spark transmitted
to it through wire connectins with a electric
battery. Though large number of cartridges
are often discharged in succession with great
rapidly, they are never fired at once, as the vi
bration in this case might seriously jar the stone
roof, opening seams for the admission of the
water.
The explosions are of tremendous force, shat
tenng the rock into fragments of a size Conven-
lent for removal. These are piled on cars drawn
by mules, running on iron tracks which are
laid in all the tunnels, aud conveyed TO the shaft
where they are hoisted up by a steam derrick.
The masses already taken out form two i'm
meuse entertainments on the river front
A building near the mouth 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 comDresSers lu-
I
| by avoiding the formation of ice in the pipes
| during severe weather. Near by is a powerful
! steam pump, which drains all the tunnels com
| paratively dry through pipes radiating from its
| base.
Before blasting it is necessary to use great
care in ascertainng the line of resistance and
| quality Of the rock, which is chiefly composed
| of granite, quartz and gneiss. The strata en-
brace great quantity Of minerals, however, in
Guiding besides various metallic deposits, veins
| of decompoSed ieldspar that are are as soft as
| clay. The testing is done with the diamond drill
| which in two instances struck sand and water
after boring twenty-eight and thirty-lour feet
| respectively, rendering it necessary to aband on
| blasting in that direction and to have the bores
| tightly plugged up. In opening tunnel heading
| No. 8, a section of rock was struck so full OF
| seams that the water poured through the root
at the rate of six hundred gallons per minute
| This was eiectually remedied by Construct
| ing massive Schilt of timber, Oakum and Ro
man cement, fourteen feet in length by twelve il
| width
The work is carried forward almost constantly
| night and day, the men beingdYided into gang
which relieve each other at regular intervals.
il is executed under the supervision OF Major
General John Newton, Of the United States en-
gineer corps, who planned it from the beginning
The superintendent in immediate charge is g.
Rethemer, an ENGINEER of wide experience il
various countries, who has devoted himSel
especially to work of this kind.
When the rock is at length completely honey
combed, and nothing remains but the roof il
supporting pillars and the outer walls, it will b.
mined with seven thousand pounds of nitro
| giycerine,' which is equal in explosive power Il
| seventy thousand pounds Of gunpowder. All
| the charges will be connected by wires with an
electric battery in the ohiceOf the superintendent
when, at the given signal, it is confidently ex-
| pected that Gthe whole vast mass will be blown
| into atoms, which will be entirely removed
from the bed of the riyer,-Ne1o York Evening"
| Post.