The New York herald. [volume] (New York [N.Y.]) 1840-1920, 1871-06-28

the reef shows psnectly horizontal stratiication,
the prevalent rock being mica heavily nterspersed
with quartz VEINS sometimes three ieet In thick
ness
AT THE SALIENT POINT:
and toward the east and northeast it changes to a
vertical stratcation OF the hardest gnelss rock 1t
may be as well TO state here that the floor line OF
the SHAFT is thirtytwo feet below mean low water.
The distance from the entrance the tunnels the
extreme point OF rock to be demolished Is three
hundred feet. The greatest distance reached so far
Is one hundred and twenty fee under the river the
remaining tunnels being IN length from sixty feet
upwards. They are sixteen feet IN width and
twenthree feet In height and are to be intersected
Is now completed, with the exception Of the piers
fifteen feet IN thickness left standing at each end
Two other galleries are now In progress.
EXPLOSIVES USED.
For opening the line OF resistance blasting powder
half pound CHARGES For cnting the elliptic arches
OF the dlferenu galleries nitro-gycerne in charges
billty OF cutting the material up In small fractions.
Samples or chamber stone are exhibited, showing
the hardest gneiss decomposed almost TO the condi
ton OF chalk by the action OF ntro-gycerine in ex-
plosion. AL the explosives are manufactured at
the works, eiiectlng saving for the government It
drilling are also manufactured on the spot from the
best American and English Steel and vary in gauge
Advancing along one OF the tunnels at the end OF
which one can just perceive the dusky forms or the
miners
DRILLING FOR BLAST,
and having for their only light small tallow candle
water running past you in small stream A cre-
vice In the rock mas been struck in blasting, and
through 1t the water pours in from the river over
head. Thus in tunnel No. On open seam having
been struck the water came In at one time at the
rate OF thirty gallons per minute The remedy APP
piled was TO drive In oak wedges with
plenty Of oakum and Roman cement. This Is
called doctOring. Sometimes an inundation Is
suddenly threatened from other causes For in
stance, some twenty eight days ago the wOrkmen In
tunnel No. while firing forward IN the race or the
tunnel, struck upon seam OF decomposed mica
twenty inches In thickness. After the ring the
water rushed In at the rate OF
SIXTY GALLONS PER MINUTE.
This seam was doctored by driving IN 200 oak
wedges, and by building up powerful shield lined
was so successful that the flow Of was reduced
to four gallons per minute. The face OF this
tunnel has now, however. to be worked
by gravity as It is technically called,
In regard TO the final explosion the superintendent
said--The elliptic arches will be destroyed by drill
ig from thirty TO thirysix holes in each arch the
holes to he two feet six inches in depth, one inch
diameter, aud drilled at an angle OIL forty five de-
grees. These will then be charged with nitro-gly.
cerine, and iired simultaneously by electricity. In
case Is found to be unsafe TO cut the piers they
viii be blown up by drilling through each gallery
charged with nitro glycerne, the elliptic arches
will then be exploded, the water viii rush
In and the explosion of the piers win
turned away from the shaft and sought the ferry
there was misty effect In the atmosphere rom the
drizzling rain. Through this mist the dreaded
Gridir0n could be located TO the minds eye Dy aid
OF the dark Flood Rock near IL. The Great Mill and
the Little Mil rocks seemed to rise into unnatu
raj prominence, and, as the mind wandered back
over this story OF twenty years OF unsatsned and
unsatisfactory labor, the question quietly intruded
itself, Will not these phantoms many OF them, still
haunt the scene when twenty years more nave
passed. and prove the same terror TO coming gene
ration OF mariners that they have been to past ones