The New York herald., 1873-10-28
UNITED STATES ENGINEER OFFICE,
NEW YORK, August 20, 1873.

e.,:............ 22l.l9 6c.................l ll3s
1877 iob................... ls4 42s
.............. iT Galleries l.0
THE PROGRESS MADE
during the past year in driving forward the tun-
nels and galleries was 2,731 neal feet. The guam
tity or rock removed during this period was:-By
hammer drilling, $50 cubic yards; by the Burlegn
ana n ns
August, ls5 cubic yardH The total removed was
o,S54 cubic yards. The number OF feet OF holes
Lineai Feu.
By hammer hammer Sl drilling lsSs sos
BY diamond drills ......... ................... 1903
Total SSRi
at the rate OF ten ineal feet OF holes drilled to
one cubic yard Of rock The quantity OF explosives
nitro-glycerine, 2is lbs OF giant powder and s.445
lbs. OF black powder, divided into 23,5s2 cart
ridges e. an average Of one cartridge to iour ur
expended was ALSO feet. The average spend Of
the hammer drilling per shift Of eight hours was
e. s Or the e Of q ~ F %an
hammer work was "a, 500, and the loss by abrasion
and dressing was 1852 lbs. OF English steel, or
Each drill In hammer work made 0.46 feet
forward before being sharpened. In hammer
n' WORK soS ieet OF hole and o9 pounds OF nitro.
glycerine correspond to one cubic yard OF rock
blasted. But
IN THE COST OF ROCK REMOVED
by the Bureigh drill that IL has been restricted by
my direction to the lew cases in practice, when
hammer work is Indispensable. The Burlelgh drills
have made for the year an average, for each ma
chine, OF 29 feet per SHIFT OF eight hours. Their
speed has steadily increased by experience gained,
feet per shift The cost Of removal by this method
is much less than by that Of hammer work or by
the use OF the diamond drill
The Loss Of steel by abrasion and drilling was
1852 pounds or at the rate OF 0.5A ounces per
lineal loot Il is proper to add, however that the
and rock encountered at Hallett's Point differ
ence in the Character OF the rock and in the cOndi
tons OF the problem might change the relative ex-
ceuence OF the several modes employed, partlcu-
larly as between the Burleigh and diamond drills.
Up to the nsca year terminating June 3o 1872, the
the intention to introduce or at least to test the
eject OF, machine drilling had always existed.
Many causes Of delay intervened. Among these
were the cost and time required for the putting
down the power apparatus required t. drive the
machine drills, and the real doubt that existed
drills to the confined headings at Haett's Point,
and to the limited length OF holes and minute
charges which we're obliged to be adopted.
WORKSHOPS.
Add to these difficulties the fact that the dia-
mond drill had not been used as q tunnelling drill
while the Burlelgh drill had made but ls or lS
in the shop under repair for each one at work The
last fact indicated the necessity OF expensive
ccssary to consider IN the general problem. How
ever in spite q delays caused, public advertise
mspss e s1sS to h Ry s and resulted
IN s N me y sa OF es Ign
same time q diamond drill was purchased-party
as an experiment-to work IN opposition
drills were worked by the company, yet In
June, 1872 the difference In progress between the
doubtful. Captain william II. Hener, corps OF en-
gneers, having been assigned to duty under me,
directed him, IN July, 1872, to experiment with
geous that additional drills were purchased.
TIE BuRLEIGH DRILL
s Years. and to this We owe the diminished amount
due to repairs. To Captain Hener's attention to
his duties and to the experienced managers Of the
drill which, as before stated, is now thirty feet per
s sks as careS 70
express my obligations for the full and detailed
statement OF the various operations at that place.
the past year a model OF Halett's Point authorized
by the Hon. Secretary OF War, was prepared ana
sent to the Vienna Exposition.
THE OPERATIONS
have hitherto been conducted with view to ex-
plore the whole area to be removed, and have to
compieton the sSditena drvns q about loo
hneal feet OF tunnels. We have been much de-
layed, and the cost OF the operations has been in.
priations not sufncient for rapid or economical
progress. These matters have been touched upon
In previous reports, and repeat them here simply
transmitted when completed.
STEAM DRILLING sC0w.
The operations or this machine were upon Dta-
mond Reef until July IL, 1872. Twelve holes were
drilled and blasted and three surface blasts made
and go tons 2. rock were removed by Morris Cum
to He'll Gate July IL, and after being moored upon
Frying Pan. commenced drilling July %; made
anchors and moved OF the reef. The scow was
anchored over Pot Rock August 8, where IT re-
uYnf
were drilled and blasted, 80 seam blasts and "A sur
face blasts were made. The surface OF the rock
stone, which was first removed by means
OF a rake in order TO drill A quantity OF stone
was thus removed from the reef, OF which no ac-
count has necessarily been kept. AS IL was impos-
sible to use Morris h Cummings .grapple In re-
moving loose rock in this locality, buckets, filled at
moval. The quantity thus removed Is estimated at
211 cubic yards. The difficulty OF mooring the scow,
so that 1t would not drag and interfere with the
rents; but this could be and was overcome. The
real source OF delays damage and danger to those
encountered while the scow was at work on Pot
Rock The delays arose from the breakage OF the
cable chains connected with the anchors, and the
period OF time required to search for and find the
ends Of the chains before the could be moored
again. II Is solely due to these accidents that the
whole OF Pot Rock was not removed last fall
THE EXPERIENCES DERIVED FROM THE OPERATIONS
OF this machine are, nrst that the cylinder on the
dome has never been OF use; It was carried on in
the remainder OF the season by a Temporary
wooden structure, which latter has been dispensed
with, and the dome is now used free OF such en-.
Second, the dome has not acted as a dam, the top
OF the cylinder having never except accidentally,
risen to the surface OF the water, while the bottom
OF the dome, not lying close to the rock but lev.
eed upon Its legs has permitted free rush OF
the currents under 1t and upon the person OF the
diver working upon the bottom.
A RAPID CURRENT,
while the tide was running, from the bottom
through the dome, discharged itself through the
top of the dome. The water In the well hole OF the
scow was always above the level OF the exterior
water, and In very rapid currents, was on level
with the curbing OF the WELL The divers have re-
ported that II was more difficult to work at the
bottom with the machine than without Its assist
ance, and the reason OF this is Is manifest, VIZ =