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9, 819. 32,9, 819. 32 9, 819. 32

Hauling.

Tabulated statement of amount of work done at Flood Rock, Hell Gate, East River, New York, during fiscal year ending June 30, 1885.

Hoisting.

Dumping.

Pumping.

Ventilating.

Timbering.

Constructing

dam.

Transportation.

Surveying.

Preparations for final blast.

2

5

2

1

4

3

3

9

97

440 1,414.875 574 53, 875 138 1,148 1, 084. 875 722. 625 2,695. 875 2, 167. 875 27, 370. 625

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Repairs to plant.

Superintendence.

Total.

Application.

Drilling.

Blasting.

Hauling.

Hoisting.

Dumping.

Tabulated statement of cost of work done at Flood Rock, Hell Gate, East River, New York, during fiscal year ending June 30, 1885.

Cost of
sharpening

Pumping.

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37,283 415, 849 86 10, 729 621, 435 63, 163 57 10, 383 742, 986 49 125 90 374 115, 154 164, 021 09 2, 976 01 6, 757 69

3.343 1.285

22,067 70

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0.388

89,241 28

6. 260 2. 132)

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33, 216 77

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Total.

bits.

2-inch.

3-inch.

OPERATIONS OF THE UNITED STATES STEAM-DRILLING SCow.
REPORT OF LIEUTENANT GEORGE M'C. DERBY, CORPS ON ENGINEERS.

ENGINEER OFFICE, UNITED STATES ARMY,
FLOOD ROCK, HELL GATE IMPROVEMENT,
Astoria, N. Y., July 1, 1885.

SIR: I have the honor to submit the following report of operations of the United States steam-drilling scow for the year ending June 30, 1885.

The drill-scow has been idle nearly the whole year, the appropriation for East River and Hell Gate for this year being by the terms of the act restricted to Flood Rock.

A small balance left from the appropriation of August 2, 1882, has sufficed for taking care of the scow during the year and for a few weeks on Pilgrim Rock.

Pursuant to your orders, I am experimenting with a view to placing a suitable grapple on the scow to utilize her for raising broken stone after the blast at Flood Rock. Respectfully submitted.

To General JOHN NEWTON,

Chief of Engineers, U. S. A.

GEO. MCC. Derby,
Lieutenant of Engineers.

(Through Col. Walter McFarland, Corps of Engineers, U. S. A.)

Statement of expenses of United States steam-drilling scow during fiscal year ending Jun

Applied.

Pilgrim Rock
Repairs..
Laid up

30, 1885.

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EXPERIMENTS WITH EXPLOSIVES.

ENGINEER OFFICE, UNITED STATES ARMY,
FLOOD ROCK, HELL GATE IMPROVEMENT,
Astoria, N. Y., May 25, 1855

SIR: I have the honor to submit the following report on the experiments with arplosives made under your direction at Jacksonville, Fla.:

RACKAROCK.

Objection to rackarock.-Experiments made at Flood Rock during the month of January had proven that this explosive, in long, narrow charges, would not explode when fired in the ordinary way more than 6 feet from the fulminate cap, and had indicated a probable falling off in the order of the detonation as a function of the distance from the fulminate cap.

Its remedy.-Assuming this to be the case, it seemed likely that by placing fulminate caps at intervals throughout the length of the charge to be exploded by the explosion of the powder in which they were imbedded, that the order of the detonation might be maintained and the explosion propagated throughout a charge of any length. I had confirmed this supposition by firing two charges 13 feet long (14 inch diameter), but was prevented from repeating the experiment enough to obtain a conclusive re sult by the appearance of ice in the river.

Object of experiments.-The object of the experiments reported below was, then, to prove beyond question that a charge of rackarock loaded substantially as the charge in the mine at Hell Gate will be, can be exploded with certainty to a distance of 19 feet (the length of the longest drill hole).

Result of experiments.-The experiments were highly satisfactory, no charge failing to explode, and prove, I think, conclusively that this explosive can be relied upon to

explode with certainty throughout the length of a drill hole 12 feet deep, provided 30-grain fulminate primer, re-enforced with an ounce of dynamite, be placed in the charge at intervals of 2 feet.

The primer.-I do not consider that the ounce of dynamite is essential to the result, but used it to re-enforce the fulminate cap, experience in the mine having indicated that a 30-grain cap is hardly strong enough to develop the full power of rackarock. These caps contain but 74 grains of fulminate, the balance being chlorate of potash, and I understand that there are practical difficulties in the way of manufacturing larger ones.

Conclusion.-The uncertainty of the whole length of the charge exploding being the only serious objection that I know of to the use of rackarock for the final blast at Hell Gate, it is my opinion that this explosive may now be considered available. The question as to whether it is actually advisable to use it is so intimately connected with the question of cost that it may best be left for decision until all the bids have been received. It has in its favor, as compared with dynamite

(1) It may all be delivered at once, and only rendered explosible the day it is loaded.

(2) Greater safety in handling and loading.

(3) Greater density (1.7 to 1.4).

(4) Cheapness (25 cents to 43 cents retail). It has against it its novelty.

DETAILS OF EXPERIMENTS.

Evidence of explosion.—In all these experiments the cartridge farthest from the inItial primer had its end in contact with the end of a green yellow-pine sapling, as shown in the sketch. When after the explosion the end of this sapling was found to

Explosive

Sapling 4 long.

8

Wax.

Rope.

be broomed (see sketch), it was considered evidence that the end of the last cartridge had exploded, and consequently the whole charge.

This is the same test as previously used at Hallet's Point and Willets Point. Cartridge. The cartridges were of thin copper, such as it is expected will be used In the mine, 24 inches diameter and 2 feet long, and weighed about 6 pounds loaded. Primer. The fulminate primer previously described was inserted into a paper cartridge 6 inches by inch, containing one ounce of No. 1 loose dynamite.

One of these primers was placed in each copper cartridge except in shots 2, 3, 4, and 5.

Exploded by sympathy.-Except in shots 3, 6, 7, 8, 10 B, and 17 B, the charge was exploded by sympathy, a small primary charge of dynamite being placed from 3 to 6 feet from a small secondary charge, the latter being lashed in contact with the first of the charges making up the charge of rackarock.

Spaces between cartridges.-The primary charge was connected with the battery. As In the drill holes in the mine the cartridges might fail to touch, in many of the charges fired spaces were purposely left between the cartridges to see if the explosion would be transmitted across them. They caused no failures, although in one shot they aggregated 4 feet in length.

Iron pipes. In all cases except shots 5, 6, 7, 8, 9, 10, 11, the cartridges were loaded into an iron pipe representing the drill hole.

This sketch shows the method used in the experiments with dynamites. In the rackarock experiments the end of the cartridge simply abutted against the end of the sapling and only the thickness of the copper separated the powder from the wood.

The shots above enumerated were simply lashed to a long stick and laid on the bottom in about 2 feet of water, this being a more severe test of the efficiency of the extra primers.

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To make certain that the powder had not been sensitized by the manufacturer specially for these experiments, I fired shots 2, 3, 4 and 4 B without extra primers.

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This result was unexpected, charges fired similarly at Hallet's Point having failed to explode more than 6 feet. Thinking this might be caused by the powerful shock communicated by the secondary primer (none having been used at Hallet's Point). I fired shot 3 without any dynamite at all, putting the exploder attached to the battery wires into the rackarock itself.

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(Result doubtful.)

SHOT III.

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Buoy-line to sapling cut; sapling lost. Jet thrown up, apparently less than usual. No pine splinters rose to surface, and charge probably did not explode entirely.

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Fired pistol (32-caliber) at range of 4 feet at cartridges of rackarock (10 ounces 18 inches by 8 inches) suspended against a board in the open air.

The shot passed through the center of cartridge without exploding it.

As under the same circumstances dynamite will explode, it is evident that in point of sensitiveness the powder used was well within the limits of safety; and the fact of charges 2 and 4 exploding entirely is probably explained by the warm weather and the confinement of the iron pipe.

It thus became necessary to find some more severe test of the efficiency of the extra primers. To do this I fired

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Only 20 inches exploded; remaining cartridges much jammed up and corrugated.

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