No. IX.
The blowing up of Flood Rock was successfully accomplished October 10, 1885. The official report is not yet issued, and hence the following account has been compiled from various sources of information. Flood Rock had a superficial area of nine acres, about 250 square feet of which was above water. The rock consisted of hornblende gneiss, with intersecting cross-veins. A sea-wall seven feet high was built around the island, and two shafts were sunk, one sixty-seven and the other forty feet deep. The main shaft was used for removing the excavated rock in blasting out the headings. The smaller shaft was used for the tubes conveying the compressed air which drove the drills. The first series of headings branched out from the main shaft at a depth of forty feet, and from the bottom of the shaft another series diverged directly under those above. The headings branched at right angles every twenty feet, and were sixty in number in each tier. The double system of headings was employed to gain a sufficient depth after the explosion without the necessity of dredging out to the extent that was found necessary at Hallet's Point. The total length of tunneling was about four miles, consisting of twenty-four galleries running north and south and forty-six running east and west. The longest of these was 1 200 feet in length, 6 feet wide and 10 feet high. There was a thickness of from 10 to 25 feet between the roof of the top tier of galleries and the water. There were 467 pillars left to support the roof; these were 15 feet square. The whole rock was honeycombed with tunnels, about 80,000 cubic feet of rock having been removed.
There were drilled in the pillars and roof 13,286 chambers for holding the cartridges, each chamber being three inches in diameter and about nine feet deep. These chambers were filled with rackarock cartridges, of which there were about forty-seven thousand used, each being two and a half inches in diameter and two feet in length, and containing about six pounds of the explosive. In addition to the rackarock cartridges, several hundred ordinary dynamite cartridges were used, to which the wires leading to the firing batteries were attached. The shock resulting from the explosion of these dynamite cartridges caused the explosion of the rackarock. Upwards of two hundred and eighty-five thousand pounds of explosives were used in the charge.
The wiring in the mine was divided into thirty-six circuits, the batteries attached to these circuits being stowed in a tool-house on the rock. The wire of the primary circuit which actuated the electromagnet that closed the secondary circuits was led across to the Astoria shore on the morning of the explosion. The firing-key was about 1200 feet from the mine.
Two siphons, one twelve inches in diameter and the other three inches, were set at work at 10 A. M., October 9, flooding the mine, and they completed their work early the following day. The first effect of the explosion was to produce a rumbling noise, and then to project a mass of water over an area of about 1200 square feet to a height of about 150 feet. Masses of rock rose in the midst of this water to a height of from 40 to 50 feet. The explosion lasted about 30 seconds. As the water fell a dense cloud of yellowish smoke arose and floated over the Astoria shore.
Observations were made in many places, at various distances about the centre of the explosion, on the time of arrival of the terrestrial and aerial disturbances, and they showed that the terrestrial effect was apparent as far south as Princeton, N. Y., and as far east as Cambridge, Mass., and, as was to be expected, that the terrestrial impulse was in advance of the aerial, at least at the stations near at hand. The rate of transmission cannot be stated until these observations are reduced.
After the explosion the rock appeared undisturbed, though on close examination it was found to be somewhat fissured. However, it slowly settled, and by October 13 the entire rock was below water. It was not intended that the rock should be broken very fine, since with the appliances at hand pieces of from ten to fifteen tons in weight could be most economically handled. The work has been in operation about nine years, and has cost upwards of 1,000,000 dollars. The cost of removing the broken rock is estimated at 600,000 dollars, and two years' steady labor will be required. The channel will then have a depth of 26 feet over an increased width of 600 feet.
In an interesting article in the Jour. Military Service Inst, of the United States, 6, 103, 1885, entitled "Recent Progress in High Explosives and their Uses in War," General H. L. Abbot, after resuming the results of recent experiments at Willet's Point, says the use of high explosives in shells, although attempted very shortly after the discovery of dynamite, is still in the experimental stage, because no certain mode of regulating the time of explosion has yet been discovered. When this has been accomplished, certain advantages will result. For field guns these advantages will chiefly come from thicker and heavier shells, broken into more numerous and regular fragments, and available for longer ranges than at present. For medium calibres, such as are used in sieges and bombardments, the shell capacity is necessarily too small to carry decisive charges, and the effects will be moral rather than physical. This is due to the intensely local action of these high explosives. The terrifying sound and frightful effect upon the object struck will perhaps appall new troops, but old soldiers will soon learn that the bark is worse than the bite. For the much larger calibres used in coast defence, it is stoutly claimed that charges of a size to be destructive in themselves may be employed even against armored ships; and experiments in this direction are now exciting so much interest that a brief resume of what has been established both in respect to the possibility and to the utility of such firing, may not be unacceptable.
In Sweden, in September, 1867, within a year of its invention, seventeen shells, each charged with 1.65 pounds of dynamite, were fired from an 18-pdr. howitzer loaded with about two pounds of gunpowder. No premature explosion occurred. In Norway in the winter of 1870-71, some trials were made with a 6.8-inch Krupp gun. At first the shell was packed full of dynamite. Several preliminary shots were successful, but when the charge was increased to 1.65 pounds of gunpowder the shell burst in the bore. Continuing the same trials, shells filled with water, and primed with an ounce of dynamite in a copper extension of the fuze plug, were fired with full charges without accident. During the siege operations of the 2d Corps of the Army of Versailles, in May, 1871, two shells charged with dynamite were fired without accident into the hostile lines; one was from a 24-pdr. howitzer and the other from a mortar. The dynamite was enclosed in a rubber bag held in position with gunpowder, and was ignited by a time-fuze in both instances.
These facts, and many others which might be cited, sufficiently prove that the use even of dynamite in shells has never been regarded as impossible; but the selection of a high explosive so sensitive to violent shocks, when others so much safer are known, is certainly not to be recommended at this late day.
Fairly successful trials with picric powder were made in England about fifteen years ago, but they were discontinued in consequence of the more favorable results with wet gun-cotton. The first trials with gun-cotton in the dry state were made many years ago, and a 7 -inch Armstrong was thus burst by an explosion in the bore. Wet gun-cotton has succeeded better, and in England safety of firing and a good arrangement for effecting the explosion after impact are claimed. Folger's successful experiments in firing gun-cotton are also cited, but the author regards those with explosive gelatine as more promising. "Should the trials with this fail, the Sprengel group will naturally receive attention. Gruson in Germany has been working in this direction for three or four years. He uses strong nitric acid in one compartment, and dinitrobenzol in another. The shock in the gun or the shock at impact, as desired, effects the combination, and explosion is caused by a fuze in the base of the shell.
"Assuming that artillerists will ultimately succeed in devising methods (1) for preventing premature explosions in the bore, and (2) for effecting explosion at the instant desired, the next question to decide is, what changes are needful to destroy the armor of modern ships of war. If this could be accomplished with moderate charges, armor-plating upon the sea would soon become as historical as the coats of mail in the Tower of London. But here an important distinction is to be observed. We already know that if the charge can be imbedded in the armor, quite moderate amounts will be effective. Popular belief attributes equal power to charges exploded in contact, or nearly so, with the plates at their outer surface. Unfortunately this is a grievous error."
The author then discusses the possibility of crushing the armor of a modern ship of war by means of exterior charges, using as his criterion the formula deduced by the Scandinavian Commission, which he deems at present our safest guide when estimating the charges necessary to produce this effect, assuming them to be exploded in contact with the plating near or even below the water surface; and he concludes: "But what calibres of guns must we have to project the charges it indicates, varying from 80 pounds for 5-inch armor, to much larger amounts for that usually carried? The capacity of a 10-inch common shell is about 25 pounds; of a 12-inch common shell, about 40 pounds; and of a 16-inch common shell, such as is now fired from guns weighing 100 tons and upward, about 75 pounds. Battering projectiles for armor carry about one-third these weights. Clearly it is quite impossible to project the needful charges, and we have little hope either now or hereafter from exterior explosions against armor-plating. High explosives with all their wonderful power must either be carried deeply into the iron before explosion or they will fail to do much damage. But to secure this penetration, initial velocities of 2000 feet and the best steel shells thus far achieved are demanded; and even then guns of less calibre than 12 inches will be of little avail. Of course such a standard will have to be approached gradually in the trials; but by appreciating at the outset the full magnitude of the problem, unprofitable labor will doubtless be avoided."
In the same number of this Journal, p. 170, is an unsigned review of the article, by the compiler of these Notes, in Van Nostrand's Eng. Mag. 32, 1, 1885, in which, after practically admitting the conditions of efficiency as set forth by us, the writer adds, "Bearing in mind that the muzzle energy of the 100-ton gun is about 60,000 foot-tons, and that this appears to suffice to break up anything but the thickest steel armor, it is still an open question whether full penetration with a small charge (which is liable to simple ignition) is better than the full detonation on the surface of a much larger charge, that charge being, however, suitably tamped both by the character of its enveloping shell and several hundred foot-tons of remaining energy of the projectile upon striking. Even a partial initial penetration would use up some of this probable tamping due to its energy and lessen the effect on the target by the explosion.
"In a field so novel, experiment can only satisfactorily demonstrate the possibilities. So far, the simple placement of a large charge of dynamite against a heavy armor plate, and then exploding it, entirely untamped, does not appear to be conclusive as to what that same charge will accomplish when hurled against the plate with a striking energy of several hundred foot-tons, the charge being encased in a shell which affords some resistance to the initial bursting efforts of the gases evolved.
"Considering the very much greater potential of the explosive relative to the possible stored-up work of a projectile, and the undoubted loss of effectiveness on the target of the charge farthest removed, it is an open question whether it is best to use a hard and necessarily thick point (thus placing the charge farther away from the point of impact), or using a soft, thin point which will "squash-up" upon striking the target and bring the explosive in as close contact as possible.
"It will be seen that a wide field must be traversed before conclusions can be safely drawn. The experiments now in hand will, I trust, determine some of the mooted points. Much will be learnt that will enable us to make the most effective use of the high explosives against an enemy. If successful, we have available a weapon (the air-gun) which will be of value to us, in our present defenceless condition, as a possible stop-gap. Owing to its limitations of range it can never be considered a substitute for the heavy ordnance so much needed. But it will be at all times a valuable adjunct to our defensive appliances.
"It is possible that the heaviest armor may withstand the shock of an explosion of a shell containing 100 pounds of explosive gelatine. If that is the case, 500 pounds may be thrown, if required for the work. But it should be borne in mind that a vessel is protected in a very limited portion by this heaviest armor; that its decks, presenting the largest target, are very vulnerable, as was demonstrated by Lieutenant-Commander Folger with the assimilated deck target; that a still wider area of vulnerability is presented in an additional area of the water zone, 16 feet in width, surrounding the ship; if the explosion takes place within this zone, a few feet under the surface, the results are very likely to be fatal."
The writer then discusses the comparison made between the air gun and the gun used in the Gavre trials, and claims that the mean available pressures, and not the maximum pressure, in the gunpowder gun should be taken as the standard for comparison. Estimating the mean pressure of the Gavre gun as 12,000 pounds per square inch and the length as 16.1 calibres, while the pressure in the air-gun is 500 pounds to the square inch and its length 120 calibres, we should have a ratio of pressures for guns of equal length of 12000:3725. "But it is proposed to use (in the air-gun) an initial pressure of 2000 pounds, giving (with a flask or reservoir capacity of ten times the bore of the gun) a final pressure of 1820 pounds or a mean pressure of about 1910 pounds. With this pressure the comparison would be stated as 12000: 14230 in favor of the air-gun, and the projectile from the latter would have the greatest penetrative ability."
The writer also notes that the projectile for the air-gun, as described, differs from that now in use. This is quite to be expected in a course of tentative experiments. He states too that in the firing of dynamite on iron plates, Lieutenant Zalinski used in the first experiment ten pounds of untamped dynamite cartridges, and in the second experiment twenty pounds of dynamite enclosed in an 8-inch wrought-iron pipe 30 inches in length, the charge being about 10 inches in height and the remainder of the pipe loosely filled with sand and debris.
At the Ann Arbor meeting of the American Association for the Advancement of Science, Commander T. F. Jewell, U. S. N., read a paper on the apparent resistance of a body of air to a change of shape, in which he described some experiments at the United States torpedo station, in which a disk of gun-cotton was exploded on a metal plate. Upon each disk of the explosive had been stamped the letters 'U. S. N,' and the year in which the material had been manufactured. After explosion upon the iron, similar indentations were found upon the plate, as if the air in the indented letters had been driven into the plate.—Science 6, 207, Sept. 11, 1885.
In the Proc. Am. Assoc. Ad. Science, 33, 174, 1885, in a paper by Charles E. Munroe, entitled "Examination of methods proposed for rendering the lighter petroleum oils inexplosive," it is stated that, it having been seriously suggested that alum, sal ammoniac and camphor could be used to render the lighter petroleum oils inexplosive, and it having been found in practice that camphor did diminish very markedly the readiness with which explosive gelatine or gum dynamite could be exploded, the author has tested the effect of the above bodies by determining their solubility in benzoline; the flashing points of benzoline and commercial kerosene when treated with these bodies and when in their original state; and also the readiness with which mixtures of the oils, in the two conditions, with air could be exploded. The results showed that alum and sal ammoniac were practically insoluble in the oils and produced no effect upon them; that the camphor was soluble, one gram of benzoline dissolving about 1.5 gram of camphor; that an equal weight of camphor raised the flashing point of a kerosene 12°; but that on the other hand the vapor of this camphorated kerosene, when mixed with air, exploded with greater readiness than the original kerosene.
The Revue d'Artill. 22, 462, Aug., 1883, under the title, "The Use of Dynamite for Driving Piles," describes a process invented by M. Pradamovic, and put into execution at Pesth. On the centre of the head of the pile he fixes a circular iron plate 395 mm. in diameter and 117 mm. thick. On the centre of this plate he places a dynamite cartridge 157 mm. in diameter and 17.7 mm. high, and weighing 612.5 grams, wrapped in parchment paper. This is detonated by electricity. The effect produced under these conditions is equivalent to that obtained from five blows of a hammer weighing 1475 kilos, falling through three metres.
Gruson, Hellhof and Halbmayer have devised a time-fuze for projectiles, which is ignited by the resistance with which the projectile meets after it is set in motion. For this purpose advantage is taken of the heat produced by the chemical action of water or acid on metallic sodium or potassium. They are placed in separate vessels within the shell, and are brought in contact by the shock. The amount and position of the materials is so arranged that the maximum effect is attained only after a desired interval of time. (Revue d'Artill. 21, 567, March, 1882.) The following note shows that the use of potassium as an igniter is not new.
The Bib. Univ., Aug., 1831, describes the method employed by Engineer Lubke in blasting under water. A leaden tube, several feet long and closed at one end, was inserted in a hole in the rock, a cartridge was inserted in the bottom of the tube, and a piece of potassium placed upon the cartridge. The upper part of the tube was funnel-shaped, and contained a thimble-shaped vessel filled with water, and supported in an upright position by a piece of touchwood, which, by a simple arrangement, would, when burnt, allow the thimble to overturn. The touchwood being set on fire, the workman rowed off to a safe distance and waited the event. The thimble being overturned, the water inflamed the potassium and the latter the powder. It was found that the powder must be very dry or the potassium would not inflame it. Common gunpowder was generally too damp—Am. Jour. Science, 22, [1], 354, 1832.
E. Turpin, of Paris, has recently patented in England an explosive formed by mixing 80 parts of potassium chlorate with 20 parts of gas tar which contains from 1 to 10 per cent, of an absorptive substance such as infusorial earth, charcoal, and the like. One part of the chlorate can be replaced by permanganate.—Bericht. Deutsch. Chem. GeselL No. 1, 1884, Patente 35.
In an abstract from the J. Soc. Ch. Lid. 3, No. 2, 132, describing kieselguhr and its practical applications, it is said that the finest earth is found at Traterleuss, between Hamburg and Hanover, Germany. From this dynamite has been made containing 82 per cent, of nitroglycerine. It has been used for the purpose of disinfection, in the form of sticks saturated with bromine, and a patent has been taken out for the use of kieselguhr as an absorbent for concentrated sulphuric acid to facilitate transportation without leakage or loss. When the acid is desired for use it is to be extracted by water.—J. Am. Chem. Soc. 6, 140, April, 1884.
According to the Annales Industrielles, M. Michalowskian engineer at Montceau-les-Mines, has invented a new explosive. It is a powder with a density little more than half as great as that of ordinary powder, with irregular grains of a slate-gray color. It does not explode by the action of fire, and detonates only under a blow, like dynamite.—Jour. Frank. Inst. 87, 315, 1884.
The London Times announces that a new explosive, known as hellhoffite, which has been invented by Hellhoff and Gruson, has been subjected to comparative trials at St. Petersburg, together with nitroglycerine and ordinary gunpowder. It is a solution of a nitrated organic compound (naphthalene, phenol, benzene, and the like), in fuming nitric acid. In preparing the hellhoffite tried in the experiments, dinitro-benzene, a solid, inexplosive, and badly burning body, was used. At the first trial glass bottles of 20 cubic centimetres each, were filled with 20 grams of the respective explosive substances and corked. A primer of fulminate of mercury was passed through the cork, a slow match being attached to the outer end of the tube for the purpose of ignition. Each of the bottles thus prepared was placed on a truncated cone of lead, the upper diameter of which was 3.5 centimetres, its lower 4.5, and its height 6. The cone itself stood on a cast-iron plate 2.5 centimetres thick. The deformation of the leaden cone by the action of the explosives could consequently be taken as a measure of their respective destructive power. The explosion of the gunpowder, as was anticipated, caused no changes. By the explosion of the nitro-glycerine the cone was compressed about a quarter of its height; its surface had assumed the appearance of a well-worn hammer: the diameter of the surface had been increased to 5.5 centimetres. The explosion of the hellhoffite caused much greater changes. The surface of the cone was completely torn; pieces five centimetres long and two centimetres thick were torn off and thrown about for several paces; only half of the cone was still a compact but entirely defaced mass. At the second experiment bottles (of 25 grams each) filled with the various explosive substances were let into corresponding cavities bored into the face of fir blocks of similar dimensions. In exploding the gunpowder the block was torn into four pieces as if split with a hatchet, the several pieces were thrown about for 18, 12, 11, and 10 paces. In exploding the nitroglycerine the block was split into several pieces. The upper portion of the block, as far as the bottle was let into it, was torn off transversely to the direction of the fibre in such a manner that a smooth cut was formed. The explosion of the hellhoffite likewise tore the portion of the block surrounding the bottle transversely to the direction of the fibre, and splintered the remainder of the block into a large number of thin fibres. The following experiments were also made with hellhoffite alone. A slow match was passed through the cork, as far as the surface of the hellhoffite in the glass bottle; no explosion followed on igniting the slow match. A quantity of hellhoffite poured into a bowl could not be exploded by a lighted match. Finally, a few drops of hellhoffite were poured on an anvil and exposed to heavy blows with a hammer, and no explosion followed. The hellhoffite, consequently, possesses the following advantages: (1) When detonated by fulminate of mercury it acts more powerfully than nitro-glycerine; (2) it may be stored and transported with perfect safety as regards concussion, as it cannot be exploded either by a blow or a shock, nor by an open flame. On the other hand, it has the following disadvantages: (1) Hellhoffite is a liquid; (2) the fuming nitric acid contained in hellhoffite is so volatile that it can be stored only in perfectly closed vessels; (3) hellhoffite is rendered completely inexplosive by being mixed with water, and consequently cannot be employed for works under water.
In General Abbot's Report on Submarine Mines, page 252, it is stated that "Franklin in his Letters on Electricity (June 29, 1751), was the first to suggest the employment of frictional electricity for ignition of gunpowder. In 1831, Moses Shaw, of New York, made the first actual application of this method to the explosion of mines. The practical difficulties arising at that date from defective insulation of the apparatus, and especially of the leading wires, were so serious that attention was directed to the heating of a fine platinum wire by a current of voltaic electricity, and that method soon superseded all others. A sketch, found among the papers of the late Samuel Colt, of Hartford…which bears date of 1836, indicates a method of firing the torpedoes at will, by the use of a fine platinum wire to be heated by a battery; and in his grand experiment upon the Potomac in 1843 he blew up a brig under full sail with a battery placed in Alexandria, five miles distant. The first application of electrical ignition in civil engineering was made by Sir Charles Pasley of the Royal Engineers, who, in 1839, successfully used low tension fuzes in the removal of the wreck of the Royal George at Spithead. He employed a form of the Daniell battery—which was invented by Becquerel in 1829, and reinvented by Daniell in 1836."
In the historical address delivered by Sir Frederick Abel before the Institution of Civil Engineers, and reprinted in these Proceedings, under the title "Electricity Applied to Explosive Purposes," no reference is made to Colt's experiments, and it is stated that "the first practical application of the voltaic battery in this direction was made about forty-five years ago (1838), by French military engineers," but otherwise he agrees with Abbot. Both of these authorities, however, seem to be unacquainted with the researches of Dr. Robert Hare, of the University of Pennsylvania.
The facts seem to be that Mr. Moses Shaw, having frequently failed in his efforts to blast rocks by the use of a frictional electric machine, applied June 1, 1831, to Dr. Hare for advice and assistance in perfecting his invention. As Dr. Hare had long used his famous deflagrator (or voltaic battery) in his eudiometrical experiments to ignite explosive gaseous mixtures, it occurred to him that it could be equally well used for firing gunpowder, and his experiments proved his belief well founded, for he succeeded in firing twelve charges of gunpowder simultaneously at a distance of one hundred and thirty feet from the battery, and he held that "there are no limits to the number of charges which may be thus ignited, excepting those assigned by economy to the size of the apparatus employed." He also added that "it must be obvious that in all cases of blasting under water, the plan of the tin tubes, and ignition by a galvanic (voltaic) circuit, must be very eligible." The igniting wire was of the "smallest size used for wire gauze." The details of these experiments, with method of preparing the cartridges, etc., are given in Am. Jour. Sci. [1], 21, 139, August, 1831, under the title, "On the Application of Galvanic Ignition in Rock Blasting."
The use of water in connection with blasting in mines and quarries is said to be rapidly extending in this country and in Europe. A tube filled with water is inserted in the bore hole next the powder cartridge, the tube being of thin plate, or even of paper. The usual tamping follows, and when the explosion occurs the tube containing the water is burst, the explosive efficiency being increased by the presence of the water, and the effect extended over the enlarged interior of the bore hole due to the space occupied by the water tube. A much larger quantity of the material to be mined or quarried is thereby brought down or loosened with a given quantity of the explosive, while the heat of the explosion converts a portion of the water into steam, which, with the remaining water, extinguishes the flame and absorbs and neutralizes the gases and smoke generated.
The Boston Journal of June 30, 1885, records a curious explosion which occurred in Brookline, Mass. On the preceding Sunday a resident of Brookline returned his watch to his pocket rather quickly, and was startled by an explosion, which was followed by others in rapid succession. Before he could remove his clothing it had been burned through to the flesh, making a painful wound. The hand in which he held the watch was also severely burned. An examination proved the explosion to have been caused by chlorate of potash tablets, which the gentleman was in the habit of carrying loose in his pocket, and which were ignited by the watch being dropped quickly upon them. The composition of troches of chlorate of potassium, according to Parrish’s Treatise on Pharmacy, p. 880, 1884, is
Chlorate of potassium, 32.50 grams.
Sugar, 124.00
Tragacanth, 6.50
Spirit of lemon, .65
and manufacturers are warned to avoid trituration and pressure in order to prevent the mixture from igniting or exploding.