In November last, at Sandy Hook, in the presence of the Army-Ordnance Board, three rounds were fired with shell charged with insensitive nitro-glycerine, according to the method of S. D. Smolianinoff, described in these Notes. The firing was from a 100-pounder Parrott. The weight of empty shell in the first two rounds was 89 pounds, and the weight, of explosive was 4.6 pounds; in the last round the shell weighed 82 pounds, explosive 4.1 pounds. Except that the turret section had no roof, the target was in all respects similar to that used in the Graydon experiments, even in the respect that it had been fired at before and showed the indentations of former shots. It was mounted in the same manner, and the range also was the same, 101 yards. The powder charge decided on was eighteen pounds Dupont powder. Previous trials had shown that this charge with an 87-pound projectile gave a velocity of 1494 foot-seconds and a pressure of 26,700 pounds per square inch.
First round.—Shell (not fuzed) struck the target in the left-hand lower corner, twelve inches below the horizontal joint and within the edge of an old indentation, and broke into minute fragments. A low order of explosion resulted, as evidenced by the black smoke and the character of the sound. The front plate was cracked to the joint, otherwise the damage was all on the surface. Several bolts that had been broken in previous firings were jarred out by the shock.
Second round.—Shell fitted with percussion detonating fuze. Struck slightly above and six inches to the left of the first shot, and broke up. Explosion, although not of the first, was much higher, order than in the previous round. A 2 ½-inch bolt was broken in two, and some slight surface damage was done. The wooden foundation of the turret was badly broken up.
Third round.—Shell (fuzed) struck a few inches above No. 2 shot and broke up. Explosion of lower order than in No. 2 round, and higher than in No. 1. No material damage done to the target.
The weakness of the cast-iron shell used in these rounds, and also the shape of the head, which was adapted to a nose-fuze, precluded any possibility of penetration, without which no really useful result could be looked for. The firing was successful in the respect that no damage was done to the gun.—Gen. Information Series (U. S. Navy), 7, 378; 1888.
Mr. Hiram Maxim, the inventor of the automatic machine and R.F. guns, has recently secured letters patent on designs for a dynamite gun, for which several advantages are claimed over the Mefford gun.
In the preamble to his specifications Mr. Maxim says: "It has heretofore been customary to utilize compressed air in dynamite guns for discharging the projectile there from; and in order to obtain a higher muzzle velocity of the projectile it has been necessary to make such guns with very long barrels, and to employ air under very high pressure. By my invention I am enabled to reduce greatly the length of the barrel and the pressure of air employed, and, at the same time, to obtain a very high muzzle velocity."
Instead, therefore, of charging the gun with compressed air alone, Mr. Maxim uses a mixture of air and some volatile hydrocarbon (gasoline, for example), in such proportions that there will be just sufficient oxygen in the air to convert the hydrogen of the hydrocarbon into water, and the carbon into carbon dioxide. This mixture may be used at a pressure equal to about one half of that ordinarily employed in pneumatic dynamite guns. After the projectile has been driven by the expansive force of the compressed gas that enters at the initial pressure, through from one quarter to one half the length of the bore, the mixture is caused to explode, and the pressure is at once increased about eightfold.
The apparatus for causing this explosion consists of a detonating cartridge, so placed in an axial chamber in the wall of the gun as to have a longitudinal play of about a quarter of an inch; the chamber being some distance in advance of the projectile when seated, and the outer end of the chamber being fitted with a steel firing pin. The compressed air and hydrocarbon having been introduced into the bore, the projectile moves forward until it uncovers the interior opening of the axial wall chamber, when the gas, impinging upon the detonating cartridge, drives the primer against the firing pin and ignites the mixture in the bore.
Two projectiles have been designed, one for rifle, the other for smoothbore guns. In the latter case the rotary motion is imparted by means of vanes or screw-blades, as with the projectile for the Mefford gun; while the bursting charge of the shell is detonated by means of a capsule and firing pin in the hollow tube to which the blades are attached. It is not understood that any gun of this description has yet been built.—(Loc. cit. 352.)
The Rival Air-Gun Company have issued a large quarto pamphlet with seven plates, entitled "The New Pneumatic Gun or Aerial Torpedo Thrower," describing a device for firing shell charged with high explosives, based upon the inventions of J.W. Graydon. This gun is in principle similar to Mefford's gun, but where the latter is from seventy to fifty-five feet in length, the former is from one half to one third as long. The reduction in length is accomplished by using a greatly increased air pressure, and the company claim to be able to do this with safety, owing to the manner in which the high explosives are packed in the projectile. Owing to this shortening of their length, these guns may be elevated, depressed and trained like any piece of ordnance, a performance which is impossible with the Mefford gun. The guns of this pattern are from three to twenty-one inches in caliber, throwing from six pounds to 1200 pounds of high explosives, under air pressures running up to 3000 pounds per square inch. The range varies with the pressure up to three miles. Besides the shortening of the gun, the great increase in pressure enables them to get a flatter trajectory and greater range than the Mefford gun yields. Other new devices offered in connection with the gun are an air valve, a new condensed fuel for use with the air compressor, and a new fuze. The firing connection for this fuze is operated by the pressure of water, and is regulated for any depth. When that depth is reached, the firing plunger is unlocked and the torpedo is exploded, while, until that condition is fulfilled, explosion from any cause is claimed to be impossible.
It is obvious from these abstracts that this invention is offered in competition with the pneumatic dynamite gun.
Graydonite is a name given to an explosive by J. W. Graydon, for which he claims absolute freedom from danger in handling or transportation, simplicity of manipulation, and a destructive power 400 to 700 per cent higher than dynamite No. 1. A circular advertisement contains very favorable reports of a trial of the explosive made at Table Rock quarry on the Potomac, in May, 1887.—(Loc. cit. 374.)
Through the courtesy of General H. L. Abbot we have received a copy of the Forum for September, 1888, containing a very thoughtful and interesting article by him, on "The Use of High Explosives in War," in which he reviews the progress which has been made in the applications of high explosives to the art of war, and shows that they have proved a most important gain for the engineer in the destruction of material, removal of obstructions in mining and in countermining; that the success thus far attained in firing shell charged with high explosives from gunpowder guns has demonstrated the weakness of our hitherto impregnable fortifications; and that the gain, as between ships and forts, is rather to the advantage of the latter, and is in favor of the rich and powerful nations rather than the poor and weak.
In concluding he remarks: "No reference need be made to the proposed mode of projecting charges of high explosives from pneumatic guns, because no official trials have yet been made with the pattern proposed by the inventors for service; because the ranges claimed are too short to meet the requirements of the problem; and because throwing the new agents from ordinary guns will do away with the supposed need of the invention. That larger charges may perhaps be thrown from a pneumatic tube than from a gun is not very important, because the destructive effect of the explosion increases only with the square root of the weight, i.e., a 400-pound charge is only twice as destructive as a 100-pound charge, and in most cases four 100-pound charges are more to be dreaded than one 400 pound charge."
The Army and Navy Jour. 25, 826, May 5, 1888, states that during the progress of some artillery experiments at Fort Tiburina, just outside of Rome, on May 1, a dynamite shell exploded and the Crown Prince of Italy was slightly wounded in both sides. The general commanding the home division of the army was also slightly wounded, two colonels received serious injuries, and two captains dangerous ones.
Melinite is generally believed to be a mixture of fused picric acid, in granules, with trinitrocellulose dissolved in ether. M. Turpin, its inventor, is now free to offer his secret to any government that may choose to purchase it, but the French claim that their melinite of to-day is so different from the original substance that not even the inventor would recognize it, and that they have reached such a state of proficiency in its use as to put them at least three years in advance of any possible rivalry. It is reported that the secret has been purchased by Sir William Armstrong. It is known that experiments with one form of melinite are now progressing in England, but so far the particulars have been carefully guarded.
Precautions are taken to guard not only the secret of the manufacturing processes, but also the performances of the explosive. Notwithstanding this, it has transpired that in the Belliqueuse experiments, the effect of the shell striking against the armored portion of the ship was practically nil, the points of impact being marked by only slight surface indentations. On the other hand, the shell that struck the unprotected parts are said to have created "terrible havoc." This expression, which is copied from various editorials of the French press, is a rather vague one, but, at all events, the havoc was such as to cause many French naval experts to advocate a reversion to complete armor; and it is said that the designs of several ships now building (the Brennus and Dupuy de Lome are mentioned by name) have since been modified especially to meet the fire of high explosive projectiles.
It is stated that the French have succeeded in firing melinite shell from high-power guns with velocities as high as 2000 foot-seconds. The weight of the melinite charge in this case is not mentioned, but it is known that charges of nearly 70 pounds have been repeatedly fired from the 22-centimeter mortar, with velocities of over 1300 foot seconds.
Max Dumas-Guilin, in the manual noticed elsewhere, states the explosive force of melinite to be only three times that of gunpowder; other statements represent it as from five to eleven times as powerful, but M. Guilin evidently has the weight of authority on his side, and is entitled to the greater credence,—(Loc. cit. 373.)
The current press reports that an explosion has occurred in a melinite factory at St. Omer, France, and that before the flames were subdued, six factories and two houses were destroyed.
The Emmens Chemical and Explosives Company, of Harrison, N.Y., have issued a "Report on Emmensite," by Baron Louis H. de L'Espee, in which it is stated that emmensite* is prepared by fusing together five parts by weight of emmens acid and five parts of a nitrate (preferably sodium or ammonium nitrate) in a paraffin bath, and then incorporating six parts of picric acid. Emmens acid is obtained by dissolving commercial picric acid, at a gentle heat, in fuming nitric acid (50° to 52° Baumé), and evaporating, when the new acid is deposited in rhomboidal prisms of a fine yellow color. According to Dr. H. Wurtz, of New York, this acid has the formula of H2C.C12H6(NO2)6O2H2O, and may be regarded as being intermediate between tri-nitro-phenol and tri-nitro-cresol. Emmens acid differs from picric acid in its crystalline form; in being less soluble in water and alcohol; in giving ruddy vapors when heated, and in possessing a golden yellow color. It is claimed that by the process of manufacture of emmensite above described, the whole mass is converted into a compound of emmens acid.
Elaborate calculations are employed to determine the explosive value of emmensite as compared with nitroglycerine and other high explosives, and taking dynamite No. 1 as equivalent to 100, guncotton is found to be 120.54, explosive gelatine 154.29, nitroglycerine 183.72, emmensite 236.60, and fulminate of mercury 1229.76. These theoretical conclusions are said to be confirmed by numerous experiments, some of which are described in this pamphlet.
It is proposed to use this explosive not only in mining, but in a granulated form as a substitute for gunpowder as a propelling agent in guns, for which purpose it is claimed to possess three times the power of gunpowder, while it produces no smoke, does not foul the piece, and is safe against violent blows or shocks.
Its sensitiveness to shocks has been tested by Lieutenant Zalinski with the following apparatus: He fits a stout tube, closed at one end, into an air-chamber, so that the mouth of the tube opens into the chamber, and he places the explosive in the tube and closes the mouth of the tube with a steel plate. Then he introduces compressed air into the chamber until it attains a pressure of 4000 pounds per square inch, or more than 300 atmospheres, when the plate breaks and the explosive is exposed to the impact of this highly compressed air. Under these conditions, nitroglycerine, gun-cotton, dynamite, and gunpowder exploded, but emmensite failed to explode.
The Pittsburgh, Pa., Dispatch states that a gun is now being constructed in that city for the American Emmensite Company, with which to demonstrate the value of their explosive. It is to be a smoothbore, 3 inches in diameter and 100 inches long, and is expected to throw a 6-inch (sic) shell filled with emmensite from 10 to 12 miles. It is explained that in rifled cannon the shell turns 1 ½ times in the length of the gun; that this causes a terrific torsional strain, which necessitates a great increase in the thickness of the shell, with a proportionate reduction in the space for the explosive; and that the Emmensite Company return to smoothbores to avoid this trouble, while they rely upon the great power of their explosive to secure the necessary range.—Ill. Nav. Mil. Mag. 9, 169; 1888.
Major J.P. Cundill, R.A., H.M. Inspector of Explosives, has reprinted in a separate volume his admirable "Dictionary of Explosives," which has appeared in installments in the Proc. Royal Artillery Inst, for 1887 and 1888. In this work, the explosives treated of are grouped in eight classes, arranged in alphabetical order in each class, and the whole carefully indexed. With each substance is given a brief but lucid statement of its composition, and, when of special importance, of its special properties and method of manufacture, while a succinct historical account and a notice of the general characteristics precedes each group. The work is an invaluable one to those engaged in the study or use of explosives, its accuracy and reliability being insured from the experience and professional position of its author. From this work we learn that Roburite consists of a mixture of ammonium nitrate and meta-di-nitro-chlorbenzene; that Romite consists of a mixture of ammonium nitrate, naphthalene or nitro-naphthalene, and potassium chlorate; and Securite consists as a rule of 74 per cent of ammonium nitrate with 26 per cent of meta-di-nitro-benzene, though other varieties have been made which contain the tri-nitro-benzene and the di- or tri-nitro-naphthalenes.
A new variety of "securite" has been prepared by Herr Schoeneweg, which is said to be flameless when exploded, and will, it is expected, be of especial value as a substitute for ordinary blasting powder and other explosives in fiery coal mines. It consists of nitrated hydrocarbons mixed with an oxidizing agent, such as chlorate of potash, and some organic salt which renders the mixture flameless. The substance is not hygroscopic, and is of a bright yellow color, and can be kept for any length of time without undergoing any change. It cannot be exploded by a flame nor by a hot substance, but only by a detonating cap. Recent experiments at Hendon have proved that the new explosive fulfills the anticipations of the inventor, and we understand that the Flameless Explosives Company have undertaken to introduce it to the notice of mine owners and others to whom an explosive of this nature should be welcome. Its power is said to be equal to that of No. 1 dynamite, and it can be manufactured at a less cost. The organic salt which is added to the "securite" to produce this effect has also the property of rendering dynamite similarly flameless when mixed with it.—Sci. Am. 58, 263: 1888.
The numerous explosions at various parts of Stockholm (there were thirteen) which occurred during one or two exceedingly hot days in the last week of June, seem all to have been caused by the spontaneous decomposition of explosives. It appears that romite was kept at eleven of the thirteen places, and that it has probably also been found at the remaining two, and further, that the explosions in two instances (at Marieberg and Skinnarviken) must have arisen through the spontaneous ignition of this same explosive. Further researches into the matter are pending.—Engineering, 66, 35; July 13, 1888.
Both in Germany and in France, extensive experiments have been carried out with the object of producing an improved powder which shall be comparatively smokeless and non-corrosive, and at the same time give higher initial velocity without corresponding increase of pressure.
In Germany, gun-cotton and nitro-lignin have chiefly been experimented with, while in France, much attention has been bestowed upon picric powders.
The French Brugère powder, which is composed of ammonium picrate and potassium nitrate, is said to give high velocities (over 2000 foot-seconds with small arms), and to cause only very slight recoil. Large numbers of cartridges of this powder were ordered for the new Lebel rifles, but it is stated that a recent examination of a quantity of this ammunition that had been stored at Chalons showed that the powder had deteriorated to such an extent that the whole lot had to be condemned.
France is now experimenting with gun-cotton powders, and has already obtained some marvellous results: some reports say velocities as high as 2500 foot-seconds have been reached. The powder is practically smokeless.
The powder with which 2380 foot-seconds was obtained from the Armstrong 36-pounder rapid-firing gun is a German invention. Although not smokeless, the smoke is much less in volume than that from ordinary powder, and is speedily dissipated. The same German experts have perfected a powder for small arms which is said to be absolutely smokeless. This has been adopted as the service powder of the German army. The right to this invention has been secured by the Chilworth Gunpowder Company, in England, and the company announces itself as already prepared to turn out both rapid-fire gun and small-arm powders in quantities as large as are likely to be required by the Government service.
Under the name of Paleina, the Rivista di Artiglieria e Genio describes a straw powder invented by a French officer which is stated to be suitable to both military and mining operations, to be smokeless, and to possess remarkable explosive force.
The mode of manufacture is as follows: The straw is first subjected to a process which makes the fiber soft and pliant, and is then washed and triturated in an apparatus similar to that employed in reducing rags to pulp. From these operations the fiber issues in the form of thin sheets, which are cut up and steeped first in a mixture of nitric and sulphuric acids, and then after careful washing to remove the excess of acid, in a solution of saltpeter and dextrine containing pulverized hardwood charcoal; the final product is dried in a current of air.
Paleina, as thus prepared, has the appearance of small disks of cardboard. In the open air it burns slowly and with a blue flame, but when detonated in a confined space it explodes with a force of about three times that of gunpowder. It makes no smoke and leaves no residue.
The straw has the property of absorbing nitroglycerine in a considerable proportion, and then forms an explosive superior to dynamite in power, and relatively safe and easy to handle.—(Loc. cit. 375.)
The Revue Maritime et Coloniale, 533, September, 1888, states that a new powder which is smokeless, while it possesses all the qualities of the best gunpowder, has been experimented with, and that it is prepared by using carbon from cork in the place of charcoal. By this means the hygroscopicity of the powder is very much reduced.
The exact nature and formula of fulminic acid and its compounds, owing to their extreme unstableness, is, comparatively speaking, little known. The following "Recent Investigations on the Fulminates," by H.N. Warren, offer further contributions to our knowledge of them.
The salt used to conduct the experiments with was silver fulminate. This being dissolved in hot water, and digested with copper filings, was transformed into cupric fulminate; the green salt obtained was dissolved in water and introduced into a tube open at either end, one extremity being closed by means of a porous diaphragm. The salt was reduced by means of nascent hydrogen, according to the usual method, by connecting the same with a small Daniell's cell, the inside of the tube being provided with a platinum electrode connected with the negative end of the battery. In the course of a few hours the whole of the copper had become reduced to the metallic form, and firmly attached to the platinum plate.
The solution obtained being thus freed from copper was next examined and was found to contain, besides large quantities of hydrogen cyanide and ammonia, distinct quantities of fulminic acid, evidently existing as ammonium fulminate. This was obtained and examined as fulminating silver by digesting with silver carbonate. In every instance an explosive fulminate was re-formed, corresponding to the normal fulminate.
In the next experiment, cupro-ammonium fulminate was obtained by the addition of an excess of ammonia to a solution of cupric fulminate. The deep-blue crystals thus formed were, after being dried by suspending them over sulphuric acid, decomposed by dry hydrogen sulphide. The product consisted, however, chiefly of copper sulphide, with urea and ammonium sulpho-cyanide.
Further, an attempt was made to combine fulminic acid with silicon, by passing a stream of dry silicon fluoride over silver fulminate, kept moist by means of petroleum. Large quantities of silver fluoride were at once formed, and the escaping gas, when collected and ignited, exploded with considerable violence. Although the results obtained from several experiments performed by the same method agree with each other identically, it still remains an open question whether such a compound as silicon fulminate does in reality exist.
Chlorine, iodine, and bromine were also used, but chiefly gave rise to chloropicrin and other bodies of an allied formula. Experiments were also performed with the view of obtaining an ethyl compound, but these require further investigation before speaking definitely of them.—Chem. News 57, 255; 1888.
Major Philip Hess states in the Mitt. Art. Genie- Wesens, Notizen, 47, 1887, that in extracting the fulminating composition for detonators for analysis, he has been accustomed to loosen the composition by carefully squeezing the caps between boards until the case was somewhat flattened, rounding it out again, and again flattening it. Then by means of a camel's hair brush the contents are completely brushed out on to glazed paper. He finds that detonators will bear a good deal of gradual compression without exploding, and that a cork squeezer may be used for the purpose described above, but it is best to employ a safety-brake with it.
A. von Cettingen and A. von Gernet have repeated the work of Bunsen, Berthelot and Vieille, and also that of Mallard and Le Chatelier upon the "Phenomena attending Explosions in Gases," making use of instantaneous photography to record the phenomena, and their results are given in a very valuable paper in the Ann. Der Physik u. Chetn. 33, 586-609; 1888. A rotating mirror was employed with a metallic pointer, to which an electric spark passed when the mirror was in the right position to reflect an image of the eudiometer tube, in which the explosion took place, into a photographic camera. The same spark served to explode the gases. The most sensitive Beernaert plate gave no trace of an image. No results could be obtained by staining the plates with cyanine or with azaline. Eastman's negative film paper, however, gave a faint image. The authors were compelled to sprinkle certain powders in the eudiometer tube. Chloride of copper gave the best results. Plates of the phases of the explosions accompany the paper. The experiments show that the explosion of hydrogen is not accompanied by light. The resulting high temperature, however, causes a disintegration of the glass of the eudiometer tube which produces a certain illumination. Three species of wave motion were observed: first, a fundamental wave, which is entitled Berthelot's wave; second, more or less parallel secondary waves; third, polygonal waves of smaller amplitude. The photographic image of the electric spark which was received upon the same plate as that of the explosion, enabled the authors to estimate the velocity of the explosion. The result obtained, 2800 meters per second, is of the same order of magnitude as that obtained by Berthelot. The authors agree in the main with Berthelot's conclusions, differing only in reference to the beginning and the end of the explosion. They explain the secondary waves on Bunsen's hypothesis of the reflex action of waves due to successive explosions produced by the electrical spark. They therefore term these Bunsen's waves.
Many experiments have proved that the velocity of sound obtained by observing from a known distance the instant of the discharge of a rifle and the arrival of the sound of the explosion at the place of observation, is frequently greatly in excess of the normal rate of propagation of sound. To determine the cause of this increase and the laws which govern it, a series of experiments have recently been carried out by M. Journée, who has presented a memoir on the subject to the French Academy of Science. His experiments show that if a bullet is fired from a rifle against an iron plate, then so long as the velocity of the bullet is in excess of the normal velocity of sound through air, the noise of the explosion and of the bullet striking the plate reach an observer, situated in the plane of fire behind the plate, at the same instant. If the distance of the plate from the rifle is increased till the velocity of the bullet before reaching it is reduced below that of sound, then the noise of the explosion reaches an observer before that of the shock against the plate. Hence the author concludes that the bullet, so long as its velocity is greater than the normal velocity of sound, is the seat of a sonorous disturbance resembling in character that due to an explosion, and this view he has substantiated by further experiments.—Comptes Rendus, 106, 244-247, Jan. 23, 1888.
The valuable paper by Sir Frederick Abel, on "Accidents in Mines," hereinbefore referred to, is an outgrowth of his studies and researches as a member of the Royal Commission appointed in 1879 to deal with this subject, and as these accidents are due to a great variety of causes, and since each of these is treated of as exhaustively as the space permits, there is much useful and valuable matter which is not germane here, while the general results arrived at in regard to matters such as explosions due to coal-dust-laden air, and to those caused by explosive gaseous mixtures moving with high velocities becoming inflamed by safety lamps, have already been referred to in these Notes. Hence we shall notice only that part of the paper which deals with the use of explosives in mines.
Formidable danger frequently attends the employment of blasting powder in coal mines on account of the flame which generally attends, though to a very variable extent, the firing of a shot tamped in the usual manner, and especially on account of the larger volume of flame which is projected to a considerable distance, either when a blast-hole is overcharged, or when the preponderating strength of the material operated upon gives rise to what is termed a "blown-out shot," the tamping being projected from the hole like a shot from a gun. These sources of danger were recognized long before any views were advanced regarding the possible connection of coal dust with mine explosions, and the precautions enacted for ascertaining the absence of any important contamination of the air at the working place with fire-damp before shots were fired, and for reducing to a minimum the number of lives subject to possible danger when shot firing was carried out, are well known.
Proposals have, from time to time, been considered by the inspectors of mines and others, for either abolishing the use of powder in fiery mines, or for greatly restricting its application by the imposition of more or less stringent conditions. When the Royal Commissioners gave this subject their attention and collected evidence bearing upon the dangers of shot-firing in mines and the possibility of dispensing with the practice, they were led to the conclusion that the abolition, or even the very considerable restriction of shot-firing as practiced under the existing laws, would be incompatible with the working of a large number of pits, except at a prohibitive pecuniary outlay. Realizing most fully, on the other hand, the dangers that frequently attend the use of powder in coal mines and the extreme difficulty of effecting any important diminution of those dangers, they devoted much attention to the question whether it might be possible to discover any powder substitute, or any method of using such substitute, which would secure immunity from danger due to the presence of coal dust and fire-damp in the localities where blasting had to be carried on.
From time to time assertions have been made as to the supposed comparative safety of different explosive agents more or less analogous in composition to blasting powder. It is not difficult to put the validity of such assertions to the test by chemical examination of the particular explosive preparations, and it may be confidently maintained, from the experience which the Royal Commission and the author individually has acquired of preparations of this class, that there are but very few practically useful explosive agents of the gunpowder type which possess any advantage in point of comparative safety over ordinary black or blasting powder.
The employment of powder in the compressed form, which has of late years become very extensive, presents important advantages in point of convenience and general safety of handling, but does not in any way affect the dangers in reference to use in coal mines, inherent in an explosive agent, the employment of which is liable at any time to be attended by the production of considerable volumes of flame. Attempts were made, in the earlier days of the history of gun-cotton, to apply that material as a blasting agent in coal mines, but the circumstance that its explosion is attended by the development of a large proportion of carbonic oxide renders it inapplicable in this direction, as its explosion (even by detonation) is liable, on that account, to be attended by the production of a considerable volume of flame. Finely divided gun-cotton may be readily incorporated with the proportion of a nitrate (saltpeter, or barium nitrate) necessary for the complete oxidation of its carbon, the generation of carbonic oxide being thus prevented or reduced to a minimum; and such preparations as nitrated gun-cotton, tonite or potentite, produced by compression of mixtures of this class, have found favor to some extent in drift work, or in the blasting of stone over and underlying coal seams, as being more powerful than powder; but their explosion is by no means unattended with the possibility of the development of flame. In this respect nitroglycerine preparations are undoubtedly superior. This explosive agent contains a proportion of oxygen slightly in excess of that required for the complete oxidation of its constituent carbon, hence its perfect explosion is unattended by the development of inflammable gas. The most common form in which nitroglycerine is commercially employed is as dynamite. When exploded by detonation, the heat developed by the metamorphosis of the nitroglycerine raises the mineral matter present to a bright red or white heat, and the detonation of this preparation is always attended by the appearance of sparks in the dark. But if even the undiluted nitroglycerine is exploded in a shot-hole, the high temperature has the effect of raising to incandescence, particles of the tamping employed, or of the coal or stone exposed to the highly heated gases and vapors developed, so that under any circumstances sparks would be liable to be projected on the firing of a nitroglycerine charge. The same holds good with any of the nitroglycerine preparations known in commerce, such as lithofracteur, blasting gelatine, or gelatine-dynamite; moreover, flame in more or less abundance may be produced by the explosion of some nitroglycerine preparations, the composition of which includes proportions of inflammable materials.
That the heat to which very finely divided solid particles may be raised, by exposure to the highly heated products of detonation of nitroglycerine preparations, is sufficient to determine the ignition of an explosive fire-damp mixture, has been amply demonstrated by experiment, and it is even possible that sparks sufficiently hot to produce that result may be carried to some distance by the blast of heated gases projected by a shot, and thus reach places at some distance from the shot-hole where gas may have lodged.
The author's long connection with the study of explosives and their application to every variety of use, naturally led to his special devotion of much attention to this branch of its investigations; and the first idea bearing upon the occurrence of casualties in coal mines which suggested itself to him was to apply the principle of most complete explosion, or detonation, of one or other of the so-called "high explosives" (chemical compounds highly susceptible of sudden metamorphosis into gaseous products or vapors) in conjunction with the method first devised by him in 1873, and communicated in that year to the Royal Society, of distributing the operation of the force developed by small charges of the explosives over a considerable area, through the agency of a comparatively large volume of water, by which the charge is enveloped.
The principle of suddenly transmitting the force of detonation of a charge of explosive uniformly in all directions, by completely surrounding with water the charge to be detonated, had already been successfully applied by him to the conversion of an ordinary shell into a projectile operating with the destructive effects of a shrapnel shell, and to several other purposes, and it occurred to him that by applying the same principle to the charging of a shot-hole, the effect might be not only to modify the destructive action of a high explosive, and thus to attain a comparatively moderate splitting or rending action instead of powerful disintegrating effects, but also to accomplish the extinction, through the agency of the water envelope, of any incandescent particles or sparks, and perhaps flame, projected by the exploding charge, the water being thrown forward together with them in a finely divided condition. It soon afterwards came to the author's knowledge that Dr. McNab had previously put into practical execution the idea of extinguishing the flame of a powder charge projected from a shot-hole, by inserting a cylinder filled with water over the charge and confining it by a small amount of tamping. The application of water in this way, in conjunction with powder, was also expected by Dr. McNab to effect important economy of time in blasting operations, by diminishing the persistency of the smoke through the solvent action of the water, thereby enabling men to return to work in a comparatively short space of time after the firing of shot. The latter result appears to have frequently been attained to a useful extent, but experience showed, on the other hand, that sufficient reliance could not be placed upon the extinguishing effects of water thus applied in conjunction with powder being sufficiently exerted to afford reliable security against the ignition by the flame from a blown-out powder-shot, of an explosive gas mixture, or of dust thickly suspended in air containing a small proportion of fire-damp. A series of experiments indicated, however, that water-tamping, as first suggested by Dr. McNab, used in conjunction with a high explosive such as dynamite, afforded very considerable, if not absolute, security against accidental explosions under the conditions just now specified.
An exhaustive series of experiments was instituted, chiefly in South Wales, with a view to ascertain whether perfect security against ignition of explosive gas mixtures, and of coal dust thickly suspended in air containing a small proportion of coal-gas or fire-damp, was secured by the application of high explosives in conjunction with water in the way suggested by Abel, the charge of explosive being enclosed on all sides by water, with or without the additional use of superposed tamping. The results appeared to justify the conclusion that the so-called water-cartridge, employed in conjunction with a high explosive, could be relied upon to afford security against accidental explosions during shot-firing in the presence of explosive gas mixtures, or of very inflammable coal dust thickly suspended in air containing some small proportion of fire-damp. The results obtained for the Royal Commission have been confirmed by experiments of a similar nature pursued by others in this country, by experimenters in Saxony, and by members of the Prussian Fire-damp Commission. In the course of these various experiments it has been found that the particular form of dynamite to which the name gelatine-dynamite has been given, is especially suitable for employment in conjunction with water, as it retains its explosive properties unimpaired under these conditions, and may, in blasting operations, be placed quite unprotected, either in a shot-hole which is filled with water, or in a cylinder full of water of suitable dimensions for insertion into the hole. In constructing a water-cartridge there is not the least necessity for employing any device for keeping the explosive in such a position that its circumference is surrounded equally on all sides by the water; it suffices simply to insert the charge with its waterproofed fuze or wires attached, into the blast-hole direct (if the latter is in perfectly solid stone or coal and in a suitable position), or into the cylinder of thin sheet metal, varnished paper or membrane which is filled with the water; it is best, however, to insert the charge nearly to the bottom of the water, so as to utilize the tamping effect of the greater part of the column. The liquid is retained by a wooden or cork plug, through which the fuze or conducting wires pass, and tamping is applied over this after insertion of a tuft of hay or other suitable padding material.
The work done in coal by a high explosive, through the agency of a column of water which encloses it (or "water-cartridge"), is different in character to that accomplished by the same charge used in the ordinary manner. Instead of exerting a crushing action immediately round the charge, whereby much small coal is produced and no large amount of displacing work performed, the force being distributed over the whole area of the water column, its action is thereby greatly moderated, and the coal is brought down in large masses, the work done extending over at least as large an area as that of the best powder-shots.
In applying this system as a safeguard against accidental ignition of coal dust or fire-damp mixtures, the quantity of water used should at least amount to four times the volume of the charge employed.
It has come to the knowledge of the author that, in a colliery where a serious explosion recently occurred, so-called water-cartridges were in use, in which, when the charge of explosive had been inserted, very little room was left for water. From the published account of the evidence given at the inquest, it appeared to have been affirmed that Abel's water-cartridge had been used at a great expense, and it was left to be implied that the calamity was due to confidence being falsely placed in the safety to be ensured by its employment.
The practical development of the principle of applying water in conjunction with high explosives cannot fail to be fruitful of improvements in the mode of operation, as indeed it has already been; thus, in order to avoid a loss or diminution of the safeguard furnished by the water from the escape of the liquid through channels or fissures in the shot-hole, or through leaks in the water-cylinder or cartridge, it has been proposed by Messrs. Heath and Frost to dissolve sufficient size or glue in the water, warmed for that purpose, to make it solidify on cooling in the case or shot-hole to a sufficiently stiff jelly to prevent such escape. Again, the experiments carried out for the Commission with water-cartridges led to the observation that a considerable proportion of the water was driven forward in a body instead of being dispersed in a very fine state of division, by the force of a blown-out shot, and a suggestion was consequently made for the employment of the water in a different manner, which was worked out by Mr. Galloway with most successful results, so far as related to the extinction of flame and sparks from a blown-out shot. By distributing the water through a very porous body (such as sponge or moss), and thus effecting an initial interruption of continuity of the mass of liquid placed over the shot, its thorough dispersion in a very finely divided condition is ensured, and its extinguishing power is greatly increased. It was found, in a number of experiments at the Dowlais works, that in holes of 2 inches diameter, the placing of 9 inches of loose tamping of moss soaked with water over a 4-oz. charge of dynamite sufficed to prevent the ignition of dust-laden air containing coal-gas by the blown-out shot, and that such a shot produced with 2 ½ oz. of dynamite, the charge being covered with only 4 inches of loose moss and water-tamping, failed to fire an explosive gas mixture. A number of comparative experiments demonstrated that the water-cartridge was on an equality with moss and water-tamping in preventing the ignition by blown-out shots produced with dynamite, gun-cotton, tonite and gelatine-dynamite, of a dense cloud of highly inflammable dust suspended in air containing a small proportion of coal-gas (the cloud produced under the same conditions being invariably inflamed by an ordinary blown-out dynamite shot); but they proved that the water-cartridge did not afford that absolute security against the ignition of an explosive gas mixture by a blown-out dynamite shot that, so far as a number of consecutive experiments showed, was attained by the comparatively simple moss and water-tamping, which can be applied without difficulty even in holes having an upward inclination.
The water-cartridge employed with various high explosives in such a way as to produce blown-out shots in the presence of coal dust and gas, has been made the subject of official experiment in Prussia and Saxony, and apparently with results as satisfactory as have now been obtained in different mining districts in this country; it may be considered to have been conclusively established that the application of water in the shot-hole in one or other of the ways indicated, in conjunction with the use of high explosives, affords most important security against accidents in blasting stone or coal in mines where dust and fire-damp co-exist.
It may be well again to emphasize the fact that neither the water cartridge nor water-tamping applied in the manner in which it has been found so thoroughly efficient in conjunction with high explosives, affords any safeguard against explosions arising from the presence of fire-damp, or coal dust associated with fire-damp, in mine workings where blasting is carried on, if powder, or any explosive agent analogous in its composition and mode of explosion to powder, be employed in conjunction with them.
Suggestions have been made to use in conjunction with powder, or as tamping over the charge, certain solid preparations which will evolve gases or vapors, when exposed for a sufficient period to heat, capable of extinguishing flame, the idea being that the heat developed by the explosion of the charge would accomplish the desired results, and that the dangers arising from blown-out shot might thus be guarded against; but the authors of these suggestions have not realized the importance of time as a factor in the establishment of chemical changes by the action of heat, and the consequent impossibility of gases and vapors being evolved, in the desired manner, within the exceedingly brief period during which the materials applied are exposed to heat. The Commission, at the author's suggestion, had experiments carried out for the purpose of ascertaining whether condensed (liquefied) carbonic acid could be applied in suitable tamping vessels, in conjunction with high explosives, as an extinguishing agent, but the results were not sufficiently encouraging to warrant perseverance in this direction of experiment.
Some attention has been attracted since the publication of the Commission's final report, by a safety blasting cartridge brought forward by Dr. Kosmann, of Breslau, which depends for its action upon the rapid development of hydrogen under high pressure from very finely divided zinc, by the action of sulphuric acid (enclosed in one compartment of a compound vessel of glass). The acid is intended to have access to the zinc after the apparatus has been fixed into the shot-hole, in such a way that the gas, which is said to speedily attain a high degree of compression, shall exert its force upon the stone or coal. The cost of each shot is stated to be only small, but the description scarcely warrants the view that the arrangement is a practically efficient one, and no account of successful experiments with it in actual blasting operation has yet reached the author.
Various proposals to apply compressed air to the getting of coal have been put forward, among which was one by Mr. Samuel Marsh, of the Clifton Colliery, Nottingham, to the practical development of which Mr. Ellis Lever devoted much trouble some years ago, but no really satisfactory results appear to have been attained with it.
The considerable increase in volume which caustic or quick-lime rapidly undergoes during the slaking process (or its conversion into hydrate by union with water), was already many years ago regarded as a source of power which might be available in lieu of powder for the bringing down of hard coal; but repeated attempts to utilize it met with no practical success until Messrs. Sebastian Smith and Moore, about six years since, made two important steps in advance. In the first place, by reducing freshly burned fat lime of high slaking power to powder, and converting this into cylinders by applying powerful pressure, they obtain the lime in an exceedingly compact form, which enabled them to utilize the full diameter of a drilled shot-hole, and which rendered the material less liable to air-slaking than when in lumps. In the second place, using the heat developed by the slaking to generate and superheat steam, they were able to supplement to an important degree the force exerted by the expanding charge of lime. The author then details the results which have been obtained in the use of the lime-cartridge, and notes some of the disadvantages which are held to accompany it.
Scribbler's Magazine, 3, 563-576, May, 1888, contains an article by Charles E. Munroe, on "Modern Explosives," in which the author has sought to present, in a popular and yet precise way, the theory of explosion, and to describe the characteristic properties and method of use of some of the more typical explosive substances. The author calls especial attention to this article, as it shows that he does not endorse many of the statements which he collates in these Notes.
The paper is well illustrated, principally from photographs and objects prepared at the Torpedo Station. The illustrations of the effects produced by detonating gun-cotton on iron plates show that the theory which he has presented in these Notes is confirmed by further experiments, for, as shown, he has bored holes of continually increasing diameter and depth in gun-cotton disks until he has pierced one completely with a hole two inches in diameter, and on detonating these on the iron plates he has obtained deeper and deeper indentations in the plates, until, when using the completely perforated gun-cotton disk, he has completely perforated the plate.
This theory is further supported in a paper by the same author in a paper published in Proc. Newport Nat. Hist. Soc. No. 6, 18-23; 1888, entitled "On certain Phenomena produced by the Detonation of Gun-cotton." He used a can such as is used for canning fruit and vegetables, placed a disk of gun-cotton in it, filled the can with sufficient water to just completely cover the disk, placed the can on an iron beam, and detonated the gun-cotton by means of a dry priming disk. The can was of such a diameter as to just receive the disk, and the end of the can in contact with the beam was the one through which the can had been filled with its fruit, and as is the case with such cans, the end had a sunken circular channel let into it, and an irregularly shaped mass of solder at the center of the face which was raised above the surrounding surface. On examining the face of the iron beam on which the detonation took place, an impression of this end of the can, with all the depressions and elevations having precisely the same value as in the original, was found to have been exactly reproduced in the iron of the beam. This is well shown in a photo-stereotype attached to the paper.
The author has also succeeded in obtaining "Wave-like Effects produced by Detonating Gun-cotton," by using a tin vessel with a smooth bottom in which to hold the explosive. The can in this case had a diameter much larger than that of the gun-cotton disk; the disk was placed on one side of the can so that the cylindrical surfaces were tangent, and the can was filled with water and detonated on an iron beam just as described in the last experiment. On examining the impression produced on the beam there was found, as was to be expected, a deep impression under the area occupied by the gun-cotton, but, as was not to be anticipated, the impression extended less deeply quite to the extremity of the area marked by the base of the can. But what was yet more remarkable was that beneath this crescent-shaped space between the peripheries of the disk and the can which had contained only water, two sets of breakers had been produced in and remained fixed in the iron, the crests of the waves being turned outwards. The exterior set of breakers consisted of waves which were easily visible to the naked eye and sensible to the touch, and their average wave-length was found to be closely 1.5 millimeter. The author hopes to be able by this method to distinguish between different explosive substances, and to learn more regarding the nature of explosive phenomena and the way in which the energy is propagated. A description of the experiment appears in Am. Jour. Sci. 26, (3), 49-51, July, 1888, with diagrams showing the method of experimenting, and an exquisite photo-stereotype of the iron beam.
The theory which we have offered regarding the way in which the indentations are produced by gun-cotton on metal plates is strongly supported by M. P. F. Chalon, in Le Genie Civil, in an article entitled "Mining without Tamping," and he extends the theory to the phenomena taking place in a drill-hole. We are indebted to him for a copy of this article, which we reserve for a later date.
"Les Explosifs Modernes," by P.F. Chalon, is a theoretical and practical treatise prepared for the use of civil and military engineers and miners, which appears in the form of a large octavo of some four hundred pages, with upwards of one hundred and sixty figures intercalated in the text. The matter is well arranged and so treated as to make this an excellent manual as well as a work of reference. While sufficient space is given to the properties of the substances which may be employed in the manufacture of explosives, to the methods of manufacture and properties of the more important explosives, to the methods of analyzing and of testing the force of these explosives, and to their uses in peace and war, yet some fifty pages are devoted to the legislative acts in Austria, England, France, and the United States, which regulate the manufacture, transportation, storage and use of explosives in these countries. This information, which is so important, but which it has hitherto been difficult to gain access to, apart from the other merits of the work, makes this book a necessary one to possess.
"La Dynamite de Guerre et le Coton-Poudre," by Max. Dumas-Guilin treats of the manufacture, transportation, storage and use of these explosives according to the orders and regulations which govern the French army concerning them. As, besides giving these regulations at length, its matter is largely drawn from the courses of instruction at l’Ecole de Guerre and l’Ecole du Genie de Versailles, the work has almost the authority of a Blue Book. As might be expected from this, we find minute and detailed descriptions of the methods to be followed in the service during storage, transportation, and use of the explosives mentioned, both in times of peace and war; the treatment of the topics of military mining and the destruction of material being especially full and explicit. The book contains about four hundred small octavo pages, with about fifty figures in the text, and is of a convenient form for a manual for use in the field. As will be seen from the description, the book is one which commends itself especially to officers of the navy and army.
M. P.F. Chalon also presents " Le Tirage des Mines par I'Electricite," in the form of a small octavo of two hundred and seventy six pages, with ninety figures and numerous tables. The book deals both with the theory and practice of firing mines by electricity, and describes at length the different blasting caps and detonators, the electrical firing apparatus, both batteries and machines, and the methods of wiring mines for large blasts.
"Die Elektrische Minenziindung," by Karl Zickler, is an octavo pamphlet of one hundred and sixteen pages, with sixty figures, and with tables, which deals more briefly with the subject treated of by Chalon in the last mentioned book.
R. Gaertner, of Berlin, announces the publication of "Die Fabrikation von Chiorsauren Kali und anderen Chloraten," by K.W. Jurisch, Ph.D.