FOOTNOTES:[Q]Seepage 185.[R]A Turkish port, situated on the east coast of the Black Sea, capable of holding several large ships when anchored head and stern, but otherwise only a few.[S]A town situated on the south bank of the Danube, about eight miles from Brailoff.[T]One of the principal mouths of the Danube.[U]A place taken from the Russians in the early part of the war, situated on the east coast of the Black Sea.
[Q]Seepage 185.
[Q]Seepage 185.
[R]A Turkish port, situated on the east coast of the Black Sea, capable of holding several large ships when anchored head and stern, but otherwise only a few.
[R]A Turkish port, situated on the east coast of the Black Sea, capable of holding several large ships when anchored head and stern, but otherwise only a few.
[S]A town situated on the south bank of the Danube, about eight miles from Brailoff.
[S]A town situated on the south bank of the Danube, about eight miles from Brailoff.
[T]One of the principal mouths of the Danube.
[T]One of the principal mouths of the Danube.
[U]A place taken from the Russians in the early part of the war, situated on the east coast of the Black Sea.
[U]A place taken from the Russians in the early part of the war, situated on the east coast of the Black Sea.
EXPLOSION may be defined as the sudden or extremely rapid conversion of a solid or liquid body of small bulk into gas or vapour, occupying very many times the volume of the original substance, and which in addition is highly expanded by the heat generated during the action.
This sudden or very rapid expansion of volume is attended by an exhibition of force which is more or less violent, according to the constitution of the original body and the circumstances of the explosion.
Any substance capable of undergoing such a change on the application of heat or other disturbing cause is called an "explosive."
Explosive Force.—Explosiveforceisdirectlyproportional to the heat of combustion and the volume of gas, andinverselyto the specific heat of the mixed products.
Explosiveeffectisdirectlyproportional to the volume of gas produced and the temperature of the explosion, andinverselyas the time required for the change to take place.
Explosive Effect and Force compared.—Explosive effect depends upon the rapidity with which the conversion is effected, while the same amount of explosive force may act suddenly or gradually.
As before stated, explosions are more or less violent according to thecircumstancesunder which they take place. These may be considered as follows:—
1.—The physical state of the explosive substance.
2.—The external conditions under which the explosive body is fired.
3.—The mode of firing.
The Physical State of the Explosive Substance.—Numerous instances may be cited to show the influence the physical condition of an explosive body has upon its explosion.
Thus, gunpowder may, by merely varying the size, shape, and density of the grain, be made to ignite rapidly but burn comparativelyslowly, or be made to ignite more slowly, but once inflamed to burn very rapidly.
Again, gun-cotton in a loose, uncompressed state, will, if ignited, only flash off; if it is spun into threads or woven into webs, its rate of combustion may be so much reduced that it can be used in gunnery or for a quick fuze; while if powerfully compressed and damp it burns slowly. Wet gun-cotton requires a primer of dry gun-cotton and a fulminate fuze to explode; dry, it may be exploded by a fulminate fuze, &c.
Then nitro-glycerine, when exploded by 15 grains of fulminate of mercury, and at a temperature above 40° F., is very violently detonated; below 40° F. it freezes and cannot be similarly exploded.
To obtain the full effect of all explosives, confinement is absolutely necessary.
The more rapid the explosion the less confinement required, approaching in the case of some explosives to so small an amount that it need not, for practical purposes, be considered.
Thus a charge of nitro-glycerine or gun-cotton, when detonated in the open air, will destroy wrought iron rails, large blocks of stones, balks of timber, &c.
In the case of the former body, the confinement of the atmosphere is sufficient.
In the latter, the mechanical cohesion due to compression is sufficient restraint.
Abel states that if the film of atmosphere surrounding the nitro-glycerine, not exceeding 1/1000 inch in thickness, be removed, the explosive effect is much lessened.
A large charge of gunpowder fired in the ordinary way under water requires a strong case to retain the gases until the action has become general, or, owing to its slow rate of burning, the case would be broken before the whole of the charge had been ignited, and part of the charge drowned.
This is often to be noticed when firing fine-grained powder in heavy guns.
Igniting the charge at several points diminishes the confinement needed.
Mode of Firing.—The application of heat, directly or indirectly, is the principal means of causing an explosion.
The flame from a percussion cap or primer, or a platinum wire heated to incandescence by an electric current, willdirectlyignite a charge. Friction, concussion, &c., willindirectlyignite a charge due to the conversion of mechanical energy into heat.
It would appear that when one explosive body is used as a means of firing another, the resultant explosion is due to the blow suddenly formed by the gas of the firing charge acting percussively upon the mass to be exploded. If such were the case, then the most powerful explosive would be the best agent for causing an explosion. But it is not so.
For example, nitro-glycerine, which is far more powerful than fulminate of mercury, requires more than 1000 grains to explode gun-cotton, while only 15 grains of the latter is needful for the same work, &c.
A small quantity of an explosive substance which is sensitive to friction or percussion is often used to ignite the original charge.
Detonation.—The instantaneous explosion of the whole mass of a body is defined as "detonation."
The essential difference between an explosion and a detonation is the comparative suddenness of the transformation of the solid or liquid explosive substance into gas and vapour.
Some explosive bodies, such as the fulminates, &c., always detonate, while the detonation of others depends on the mode of firing.
Nitro-glycerine always explodes violently, but when fired with an initiatory charge of fulminate of mercury it is much more powerful than when fired with gunpowder.
Compressed gun-cotton in the air-dry state can be detonated by 2 grains of fulminate of mercury embedded in the material, but when it contains 3 per cent. of water over and above the 2 per cent. which exists normally in the air-dry substance, 15 grains of the fulminate will not always do so.
Theory of Detonation.—The theory of detonation is not yet thoroughly understood. That it is not alone due to the heat caused by the impact of the mechanical energy of the particles of gas, set free from the initiatory charge on the principal mass, is proved by the fact of its being possible to detonate wet gun-cotton.
Professor Bloxam terms detonation to be "sympathetic" explosion.
Experiments carried on in England by Professor Abel, and inFrance by MM. Champion and Pellet, tend to show that it is due to the vibratory action of the detonating agent.
Thus a glass may withstand a strong blow, though a particular note or vibration will smash it.
All explosive compounds and mixtures, including gunpowder, are susceptible of violent explosion through the agency of a detonation.
Roux and Sarrau.—Roux and Sarrau divide explosions into two orders:—
1st order.—Detonations.
2nd order.—Simple explosions.
Simple explosions are produced by direct inflammation, or by a small charge of gunpowder.
Detonations are obtained from nitro-glycerine, gun-cotton, &c., by exploding with fulminate of mercury.
They state that fulminate of mercury does not detonate gunpowder; but if the exploding charge is a small amount of nitro-glycerine, itself detonated by fulminate of mercury, then an explosion of the first order is obtained.
The relative effects were approximately measured by determining the quantities necessary to rupture small cast iron shells of supposed equal strength.
Results of their Experiments.—The following are some of the results:—
Explosive Effect.2nd Order.1st Order.Gunpowder1·004·34Gun-cotton3·006·46Nitro-glycerine4·8010·13
According to the above table, nitro-glycerine is more than ten times, and gun-cotton more than six times, as powerful as gunpowder fired in the ordinary way (2nd order).
The want of reciprocity between two detonating agents is shown in a remarkable degree by the following experiments, carried out by Professor Abel:—
1.—The detonation of 1/4 ounce of gun-cotton (the smallest quantity that can be thus applied) induced the simultaneous detonationof nitro-glycerine, enclosed in a vessel of sheet tin, and placed at a distance of 1 inch from the gun-cotton.
2.—The detonation of 1/2 ounce of gun-cotton produces the same effect with an intervening space of 3 inches between the substances.
3.—The detonation of 2 ounces of nitro-glycerine inclose contactwith compressed gun-cotton failed to accomplish the detonation of the latter, which was simply dispersed in a fine state of division, in all the instances but one, in a large number of experiments.
Explosive agents are divided into explosive mixtures and compounds.
In the former the ingredients are mechanically mixed, and can be separated by mechanical means.
In the latter the ingredients are chemically combined, and can only be separated by chemical change.
Torpedo Explosive Agents.—The explosive agents that are practically the most important, as far as their employment as torpedo charges are concerned, are as follows:—
Explosive Mixtures.—A.—Explosive mixtures.
1.—Gunpowder.Nitrate class2.—Ammonium picrate, or picric powder.
Explosive Compounds.—B.—Explosive compounds.
Gunpowder.—This explosive mixture is composed of seventy-five parts of nitre (saltpetre), fifteen parts of charcoal, and ten parts of sulphur.
On being ignited, the oxygen which is feebly held by the nitrogen combines with the carbon, forming carbonic oxide gas, whilst the sulphur unites with the potassium of the nitre, the whole combination being accompanied by a great evolution of heat and expansion of gas, and the nitrogen is set free.
Properties, &c.—A spark, friction between hard bodies, or a temperatureof 572° F., are any of them sufficient to cause an explosion of gunpowder.
Slight moisture, due to damp air, &c., produces caking and deterioration.
Wetting causes permanent destruction.
Frost does not injure it.
It can be fired by ordinary methods.
It can be transported and handled with safety and great ease.
It is not a suitable explosive agent for torpedoes, on account of its liability to be injured by damp, as well as its not being sufficiently violent, though for the sake of convenience, &c., it is often employed for such work.
The effect produced by the explosion of a charge of gunpowder, ignited by the ordinary method, is that of an uplifting rather than a shattering effect.
This evil may be greatly remedied, when gunpowder is used as the charge of a torpedo, by firing it with a detonator, by which means its fullest explosive effect is developed.
Picric Powder.—The picrates are salts of picric acid.
Picric acid is formed by the action of nitric acid on carbolic acid.
The picrate employed by Professor Abel is prepared from picric acid and ammonium. This preparation, or salt mixed with nitre (saltpetre), forms Abel's picric powder.
Properties, &c.—It is prepared for use in a similar manner to gunpowder, and it can be handled in the same way.
It is less violent than dynamite or gun-cotton, though much more so than gunpowder.
It is difficult to explode it by blows or friction.
If flame be applied to it, the part touched burns, but the combustion does not become general.
This explosive agent will probably be used for spar torpedoes, when gun-cotton or dynamite are not employed.
Nitro-glycerine.—Nitro-glycerine is formed by the action of nitric acid upon glycerine at a low temperature.
The manufacture of this compound consists, first, in the slow mixtureof the glycerine with the acid, at a low temperature; secondly, in washing the nitro-glycerine from the excess of acid with water.
The nitric acid before use is mixed with a certain proportion of strong sulphuric acid, so that the water formed during the reaction may be taken up, and thus any dilution of the nitric acid is prevented.
Nitro-glycerine is composed of carbon, hydrogen, nitrogen, and oxygen, as indicated by the equationC3H5N3O9.
Properties, &c.—At ordinary temperatures nitro-glycerine is an oily liquid, having a specific gravity of 1·6. Freshly made it is creamy white and opaque, but clears and becomes colourless on standing for a certain time, depending on the temperature.
It does not mix with, nor is it affected by, water. It has a sweet, aromatic taste, and produces a violent headache if placed upon the tongue.
The opaque, freshly made nitro-glycerine does not freeze until the temperature is lowered to 3°-5° below zero, F., but, when cleared, it freezes at 39°-40° F. Nitro-glycerine freezes to a white crystalline mass, and in this state it can be thawed by placing the vessel containing it in water, at a temperature not over 100° F.
If flame is applied to freely exposed nitro-glycerine, it burns slowly without explosion.
Nitro-glycerine in a state of decomposition becomes very sensitive, exploding violently when struck, even when unconfined.
Pure nitro-glycerine does not spontaneously decompose at any ordinary temperature, but if it contains any free acid, then decomposition may happen. When pure, it is not sensitive to friction, or moderate percussion. If struck with a hammer, only the particle receiving the blow explodes, the remainder being scattered.
The firing point of nitro-glycerine is about 356° F., though it begins to decompose at a lower temperature.
The mode of firing nitro-glycerine usually employed is that of a fulminate of mercury detonating fuse.
Nitro-glycerine in the frozen state cannot be fired even by large charges of fulminate.
In one instance, 1600 lbs. of liquid nitro-glycerine exploded in a magazine containing 600 lbs. of the same substance in a frozen state, but failed to fire the latter, only breaking it up and scattering it in every direction.
Dynamite.—This explosive compound is merely a preparation in which nitro-glycerine is itself presented for use, its explosive properties being those of the nitro-glycerine contained in it, as the absorbent is an inert body.
Dynamite is formed of seventy-five parts of nitro-glycerine absorbed by twenty-five parts of a porous siliceous earth or "kieselguhr."
The best substitute for "kieselguhr" is ashes of bog-head coal.
Dynamite is a loose, soft, readily moulded substance, of a buff colour.
The preparation of dynamite is very simple.
The nitro-glycerine is mixed by means of wooden spatulas with the fine white powder (kieselguhr) in a leaden vessel.
It freezes at 39°-40° F., and when solidly frozen cannot be exploded, but if in a pulverised state it can be exploded, though with diminished violence.
It can be easily thawed, by placing the vessel containing it in hot water.
Friction or moderate percussion does not explode it.
Its firing point is 356° F.
If flame be applied to it, it burns with a strong flame.
It is fired by means of fulminate of mercury, and its explosive force is about seven times that of gunpowder.
For ground and buoyant mines, where actual contact between the hostile vessel and the torpedo will be rarely achieved, this being next to nitro-glycerine the most violent of all known explosive agents, and being cheaply and readily procured, is the very best explosive for such torpedoes.
That it is not generally adopted is owing to its containing a large proportion of that seemingly dangerous substance, nitro-glycerine, which makes the handling of dynamite a somewhat hazardous operation.
According to Professor Abel, there are now as many as fifteen dynamite factories in different parts of the world (including a very extensive one in Scotland) working under the supervision of Mr. Nobel, the originator of the nitro-glycerine industry; and six or seven other establishments exist where dynamite or preparations of very similar character are also manufactured.
The total production of dynamite in 1867 was only eleven tons, while in 1878 it amounted to 6140 tons.
This explosive compound is most extensively used for generalblasting purposes all over the world, and for this purpose, owing to its cheapness and the convenience in manipulating it, is far superior to compressed gun-cotton.
Gun-cotton is formed by the action of concentrated nitric acid on cotton, its composition being indicated by the formulaCH7(NO2)3O5.
Professor Abel's process for manufacturing pulped and compressed gun-cotton is as follows:—
Cotton waste is the form of cotton used; it is picked and cleaned, thoroughly dried at 160° F., and then allowed to cool.
The strongest nitric and sulphuric acids are employed, mixed in the proportion of one part of the former to three of the latter by weight. These are mixed in large quantities, and stored in cast-iron tanks.
The cotton in 1-lb. charges is immersed in the acid mixture, which is contained in a trough surrounded by cold water. After being subjected to the action of the acid for a short space of time, the cotton is taken up, placed upon a perforated shelf, and as much as possible of the acid squeezed out of it. It is then put into jars, covered with fresh acid, and the jars placed in fresh water, remaining there for twenty-four hours.
To remove the acid, the gun-cotton from the jars is thrown into a centrifugal strainer, by which nearly all the acid is expelled. It is then diffused quickly in small quantities through a large volume of water, and again passed through a centrifugal machine.
The next process is that of thoroughly washing the gun-cotton, for the purpose of removing the traces of the acid still adhering to it. By pulping, which operation is performed in pulping engines or beaters, the washing is expeditious and thorough.
Abeateris an oblong tub in which is placed a revolving wheel carrying strips of steel on its circumference. From the bottom under the wheel project similar steel strips.
The action of this machine is as follows:—
By the rotation of the wheel, the gun-cotton which is suspended in water circulates around the tub, and is drawn between the two sets of steel projections, by which it is reduced to a state ofpulp.
The bottom of the tub is movable, and thus the space through which the gun-cotton must pass may be contracted, as the operation proceeds.
The pulping being complete, the contents are run intopoachersfor the final washing.
Apoacheris a large oblong wooden tub. On one side at the middle is placed a wooden paddle-wheel, which extends half way across the tub.
In the poacher the pulped gun-cotton is stirred for a long time with a large quantity of water. The revolution of the paddle-wheel keeps up a constant circulation, and care is taken that no deposit occurs in any part of the tub.
Having converted the cotton into gun-cotton, reduced it to a state of pulp, and thoroughly washed it, the next process is to separate the water from the pulp, and compress it into cakes or discs.
This is accomplished by means of two presses, the first of which has 36 hollow cylinders, in which perforated plungers work upwards.
These plungers having been drawn down, the cylinders are filled with the water-laden pulp, and their tops covered with a weight; the plungers are then forced up by hydraulic power, compressing the pulp, and forcing the water to escape through their perforations.
The second one is used to more solidly compress the cylindrical masses of gun-cotton formed by the action of the first press, a pressure of 6 tons to the inch being in this case applied.
About 6 per cent. of moisture still remains in the discs, which can be readily removed by drying.
Properties.—Cotton converted into gun-cotton is little changed in appearance, though the latter is harsher to the touch than the former.
If a flame be applied to dry loose gun-cotton, it flashes up, without explosion; if compressed it burns rapidly, but quietly.
Moist compressed gun-cotton under the same circumstances burns away slowly.
Gun-cotton containing 12 to 14 per cent. of water is ignited with much difficulty on applying a highly heated body. As it leaves the hydraulic press upon being converted from the pulped state to masses, it contains about 15 per cent. of water; in this condition it may be thrown on to a fire or held in a flame without exhibiting any tendency to burn; the masses may be perforated by means of a red-hot iron, or with a drilling tool, and they may with perfect safety be cut into slices by means of saws revolving with great rapidity. If placed upon a fire and allowed to remain there, a feeble and transparent flame flickersover the surface of the wet gun-cotton from time to time as the exterior becomes sufficiently dry to inflame; in this way a piece of compressed gun-cotton will burn away very gradually indeed.
To test the safety of wet gun-cotton, the following two experiments among many have been made:—
Quantities of wet gun-cotton, 20 cwt. each, packed in one instance in a large, strong wooden case, and in the other in a number of strong packing cases, were placed in small magazines, very substantially built of concrete and brickwork. Large fires were kindled around the packages in each building, the doors being just left ajar. The entire contents of both buildings had burned away, without anything approaching explosive action, in less than two hours.
This comparatively great safety of wet gun-cotton, coupled with the fact that its detonation in that state may be readily accomplished through the agency of a small quantity of dry gun-cotton, termed a "primer," which, by means of a fulminating fuze, or detonator, is made to act as the initiative detonating agent, gives it important advantages over other violent explosive agents, when used for purposes which involve the employment of a considerable quantity of the material, on account of the safety attending its storage and necessary manipulation.
From experiments conducted by engineer officers in Austria, it was found that if boxes containing dry compressed gun-cotton are fired into from small arms, even at a short range, the gun-cotton is generally inflamed, but never exploded, the sharpness of the blow essential to effect an explosion, which the bullet might otherwise give, being diminished by its penetration through the side of the box before reaching the explosive. Wet gun-cotton, containing even as little as 15 per cent. of water, is never inflamed on these conditions.
Dynamite, on the other hand, is invariably detonated when struck by a bullet on passing through the side of the box.
Gun-cotton is insoluble in and unaffected by water.
The firing point of gun-cotton is about 360° F.
The temperature of explosion of gun-cotton is about 8700° F., being more than double that of gunpowder. Gun-cotton is not sensitive to friction or percussion.
If not perfectly converted or thoroughly washed, gun-cotton isliable to spontaneous decomposition, which under favourable conditions may result in explosion.
Compressed gun-cotton is free from such danger, as it may be kept and used saturated with water. It is stored in the wet state, care being taken that it is not exposed to a temperature that will freeze the water in the cakes, as if this occurs they are liable to be disintegrated by the expansion of the water in freezing.
Gun-cotton is the agent most extensively used for all kinds of military engineering and submarine operations in Great Britain, it being especially manufactured by the English government for that express purpose; but in other countries it is not so manufactured, and therefore, as it is little used for other than military purposes, it is not to any extent privately manufactured, as is the case with other explosives, such as dynamite, dualine, lithofracteur, &c., and thus, in case of war, would be somewhat difficult to obtain out of England.
Compared with dynamite, it is not so violent, and occupies more space, weight for weight, and also requires a more complicated means of detonating it. On the other hand, gun-cotton is infinitely safer to store and manipulate, and is not so subject to detonation by concussion (not being so sensitive) as dynamite.
Fulminate of Mercury.—Fulminate of mercury is formed by the action of mercuric nitrate and nitric acid upon alcohol. The mode of preparation is as follows:—
Dissolve one part of mercury in twelve parts of nitric acid, and pour this solution into twelve parts of alcohol.
Pour this mixture into a vessel which is placed in hot water until it darkens and becomes turbid and begins to evolve dense white fumes, then remove it from the water. The reaction goes on, with strong effervescence and copious evolution of dense white ethereal vapours. If red fumes appear, cold alcohol should be added to check the violence of the action.
The operation should be performed at a distance from a fire or flame, and in a strong draught, so that the vapours may be carried off.
When the liquid clears, and the dense white fumes are no longer given off, further action is stopped by filling up with cold water. The fulminate settles to the bottom of the vessel as a grey crystalline precipitate. The liquid is then poured off, and the fulminate washed several times by decantation or upon a filter.
Dry fulminate of mercury explodes violently when heated to 367° F., when forcibly struck by the electric spark, &c.
When wet it is inexplosive, and therefore it is always kept wet, being dried in small amounts when required for use.
Fulminate of mercury is applied in many ways, either pure or mixed with other substances, as in percussion caps, percussion powder, primers, detonators, &c.
For the purpose of detonating nitro-glycerine or its preparations, 15 grains of the fulminate are sufficient, but to detonate gun-cotton 25 grains are necessary. The fulminate in detonating fuzes should be enclosed in a copper case or cap, and must never be loose. The fulminate should be wet when charging the detonators, as it is very dangerous to handle when dry.
Great care is requisite in handling this explosive compound.
In addition to the foregoing explosive compounds and mixtures, the following explosive agents have also been employed for the purposes of submarine operations, though only to a small extent.
Dualin.—Dualin is a nitro-glycerine preparation formed by mixing sawdust and saltpetre with that substance.
This preparation, inferior to dynamite, was employed by the Germans as the explosive agent for their submarine mines during the Franco-German war (1870-71).
Lithofracteur.—Lithofracteur is also a preparation of nitro-glycerine. It is composed of the following materials:—Nitro-glycerine, kieselguhr, coal, soda, saltpetre, and sulphur.
This explosive agent, also inferior to dynamite, is used, though not very extensively, by the French for their submarine mines.
Horsley's Powder.—Horsley's powder is a chlorate mixture formed of potassium, chlorate, and galls. This explosive mixture was formerly used by Captain Harvey for his towing torpedo, but has recently been discarded for compressed gun-cotton.
Abel's Detonation Experiments.—The following are the results of experiments carried out by Professor Abel, C.B., F.R.S., on the subject of detonation:—
1.—A fuze containing rather more than 1 ounce of gunpowder, strongly confined, exploded in contact with a mass of compressed gun-cotton,only inflames it, although the explosion of the fuze is apparently a sharp one.
2.—45 grains of fulminate of mercury, exploded unconfined on the surface of a piece of compressed gun-cotton, only inflames or disperses it.
3.—A fuze containing 9 grains of fulminate of mercury, strongly confined, exploded in contact with compressed gun-cotton, or dynamite, detonates it with certainty.
4.—An equal quantity of fulminate of mercury, similarly confined, does not detonateuncompressedgun-cotton in which it is imbedded, but merely disperses and inflames it.
5.—150 grains of compressed gun-cotton, detonated in proximity to dynamite,detonates the latter.
6.—3 ounces of dynamite, and very much larger quantities, detonated in contact with compressed gun-cotton, only disperses it.
7.—A wrought-iron rail can be destroyed by detonating 8 ounces of compressed gun-cotton placed unconfined on the rail.
8.—A piece of wet gun-cotton, quite uninflammable, removed from a fire, and detonated upon a block of granite, using a small primer of dry gun-cotton, shatters the block.
9.—A submerged charge of wet gun-cotton, open on all sides to the water, and merely confined around the dry initiative, or primer, by means of a net, can be exploded.
Explosive Agents in Torpedoes.—The explosive agents that at the present time are most generally used in torpedoes are gunpowder, gun-cotton in the wet compressed state, and dynamite, and these may be compared as to their properties and their explosive effects.
Gunpowder.—Gunpowder is a familiar material, in general use for all military purposes. It can be handled and transported with safety and ease, and it can be fired by ordinary methods. But for submarine purposes it has the disadvantage of being very easily injured by water, so that it is absolutely necessary to enclose it in water-tight cases.
Gun-cotton.—Gun-cotton is free from liability to accidents, and in this matter, and the safety of its manufacture, it compares favourably with gunpowder.
It is peculiarly adapted to submarine work, being unaffected by water. And as it may be kept in water, ready for use, it can be safely carried on board ship in large quantities. It is far more violent in itsaction when detonated than gunpowder. The chief objection to its use is, that being applied only for special purposes, it is not readily obtained. Also it requires a peculiar and somewhat complicated mode of firing it.
Dynamite.—Dynamite is more easily manufactured than the two foregoing explosives. The fact of it containing nitro-glycerine, which has a bad reputation, has militated against its use as a torpedo explosive agent, though for blasting purposes it is most extensively used. Though not directly affected by water, its firing is hindered when diffused through water. Another disadvantage is its high freezing point. Like gun-cotton, it requires special means to fire it, though much simpler, and also is much more powerful than gunpowder. The explosive effect of dynamite or gun-cotton is a rending or a shattering one, while that of gunpowder is an uplifting or heaving one.
Again, it is necessary when using gunpowder that the object be in the line of least resistance, but with dynamite or gun-cotton the effect is nearly equal in every direction, therefore for submarine operations, either dynamite or gun-cotton is the explosive agent that should be invariably used.
Size of Torpedo Charges.—For permanent mines, a charge of 700 lbs. to 1000 lbs. of gun-cotton is quite sufficient, though too large a charge cannot be employed, except as regards the matter of convenience.
For buoyant mines, 500 lbs. to 700 lbs. of gun-cotton is an ample charge, and for contact mines, 200 lbs. to 300 lbs. of gun-cotton is sufficient. In spar torpedoes, where lightness is a consideration, gun-cotton charges of 30 lbs. to 50 lbs. will be found ample, and similarly in the case of the towing or locomotive torpedoes. Of course, with regard to such a submarine weapon as the Lay torpedo boat, any size charge may be carried, according to the wish of the builder.
Torpedo Explosions illustrated.—AtFig. 166is represented a sketch of a torpedo explosion, from a photograph taken at the moment the column of water was at its greatest elevation. The torpedo contained 432 lbs. of gun-cotton, and was exploded under 27 feet of water.
The height of the column thrown up measured 81 feet, and the diameter at the base 132 feet.
SUBMARINE MINE EXPLOSION.Plate LII
SUBMARINE MINE EXPLOSION.
Plate LIIISUBMARINE MINE EXPLOSIONS.
SUBMARINE MINE EXPLOSIONS.
AtFig. 165is shown a sketch of two submarine mine explosions from an instantaneous photograph; the schooner which is shown inthe sketch happened to be passing at the moment of explosion, thus affording a comparison as to the size of the columns of water thrown up.
The column on the left was due to the explosion of a submarine mine containing 100 lbs. gunpowder at a depth of 10 feet below the surface. That on the right was the result of an explosion of a similar mine, but at a depth of 41 feet below the surface. Its extreme height was 400 feet.
THE following are some of the more important torpedo experiments that have been carried out in England and Europe, to investigate the subject of submarine explosions as applied to ships and to mines, &c., these experiments extending over a space of thirteen years.
Experiment at Chatham, England, 1865.—This experiment was carried out to ascertain the effect of gunpowder torpedoes on the bottom of a wooden ship.
Target:—H.M.S.Terpsichore, a wooden sloop of war.
Torpedo:—150 lbs. of fine-grained powder. Two were used. They were placed on the ground, about 13' below the ship's keel, and 2' horizontally clear of her side.
Effect of explosion:—A hole of about 4' radius was made, about 19' nearly vertical from the charge; theTerpsichoresinking a few minutes after the explosion.
Experiment in Austria.—The object of this experiment was to ascertain the effect of a very large charge of gun-cotton exploded at some distance from the side of a wooden vessel.
Target:—A wooden sloop.
Torpedo:—400 lbs. of gun-cotton, placed 10' below the surface of the water, and 24' horizontally from the bottom of the vessel.
Effect of explosion:—Complete destruction of the vessel.
Experiments at Carlscrona, Sweden, 1868.—These experiments were made to investigate the effect of submarine contact mines, charged with dynamite, against a strong wooden vessel, as well as against a double-bottomed iron vessel. They were carried out under the supervision of Lieut.-Colonel Zethations, of the Royal Swedish Navy.
Target:—The hull of a 60 gun frigate, which had been built in 1844; it had been cut down to the battery deck, and the copper removed. Her timbers and planking were quite sound; timbers of oakabout 13" square, and 1" apart; planking of Swedish pine, 5-1/2"; bottom strengthened inside with wrought-iron diagonal bands, 6" by 1-1/4"; inside planking running half way up to the battery deck of oak; 6" thick. This completes the wooden target.
On the port side a quadrangular opening was made, and fitted with a construction representing a strong double iron bottom, firmly fastened to an oaken frame that had been put on inside, on the four sides of the opening, and with through-going bolts, 1" in diameter, to the timbers.
Torpedoes:—No. 1.—13 lbs. dynamite, enclosed in 1/12" iron case. It was placed on the starboard side, amidships, 7' below the water line, and 2' 2" from the bottom of the ship.
No. 2.—16 lbs. dynamite, enclosed in a glass vessel. It was placed on the starboard side, 7-3/4' below the water line, 3' from the bottom of the ship, and 40' from her stern.
No. 3.—16 lbs. dynamite, enclosed in 1/12" iron case. It was placed on the port side, 5-3/4' below the water line, 2' from the bottom of the ship, and 30' from her stern.
No. 4.—10 lbs. dynamite, in a case as above. It was placed on the port side, 6-1/2' below the water line, 2-1/6' from the bottom of the ship, and 70' from her stern.
No. 5.—13 lbs. dynamite, in case as above. It was placed 7-1/3' below the water line, 2-1/6' from the centre of theironbottom.
These five torpedoes were fired at the same moment.
Effect of explosion:—The hull of the ship was lifted about a foot, and sunk in 1-1/2 minutes.
No. 1 Mine.—Timbers broken and thrown inside, into the hold, on a space of about 15' × 8'; three more timbers on one side of this hole broken; inside oak planking rent off on a length of 14'; two iron bands torn up and bent, one of them broken in two places; outside planking torn off on a space of 21' × 12'; several planks still higher up broken.
No. 2 Mine.—Timbers blown away on a space of about 8' square; inside planking torn off on a length of 20'; two iron bands broken, and torn up and bent; and outside planking rent off on a space of 19' × 12'.
No. 3 Mine.—Timbers blown away on a space of 10-1/2' × 12' at one end, and 6' at the other; inside planking off for a length of 14'; one ironband torn up, and one broken; outside planking off on a space of 18' × 25' × 15'.
No. 4 Mine.—Timbers blown away on a space 4' × 16'; on the sides of this hole, ten timbers were broken; two iron bands torn up, and one broken; inside planking off for a length of 20'; outside planking off for a space of 20' × 23' × 10', and 13 feet.
No. 5 Mine.—The gas sphere of this mine had hit the middle of the outside plates on one of the angle-iron ribs. This rib was torn from the timbers and bent up, nearly 2' in the middle, but not broken. There was an oval hole in the outside plates 4' × 3' between two ribs, which ribs, with the plates on edge riveted to them, were bulged out about 5 inches. The inner plate, one large piece was blown up in a vertical position, after having cut all the bolts and rivets, sixty of 1", and thirty of 3/4", save those that fastened the lower side to the oaken frame and timbers. On a length of 30' and height of 20', the bottom, on all sides of the iron construction, had been bent inwards; the greatest bend was about 5"; three deck beams above had been broken.
By the joint effect of all the mines, almost all the iron deck beam knees had been rent from the side, and there was an opening between deck and hull on both sides for a length of about 130 feet.
Experiment at Kiel.—Target:—A large gun-boat, greatly strengthened internally by solid balks of timber.
Torpedo:—200 lbs. gunpowder. It was placed nearly under her keel, at a distance of 15 feet.
Effect of explosion:—Complete destruction of the vessel.
Experiment in England, 1874.—Target:—A rectangular iron case 20' long, 10' high, and 8' wide, divided into six compartments by means of one longitudinal bulkhead midway between the front and rear faces of the target, and two athwartship bulkheads equidistant from the ends of the target. Thickness of front and rear faces 11/16", of longitudinal bulkhead 1/4", of athwartship bulkheads 3/8".
Torpedo:—100 lbs. of gunpowder, enclosed in a spar torpedo case and fired by two detonators. It was exploded in contact with the target, 7-1/2' below the surface of the water, and 7' from top of target.
Effect of explosion on the target:—"Front of centre compartment destroyed and top blown off. Plate representing inner skin destroyed. Back of centre compartment (rear face of the target) much bulged, and penetrated; the hole measured 36' × 15". Large portions of thetarget were thrown to a height of 150 to 200 feet, and from 80 to 100 yards' distance."
The effect of explosion on a ship's pinnace, which had been placed 16 feet from and at right angles to the front face of the target, with steam up, and canopy and shield in position, was that a large quantity of water was thrown back in the boat, putting the fires out, and filling the boat up to her thwarts, but otherwise the boat was uninjured.
Experiments at Copenhagen, Denmark, in 1874.—The object of these experiments was to ascertain if a ship's armoured side would be seriously injured by a torpedo exploded in contact with it.
Target:—1" thick, and 2' × 2', supported in a horizontal position on a substructure consisting of 8" timber resting on two pieces of 6" timber under two sides, and completely supported by earth up to lower edge of substructure.
Torpedo:—33 lbs. of dynamite, enclosed in a square wooden case 2-1/4" high, and 5·5" × 5·5"; it was placed on the middle of the earth with 8" of earth tamping; this tamping representing the resistance of a thin stratum of water.
Effect of explosion:—The plate was broken into four pieces, and substructure crushed.
Target:—2" thick, and 2' × 2-1/2', supported in a horizontal position on a substructure as above, but resting on four piles of 6" x 6" timber.
Torpedo:—8·9 lbs. of dynamite, enclosed in a wooden case 4" high, and 5" × 10". It was laid with one edge on the plate, the other edge 3" above the plate; same tamping as above.
Effect of explosion:—The plate broken into three pieces, and substructure crushed.
Target:—5" thick, and 3' 8" × 4' 7", supported in a horizontal position on a substructure as above, but eight piles of 6" × 6" timber used. Plate bolted to the structure with eights.
Torpedo:—44·4 lbs. of dynamite, enclosed in a wooden case, ofsame thickness as the Harvey torpedo, and 4" × 13" × 21"; it was placed with surface against the plate, one edge 2" and the other 5-1/2" from the plate; tamping as before.
Effect of explosion:—Plate bulged 3-1/4" in the middle; substructure completely crushed.
Target:—5" thick, and 3' 8" × 4' 7"; this was the same plate as used in the previous experiment, laid with bulge uppermost on two beams under the short sides.
Torpedo:—44·4 lbs. of dynamite, enclosed in a cylindrical tin box 7-1/2" × 2'; it was placed on top of plate 11" from one side and with ends 9-1/2" from edge of plate; tamping as before.
Effect of explosion:—A corner of the plate broken off.
Target:—Same plate placed vertically in the earth.
Torpedo:—44·4 lbs. of dynamite, enclosed in a cylindrical tin box 8·5" × 18"; it was placed on timber, so as to rest against the face and centre of the plate; tamping as usual.
Effect of explosion:—Plate broken into four pieces, two of which were large; pieces hurled over parapet, one fell at a distance of 400 feet.
Experiments at Carlscrona, Sweden, in 1874-75.—These experiments were carried out by the Swedish torpedo authorities, to ascertain the effect of different sized charges of dynamite and gunpowder, enclosed in divers cases, and exploded at various distances from a target which represented in all respects, with the exception of the armour, a section of the side of H.M.S.Herculesbefore the boiler room, she being at that time one of the most powerful vessels afloat.
Target:—32' in length, and fitted into the side of an old line of battle ship. Similar in shape to a wing tank, and comprised a double bottom in four water-tight compartments, a wing passage in two water-tight compartments, and two large water-tight compartments in rear of all. It extended from 2' above the water line to within about 5' of the vessel's keel. The thickness of the plates forming the target were:—outer bottom, lower portion 13/16"; part where torpedo took effect, 3/4".Inner bottom, and wing passage bulkhead, 1/2". Vertical and longitudinal frames, both solid and bracket, 7/16". The longitudinal frames were bracket frames, with the exception of the second, which was solid and water-tight, with its outer edge about 8' below the water line. The vertical frames, of which there were seven, were placed 4' apart, the central one being solid and water-tight, the others being bracket frames. The ship was moored in 42 feet of water; the charges were detonated, one fuze being used in all but No. 3 experiment, when five fuzes were employed.
Torpedo:—33 lbs. of dynamite, enclosed in cylindrical steel case, no air space; height 10·75", diameter 10·75", and thickness 1/32". It was placed 25·5' from the target, opposite No. 7 frame, and 9·25' below the surface of the water.
Effect of explosion:—Ship appeared to be lifted bodily. A rivet in the midship longitudinal bulkhead of fore compartment was loosened. The torpedo was fired from the ship, and the shock felt was not very great.
Torpedo:—47·2 lbs. of dynamite, in cylindrical steel case, no air space; height 12", diameter 12", and thickness 1/32". It was placed 25·5' from No. 5 frame, 9·25' below the surface of the water.
Effect of explosion:—Ship appeared to be lifted bodily. A leak was started in the outer bottom opposite to charge, caused by the loosening of five rivets.
Torpedo:—112 lbs. of gunpowder, rifle small grain, enclosed in cylindrical steel case placed inside an iron case, with an air space all round; steel case, 9-1/2" × 22-1/2" × 1/32"; iron case 33" × 25" × 1/4". It was placed 12' from No. 5 frame, 9·25' below the surface.
Effect of explosion:—Centre of ship lifted bodily, as if her back was broken; ship then rolled heavily to port. On board fire engines and troughs displaced several feet: shores and struts started, showing that the shock was considerable. The outer bottom on each side of thecentre dividing plate indented to a depth of 1 to 1-1/2 inches; numerous rivets started, and some sheared. The leak was considerable, owing to the number of rivets that were started. The strength of the plates was not considered to be materially affected by the indentations; the rivets, 239 in number, were replaced; and the target prepared for the next experiment.
Torpedo:—33 lbs. of dynamite, enclosed as in first experiment. It was placed 15' from No. 7 frame, 9·25' below the surface of the water.
Effect of explosion:—Ship rolled slightly to port. A bolt securing the midship transverse bulkhead to beam was sheared. No damage done to the target.
Torpedo:—66 lbs. of dynamite, enclosed in steel cylindrical case, no air space, 13·5" × 13" × 1/32". It was placed 21' from No. 3 frame, 9·25' below the surface of the water.
Effect of explosion:—A rivet in outer bottom, above water line at fore end of target, was sheared. A few rivets in outer bottom opposite charge, and two in after compartment, were started, but no leak was perceptible. Several shores slightly displaced.
Torpedo:—33 lbs. of dynamite, enclosed as in first experiment. It was placed 12·75' from No. 7 frame, 9·25' below the surface of the water.
Effect of explosion:—Ship not lifted as much as was the case in No. 3 experiment; but explosion much sharper. On board, fire engines were capsized, and vertical shores displaced. Outer bottom opposite charge indented to a depth of about 1/2 an inch, other parts less bulged, and many rivets started.
Torpedo:—33 lbs. of dynamite, enclosed as in first experiment. It was placed 4' from No. 4 frame, 9·25' below the surface of the water.
Effect of explosion:—Effect very great; ship hurled suddenly tostarboard. On going on board two minutes after the explosion, the fore compartment was found full, the after compartment became full ten minutes later. Shores and struts were considerably displaced, and there was evidence that the ship had sustained a severe shock. Outer bottom injured over an area 14' × 16', the plates being split in all directions; one piece, 5' square, was torn completely off, and an irregular hole was formed in the outer skin 14' × 12'. In the inner bottom below the wing passage bulkhead a piece 6' × 9' was blown completely out; the wing passage bulkhead was torn from the longitudinal frame and split from top to bottom. The inner skin above the upper longitudinal frame was torn from the latter, and forced in and upwards, but was not otherwise damaged. The vertical bracket frames Nos. 3 and 4, the latter opposite the torpedo, were destroyed, but the solid frame No. 5 was almost uninjured. The outer bottom, where it was not torn off, was forced in 7', or 4' beyond where theinnerbottom had been.
Torpedo:—660 lbs. of gunpowder, enclosed in a buoyant cylindrical 1/4" iron case. It was placed 32·3' from No. 4 frame, 29·25" below the surface of the water.
Effect of explosion:—The ship and target had been thoroughly repaired, and were in good condition when this experiment was made; the ship was in this case moored in 65 feet of water. No effect was produced on the target by the explosion.
Torpedo:—19 lbs. of dynamite, enclosed in a cylindrical steel case with arched ends. It was placed 10·5' from No. 3 frame, 9·25' below the surface of the water.
Effect of explosion:—Effect produced apparently equal to that by No. 3 charge of 112 lbs. of gunpowder at 12'; indentation being from 1/2 to 1-1/4 inches in the outer skin opposite the torpedo.
Torpedo:—19 lbs. of dynamite, enclosed in a case similar to that used in the 9th experiment. It was placed 3·3' from No. 7 frame, 9·25' below the surface of the water.
Effect of explosion:—Hole produced in outer skin, 6·5' × 2' to 5'; inner skin only bulged and slightly cracked in two places. Above the longitudinal frame, a bulge was made in the outer skin 8' × 7', with the above-mentioned hole; below the longitudinal frame the indentation was 14' × 5' and 2·1" deep, with two horizontal cracks 10' x 13', and several inches broad.
Torpedo:—112 lbs. of gunpowder, enclosed in a cylindrical case of 3/64" steel, placed in a 3/16" steel case, with 223 lbs. of buoyancy. Ignition effected by a glass igniting bottle. It was placed 5·75' from No. 5 frame, 9·25' below the surface of the water.
Effect of explosion:—There was but little upcast of water outside the ship, but a great upcast through the ship. She immediately lurched to starboard, and on boarding her five minutes after, the target was found full of water.
The effect on the target was as follows, above the 2nd longitudinal frame, where strengthened by the wing passage bulkhead:—Outer bottom blown away from the 4th to the 6th frames for a length of 8 feet and a height of 4-1/2 feet, and bent in 6-1/2 feet. Inner bottom bent in and broken through between the 4th and 5th frames, with an irregular hole 8' square, and between the 5th and 6th frames, a similar sized hole. Wing passage bulkhead was bent in 2" to 3", and riven for a length of 29'; in the water-tight middle bulkhead athwartships the rivets in two vertical joints were completely torn away.
Between the 2nd and 3rd longitudinal frames, and below the wing passage bulkhead, both the inner and outer bottoms were completely blown away for a length of 12 feet and a height of 4 feet. The vertical and horizontal frames between the two bottoms had kept their position unchanged, and excepting that the bracket plate by frame No. 6 was bent, cracked, and torn away, the damage they had sustained was limited to some comparatively slight bending. The open hole formed in the target measured 76 square feet in outer bottom, and 60 square feet in inner bottom.
Comparing the effect of this torpedo with the 7th, 33 lbs. of dynamite; with the latter charge the breach was made at the cost of the bottom plates as well as the vertical and longitudinal frames, which were completely torn asunder and strained; with the gunpowdercharge, only the bottom plates were broken through, whilst the plates whose directions were nearly parallel to the lines of explosive effect were but little affected.
Experiments at Portsmouth, England, 1874-75.—The object of these experiments was to ascertain the effect of 500 lbs. gun-cotton torpedoes exploded at various distances from a target representing the double bottom of H.M.S.Hercules.
They were carried out in Stokes Bay, under the supervision of officers belonging to the torpedo department of the Royal Engineers, and a torpedo committee, composed of naval and military officers.
TheOberon, the vessel chosen for these experiments, was fitted with a double bottom, representing as nearly as possible that of theHerculeswithout the armour; also with a surface condenser, and its connections; a donkey Kingston feed-valve; and athwartship water-tight bulkheads, which divided the ship into seven water-tight compartments. The outer skin was composed of 3/16" and 7/8" iron plates. In her starboard side at different points were fixed forty-four crusher gauges, and over each side were suspended six shots, each fitted with a crusher gauge.
Displacement of theOberonabout 1100 tons.
The ship was anchored head and stern. Her mean draught of water during the experiments was 11 feet.
Torpedo:—500 lbs. of gun-cotton, in discs saturated with water, and enclosed in an iron cylindrical case, 34" × 30" × 1/4", with arched ends; the primer consisted of two dry discs, and two detonators. It was placed 101' horizontal from the target, and opposite the condenser on the starboard side; 47' below the surface of the water, on the ground.
Effect of explosion:—No damage was done to the hull, or condenser, but light articles, such as bunker plates, gratings, tank lids, &c., were displaced.
Torpedo:—As in first experiment. It was placed on the ground, 80' horizontal and opposite the condenser on the starboard side, 48' below the surface of the water.
Effect of explosion:—No damage was done to the hull, of condenser,but the bunker plates, gratings, &c., were displaced to a greater extent than in the previous experiment.
Torpedo:—As before. It was placed on the ground, 60' horizontal, and opposite the condenser on the starboard side; 47' below the surface of the water.
Effect of explosion:—No damage was done to the hull. Flanges of the condenser inlet pipe were cracked, and several of the joint bolts were broken. The condenser had been thrown up bodily, and had torn away its holding down bolts; but it was not as well secured as it would have been had it formed part of the machinery of a ship.
Torpedo:—As before. It was placed on the ground, 50' horizontal, and opposite the condenser on the starboard side; 48' below the surface of the water.
Effect of explosion:—Outer bottom on starboard indented over a length of about 100', being forced in between the frames; maximum indentation, 3/4". Many bracket frames were disturbed, and outer angle iron of water-tight longitudinal was started for a length of 30', and made to leak slightly. The shell of the condenser was cracked in two places, 3' and 5' in length. Bolts securing condenser, and flanges of pipes and valves, were all more or less damaged. Condenser was rendered unserviceable.
Torpedo:—Same charge as before, but the primer consisted of four dry discs, and two detonators. It was placed 28·5' horizontal, opposite No. 9 frame, on the starboard side, 36' from the stern; 48' below the surface of the water, and 22' from the ground.
Effect of explosion:—Bow observed to be lifted several feet. Several angle irons and bracket frames were cracked, and numerous rivets in outer bottom were broken off. The outer bottom on the starboard side was indented between the frames, and brackets were disturbed over a space of 100 feet; inner bottom uninjured.
Torpedo:—As in previous experiment. It was placed on the ground, 28·5' horizontal, opposite No. 36 frame on the starboard side, and 30 feet from the stern; 49·5' below the surface of the water.
Effect of explosion:—Several plates in the outer bottom were cracked, and outer bottom made to leak in several places, owing to the fractures in the plates, rivets being started, and seams being opened. Considerably more damage was effected than in previous experiment, but inner bottom still remained uninjured.