To secure complete combustion some of the larger pellets are made with a central hole, or even pierced by many holes, so that the fire penetrates the entire ma.s.s and carries off all its explosive qualities.

Our _cordite_ consists of nitro-glycerine dissolving di-nitro cellulose by the acid of a volatile solvent and a mineral jelly or oil. This compound is semi-fluid, and being pa.s.sed like macaroni through round holes in a metal plate it forms strings or cords of varying size according to the diameter of the holes. Hence the name, cordite.

Many experiments in search of more powerful explosives resulted in an almost universal adoption of picric acid as the base. This acid is itself produced by the action of nitric acid upon carbolic acid, and each nation has its own fashion of preparing it for artillery.

The French began with _melinite_ in 1885, this being a mixture of picric acid and gun-cotton.

The composition of _lyddite_ (named from its place of manufacture, Lydd, in Kent) is a jealously-guarded British secret. This substance was first used in 5-inch howitzers during the late Soudan campaign, playing a part in the bombardment of Omdurman. The effect of the 50-lb. lyddite sh.e.l.ls upon the South African kopjes is described as astounding. When the yellow cloud had cleared away trees were seen uprooted, rocks pulverised, the very face of the earth had changed.

Several attempts have been made to utilise dynamite for sh.e.l.ls, some of the guns employing compressed air as their motive power. The United States some years ago went to great expense in setting up for this purpose heavy pneumatic plant, which has recently been disposed of as too c.u.mbrous. Dudley's "Aerial Torpedo" gun discharged a 13-lb. sh.e.l.l containing explosive gelatine, gun-cotton, and fulminate of mercury by igniting the small cordite charge in a parallel tube, through a vent in which the partially cooled gases acted on the projectile in the barrel. This was rotated in the air by inclined blades on a tailpiece, as the barrel could not be rifled for fear of the heat set up by friction. Some guns actuated on much the same principle are said to have been used with effect in the Hispano-American war. Mr. Hudson Maxim with his explosive "maximite" claims to throw half a ton of dynamite about a mile, and a one-ton sh.e.l.l to half that distance.

But even these inventors are outstripped by Professor Birkeland, who undertakes to hurl a projectile weighing two tons from an iron tube coiled with copper wire down which an electric current is pa.s.sed; thus doing away entirely with the need of a firing-charge.

IN THE GUN FACTORY.

Let us pay a visit to one of our gun factories and get some idea of the multiform activities necessary to the turning out complete of a single piece of ordnance or a complicated machine-gun. We enter the enormous workshop, glazed as to roof and sides, full of the varied buzz and whirr and clank of the machinery. Up and down the long bays stand row upon row of lathes, turning, milling, polishing, boring, rifling--all moving automatically, and with a precision which leaves nothing to be desired. The silent attendants seem to have nothing in their own hands, they simply watch that the cutting does not go too far, and with a touch of the guiding handles regulate the pace or occasionally insert a fresh tool. The bits used in these processes are self-cleaning, so the machinery is never clogged; and on the ground lie little heaps of bra.s.s chips cut away by the minute milling tools; or in other places it is bestrewn with shavings of bra.s.s and steel which great chisels peel off as easily as a carpenter shaves a deal board.

Here an enormous steel ingot, forged solid, heated again and again in a huge furnace and beaten by steam-hammers, or pressed by hydraulic power between each heating till it is brought to the desired size and shape, is having its centre bored through by a special drill which takes out a solid core. This operation is termed "trepanning," and is applied to guns not exceeding eight inches; those of larger calibre being rough-bored on a lathe, and mandrils placed in them during the subsequent forgings. The tremendous heat generated during the boring processes--we may recall how Benjamin Thompson made water boil by the experimental boring of a cannon--is kept down by streams of soapy water continually pumped through and over the metal. We notice this flow of lubricating fluid in all directions, from oil dropping slowly on to the small bra.s.s-milling machines to this fountain-play of water which makes a pleasant undertone amidst the jangle of the machines.

But these machines are less noisy than we antic.i.p.ated; in their actual working they emit scarcely the slightest sound. What strikes us more than the supreme exactness with which each does its portion of the work, is the great deliberateness of its proceeding. All the hurry and bustle is above us, caused by the driving-bands from the engine, which keeps the whole machinery of the shed in motion. Suddenly, with harsh creakings, a great overhead crane comes jarring along the bay, drops a chain, grips up a gun-barrel, and, handling this ma.s.s of many tons'

weight as easily as we should lift a walking-stick, swings it off to undergo another process of manufacture.

We pa.s.s on to the next lathe where a still larger forging is being turned externally, supported on specially devised running gear, many different cutters acting upon it at the same time, so that it is gradually a.s.suming the tapering, banded appearance familiar to us in the completed state.

We turn, fairly bewildered, from one stage of manufacture to another.

Here is a gun whose bore is being "chambered" to the size necessary for containing the firing charge. Further along we examine a more finished weapon in process of preparation to receive the breech-plug and other fittings. Still another we notice which has been "fine-bored" to a beautifully smooth surface but is being improved yet more by "lapping" with lead and emery powder.

In the next shed a marvellous machine is rifling the interior of a barrel with a dexterity absolutely uncanny, for the tool which does the rifling has to be rotated in order to give the proper "twist" at the same moment as it is advancing lengthwise down the bore. The grooves are not made simultaneously but as a rule one at a time, the distance between them being kept by measurements on a prepared disc.

Now we have reached the apparatus for the wire-wound guns, a principle representing the _ne plus ultra_ of strength and durability hitherto evolved. The rough-bored gun is placed upon a lathe which revolves slowly, drawing on to it from a reel mounted at one side a continuous layer of steel ribbon about a quarter of an inch wide. On a 12-inch gun there is wound some 117 miles of this wire! fourteen layers of it at the muzzle end and seventy-five at the breech end. Heavy weights regulate the tension of the wire, which varies for each layer, the outermost being at the lowest tension, which will resist a pressure of over 100 tons to the square inch.

We next enter the division in which the gun cradles and mounts are prepared, where we see some of the heaviest work carried out by electric dynamos, the workman sitting on a raised platform to keep careful watch over his business.

Pa.s.sing through this with interested but cursory inspection of the cone mountings for quick-firing naval guns, some ingenious elevating and training gear and a field carriage whose hydraulic buffers merit closer examination, we come to the sh.e.l.l department where all kinds of projectiles are manufactured. Shrapnel in its various forms, armour-piercing sh.e.l.ls, forged steel or cast-iron, and small bra.s.s cartridges for the machine-guns may be found here; and the beautifully delicate workmanship of the fuse arrangements attracts our admiration.

But we may not linger; the plant for the machine-guns themselves claim our attention.

Owing to the complexity and minute mechanism of these weapons almost a hundred different machines are needed, some of the milling machines taking a large selection of cutters upon one spindle. Indeed, in many parts of the works one notices the men changing their tools for others of different size or application. Some of the boring machines work two barrels at the same time, others can drill three barrels or polish a couple simultaneously. But there are hundreds of minute operations which need to be done separately, down to the boring of screw holes and cutting the groove on a screw-head. Many labourers are employed upon the lock alone. And every portion is gauged correctly to the most infinitesimal fraction, being turned out by the thousand, that every separate item may be interchangeable among weapons of the same make.

Look at the barrel which came grey and dull from its first turning now as it is dealt with changing into bright silver. Here it is adjusted upon the hydraulic rifling machine which will prepare it to carry the small-arm bullet (.303 inch). That one of larger calibre is rifled to fire a small sh.e.l.l. Further on, the barrels and their jackets are being fitted together and the different parts a.s.sembled and screwed up. We have not time to follow the perfect implement to its mounting, nor to do more than glance at those howitzers and the breech mechanism of the 6-inch quick-firers near which our guide indicates piles of flat cases to keep the de Bange obturators from warping while out of use. For the afternoon is waning and the foundry still unvisited.

To reach it we pa.s.s through the smith's shop and pause awhile to watch a supply of spanners being roughly stamped by an immense machine out of metal plates and having their edges tidied off before they can be further perfected. A steam-hammer is busily engaged in driving mandrils of increasing size through the centre of a red-hot forging.

The heat from the forges is tremendous, and though it is tempered by a spray of falling water we are glad to escape into the next shed.

Here we find skilled workmen carefully preparing moulds by taking in sand the exact impression of a wooden dummy. Fortunately we arrive just as a series of casts deeply sunk in the ground are about to be made. Two brawny labourers bear forward an enormous iron crucible, red-hot from the furnace, filled with seething liquid--manganese bronze, we are told--which, when an iron bar is dipped into it, throws up tongues of beautiful greenish-golden flame. The smith stirs and clears off the sc.u.m as coolly as a cook skims her broth! Now it is ready, the crucible is again lifted and its contents poured into a large funnel from which it flows into the moulds beneath and fills them to the level of the floor. At each one a helper armed with an iron bar takes his stand and stirs again to work up all dross and air-bubbles to the surface before the metal sets--a scene worthy of a painter's brush.

And so we leave them.

DIRIGIBLE TORPEDOES.

The history of warlike inventions is the history of a continual see-saw between the discovery of a new means of defence and the discovery of a fresh means of attack. At one time a shield is devised to repel a javelin; at another a machine to hurl the javelin with increased violence against the shield; then the shield is reinforced by complete coats of mail, and so on. The ball of invention has rolled steadily on into our own times, gathering size as it rolls, and bringing more and more startling revolutions in the art of war. To-day it is a battle between the forces of nature, controllable by man in the shape of "high explosives," and the resisting power of metals tempered to extreme toughness.

At present it looks as if, on the sea at least, the attack were stronger than the defence. Our warships may be cased in the hardest metal several inches thick until they become floating forts, almost impregnable to the heaviest sh.e.l.ls. They may be provided with terrible engines able to give blow for blow, and be manned with the stoutest hearts in the world. And yet, were a sea-fight in progress, a blow, crushing and resistless, might at any time come upon the vessel from a quarter whence, even though suspected, its coming might escape notice--below the waterline. Were it possible to case an ironclad from deck to keel in foot-thick plating, the metal would crumple like a biscuit-box under the terrible impact of the torpedo.

This destructive weapon is an object of awe not so much from what it has done as from what it can do. The instances of a torpedo shivering a vessel in actual warfare are but few. Yet its moral effect must be immense. Even though it may miss its mark, the very fact of its possible presence will, especially at night-time, tend to keep the commanding minds of a fleet very much on the stretch, and to destroy their efficiency. A torpedo knows no half measures. It is either entirely successful or utterly useless. Its construction entails great expense, but inasmuch as it can, if directed aright, send a million of the enemy's money and a regiment of men to the bottom, the discharge of a torpedo is, after all, but the setting of a sprat to catch a whale.

The aim of inventors has been to endow the dirigible torpedo, fit for use in the open sea, with such qualities that when once launched on its murderous course it can pursue its course in the required direction without external help. The difficulties to be overcome in arriving at a serviceable weapon have been very great owing to the complexity of the problem. A torpedo cannot be fired through water like a cannon sh.e.l.l through air. Water, though yielding, is incompressible, and offers to a moving body a resistance increasing with the speed of that body. Therefore the torpedo must contain its own motive power and its own steering apparatus, and be in effect a miniature submarine vessel complete in itself. To be out of sight and danger it must travel beneath the surface and yet not sink to the bottom; to be effective it must possess great speed, a considerable sphere of action, and be able to counteract any chance currents it may meet on its way.

Among purely automobile torpedoes the Whitehead is easily first. After thirty years it still holds the lead for open sea work. It is a very marvel of ingenious adaptation of means to an end, and as it has fulfilled most successfully the conditions set forth above for an effective projectile it will be interesting to examine in some detail this most valuable weapon.

In 1873 one Captain Lupuis of the Austrian navy experimented with a small fireship which he directed along the surface of the sea by means of ropes and guiding lines. This fireship was to be loaded with explosives which should ignite immediately on coming into collision with the vessel aimed at. The Austrian Government declared his scheme unworkable in its crude form, and the Captain looked about for some one to help him throw what he felt to be a sound idea into a practical shape. He found the man he wanted in Mr. Whitehead, who was at that time manager of an engineering establishment at Fiume. Mr. Whitehead fell in enthusiastically with his proposition, at once discarded the complicated system of guiding ropes, and set to work to solve the problem on his own lines. At the end of two years, during which he worked in secret, aided only by a trusted mechanic and a boy, his son, he constructed the first torpedo of the type that bears his name. It was made of steel, was fourteen inches in diameter, weighed 300 lbs., and carried eighteen pounds of dynamite as explosive charge. But its powers were limited. It could attain a rate of but six knots an hour under favourable conditions, and then for a short distance only. Its conduct was uncertain. Sometimes it would run along the surface, at others make plunges for the bottom. However, the British Government, recognising the importance of Mr. Whitehead's work, encouraged him to perfect his instrument, and paid him a large sum for the patent rights. Pattern succeeded pattern, until comparative perfection was reached.

Described briefly, the Whitehead torpedo is cigar-shaped, blunt-nosed and tapering gradually towards the tail, so following the lines of a fish. Its length is twelve times its diameter, which varies in different patterns from fourteen to nineteen inches. At the fore end is the striker, and at the tail are a couple of three-bladed screws working on one shaft in opposite directions, to economise power and obviate any tendency of the torpedo to travel in a curve; and two sets of rudders, the one horizontal, the other vertical. The latest form of the torpedo has a speed of twenty-nine knots and a range of over a thousand yards.

The torpedo is divided into five compartments by watertight steel bulkheads. At the front is the _explosive head_, containing wet gun-cotton, or some other explosive. The "war head," as it is called, is detachable, and for practice purposes its place is taken by a dummy-head filled with wood to make the balance correct.

Next comes the _air chamber_, filled with highly-compressed air to drive the engines; after it the _balance chamber_, containing the apparatus for keeping the torpedo at its proper depth; then the _engine-room_; and, last of all, the _buoyancy chamber_, which is air-tight and prevents the torpedo from sinking at the end of its run.

To examine the compartments in order:--

In the very front of the torpedo is the pistol and primer-charge for igniting the gun-cotton. Especial care has been taken over this part of the mechanism, to prevent the torpedo being as dangerous to friends as to foes. The pistol consists of a steel plug sliding in a metal tube, at the back end of which is the fulminating charge. Until the plug is driven right in against this charge there can be no explosion.

Three precautions are taken against this happening prematurely. In the first place, there is on the forward end of the plug a thread cut, up which a screw-fan travels as soon as it strikes the water. Until the torpedo has run forty-five feet the fan has not reached the end of its travel, and the plug consequently cannot be driven home. Even when the plug is quite free only a heavy blow will drive it in, as a little copper pin has to be sheared through by the impact. And before the screw can unwind at all, a safety-pin must be withdrawn at the moment of firing. So that a torpedo is harmless until it has pa.s.sed outside the zone of danger to the discharging vessel.

The detonating charge is thirty-eight grains of fulminate of mercury, and the primer-charge consists of six one-ounce discs of dry gun-cotton contained in a copper cylinder, the front end of which is connected with the striker-tube of the pistol. The fulminate, on receiving a blow, expands 2500 times, giving a violent shock to the gun-cotton discs, which in turn explode and impart a shock to the main charge, 200 lbs. of gun-cotton.

The _air chamber_ is made of the finest compressed steel, or of phosphor-bronze, a third of an inch thick. When ready for action this chamber has to bear a pressure of 1350 lbs. to the square inch. So severe is the compression that in the largest-sized torpedoes the air in this chamber weighs no less than 63 lbs. The air is forced in by very powerful pumps of a special design. Aft of this chamber is that containing the stop-valve and steering-gear. The stop-valve is a species of air-tap sealing the air chamber until the torpedo is to be discharged. The valve is so arranged that it is impossible to insert the torpedo into the firing-tube before the valve has been opened, and so brought the air chamber into communication with the starting-valve, which does not admit air to the engines till after the projectile has left the tube.

The _steering apparatus_ is undoubtedly the most ingenious of the many clever contrivances packed into a Whitehead torpedo. Its function is to keep the torpedo on an even keel at a depth determined before the discharge. This is effected by means of two agencies, a swinging weight, and a valve which is driven in by water pressure as the torpedo sinks. When the torpedo points head downwards the weight swings forward, and by means of connecting levers brings the horizontal rudders up. As the torpedo rises the weight becomes vertical and the rudder horizontal. This device only insures that the torpedo shall travel horizontally. The valve makes it keep its proper depth by working in conjunction with the pendulum. The principle, which is too complicated for full description, is, put briefly, a tendency of the valve to correct the pendulum whenever the latter swings too far. Lest the pendulum should be violently shaken by the discharge there is a special controlling gear which keeps the rudders fixed until the torpedo has proceeded a certain distance, when the steering mechanism is released. The steering-gear does not work directly on the rudder. Mr. Whitehead found in his earlier experiments that the pull exerted by the weight and valve was not sufficient to move the rudders against the pressure of the screws. He therefore introduced a beautiful little auxiliary engine, called the servo-motor, which is to the torpedo what the steam steering-gear is to a ship. The servo-motor, situated in the _engine-room_, is only four inches long, but the power it exerts by means of compressed air is so great that a pressure of half an ounce exerted by the steering-gear produces a pull of 160 lbs. on the rudders.

The engines consist of three single-action cylinders, their cranks working at an angle of 120 to one another, so that there is no "dead"

or stopping point in their action. They are very small, but, thanks to the huge pressure in the air chamber, develop nearly thirty-one horse-power. Lest they should "race," or revolve too quickly, while pa.s.sing from the tube to the water and do themselves serious damage, they are provided with a "delay action valve," which is opened by the impact of the torpedo against the water. Further, lest the air should be admitted to the cylinders at a very high pressure gradually decreasing to zero, a "reducing valve" or governor is added to keep the engines running at a constant speed.

Whitehead torpedoes are fired from tubes above or below the waterline.

Deck tubes have the advantage of being more easily aimed, but when loaded they are a source of danger, as any stray bullet or sh.e.l.l from an enemy's ship might explode the torpedo with dire results. There is therefore an increasing preference for submerged tubes. An ingenious device is used for aiming the torpedo, which makes allowances for the speed of the ship from which it is fired, the speed of the ship aimed at, and the speed of the torpedo itself. When the moment for firing arrives, the officer in charge presses an electric b.u.t.ton, which sets in motion an electric magnet fixed to the side of the tube. The magnet releases a heavy ball which falls and turns the "firing rod."

Compressed air or a powder discharge is brought to bear on the rear end of the torpedo, which, if submerged, darts out from the vessel's side along a guiding bar, from which it is released at both ends simultaneously, thus avoiding the great deflection towards the stern which would occur were a broadside torpedo not held at the nose till the tail is clear. This guiding apparatus enables a torpedo to leave the side of a vessel travelling at high speed almost at right angles to the vessel's path.

It will be easily understood that a Whitehead torpedo is a costly projectile, and that its value--500 or more--makes the authorities very careful of its welfare. During practice with "blank" torpedoes a "Holmes light" is attached. This light is a canister full of calcium phosphide to which water penetrates through numerous holes, causing gas to be thrown off and rise to the surface, where, on meeting with the oxygen of the air, it bursts into flame and gives off dense volumes of heavy smoke, disclosing the position of the torpedo by night or day.

At Portsmouth are storehouses containing upwards of a thousand torpedoes. Every torpedo is at intervals taken to pieces, examined, tested, and put together again after full particulars have been taken down on paper. Each steel "baby" is kept bright and clean, coated with a thin layer of oil, lest a single spot of rust should mar its beauty. An interesting pa.s.sage from Lieutenant G. E. Armstrong's book on "Torpedoes and Torpedo Vessels" will ill.u.s.trate the scrupulous exactness observed in all things relating to the torpedo depots: "As an example of the care with which the stores are kept it may be mentioned that a particular tiny pattern of bra.s.s screw which forms part of the torpedo's mechanism and which is valued at about twopence-halfpenny per gross, is never allowed to be a single number wrong. On one occasion, when the stocktaking took place, it was found that instead of 5000 little screws being accounted for by the man who was told off to count them, there were only 4997. Several foolscap letters were written and exchanged over these three small screws, though their value was not more than a small fraction of a farthing."

The cla.s.sic instance of the effectiveness of this type of torpedo is the battle of the Yalu, fought between the j.a.panese and Chinese fleets in 1894. The j.a.panese had been pounding their adversaries for hours with their big guns without producing decisive results. So they determined upon a torpedo attack, which was delivered early in the morning under cover of darkness, and resulted in the destruction of a cruiser, the _Ting Yuen_. The next night a second incursion of the j.a.panese destroyers wrecked another cruiser, the _Lai Yuen_, which sunk within five minutes of being struck; sank the _Wei Yuen_, an old wooden vessel used as a training-school; and blew a large steam launch out of the water on to an adjacent wharf. These hits "below the belt" were too much for the Chinese, who soon afterwards surrendered to their more scientific and better equipped foes.

If a general naval war broke out to-day most nations would undoubtedly pin their faith to the Whitehead torpedo for use in the open sea, now that its accuracy has been largely increased by the gyroscope, a heavy flywheel attachment revolving rapidly at right angles to the path of the torpedo, and rendering a change of direction almost impossible.

For harbour defence the Brennan or its American rival, the Sims-Edison, might be employed. They are both torpedoes dirigible from a fixed base by means of connecting wires. The presence of these wires const.i.tutes an obstacle to their being of service in a fleet action.