The torpedoes used by and against the different navies of the world may be classed under two general heads, viz., offensive and defensive.

Offensive torpedoes may be classified in accordance with the manner in which they are used, as Locomotive, Towing, Spar, and Drifting.

LOCOMOTIVE TORPEDOES.

The Whitehead Torpedo.

The Whitehead torpedo consists of a projectile, or more properly speaking a boat, containing a heavy explosive charge, an engine driven by compressed air, screw propellers, and mechanism for regulating the speed, depth of flotation, distance of run, and security of firing arrangements. The general exterior appearance of the torpedo is that of a spindle of revolution, its greatest diameter being in the middle and the lines being so curved as to present a surface of minimum resistance to the water. The dimensions of the torpedo range from fourteen feet in length by sixteen inches in diameter to nineteen feet by seventeen inches. The speed ranges from seven knots for a distance of eight hundred yards up to twenty-five and a quarter knots for two hundred yards, the most powerful combination being fifteen and a half knots for one thousand yards.

This torpedo, if adjusted to run at any desired depth of water of from five to fifteen feet, and if it be projected from either above water, at the water-line, or below the surface, will rapidly attain the desired depth and maintain it throughout the run. If fired in still water, it will make a straight run in the line of projection, allowance being made for the sweep of currents. It can be adjusted to stop after having run any distance up to its extreme range, and after stopping, it will sink, float, or explode as desired.

The gun-cotton charge is placed in what is termed a cartridge-case, which is a wooden case similar in shape to the forward section of the torpedo, somewhat smaller, and held in place in its compartment by wooden wedges. This charge is ignited mechanically, the arrangement being as follows: Extending from the nose of the torpedo to the cartridge-case is a tube terminating in a copper case, in which is placed the priming charge and the detonating composition; within the tube is a steel rod, two feet long, fitted with a needle-point at its inner end and having its outer end screwed into a frame; this frame is capable of moving in and out, and is connected with a spiral spring which tends to force it, and consequently the steel rod, inwards, the action being similar to that of the firing-pin of breech-loading small-arms. By compressing this spiral spring, the inner end of the frame is brought forward to a catch and held retracted. If now this catch is disengaged in any manner, the rod flies back, acting like an ordinary firing-pin on the detonating composition. The extreme forward point of the torpedo, called the nose-piece, is so fitted that it is capable of being forced inwards, but in a position of rest its inner edge is just clear of the catch. This nose-piece is provided with short horizontal and vertical arms, so as to insure good contact with the body struck. The collision of the nose-piece against any resisting body forces it back and releases the firing-pin. In order to secure against accident, the nose-piece is provided with a safety-wedge and key. Before discharging the torpedo the key is removed, and after the discharge the wedge is withdrawn by the action of mechanism, and is so arranged that it may be replaced automatically and thus disarm the torpedo after its run, in case it is desired to recover it.

The arrangement for adjusting the length of range and for drawing and replacing the wedge is as follows: Two cog-wheels, a large one and a small one, are fixed on the upper part of the after-end of the torpedo, just in front of the propellers. The small wheel has thirty teeth, gearing in an endless screw attached to the propeller-shaft, and of such a pitch that one revolution of the propeller moves the wheel one tooth. The big cog-wheel is so arranged as to move one tooth for each revolution of the small wheel. In front of this gearing is a small stud that works fore and aft in a slot, being provided with a spring which tends to force it towards the after-end of the slot. This stud is connected by a rod to the valve which admits the compressed air to the cylinders of the engine. When the stud is in the forward part of the slot the valve is open, in the after part it is closed. By means of a lever the spring of the stud is compressed, and the stud is moved to the fore part of its slot; the big wheel is then moved around until a stud on its face is the desired number of teeth above the lever. Now for every thirty revolutions of the propeller, or one tooth of the big wheel, a certain known distance is travelled, varying according to the pattern of the torpedo, slip, etc. When the propeller has made the number of revolutions corresponding to the desired length of range, the stud on the big wheel presses against the lever of the spring and releases the latter, forcing the valve-rod back and closing the valve. Attached to the axle of the big wheel is a small brass arm which is connected by means of a brass rod to the safety-wedge, and is so arranged that after any required number of revolutions of the propeller the safety-wedge will be drawn out; or it may be drawn out at the instant of discharge. By means of an additional lever at the fore port of the torpedo, which is connected by means of a rod to the valve of the engine, and by arranging the attachment of the safety-wedge to the brass rod from the big wheel so that on the wedge being withdrawn it is released from the brass rod, the action of the closing of the valve after the run of the torpedo is completed, forces the wedge into its securing position again.

Naturally the torpedo would float at the end of its run from its difference of buoyancy, owing to the compressed air used in working the engines.

To sink the torpedo at the end of its run, a spiral-spring valve is placed in the after wall of the adjustment chamber, which can be attached to the brass rod working the engine-valve in such a way that when the latter valve is closed the spring-valve is opened, admitting water to the chamber and thus sinking the torpedo. If it is desired to explode the torpedo at the end of the run, the nose-piece is connected to the engine-valve, which, on closing, draws it violently back and releases the firing-pin. To adjust the depth of flotation, a small wheel, the face of which is marked in feet, is placed in the adjustment chamber, and is turned by means of a key until the number of feet desired comes under a pointer.

The secret of the Whitehead is in the mechanism by which the torpedo maintains a desired depth. The adjustment chamber, which is next abaft the explosion chamber, is connected by screw to the forward and after chambers in such a manner that by means of a number of small holes bored around the circumference the faces of the chamber are exposed to the pressure of the outside water, which varies with the depth to which the torpedo descends. Within the adjustment chamber is an endless strong spiral spring, attached to the after face of the chamber, and so arranged that after being set to a certain tension, capable of resisting an equivalent pressure on the outside of the face, any increase or decrease in this pressure will cause this spring to work a rod by which the horizontal rudders of the torpedo are regulated. Within this adjustment chamber is also placed an automatic balance, which assists in maintaining the torpedo at the desired depth by swinging forward on the torpedo’s descending or aft on ascending, and thus assisting the rudders.

The Whitehead may be discharged through a submerged tube in the stern or in broadside, from a carriage above the water-line, or from the surface.

For discharging under water a tube is fitted to an orifice in the stern or broadside, closed by a water-tight valve; the inner end is closed by a water-tight door. The torpedo, being prepared, is placed in the tube, the door is shut, water is admitted to the interior, and the valve is opened. The torpedo is then shot out and started by means of a piston bearing against its rear end and worked by compressed air. To prevent it from slipping out before the time, a stop is provided at the forward end of the tube, which is removed automatically at the same time that the compressed air is admitted to the piston. In the case of broadside discharge, the tube works inside an iron casing, through a stuffing-box at the inner end and in a shield at the outer end. The shield, placed on the forward side of the orifice, is of such a length as to protect the torpedo from the pressure of the water passing the vessel.

In projecting from above water, an iron carriage is used, which is fitted with a frame in which the torpedo rests. The outer end of this frame is provided with a lip a few feet long, by means of which the rear end of the torpedo is slightly canted up on leaving the frame, preventing undue strain on the extreme end. The frame is mounted in the carriage in such a way that it can be elevated or depressed by means of a screw, like a gun. The torpedo is ejected by means of a piston as before, the carriage being provided with a small reservoir of compressed air so that it may be moved to any point aboard ship.

To project from the surface, no tube is necessary; all that is required is to set it for the depth, point it, and turn back the lever by hand, when it starts off of its own accord.

For discharging from boats, the torpedo is either mounted on its carriage forward or carried in iron slings suspended from davits. In the latter case the davits are pivoted, so that normally the torpedo rests in a cradle on deck; but the cradle being removed, the davits are swung over, lowering it to about two feet below water, where it is held securely until discharged.

The propeller is worked by means of a pair of Brotherhood engines, working to 60 indicated horse-power and giving 1000 revolutions a minute. Weight of charge, 33 lbs. gun-cotton; weight of torpedo, 500 lbs.

THE LAY TORPEDO.

The shape of the Lay torpedo is quite similar to that of the Whitehead, although it is considerably larger. As in the Whitehead, the forward section forms the explosion chamber. Next abaft this is a chamber for holding the gas reservoirs, carbonic-acid gas being the motive power. Next aft is the compartment for holding an electrical cable, which forms a constant connection between the torpedo and the operator. In rear of this is the compartment for the engines and steering apparatus. These sections are separated from each other by water-tight bulkheads. The torpedo is propelled by double screws, the propellers working in opposite directions and being placed one abaft the other, the shaft of the forward one being hollow and that of the after one passing through it. The torpedo has four horizontal fins or wings, two forward and two aft; these wings are mounted on shafts or spindles passing transversely through the boat. A guide-rod or short staff is provided at each end of the torpedo to enable the operator to regulate the course. At night lanterns are hung on these rods. The electrical cable, made up of two insulated wires, is wound on a reel, and pays out through a hole in the bottom of the compartment as the boat advances. By means of one of these wires the boat is started, stopped, and steered, and by the other it is fired.

A double steering-rudder is used, one half being above and the other below the line of the propellers; these rudders are worked by means of a small auxiliary, engine, which is started, stopped, and reversed by means of the electrical current. The current passing in one direction starts the engine ahead, putting the helm to starboard. If the current is broken, the engine stops and the rudder swings amidships. The current passing in the opposite direction reverses the engine and puts the helm to port.

In the firing circuit there are two resistance-coils, one in the boat and one by the operator; the charge may be fired through either one of the coils, but not through both. When the nose of the torpedo strikes a resisting object the coil in the boat is cut out of circuit and the charge is exploded. If the operator desires to fire before striking, he can at any moment cut the coil near him out of the circuit and thus fire.

The propelling engines have a throttle-valve which controls the admission of gas from the reservoirs to the cylinders, the valve being in connection with a balanced lever. The current passing one way draws down one end of the lever, opening the valve, and passing the other draws the other end down, closing it.

In one modification of this torpedo the forward compartment or magazine is made detachable, so that on striking an object it breaks adrift and sinks a short distance before exploding, thus gaining the best depth of water. In launching these torpedoes from a vessel, a tube is provided opening below the water-line and being provided with a forward water-gate and a rear loading-door. The torpedo being put in place, the rear door is closed, the gate raised, admitting the water, and the torpedo launches itself after the engine is started. In order to sink or raise the boat, a water-chamber is supplied having a valve for admitting outside water and another for the admission of gas. By sending a current one way, the water-valve is opened and water is admitted until the torpedo is sunk to the required depth. By sending the current the other way, the gas-valve is opened and the pressure of the gas forces the water out and the torpedo rises.

The Lay torpedo may be used for clearing river obstructions, by laying out small charges in any position or by dragging a grapnel. In the latter case, an exploding charge is attached to the upper end of the grapnel-chain. When the grapnel holds fast to any obstruction the operator is notified, and by means of an electrical current he detaches the charge, which slides down the grapnel-chain and explodes at the obstruction, blowing it away.

TOWING TORPEDOES.

The Harvey Torpedo.

The general form of the Harvey torpedo is that of a box of a rectangular vertical and trapezoidal horizontal section, intended to float on end and tow at an angle from the ship’s keel. The case is generally made of copper or Muntz’s metal sheathed with wood; the upper inner edges being provided with shackles for attaching a towing-span. The body of the torpedo is also the magazine, large enough to hold from 33 to 58 lbs. of gun-cotton. The firing-bolt with its fuse attachment enters the magazine from the middle of the top or deck of the torpedo. This bolt is acted upon by a series of levers so arranged that if the torpedo strikes in any position, one of the levers will drive the bolt down and explode the fuse. In the later patterns of Harvey torpedoes there is also a small rudder attached, by which the course of the torpedo is regulated when the tow-rope is suddenly slacked. The sling is made with four legs going to the corners of the torpedo and of a length to bring the centre of effort in the right position for towing the torpedo at a good angle of divergence. The firing-bolt is so arranged that the torpedo may be fired in three different ways: electrically on contact, mechanically on contact, or electrically at will. The mechanical arrangement is an ordinary chemical fuse placed in the firing-bolt in connection with a small vial of sulphuric acid. When the firing-bolt is forced down by the contact of the levers with any resisting substance, the vial is broken by coming in contact with a stout needle and the acid ignites the fuse. For firing electrically at will, a platinum-wire fuse is used; one terminal going to earth at the torpedo, and the other passing through the firing-bolt and attaching to the insulated wire core of the tow-rope leading aboard ship. To fire on contact electrically, a resistance-coil is introduced in the circuit at the fuse in such a manner that by forcing the firing-bolt down the resistance-coil is cut out of the circuit and the fuse is fired by the short circuit.

The firing-bolt is fitted to act with a pressure of from 30 to 40 lbs. on its head, and under ordinary circumstances is secured by a key in the ordinary manner of keying bolts. If these torpedoes are left to sink of themselves, they will explode at a depth of about 60 fathoms from the pressure of the water on the head of the bolt.

In order to hold the torpedo steady when towing, it is provided with cork buoys which tow astern of it. The buoy-rope is rove through a ring at the after-end of the torpedo, and has an eye spliced in its end to which the tow-rope knots after reeving through the eye of the sling.

The firing-bolt key has a small line attached to it by which it is withdrawn whenever desired after the torpedo has been launched. The tow-rope coming from the torpedo reeves through a leading-block on a spar lashed about 25 feet above the deck, and, coming inboard through another leader, passes to a reel secured on deck and controlled by friction-brakes.

To launch this torpedo, it is hoisted by its tow-rope clear of the side, and the rope then being rapidly veered until the torpedo strikes the water and then gradually checked, it diverges at once. Veering then slowly, the torpedo takes its position at an angle of about 45° from the ship’s side. In attacking a vessel, when the torpedo has been towed to within a short distance of the desired point, the tow-rope is rapidly veered and the torpedo dives; checking the rope, it rises almost immediately, and at a very sharp angle bringing up against the vessel’s bilge. In case it becomes necessary to get rid of the torpedo, the tow-rope is cut at the reel and unreeves and the torpedo sinks. There are two rings for reeving the buoy-rope through, a large one and a small one. If the rope is rove through the large ring, the torpedo is lost when the tow-rope is cut; if rove through the small ring, the knot connecting the buoy-rope and the tow-rope brings up against it, and the torpedo is held up and buoyed the length of the buoy-rope below water. In securing the torpedo after the key has been withdrawn from the firing-bolt, a pair of tongs is used to grasp the bolt and keep it from being forced down.

The Menzing Towing Torpedo.

This is a modification of the Harvey, used in the German service, intended to overcome objections to the original in regard to facility of use. The general shape is slightly different, the forward end being wedge-shaped so that the torpedo may be towed on either side. This torpedo has two tow-ropes, each rove in a similar manner. The ends of the ropes are provided with two legs which are made fast to the after-end of the torpedo, where is a small rudder, the ropes coming to it and acting on it in such a manner that when a strain is brought on one it turns the rudder in the opposite direction. Secured to the bow of the torpedo is a crane, having at its end an eye through which the main part of both tow-ropes reeves. If it is desired to tow on the starboard side, the starboard tow-rope is slackened, bringing the entire strain on the port one; the crane at the bow of the torpedo swings around by the strain until it brings up against a knot at the splice of the legs, thus forming with the legs a complete bridle; the divergence of the torpedo is at the same time assisted by the action of the rudder. Levers for firing mechanically are applied in much the same manner as in the Harvey. A circuit-wire for electrical firing and buoys for steadying the torpedo are also used. By these arrangements the torpedo may be towed astern until required for use, and then by slacking the necessary tow-rope it may be swung out on either quarter desired.

The French Towing Torpedo.

This torpedo is in the shape of a long box tapered at the forward end. It is made of wood, with a cork bow, the powder-chamber being hung between the cork and the main body in such a manner that it may be detached automatically. This is secured by a bolt projecting from the top of the powder-case, whose head is held by a movable plate. The slot in the plate through which the bolt-head passes is larger than the bolt-head, so that when the plate is knocked back the bolt slips through and the magazine is detached. Two curved whiskers project forward from the plate as contact-points. In order that the torpedo may be exploded at the proper depth, two shafts are pivoted to the bottom of the float and attached to the magazine. When the latter is detached it drops down the full length of the shafts (9 feet below the surface), and on reaching that position the electrical circuit is closed and the charge is fired automatically. To fire the torpedo at will, a miniature gun is mounted on the after-part of the plate, which is fired by electricity; the recoil draws the plate back and thus releases the chamber. The magazine of this torpedo holds 33 lbs. of dynamite.

SPAR-TORPEDOES.

The American Torpedo.

American spar-torpedoes are of two general forms. The first, for gunpowder charges, is in the shape of a long cylinder with hemispherical ends. The second, for dynamite charges, is in the shape of a large double convex lens. The powder torpedoes have a capacity for a charge of from 75 to 100 lbs. of small-grain powder; the dynamite ones have a capacity of from 15 to 30 lbs. In the gunpowder torpedo a large hollow spindle passes through the axis, closed and secured at one end by a large nut. This spindle is pierced with flame-holes at short distances, so as to permit the flame from the fuse to penetrate and ignite all parts of the powder-charge at once. Around this spindle is a guard of wire gauze to prevent the powder from the charge sifting into and choking the flame-passages. This spindle projects some little distance beyond the inner end of the torpedo-case, forming a handle or support by which the case is attached to a spar. At the inner end on each side of the spindle is a loading-hole secured by nuts and washers. There are also four handles, two on each side of the case, for convenience in transporting. The 100-pdr. torpedo loaded and fused weighs about 360 lbs. The torpedo-fuse, which is an electric one, finds a place by itself inside the spindle, the terminal wires passing through a simple water-tight gland.

On the end of the torpedo-spar is lashed a cast-iron sleeve into which the end of the spindle is keyed. The torpedo-spar for use on the bows or broadsides of vessels varies in length from 20 to 50 feet, and is supported and pointed by guys and lifts in the same manner as is common with swinging spars generally. The wires from the fuse are brought in along the spar to the electrical machine and firing-keys arranged in suitable positions.

The spars used in boats are generally arranged on a different principle from those attached to the bows or beams of high-sided vessels. Arranged to work in a swivelled sleeve with a martingale at the rear end to regulate the depth to which they shall sink, the spar is either launched or dropped over and is permitted to swing without guys, the operator watching and exploding it as it is brought abeam and into the desired position by the driving ahead of the boat.

The spar used with the dynamite torpedo is an iron or steel bar of diminished cross-section in order to offer a minimum resistance to the water, with a hinged piece at its rear end bolting to the keelson of the boat and acting as a martingale.

TORPEDO VESSELS.

In several of the navies of the world gun-boats have been designed for the purpose of using torpedoes, either locomotive or spar, to the total exclusion of battery—or, in some cases, with a limited artillery—fire.

Pietro Micca (Italian).

This vessel, having a displacement of about 530 tons, is built very low in the water, with a curved deck or cover, and is not armored except as regards a deck under the curved cover and over the engines, intended to resist the penetration of plunging projectiles, and which is of laminated steel 2¼ inches thick. Her estimated speed is 18 knots, and she is provided with tubes for discharging Whitehead torpedoes ahead, abeam, and astern.

Rau (Swedish).Ziethen (German).

Vesuvius (English).Uzreef (Russian).

Whitehead torpedo gun-boats of from 400 to 700 tons displacement and an estimated speed of from 13 to 16 knots. The peculiarity of the Vesuvius is in having an elbowed smoke-stack carried along the deck. The Rau carries a light rifled gun. All carry machine-guns.

The Alarm (American).

The Alarm is an iron ram gun-boat, built on the transverse bracket system, with a double bottom and water-tight bulkheads every 25 feet. Her dimensions are: length, 173 feet; beam, 28 feet; draft, 11 feet—which may be increased by sinking the vessel to the level of the upper-deck beams, arrangements having been made for the admission and ejection of water in the compartments formed by the double hull. The torpedo system of this vessel consists of three hollow steel tubes, one projected from the end of the ram a distance of 30 feet, and one from each broadside, 17 feet. These tubes slide in and out on frames, and are worked by small auxiliary engines and winches; the torpedo is fitted to the end of the spar and is fired by electricity. The port from which the spar is projected, being below the water-line, is provided with a water-box and double doors and heavy rubber washers, which grip the spar water-tight as it is run out.

In addition to the torpedo system, this vessel is arranged to carry a 10-inch rifle forward. Her ram is strengthened, and her bow is protected for some distance by a plating of 4½ inches. On her rail she carries machine-guns to resist the attack of torpedo-boats. Her propeller is of a novel pattern, serving as steering-gear and propelling power. This vessel was originally fitted with a propelling apparatus known as the Fowler steering-wheel, a novel propeller which both gave the vessel headway and steered her. The blades of the propeller were worked by means of a simple steam-valve arrangement manipulated by the helmsman. The steering qualities with this apparatus were little short of marvellous, as she could be driven and steered with as great facility astern as ahead, and could even be worked sideways. Her speed, however, was deficient, never reaching ten knots. At present the vessel has been fitted with the Mallory steering propeller, a form of screw with a jointed shaft so that it may be revolved about a vertical axis. This screw promises to give a speed more nearly warranted by the fine lines of the vessel.

The Intrepid (American).

This vessel is a gun-boat of about the dimensions of the Alarm, having a short, heavy ram bow and an armored belt at the water-line of five inches thickness all around. Her load draft brings her upper deck to within three feet of the water-line. This vessel carries no armament except a few Gatling guns on the rail, and her torpedo system consists of four ordinary swinging-spar torpedoes, two on each beam. Ordinarily these spars lie in crutches alongside, and they are manipulated by topping-lifts and guys in the ordinary way. The torpedoes are exploded by electricity.

The Destroyer (American).

This vessel is 130 feet long by 12 feet beam and 10 feet draft, built with a straight bow, bow and stern lines being the same and very sharp. She has no upper-deck rail, this deck being very low, with a long superstructure rising amidships. There are no openings in the sides of this superstructure, so that if desirable the vessel may be run with her upper deck completely under water. Thirty-two feet from the bow a heavy armored bulkhead crosses the vessel, inclined at a vertical angle of 45°, and intended as a thorough protection to the engines and boilers, enabling the vessel to approach bows on with impunity. Her armament consists of a bow-torpedo, which is projected from a tube in a manner not unlike the firing of a projectile from a gun. This torpedo consists of a solid block of light wood having inserted in its forward end a heavy bursting-charge in a steel case. The transverse section of this torpedo is square; longitudinally it is a rectangle with sharpened ends. Ignition of the charge is obtained by means of a percussion fuse. To project this torpedo, it is inserted in a tube provided with water-gates, fixed in the bow of the boat just above the keel. A steam piston-rod fits against the after-end and pushes the torpedo out with a velocity sufficient to send it at least 100 feet. The weight of the torpedo is about 1400 lbs. This vessel has been tried, but the system is not yet perfected.

The Uhlan (German).

This vessel is of a novel type, consisting of two separate hulls, one within and abaft the other, the intervening space being filled with cork. She carries affixed to a ram which projects ten feet forward from the stem a dynamite contact torpedo. Arranged to travel at a high speed, the idea is to carry her at full speed against the enemy, the crew finding refuge on a small raft which she carries and which is detached just before her striking. It is not expected that the main hull, in which are the engines and steering-gear, will be injured by the explosion. The raft, it is understood, is not completely detached from the vessel, but a long tow-line is paid out rapidly, and after the explosion of the torpedo the crew haul alongside and take the boat clear ready for another attack.

TORPEDO-BOATS.

The Thornycroft Torpedo-Launch.

This boat is built to combine great speed with a moderate seaworthiness and resisting power. The dimensions range as follows: length, 57 to 85 feet; beam, 7½ to 10 feet; draft, 3 to 4 feet. They are built of steel of an average thickness of ³/₁₆ an inch, being completely decked over. Generally they are divided into six separate water-tight compartments. The forward and after ones are store-rooms; the second one is arranged for the accommodation of the crew; the third is the pilot-house; fourth, engine and fire room; and fifth, for the accommodation of officers. The single-screw shaft projects some distance beyond the stern-post to allow the double rudder to work forward of it. The screw itself is of a peculiar construction, so built as to project the water straight aft instead of radially. These launches are fitted for either spar or Whitehead torpedoes. In the former case the swivelled sleeve in which the spar works pivots abreast the pilot-house. In the latter case two methods are in use. By one, a Whitehead is carried on deck on each side mounted on a carriage running on rails, by which they may be run up to a firing-case on the forward part of the deck. This firing-case is mounted on a pivot-carriage and has depressing-gear, so that the torpedo may be pointed in any desired direction. A pointing apparatus is provided in the pilot-house by means of which allowance of angle may be made for the movements of the boat or of the attacked vessel. The pivot-circle is graduated so that the torpedo may be correctly aimed with but little difficulty. By the other arrangement, a Whitehead is carried on each side on pivoted davits in a sling, so that it may be lowered into the water; the machinery is then started by hand, and the torpedo moves off without being projected. In this case the torpedo can only be fired right ahead.

The Yarrow Torpedo-Boat

This is a launch of the same general construction as the Thornycroft, although a higher rate of speed is attained by this type, and there are several important modifications. The fire-room, or stoke-hole, is completely separated or bulkheaded off from the boiler, except the front part, so that in case the boiler collapses or is pierced by a shot there is no danger of scalding the crew. The pilot-house is placed aft in the compartment occupied by the officers. There is no visible smoke-stack. Two ports are cut in the sides of the launch, one on each side, and the products of combustion may be carried through either or both. The ports are provided with valves, which are held open by the force of the blast, but which close immediately if struck by a wave. The helmsman can direct the smoke through either port, so that in approaching a vessel the one on the side next to her is closed and the smoke through the other port is partially masked by the side of the boat. When running in a seaway both these ports may be closed, and a temporary smoke-pipe is shipped in the usual place.

These boats are provided with a rudder at each end, both rudders being operated by the wheel at the same time. The forward rudder may be drawn up into a well, if desired, or in case that it gets fouled it can easily be dropped overboard. These boats have attained in smooth water a speed of 22 knots an hour. The torpedo arrangements are similar to those of the Thornycroft. Above 18 knots there is no noticeable vibration of the frame.

The Herreshoff Torpedo-Boat.

The general type of hull is the same as that of the Yarrow and Thornycroft, except that it is of composite construction, having a steel frame with wood planking below water and steel above. The propeller is a single two-bladed screw, placed under the keel just abaft the middle of the boat, the hollow steel screw-shaft being put in on a curve. The rudder is of the balanced type, and is suspended underneath the after-part of the keel. The pilot-house is abaft the smoke-pipe. The boiler of this boat is of a novel character. It consists of a cylindrical combustion chamber about 4 feet in diameter, within which is a spiral coil of about 300 feet of two-inch pipe. This coil is continued at the top so as to form a kind of dome under the cover of the combustion chamber. By the side of the boiler is a separator into which the steam passes before it goes to the engine. The water from the feed-pump is admitted at the top of the coil, and during its course to the bottom the greater part of it becomes converted into steam. Having passed through the entire length of the coil, the steam and water are discharged together into the separator, in such a manner that the water is entirely separated from the steam and can be blown off as required. The steam is taken from the top of the separator and returns through a short coil placed inside the combustion chamber, where it becomes superheated and is led thence to the engines. By means of this boiler a good working pressure can be obtained in about five minutes from the time of lighting the fires. This boat may be rigged to carry either the Whitehead or the spar torpedoes. Its speed is about 18 knots, equal to that of the Thornycroft.

SHIPS’ BOATS.

Steam-launches are at present, as a rule, fitted with spar or Whitehead torpedo-gear of a general and simple type. It is not intended that these boats should be classed as fighting torpedo-boats, as they lack the requisite speed and protection, and, as a rule, are too noisy to be of use except in a general or concentrated attack. Such boats find their greatest sphere of usefulness in clearing channels of obstructions and countermining. For the former work many are now provided with electrical valve-gear and steering apparatus, by which they may be controlled from a boat towed some distance astern, as in the manipulation of the Lay torpedo.

SUBMARINE BOATS.

At different times during the development of torpedo warfare there have been many attempts to construct and perfect submarine boats of different types, but in no case has an attempt to use one been successful. The United States corvette Housatonic was sunk off Charleston Harbor in 1864 by a submarine torpedo-boat, but there are excellent reasons for believing that she was at the time of the attack used as an ordinary surface-boat with a bow-torpedo on a spar. In most cases the boats used, or rather designed, have been propelled by hand-power, their rate of speed being very low. Attempts are being made in all countries to perfect some form of submarine boat, and, judging from the experimental success attained heretofore, it is fair to suppose that some type will finally prove successful, although in any case its use would be extremely limited.

DRIFTING TORPEDOES.

Torpedoes of this description have been used in great numbers in time of war, but only with indifferent success. The especial function of the drifting torpedo is the destruction of vessels lying at anchor, the torpedo being sent adrift at a convenient point and allowed to float either at the surface or by means of a buoy at some distance below, and by the action of the current to be carried into contact with the vessel, being exploded by a contact-fuse. There is no especial shape considered superior for this type, and generally the torpedoes are extemporized from the most convenient materials at hand. Of the many types that have been tried there are two which may be considered especially dangerous.

The first of these is a torpedo intended to be dropped by a vessel being chased, to be caught by the one in her wake. This type may be described in general as two torpedoes of a size sufficient to contain 20 or 30 lbs. of dynamite, connected by a rope or light chain bridle, and floated by flat water-colored buoys. Dropped from the stern of a vessel, the bridle is caught by the bow of the chaser, and the torpedoes being swept alongside explode against the bilges.

Lewis’s Drifting Torpedo.

This torpedo, intended to reach a vessel at anchor and surrounded by a boom of logs, consists of a case of powder or dynamite resting loosely on a small shelf attached to one extremity of a heavy pine beam, ballasting it in such a manner that it will float on end with the top just above water. The torpedo is attached to the beam by a loose chain bridle, the ends of which are stapled respectively to the lower end and just above the centre of gravity of the beam. The shelf itself is hinged, and is held in position by a catch operated by a small bell-crank lever on top of the beam. This beam on coming in contact with a boom is canted slightly, and the lever being tripped the shelf drops from under the torpedo, which, hanging by its bridle, cants the beam almost horizontally, thus allowing it to slip under the boom and float on against the ship’s side, where the torpedo explodes on coming in contact.

DEFENCES AGAINST OFFENSIVE TORPEDOES.

Vessels at anchor in protecting themselves against torpedoes establish three separate lines of defence. The outer line consists of guard-boats; the boats of the ship, either carrying machine and boat guns or having their crews armed with rifles, patrolling the approaches to the ship at such a radius as may be well guarded by the number of boats employed. The second line consists of a boom of logs or spars arranged around the ship at a distance of from twenty to fifty feet, having in addition, wherever practicable, heavy nets which hang down below the level of the keel. The third and inner line consists of the machine-guns and small-arms of the crew, the double hull and compartment construction of the vessel itself, and powerful electric lights which at intervals sweep the water in the vicinity of the vessel, lighting up every approaching object.

DEFENSIVE TORPEDOES.

Torpedoes of this class may be described generally as being either heavy cases of explosive material resting on the bottom of shallow channels and fairways, and usually exploded at will by electrical fuses, or smaller torpedoes anchored and either buoyed or supported at from three to twelve feet below the surface. The first class of torpedoes is of crude and varied construction, being simply heavy cases of boiler-iron of a capacity for from 100 to 200 lbs. of dynamite or 1000 to 2000 lbs. of powder, caulked water-tight and sunk generally within easy range of a heavy battery, in a position where a vessel would probably stop or anchor to open fire, or else in a shallow channel where a ship must pass directly over it.

The buoyant torpedoes are of different form; the most successful types being

The Frame-Torpedo.

This consists of a row of heavy beams planted across a channel similar to a “chevaux de frise.” The inner ends of the beams are securely anchored to the bottom, the latter giving them a support when they are ran into. The outer ends carry each a single torpedo shaped like a large rifled shell and holding from 60 to 100 lbs. of powder; bolted to it so that the tops of the torpedoes are about eight or ten feet below water. These ends are moored so as not to swing about too much in the current. Just under the outer ends a frame is constructed to support the beams in case they get waterlogged. Contact-fuses are used with these torpedoes, and the whole arrangement serves the double purpose of acting as a torpedo and as a construction defence. These beams are also used singly in many cases.

Brooks’s Torpedo.

This form of torpedo is intended to baffle attempts at removal by sweeping with drags and grapnels. The beam used in this case is of a length sufficient to allow the top of the torpedo to be at the proper distance below water when it is vertical. The heel of the spar is shod with a pointed iron casing having a ring in the end connected to an anchor-shackle, the anchor being completely buried. In this manner the beam is free to oscillate. The torpedo, which is conical with a dome cover, ships on the upper end of the beam, all sharp corners and edges where a rope or grapnel might catch being avoided. In the top of the torpedo are placed five contact-fuses. In order to make this torpedo still more difficult of removal, it is placed in connection with a heavy ground-torpedo called a turtle-back in such a manner that any attempt to remove it from its berth causes the explosion of the turtle-back.

Singer’s Torpedo.

This torpedo contains an air-chamber in the upper part, whilst all the lower portion is devoted to the charge, varying in weight from 50 to 100 lbs. of powder. On top of the case is a heavy conical iron cover loosely secured, so that if the torpedo is struck a violent blow or is canted well over it will fall off. This cover is secured by a wire to a mechanical fuse (there are several different types) in such a way that the jerk given to the wire when the cover falls off will explode it.