Torpedo, a machine for destroying hostile shipping, ponton bridges, etc, through the agency of subaqueous explosions; that is, a military mine used under water. The germ of the device is to be found in floating powder vessels, which were first used at the siege of Antwerp in 1585, and received their latest application in the attempt upon Fort Fisher, N. C, during the late civil Avar. David Bushnell, a captain of engineers in the American revolutionary army, made the first practical application of the idea to ordinary warfare. He devised a submarine boat to carry a torpedo, charged with 150 lbs. of gunpowder, to be attached by a wood screw to the bottom of an enemy's vessel, and fired by a clockwork fuse. The first actual trial of the invention was made in 1776, when the boat, under the guidance of Sergeant Ezra Lee, was placed under the bottom of the Eagle, an English ship of war carrying the flag of Lord Howe, lying at anchor in New York harbor. But the sergeant found it impracticable to attach the torpedo, which was cut adrift, and soon exploded. In 1777 Capt. Bushnell directed a drifting percussion torpedo against the frigate Cerberus, lying off New London, and it destroyed a schooner moored alongside.

Similar torpedoes were set adrift on the Delaware, but did no harm. (See Bushnell, David.) Twenty years later Robert Fulton made vigorous attempts to bring the new weapon into notice, under the name of "torpedo," then first applied by him. Unsuccessful in France, he went to England in 1804, and in 1805 was authorized to make an attempt to destroy the French fleet at Boulogne, which proved unsuccessful. In the same year he blew up the brig Dorothea, assigned to him for experimental trial, in the harbor of Deal. This was accomplished by two drifting torpedoes, which, connected by a rope, fouled the hawser; and one of them, charged with 170 lbs. of powder, exploding by clockwork under her bottom, utterly destroyed her. Notwithstanding this triumph, motives of policy, resulting from their sovereignty of the sea, caused Fulton and his new weapon to be rejected by the English government; and he returned to America to encounter ultimately a like repulse, although in 1807 he repeated his experiment successfully in the harbor of New York. Fulton's system included four classes of torpedoes : buoyant mines, held in place by anchors, and provided with a mechanical device by which explosion ensued when they were struck by a vessel; line torpedoes, of the kind used in the destruction of the Dorothea; harpoon torpedoes, to be attached to the enemy's vessel by a harpoon shot from a gun, and then to be exploded by clockwork; and lastly " block-ship " torpedoes, to be carried on spars projecting from a peculiar kind of vessel, and exploded by contact with the enemy.

Just before the close of the war of 1812 preparations were made for an extended use of torpedoes in the defence of our harbors. Col. Samuel Colt first practically applied electricity to the ignition of torpedoes. After experimenting for 14 years, and blowing up several vessels at anchor, he finally, on April 13, 1843, destroyed a brig under full sail on the Potomac, operating by electricity from a station in Alexandria, 5 m. distant. He elaborated a complete system of buoyant submarine mines, which were to be planted in groups quincuncially in the channel to be defended. To connect them with the shore he devised one of the very first insulated cables ever attempted, which was connected with a platinum wire fuse imbedded in a priming of gunpowder. He proposed to arrange a reflector to throw the image of the ship upon a map of the mines at the operator's station. This project, bearing the date of 1836, was discovered among Colt's papers after his death. Although much progress was made in submarine blasting, and an elaborate system of electrical submarine mines was prepared by Capt. Hennebert of the French engineers, no opportunity offered for the further use of torpedoes until the Anglo-French war with Russia. In 1855 a new kind of contact mine, devised by Jacobi, was planted off Cronstadt and at Sebastopol; explosions occurred under the frigates Merlin and Firefly, but did no serious damage.

The Jacobi fuse consisted of a little bottle of sulphuric acid bedded in a mixture of potassium chlorate and sugar. This bottle being broken by the shock, an explosion ensued, which communicated with the charge and ignited the mine. Had not this engineer employed too small charges of powder (8 or 9 lbs.), his success would probably have been more marked. His system included electrical mines as well as mechanical. The destruction of the docks at Sebastopol was effected by the French engineers through the agency of submarine explosions, and the attention of all nations was thus again called to the subject. The result appeared in the defence of Venice in 1859 by Col. Von Ebner of the Austrian engineers, who originated a system more complete than any which had preceded it. During the civil war in the United States, when the confederates had no fleet, the southern ports and rivers were much exposed to attack, and this method of defence was largely used. The first torpedoes in position were discovered in Mud river, near Fort Pulaski, in February, 18G2; they belonged to the simple contact class, and occasioned no damage.

In October, 18G2, the service was formally legalized by the confederate congress, and a torpedo bureau was soon established at Richmond. A special corps of officers and men was raised and trained for submarine warfare; inventions multiplied, and agents were sent to Europe to provide material and get the latest ideas. The southern waters soon became so dangerous as to interfere seriously with naval operations. The first vessel actually blown up by the new machines was an ironclad, the Cairo, which was totally destroyed on Yazoo river in December, 1862. During the remainder of the war seven United States ironclads, eleven wooden war vessels, and six army transports were destroyed by torpedoes, and many others were temporarily disabled. The confederates lost a fine ironclad, the Albemarle (see Plymouth, N. C), two steamers in Charleston harbor, and a flag-of-truce boat on James river, in the same manner, the last three accidentally by their own torpedoes. This great destruction chiefly occurred in the last two years of the war. In the Schleswig-Holstein war of 1804, Denmark resorted to ingenious stationary submarine mines, and one of the invading vessels was destroyed.

Paraguay employed torpedoes in defending its river coast against Brazil and her allies in 1865-8. By these the ironclad Rio de Janeiro was destroyed and the Taman-dare disabled, although the engineers were crippled by the want of supplies. During the Franco-German war of 1870-'71 the coasts of the Baltic and North seas were effectively protected against the French fleet by torpedoes; and various attempts were made to defend the French rivers in a similar manner. - The recent changes in naval architecture, which have produced iron-clad vessels capable of enduring for a few moments the heaviest fire of modern artillery, have rendered it necessary to devise means of striking the remaining vulnerable points, viz., the deck and the bottom. The former can be attacked advantageously in many localities only by the vertical lire of mortars; the latter can be most effectively assailed by the torpedo. The chief nations have accordingly established special schools for investigating the subject of submarine warfare, and all possible secrecy is thrown around these studies. In the United States, Great Britain, and other countries a distinction is made between the defensive and offensive branches. The American school for defensive torpedoes is at Willet's Point, New York harbor.

The general principles which must govern this service are well established. The most vulnerable points of maritime nations are now their great seaboard cities; hence it is of primary importance to protect the seaports. The invention of the screw propeller and of iron armor has enabled fleets to steam rapidly past the forts, under cover of night or fog, and anchor securely in positions where their fire can either destroy the city or compel the payment of an enormous ransom. The great problem of coast defence is, therefore, to devise an effective obstruction of the channel, which, while allowing the free passage of friendly vessels, shall bar the way to an enemy. This is supplied by defensive torpedoes planted and operated from the forts. If by their aid the enemy can be detained 100 hours under the fire of the forts, when without it he could pass in one hour, the number of the guns is virtually multiplied by 100. For these reasons military engineers are giving the closest possible study to defensive torpedoes, or submarine mines as they are often called. While the details of our system of submarine defences are not made public, its general features have been announced.

In a deep casemate of the fort, secure from the fire of the enemy, are placed electrical batteries, operating apparatus, testing galvanometers, etc, under the charge of a thoroughly trained engineer sergeant. A telegraph wire keeps him in constant communication with his officer, who is posted at some commanding point, where the whole channel lies like a map before him. Radiating from the casemate, in subterranean galleries, the torpedo cables extend to the channel, where they terminate in multiple groups of mines so arranged as to be perfectly flanked by the guns of the work. The details of these mines are not public, but an idea of their general construction can probably be formed from fig. 1, which represents the Aus-trian type. It consists of an anchor, a; a buoyant case, b, containing the charge, fuse, and circuit-closing apparatus; and the electric cable, d, extending to the operating room on shore. These groups are so placed, in successive lines and outlying mines, as to render it impossible for a vessel to pass without moving over some of them. Thickly rising, but never exposed to view, are numerous buoys, each containing a simple electrical apparatus, which instantly reports to the sergeant the locality of any vessel touching them.

If friendly, the ship passes in safety; but if an enemy, a single motion of the sergeant makes every mine an automatic agent of destruction, ready to deal a tremendous blow at the precise instant when it will be most effective. As the buoys may be slightly in rear of the mines, all attempts to protect the vessel by outrigging frames or nets are futile. Any boat attempting to grapple the torpedoes by night will be overwhelmed by a fire of grape or case shot from the fort, fired automatically by electricity, without the agency of the soldiers sleeping quietly by the guns. The mines are as effective a year after they are planted as when first laid; and if a single cable be injured or a single charge be wet, the fact is automatically reported, and within five minutes after the injury has occurred its existence and nature are known in the fort. A mine can be fired without the aid of the buoys. For secondary channels, the use of which could be sacrificed for a time, less elaborate kinds of torpedoes are provided, not unlike those employed by the confederates in the late war. These mines, once planted, are dangerous alike to friend and foe, as they explode on contact with any vessel. The electric light is employed to aid the forts in arresting operations attempted under cover of the night.

Where constant currents exist, as in rivers, use can sometimes be made of double drifting torpedoes, so arranged as to foul with the connecting rope the hawsers of vessels at anchor. On the torpedoes being brought alongside by the force of the current, the same agency, acting on a simple piece of mechanism, soon releases a hammer and causes an explosion. - Offensive torpedoes are employed in the battles of vessels with vessels, and require technical naval skill. They are various in principle, and are receiving the careful study of many naval officers of all nations. The American school for offensive torpedoes is at Newport, R. I. The principal types of this class are the following: spar torpedoes, automatic fish torpedoes, otter or Harvey torpedoes, submarine rockets, and submarine boats. Besides these, there is a mixed class, that of fish torpedoes, which may be directed and controlled through the agency of electricity. These last may be either offensive or defensive. The spar torpedo has given occasion for some of the most brilliant naval exploits on record, such as that of Lieut. Cushing in the destruction of the Albemarle. Fig. 2 represents the Wood and Lay apparatus used by him. A reserve torpedo, a, is shown on its spar b.. The port torpedo c is about to explode.

It has been detached from its spar d by a pull on a rope, and is rising by its own buoyancy to be fired at the proper moment by the lanyard e. Since the civil war boats especially fitted for this kind of attack have been devised by many nations, but the same kind of torpedo may be used from any vessel possessing the requisite speed. The automatic fish torpedo, of which the Luppis Whitehead is most widely known, consists of a small cigar-shaped boat a, fig. 3, carrying a contact torpedo in the bow, and containing an engine driven by some powerful agent, like compressed air, which, acting on the propeller b, gives it an effective range of about 300 yards. It is started usually from a large vessel, but sometimes from a launch or boat, and passing under water strikes and destroys the object of attack. Usually a directing tube is employed, but for simplicity the engraving shows a device sometimes used in experiments. The otter or Harvey torpedo is emphatically a sailor's weapon, requiring high nautical skill for its use.

It consists of a thin vertical copper torpedo case, enclosed in wood, a a, fig. 4, and so attached to a tow rope, b, leading from a reel on deck through a leading block on the yardarm, as to diverge from the quarter of a fast vessel, whose duty it is to move rapidly past the enemy. The course is so directed as to bring the torpedo in contact and explode its charge under his bottom. This is accomplished by skilfully causing the case to dive at the proper moment, by the slackening of the tow rope, and then, by suddenly checking the latter, making the torpedo rise and explode by contact, either through the agency of a contact fuse acted upon by the levers c c, or by electricity. The cork buoys d d are used to give the requisite flotation. Official trials in England have shown that when properly handled this is a most effective weapon, and ore which admits of use on the high seas as well as in harbors. Submarine rockets, in connection with sub-taiai-ine guns, are now receiving much attention. The design is to render it possible to attack the enemy under his armor by a movable torpedo, in a manner analogous to the ordinary fire of artillery in air. Experiments lead to the belief that this project will ultimately be successful, for the short ranges usual in the combats of armor-plated ships.

Submarine torpedo boats have been an object of study since the days of Bushnell; and, under the name of Davids, they played a conspicuous part during the civil war, in which the Housatonic was sunk off Charleston by a night attack of this description. The French plongeur is a more elaborate type of the same class. The general idea is to form a water-tight vessel, propelled by compressed air, which can be navigated under water to the enemy, there to deliver a blow through the agency of a contact torpedo. As success, and even failure, has heretofore often involved the lives of the crew, the project is not now regarded with much favor. Indeed, it may be said to be superseded by fish torpedoes controlled by electricity, which may be made equally effective without endangering the operators. This device consists essentially of an ordinary fish torpedo, which carries a coil of insulated wire to be paid out as it proceeds. One end of the wire remains with the operator, who can thus at will send a current of electricity, positive or negative, through certain electro-magnets in the fish, causing a motion of the armatures in either of two directions. This enables him by ingenious devices to control valves which apply the motive power as desired, and thus start, stop, and steer the boat.

The idea was first patented by Lieut. Col. Ballard, R. E., but it has been independently elaborated by Mr. Lay, by Mr. H. J. Smith of this country, and by Col. Sche-liha in Russia. A modification of the idea has been made by Capt. Ericsson, who places his motive power (compressed air) with the operator, and supplies it to the fish through a flexible tube, thus enabling him to control both its speed and direction. The tube is drawn after the fish as it advances. This kind of torpedo seems to be especially fitted for use on shipboard, where the engines may be made to supply the compressed air, and where, by advancing upon the enemy, a short range can usually be secured.

Austrian Submarine Mine.

Fig. 1. - Austrian Submarine Mine.

Wood and Lay Torpedo.

Fig. 2. - Wood and Lay Torpedo.

Luppis Whitehead Torpedo.

Fig. 3. - Luppis Whitehead Torpedo.

Harvey Torpedo.

Fig, 4. - Harvey Torpedo.