Torpedoes and Torpedo Warfare / Containing a Complete and Concise Account of the Rise and Progress of Submarine Warfare

Take the case of a Voltaic cell composed of zinc and copper plates immersed in water.

The passage of electricity through the water will decompose it into its elements hydrogen and oxygen, the latter having an affinity for both the plates, but considerably more so for the zinc plate.

Then, an electro-motive force will be generated at each metal, and these forces will act in opposition to each other, but the greater strength of the one will overcome the weaker, and the real power of the electric current will be the difference between the two.

Definition of "Elements."—The battery plates are termed the positive and negative elements. A Voltaic battery has two poles—a positive and a negative—which are the terminations of the plates.

Direction of Current.—The course of the current in a Voltaic cell is as follows:—Within it leaves the electro-positive plate (or element), and flows to the electro-negative plate, but outside the cell (or as it were on its return path) it flows from the positive pole to the negative pole. The current always leaves the battery by the positive pole, and thus the copper is the negative element, but the positive pole, because the current leaves the battery by it; and the zinc is the positive element because the current begins there, within the cell, and the negative pole because it ends there, outside.

The positive pole is the terminal of the negative plate, and vice versâ. There is but one current from a battery, viz. a positive one; what is called a negative current is merely the positive current passing in the reverse direction from the same pole, that is, the positive pole.

Single and Double Fluid Batteries.—Galvanic batteries may be divided into single fluid and double fluid batteries. The simplest form of galvanic cell practically in use is a single fluid cell, consisting of a zinc and a copper element, immersed in water slightly acidulated by the addition of a little sulphuric acid. In a battery of several cells, the zinc and copper plates are generally soldered together in pairs, and placed in a long stoneware or glass trough, divided into separate cells by means of partitions. By filling the cells with sand, this battery is made more portable, the plates being thus supported, and the liquid prevented from splashing about during transit.

In this form it is called the common sand battery.

Action in a Single Fluid Cell.—The following process goes on in the single fluid cell when the circuit is closed—that is, when the battery is set to work.

The water (composed of hydrogen and oxygen) is decomposed by the passage of the electric current, and oxide of zinc is formed. The oxygen of the water having greater affinity for the zinc, leaves the hydrogen. The zinc during the process is being consumed, as coal is consumed when it burns, while combining with the oxygen of the air. This oxide of zinc combines with the sulphuric acid, and forms sulphate of zinc; this salt is found to accumulate in solution in the liquid of the cell. At the same time the hydrogen of the water goes to the negative or copper plate, and gathers over it in bubbles.

The process will be better seen by the accompanying plan of the chemical decomposition and recombinations.

No single fluid cell can give a constant electro-motive force because of the polarisation of the plates.

Definition of the term Polarisation.—The word polarisation means that the plates become coated with the products of the decomposition of the electrolyte, producing a diminution of current. In the above described battery, the hydrogen gathers on the surface of the copper plate, and an electro-motive force is set up which counteracts the electro-motive force producing the current—the copper plate is said to be polarised. By the bubbles of hydrogen collecting on the face of the negative plate, the surface in contact with the liquid is gradually decreased; thus the plate becomes practically smaller, and a single fluid cell which at starting gave a good current soon shows that it is really weakened. The consequence is that the zinc is consumed extravagantly as well as the acid, and the cell working with poor results. Also the resistance of the cell is increased, due to the sulphuric acid, which is added to the water to increase its conductivity, being gradually used up, by combining with the oxide (see plan) and forming sulphate of zinc. Liquids are very bad conductors of electricity; the greater part of the ordinary internal resistance of a battery arises from this cause. The common sand battery is the worst of all batteries as regards constancy of electro-motive force, the polarisation being greater in this battery than any other because the gas cannot readily escape. The common copper and zinc cell is the next in order of demerit. The Smee single fluid cell, in which the negative plate is a platinum instead of a copper one, is better than the copper zinc cell, because the free hydrogen does not stick to the rough surface of the platinum plate so much as to the copper.

Double Fluid Batteries.—All the defects of the single fluid battery, which are as follows—

The Chemical Action of a Daniell Cell.—The chemical action of this form of Daniell cell is as follows:—

The zinc electrode combines with oxygen; the oxide thus formed combines with sulphuric acid and forms sulphate of zinc. Oxide of copper is separate from the sulphate; and the copper in this oxide is separated from the oxygen. The oxygen of the water is separated at the zinc electrode from the hydrogen, and at the other electrode this hydrogen recombines with the oxygen from the oxide of copper. This alternate decomposition and recombination of the elements of water can neither increase nor decrease the E.M.F. of the cell, the actions being equal and opposite. The result of the series of actions above described is that the sulphuric acid and oxygen of the sulphate of zinc are transmitted to the zinc, combine with it, and form fresh sulphate of zinc; the sulphuric acid and oxygen of the sulphate of copper are transmitted to the zinc set free by the above process, and reconvert it into sulphate of zinc; the copper of the sulphate of copper is transmitted to the copper electrode, and remains adhering to it. The whole result is therefore the substitution of a certain quantity of sulphate of zinc for an equivalent quantity of sulphate of copper, together with a deposition of copper on the copper or negative electrode.[X] The following is a plan of the process:—

Description of the "Callaud" and "Marié-Davy" Batteries.—The Voltaic batteries in general use for the different purposes of torpedo warfare have been fully described in Chapter IV., and therefore it will be only necessary here to explain the construction of the "Callaud" and "Marié-Davy" batteries, these being much used abroad in connection with telegraphy.

The Callaud cell, named from the inventor, is a modification of the Daniell cell, and is also called a gravity battery, the liquids being simply prevented from mixing by the law of gravity forbidding the heavier of the two from rising through the lighter. It consists of a thin plate of copper, which is laid on the bottom of a good insulating jar having an insulated wire leading up the side, and on this plate are placed crystals of sulphate of copper. A solution of sulphate of zinc is then poured in, and on the top is fitted a zinc plate, which forms the positive element. The vessel must not be shaken, or the sulphate of copper when dissolving will mix with the solution above it.

The Marié-Davy cell consists of a carbon electrode in a paste of proto-sulphate of mercury and water contained in a porous pot, and a zinc electrode in dilute sulphuric acid, or in sulphate of zinc.

The Circuit.—In connection with the manipulation of batteries, there is one important item to consider, viz. the resistance in the circuit, which may be divided into external and internal.

Resistances.—The external resistance in practice is that which exists in the conducting line, and the various instruments connected with it.

The internal resistance is that which exists in the battery itself. All known conductors oppose a sensible resistance to the passage of an electric current, and the strength of the current, or in other words, the quantity of electricity passing per second from one point to another, when a constant difference of potentials is maintained between them, depends on the resistance of the wire on the conductor joining them. A bad conductor does not let the electricity pass so rapidly as a good conductor, that is, it offers more resistance.

Resistance in a wire of constant section and material is directly proportional to the length, and inversely proportional to the area of the cross section.

The electrical resistance of a conductor must not be considered as analogous to mechanical resistance, such as the friction which water experiences in passing through a pipe, for this frictional resistance is not constant when different quantities of water are being forced through the pipe, whereas electrical resistance is constant whatever quantity of electricity be forced through the conductor.

Application of Ohm's Law.—Ohm's law, which governs the strength of the current, is expressed by the equation

• Where C is the strength of the current;
• E is the E.M.F. or difference of potentials;
• and R is the resistance of the circuit.

In words, Ohm's law means that the strength of the current is directly proportional to the E.M.F., and inversely proportional to the resistance of the circuit.

As before stated, the resistance of the circuit consists of an external and an internal resistance, therefore when these resistances are separately considered, the equation C = E / R must be converted into C = E / (x + r), where x is the external, and r the internal, resistance.

The resistance of the battery or the internal resistance depends on the size of the plates and the distance between them, that is, it is directly proportional to the distance, and inversely proportional to the size.

The electro-motive force of a battery is dependent generally on the number of cells joined in series, and not on the size of the plates. The cells of a battery may be joined in two ways, as follows:—

If the conductor between the battery poles be such that the external resistance x may be practically left out, then C = E / r, and no change in the strength of the current will be effected by adding any number of cells in series, as r will increase equally with E, and therefore C will remain the same; but if under the same conditions the cells be joined in multiple arc, then r will decrease as E increases, and therefore C will be increased.

Thus with a short circuit of small external resistance, the strength of the current will be increased by increasing the size of the plates, or by joining the cells in multiple arc, but not in series.

If the conductor between the poles of the battery be such that the external resistance x becomes very great, then C = E / (x + r), where x is very great compared to r. By joining the cells in multiple arc r is decreased, but E and x remain the same, and therefore C is not materially altered, as x is very great compared to r. By connecting the cell in series, r is increased, and so is E, but as r is still very small compared to x, the strength of the current C is increased.

Thus with a long circuit of great external resistance, the strength of the current will be increased by joining the cells in series, but not in multiple arc.

When the external resistance x is neither very large nor very small in comparison with the battery or internal resistance r, then the strength of the current C will be increased by adding the cells in series, and also in multiple arc. By the former process the E.M.F. E is increased more than the resistance of the circuit R or (x + r), and by the latter process, the E.M.F. E is unaltered, whilst the circuit resistance (x + r) is decreased. All the above may be practically demonstrated by the employment of suitable galvanometers.

Frictional Electricity.—Frictional electricity is produced by the friction of two insulators. There is no difference whatever in kind between "Voltaic" and "frictional" electricity.

Comparison with Voltaic Electricity.—The electricity generated by friction possesses a great electro-motive force, producing on even a small conductor a large charge, whereas the electricity generated by the galvanic cell possesses a very small electro-motive force, and produces only a small charge on a small conductor. But when the conductor is large, the electricity produced by the galvanic cell will almost instantaneously charge the conductor to the maximum potential it can produce, the galvanic cell developing an immense quantity of electricity by the chemical reaction; whereas the quantity developed by friction between two insulators is so small, that if it be diffused over a large conductor the potential of the conductor will be very little increased.

The late Professor Faraday has proved that one cell of a Voltaic pile possesses the same quantity of electricity as an ordinary sized frictional machine after being wound round 800,000 times, thus showing the contrast between the qualities of frictional and Voltaic electricity.

The electricity of the frictional machine and that of the galvanic battery may be made to produce the same effect, there being no difference in kind between them. Frictional electricity can be made to pass in a current, but it is comparatively feeble. Again, Voltaic electricity can be made to produce a spark, but under ordinary circumstances it scarcely amounts to anything.

Description of a Frictional Electric Machine.—A frictional electrical machine consists of a vulcanite or glass disc or cylinder, which is made to revolve between cushions or rubbers of leather or silk. By the friction the (silk) rubbers become negatively, and the glass disc or cylinder positively, electrified. The revolving disc immediately after contact with the fixed rubbers passes close by a series of brass points, which are connected with a condenser. These points collect the positive electricity of the glass, the rubbers being put to earth. The positive electricity which the glass loses is supplied through the rubber; a stream of negative electricity flows from the rubbers to the earth during the charging of the conductor or condenser; in other words, the positive electricity flows from the earth to the rubber, whence it crosses to the glass disc and so to the condenser.

Definition of a "Condenser."—A condenser is an arrangement for accumulating a large quantity of electricity on a comparatively small surface.

The "Leyden Jar."—The Leyden jar, which is the original type of the condenser, or accumulator, consists of a glass jar coated inside and out, up to within a few inches of the mouth, with tinfoil pasted on, but having no connection with each other. The mouth is usually closed by means of a wooden stopper, through which a brass rod passes, to the head of which is affixed a brass knob, &c., the rod and knob being metallically connected with the inner coating by means of a chain.

The "Leyden jar" may be charged either by connecting the outer coating to earth (the rubbers of the machine being also to earth), and the inner coating to the conductor of the machine; or else by connecting the outer coating to the rubbers, and the inner coating to the conductor, a complete circuit being necessary to charge the jar as highly as the frictional electrical machine will admit of.

The conductor of the machine being charged, also forms a kind of Leyden jar, the conductor in this case being the inner coating, the air, the dielectric, and the nearest surrounding conductors, such as the walls of the room, &c., being the outer coating.

Meaning of "Dielectric."—By dielectric is meant a non-conducting medium, which in the case of the "Leyden jar" is the glass.

Frictional Electricity very little used for Torpedo Purposes.—Frictional electricity is now seldom used in connection with torpedo warfare, as on account of its very great power, or electro-motive force, a very perfectly insulated cable must be employed, which is somewhat difficult to obtain; it is also necessary to employ a condenser, which requires a certain time to charge. For these and other reasons, frictional electricity has been abandoned for the far more practical Voltaic electricity.

Magnetism.—A magnet is a piece of steel, which has the peculiar property, among others, of attracting iron to its ends.

Certain kinds of iron ore, termed the loadstone, have the same properties. The word "magnet" is taken from the country Magnesia, where the loadstone was first discovered.

Magnetism in a body is considered to be a peculiar condition caused by electrical action. Both electricity and magnetism have the power of communicating their properties to other bodies without being in contact with them, i.e. inducing the power, which on the bodies being placed far apart becomes insensible.

The "Poles" of a Magnet.—Every magnet has two poles, called the north and south poles. A magnetic steel needle if pivoted on an upright point, or suspended from its centre, will fix itself, pointing north and south; in England the end of the needle pointing to the north is termed the north pole, but in France it is termed the south pole. The reason of this difference is owing to the fact that the north pole of one magnet attracts the south pole of another, and therefore, as the earth is considered as one vast magnet, the end of the magnetic needle attracted to the north pole of earth magnet should be the south pole of the magnet; thus the French south pole in a magnet is the English north pole, and vice versâ.

Permanent Magnets.—A piece of steel when magnetised is termed a permanent magnet, because it retains its magnetism for a considerable length of time; but soft iron cannot be permanently magnetised.

A piece of soft iron rendered magnetic by induction retains a portion of its magnetism for some time after it has been removed from the magnetic field, by reason of what is called its coercive force. This remnant of magnetisation is called residual magnetism.

Effect of an Electrical Current on a Magnetic Needle.—A magnetic bar or needle pivoted on its centre will point north and south, but if an electric current is caused to flow along a wire parallel to and either over or under the magnetic needle, the latter will be turned from its position, and remain so as long as the current continues; on the current ceasing the needle will resume its original position.

The magnetic needle can be turned either to the east or the west, according to the direction and course of the electrical current.

Thus:—

• Current from S. to N. over deflects to W.
• Current from N. to S. under deflects to W.
• Current from N. to S. over deflects to E.
• Current from S. to N. under deflects to E.

The Galvanometer, the "Mirror," and "Thomson's reflector" all depend on this principle for their usefulness. These instruments have been fully described in Chapter IV.

The Electro-Magnet.—If a piece of insulated wire be coiled round a rod of soft iron, and a current of electricity be made to pass through the coil, the iron core becomes magnetic as long as the current passes; when the current ceases the magnetism disappears.

During the passage of the electric current, the iron core possesses all the properties of a magnet. Therefore if a piece of iron were placed near its poles it would be attracted and released from attraction as often as the current passed or ceased; and supposing such a piece of iron to be retained by a spring, &c., a series of movements, attraction, and drawing back would be effected.

A piece of iron so arranged is termed an armature, and the instrument is called an electro-magnet.

The coil of wire must be carefully insulated, or else the electric current will pass through the iron core to earth instead of performing its proper work.

An electro-magnet is much more powerful than a steel magnet of equal dimensions, and depends on the strength of the current by which the magnetism is induced, and the number of turns of wire round the core. The north and south poles of an electro-magnet are determined by the direction in which the current flows through the wire.

At the south pole the current passes with the hands of a watch, and at the north pole against the hands of a watch.

Definition of the "Ohm."—The "ohm" is the standard used for electrical resistance; it is obtained by observing what effect is produced by a current of electricity on a certain conductor in a certain time.

The ohm is a small coil of German silver wire representing the resistance overcome by a current in a certain time.

APPENDIX.

McEvoy's Single Main System.—Hitherto in connection with a system of electrical submarine mines, it has been necessary to employ either a single cable between each submarine mine and the torpedo station, or a single cable, termed a "multiple cable," containing a limited number of insulated wires, leading from the station, and branching off from a junction box to each mine, by which considerable cost and complication is incurred. To remedy the above serious defects of such a system, and also to simplify the arrangement of electrical tests, Captain McEvoy has devised and patented the following apparatus; at the firing, or torpedo station, the end of the single main cable, that is, the single core cable leading to the junction box, is connected to a make and break contact apparatus, by which, by the movement of a dial or pointer around a fixed centre, a battery can be successively put in connection with the wire, and disconnected from it, in a somewhat similar manner to Wheatstone's step by step dial telegraphs. In the junction box at the opposite end of the single core main cable is an electro-magnetic apparatus for working a dial or pointer in exact unison with the aforesaid dial or pointer at the torpedo station. This junction box dial or pointer serves as a contact maker to put the wire of the main cable successively in contact with the branch wires leading to the several torpedoes, as it is caused to turn with a step by step motion by the sending of a succession of currents from the firing station.

As the contact maker completes the circuit between the main cable and one of the branch wires, the current passes from the cable through the wire, and through the fuze of that particular torpedo to "earth"; but when any one or other of the torpedoes is to be exploded, the circuit between the main cable and the torpedo wire being completed, it is only necessary to send a current through the main cable of sufficient strength to ignite the fuze, and so explode the mine.

The strength of the current used for giving the aforesaid step by step motion to the junction box dial or pointer is not sufficient to cause the ignition of the fuzes in the torpedoes.

Again, if it be desired that the torpedoes should be so arranged that when any of them are struck by a passing vessel, the fact of its having been struck should be instantly signalled to the firing station. The dial apparatus in the junction box is arranged so that at one point of its revolution, termed the "zero point," all the torpedo branch wires are in circuit with the main cable, and that then a constant current is passing from the firing station through all the circuit closers, and out through resistance coils to "earth." In this case, if one of the circuit closers be struck, and therefore short circuit formed, the current passes direct to earth without going through the aforesaid resistance, and the fact of its having done so is at once indicated by a galvanometer at the firing point, by the movement of which a bell is rung at the station. The operator can then explode such torpedo at once by merely switching in the firing battery.

At the same time the passage of the strong firing current may fuze a connection in the junction apparatus, by which the exploded torpedo is detached, i.e. the direct "earth" connection of such a torpedo is cut off, and the remaining submarine mines are left in proper working order; this effect may also be arrived at by other means.

General Description of Apparatus.—The following is a general description of this exceedingly clever and useful invention:—

At Fig. 168 is shown a diagram view of the apparatus.

A is the instrument at the firing point on the shore or vessel; B is the cable wire led to a submerged box situated near the spot where the several torpedoes are grouped; C is the instrument enclosed in the submerged box; D, D are insulated wires led away from the box to the several torpedoes, there being a separate wire for each torpedo.

Each of the wires D is coupled to one or other of a series of metallic contact pieces E ranged in a circle round the axis of a metallic pointer F, which can be turned with a step by step motion and successively brought into electrical contact with the several contact pieces E. The axis of the pointer is in electrical communication with the wire of the cable. The wire from the cable is first led to the coils of an electro magnet G, and thence passes to the axis of the pointer. H is a magnetic armature in front of the electro magnet G; when a positive current of sufficient strength is sent through the cable the armature is rocked in one direction, and when a negative current is sent, it is rocked in the opposite direction. From the armature motion is transmitted to a pawl which works into the teeth of a ratchet wheel on the axis of the pointer F, so that by sending a succession of reversed currents of sufficient strength through the cable, the pointer F is turned with a step by step motion and is successively brought into electrical contact with the several contact pieces E.

In the instrument, at the firing point a is a handle, by the turning of which a step by step motion is given to the pointer of a dial b and a simultaneous movement to the pointer F of the instrument C in the submerged box. When the handle a has made a half turn it couples one pole of the battery to the cable and the other to the earth connection, and when it has made a complete turn the connections are reversed. The pointer of the dial b then moves forward from one division of the dial to the next, and simultaneously the pointer F is turned in unison with it. The operator at the firing point can therefore always see which of the torpedoes is in electrical connection with the wire of the cable, and he can test each torpedo in succession by moving a handle, say at h, to cause the current passing back from the torpedo to pass through a galvanometer at e, and by the movement of the needle of the galvanometer it can be seen whether the resistance of the circuit through this torpedo is in its normal and proper working state.

When the pointer of the dial b is brought to zero, or as it is marked in the drawing to "signal," then the pointer F of the apparatus C is in electrical communication with a contact point which is coupled to all of the branch wires D, and usually the apparatus is left in this condition, the handle a being then locked and prevented from turning by a bolt actuated by a handle at G.

The current from the battery at the firing point then passes to earth through the resistances in all of the torpedoes. If now any one or other of the torpedoes is struck by a passing vessel and the wire from its fuze put directly to earth, so that the current passes freely to earth instead of having first to pass through the resistance, the fact of the current passing freely to earth is notified at the firing point by the movement of the needle of a galvanometer d; the movement of the needle of this galvanometer effects an electrical connection by which a small battery is caused to sound a bell at c. The operator at the firing point can then if he pleases at once fire the torpedo that has been struck by moving a handle at f and coupling up to the wire of the cable a battery of greater strength; the strong firing current will pass to earth through the fuze of the torpedo that has been struck, and will ignite this fuze, but will not affect the fuzes of the other torpedoes, as to pass through these fuzes it has also to pass through resistances which impede its passage and reduce its strength, so that the portion of the current which passes to earth through them is not of sufficient strength to ignite the fuzes.

When the fuze of any one or other of the torpedoes is exploded by the passing of a strong firing current through it, the wire leading from the box C to this torpedo is simultaneously cut off from electrical connection with the contact pin E to which it was previously connected, and this pin is put to earth through a resistance either somewhat greater or less than the resistances in the torpedoes, so that the firing of one or more of the torpedoes does not interfere with the power of being able to turn the pointer F of the apparatus C in unison with the pointer of the dial b.

Afterwards the operator at the firing point can ascertain which of the torpedoes has been fired by passing the pointer of the dial b to each of the divisions of the dial in succession, and ascertaining by the galvanometer a the resistance of the circuit through each of the torpedoes, so that he at once ascertains which torpedo has been put to earth through the greater or less resistance.

The cutting off of the wire D from its contact E when a strong current is passed through it may be effected by the wire being coiled around an iron core forming an electro magnet, which when a strong current is passed through the wire is of sufficient strength to shift the position of a contact apparatus and then effect the required alterations in the connections, but which is not of sufficient strength to effect any change when the weaker currents used for the signalling and testing operations are passed through the wire.

It will be evident that with the above described apparatus any one or other of the torpedoes can if desired be exploded by the operator at the firing point whenever he desires to do so. To effect this he would by turning the handle a bring the pointer of the dial b opposite to the division of this dial; that would indicate that the cable had been brought into electrical communication with the torpedo required to be exploded, and then when it is ascertained by previously adjusted sight points that the vessel is above the torpedo, he can fire the torpedo by passing a strong firing current to the cable.

In this way the apparatus can be used for firing any one or other of a group of sunken torpedoes, or if the torpedoes are buoyant ones, they need not be fitted with apparatus for putting the wire from their fuze directly to earth whenever the torpedo is struck by a passing vessel. The same arrangement of apparatus can also be used for firing any one or other of a number of mines or torpedoes on land and for separately testing the firing mechanism of each mine whenever desired.

Captain McEvoy's single main system will shortly undergo a series of experiments under the supervision of the English torpedo authorities at Chatham, which will most probably result in its adoption by the English government, and also by the principal continental powers.