CHAPTER XI.

ELECTRICITY.

_THEORY of Electricity._--The theory most readily understood, and which most satisfactorily explains the various electrical phenomena, is as follows:--

"That every substance and every atom of the world is pervaded by a peculiar, subtle, imponderable fluid which is termed _Electricity_, but which is not known to exist, or remains in a state of _electrical equilibrium_, until evoked by certain causes."

The effect of causing a disturbance of this equilibrium is to increase the normal, or natural, electricity in some particles, and to equally decrease it in other particles, i.e. what one loses the other gains. An excess of natural electricity is denoted by the term _positive_, or mathematical symbol (+) while a deficiency is denoted by the term _negative_, or symbol (-).

_Like electricities repel each other._

That is to say, two bodies charged with an excess of, or positive, electricity, being brought together repel each other, neither wishing to increase the excess that has been evoked in them.

Similarly in the case of two bodies charged with a deficiency of, or negative, electricity, neither wish to add to the deficiency already there.

In both these cases there can be no tendency to electrical equilibrium, which is the principle at work. In the former case, there being already too much, more will but increase the disturbance.

In the latter case, further deficiency will but add to the irregularity.

_Unlike electricities attract each other._

That is to say, if two bodies, one charged with positive, or having an excess of electricity, the other charged with negative, or having a deficiency of electricity, be brought together, they will attract each other; both being desirous of altering their existing state, the one by decreasing its excess, and the other by decreasing its deficiency of electricity.

In this case, there will be a tendency to equilibrium, caused by attraction. The earth is supposed to be a vast reservoir of electricity, from which a quantity can be drawn to fill up a deficiency, and which is always ready to receive an excess from other bodies. Every body in nature has its own natural quantity of electricity, and when an object is negatively electrified, or has a deficiency in its normal quantity, there is a tendency to receive a supply from any convenient source. Such an object would receive electricity from the earth if means were afforded; and a body _positively_ electrified, would tend to part with its excess in the same manner. Where such facilities for establishing electrical equilibrium are afforded, the result is the passage of a _current_ of electricity.

_Conductors._--Sensible effects can be produced by electricity at great distances from the source, provided there be a medium of communication, that is, good _conductors_ to transfer it. When a glass rod is rubbed with a piece of silk, it becomes charged with an excess of, or positive, electricity, and at the same time the silk becomes charged with negative electricity.

The glass rod will retain the positive electricity upon it for some time, unless touched with the wet hand, a wet cloth, a metal, &c., when it will instantly cease to be electrified. The electricity is then said to have been conducted away, and the bodies which allow it to run off the glass are called _conductors_ of electricity. Metals, water, the human body, charcoal, damp wood, and many other bodies are conductors.

Those bodies which conduct electricity hardly at all, such as the air, silk, glass, sealing wax, gutta percha, india rubber, &c., are termed _nonconductors_ or _insulators_.

Strictly speaking, all substances _conduct_ electricity in some degree, and a _nonconductor_ is merely a _bad_ conductor.

In the following table the bodies are arranged in their order of conductivity, i.e. each substance conducts better than that which precedes it; the first-named body is the best insulator, and the last-named one is the best conductor.

Dry air. Ebonite. Paraffin. Shellac. India rubber. Gutta percha. Resin. Sulphur. Sealing wax. Glass. Silk. Wool. Dry paper. Porcelain. Dry wood. Stone. Pure water. Rarefied air. Sea water. Saline solutions. Acids. Charcoal, or Coke. Mercury. Lead. Tin. Iron. Platinum. Zinc. Gold. Copper. Silver.

Though two substances are near one another in the above list, they do not necessarily approach one another in their power of conducting. For instance, taking the conducting power of pure silver as represented by the number 100, then

Pure Copper will be equal to 99·9, Gold will be equal to 78·0, while Zinc will be only equal to 29·0,

and pure water, which is half-way down the list, will offer 6,754 millions more resistance than silver to the passage of the electric current.

The metals being the best known conductors, are usually employed as the means of transferring the electric current from one place to another.

_Electric Circuit._--The conditions attending this operation are different from those of any other known method of transmission.

A complete _circuit_ must always be formed by the electric current, i.e. it cannot start from one place _A_, travel to another place _B_, and cease there, but the current must be completed before it can be said to have reached _B_. There cannot be a current of electricity without a means of recombination, which recombination must be at the _source_, or place of original disturbance.

This "place of disturbance" or _source_ must be considered as having two sides, i.e. at some spot the normal or natural electrical equilibrium is disturbed, and electricity is separated into too much (positive) on one side, and too little (negative) on the other side. If then no means of recombination be afforded, the electricities remain separated, and no current exists; but if a _conductor_ be made to connect the two sides, electricity is set in motion, and a current established. Originally to form a circuit between two stations _A_ and _B_, a conducting wire and a return wire were necessary, but in 1837 Steinway discovered that the earth itself answered all the purposes of a return wire, in fact under favourable conditions much better. Thus, to form a circuit between _A_ and _B_, a conducting wire is required, and a buried metal plate at _A_ and _B_, the earth by these means taking the place of the return wire.

The aforesaid metal plates are technically termed _earth plates_. The greater the size of the earth plates (up to certain limits), the deeper they are buried, and the better the conducting power of the soil surrounding them, the better conductors the plates become, or the less resistance the earth portion of the circuit offers. If either plate be not in communication with the earth, or else be separated from the wire, the circuit is not complete, or, as it is termed, "it is broken," and no current will flow, the signal not made, torpedo not fired, &c.

_"Short" Circuit._--Due to the fact that recombination, or a tendency to equilibrium, is always at work when electricity has been evoked, the conducting path along which the electric current flows must be covered with a nonconducting substance, or, as it termed, "insulated," or else the current would not perform its duty, but escape to earth, and so form what is termed a "short circuit."

A current of electricity always chooses the _easiest path_ to effect recombination, or electrical equilibrium.

_Insulators, &c._--On land, telegraph wires are as a rule laid above the ground, and therefore require supporting at every few yards; this is done by means of posts, and as these are formed of substances which are conductors of electricity, the wires require to be insulated from them. The insulators generally employed for such purposes are cup-shaped pieces of porcelain, or pottery, fixed to the head of the telegraph posts. By means of these insulators, the current of electricity is prevented from escaping to the earth by the post conductors.

A certain amount of leakage, or loss of electricity, must occur at each of these posts, as there is no such thing as a perfect insulator. When the wires are laid on the ground or under ground, or under water, they are insulated by covering them with gutta percha, india rubber, &c., and any loss of current is thus prevented.

_Methods of generating Electricity._--For the purposes of torpedo warfare there are two methods of evoking electricity, viz.--

1.--By _chemical action_.

2.--By _friction_.

_By Chemical Action._--_Chemical action_ is the chief source of free electricity, the representative of which is the galvanic, or Voltaic, battery.

The electricity so generated is also termed dynamical electricity, due to there being a constant electric current, so long as the poles of the battery producing it are kept closed; the electricity being thus in a _dynamic_ or moving state.

By chemical action is signified that which occurs when two or more substances so act upon one another as to produce a third substance differing altogether from the original ones in its properties, or when one substance is brought under such conditions that it forms two or more bodies differing from the original ones in their properties.

_Definition and Properties of a Voltaic Cell._--The _Voltaic_ cell consists of an insulating jar, containing a liquid, in which are placed two plates or pieces of dissimilar metals; the liquid must be composed of two or more chemical elements, one of which at least tends to combine with one or other of the metals, or _with both in different degrees_.

By a Voltaic _battery_ is meant a number of cells above one; this term, however, is often applied to a single cell when working by itself.

A "_simple_ Voltaic cell," "element," or "couple," consists of two metals placed in a conducting liquid. If two metals--for instance, zinc and copper--are placed in water slightly acidulated, without touching each other, no effect is apparent; but if they be made to touch, bubbles of hydrogen gas are formed over the copper plate, and continue forming these until the plates are separated. After being in contact for some time, the copper plate will be found unaltered in weight, but the zinc plate will have lost weight, and the portion so lost will be found in the liquid in the form of sulphate of zinc. The same effects are also produced by connecting the two plates by means of some conducting substance, instead of placing them in contact.

Zinc is invariably employed as one of the metal plates, on account of the ease with which it dissolves in dilute acids; and the greatest results are obtained when the second metal plate is not acted upon at all by the liquid, for then the whole effect due to the oxidation of the zinc plate is obtained; but when the second plate is also chemically acted upon, then only the effect due to the difference between the two chemical actions is obtained, for, as will be explained further on, they each act in directly opposite directions.

_Voltaic Current._--The Voltaic current makes its appearance under the general laws of electrical action.

When a body charged with an _excess_ of, or _positive_, electricity, is connected with the earth, electricity is transferred _from_ the charged body to the earth; and similarly when a body is charged with a _deficiency_ of, or _negative_, electricity, is connected with the earth, electricity is transferred _from_ the earth to the body.

Generally whenever two conductors in different electrical conditions are put in contact, electricity will flow from one to the other. That which determines the direction of the transfer is the relative _potential_ of the two conductors. Electricity always flows from a body at _higher potential_ to one at _lower potential_, when the two are in contact, or connected by a conductor. When no transfer of electricity takes place under these conditions, the bodies are said to be at the _same potential_, which may be either _high_ or _low_. The _potential_ of the earth is assumed to be _zero_.

_Definition of Potential._--"The _potential of a body or point, is the difference between the potential of the body or point, and the potential of the earth_."

Difference of potential for electricity is analogous to difference of level for water. Now, since, when a metal is placed in a vessel containing a liquid, electricity is produced, the liquid becomes of a different potential to the metal, each being electrified in an opposite way; and therefore, as above stated, there being a _difference_ of potentials, electricity will tend to flow from one to the other.

This is evidence of a _force_ being in action, for there can be no motion without some force to produce it.

_Electro-motive Force._--_Electro-motive force_ is the name given to a peculiar force to which is due the property of producing a difference of potentials. When it is said that zinc and water produce a definite electro-motive force, what is meant is, that by their contact a certain definite difference of potentials is produced.

The _electro-motive force_ of a Voltaic element may be termed its _working_ power, in the same way as the pressure of steam is the working power of a steam engine, though this is not to be considered as the real source of power, which, as will be seen, is uncertain. Due to the difference of potential of the metal and the liquid, a current of electricity will flow from one to the other, causing the chemical decomposition of the liquid, and the reaction may be taken as the origin of the power employed.

But while the expenditure of energy (which is necessary to produce a _force_) is accounted for by taking the chemical action as the source of power, the preceding cause of this chemical action, viz. the flowing of the current of electricity due to the difference of potential of the metal and the liquid, must also have first involved the expenditure of energy; thus the real source of power is very uncertain.

_Electrolytes._--As before stated, a Voltaic cell consists of two plates of dissimilar metals, which must be immersed in a liquid composed of two or more chemical elements, one of which at least will combine with one or other of the metals, or both in a different degree. Those liquids which are thus decomposed by the passage of a current of electricity are termed _electrolytes_.

The elements, then, forming the electrolyte may have chemical affinity for both metals, though in a greater degree for one than the other.

"Oxygen" is the most important element of an electrolyte, and to the _affinity for oxygen of the metals_ is the magnitude of the result and effect.

_Terms Electro-positive and Electro-negative._--All metals have a definite relation to each other as to the potential which any one may have when brought into contact with another. Thus, when zinc is brought into contact with copper, the former has a potential positive to the latter, i.e. a current of electricity will tend to flow from the zinc to the copper. The metals may be so placed in a list that each one would be positive to any of those that follow it; it is then said to be electro-positive to them, and they are electro-negative to it. As those metals which are electro-positive to others have a greater affinity for oxygen, and those that are electro-negative to others a less affinity for this element, the terms electro-positive and electro-negative signify, in effect, greater or less affinity for this element. Conversely, oxygen will combine more readily with the former than with the latter.

The following list shows the commoner metals arranged in electro-chemical order.

+ Zinc. Lead. Tin. Iron. Antimony. Copper. Silver. --Gold.

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.

Sulphuric Acid } Zinc } }Sulphate of zinc found at { Oxygen } Oxide of Zinc } positive plate. Water{ Hydrogen Hydrogen found at negative plate.

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--

1. Diminution of electro-motive force,

2. Inconstancy,

3. Increase of internal resistance,

are remedied in the _double fluid_ battery, of which the _Daniell's cell_ was the first invented, and is a good example. Of this kind of cell many forms are in use, but the principle is the same throughout. There is a positive and negative element, and the cell is divided into two receptacles for the two fluids. In the most constant form of Daniell cell, the zinc is plunged into a semi-saturated solution of sulphate of zinc, the copper in a saturated solution of sulphate of copper, and these two solutions are separated either by a porous barrier, or by taking advantage of the different specific gravities of the two solutions. By a _saturated_ solution is meant a liquid which has dissolved as much of the substance as it possibly can.

_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:--

Zinc............} } .{ Sulphate of Zinc found } Oxide of Zinc..} . { at positive plate. Water { Oxygen..} }. { Hydrogen.................}......} { Sulphuric Acid.....} } Water. Sulphate of { { Oxygen..} Copper { Oxide of Copper { { Copper at negative { Copper....{ plate.

_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

C = E / R or R = E / C or E = CR.

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:--

1. In series: that is, by connecting the negative element of one cell to the positive element of another, and so on.

2. In multiple arc: that is, by connecting negative to negative, and positive to positive; which is the same as increasing the size of the cells.

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.

FOOTNOTES:

[Footnote X: Jenkins' 'Electricity.']

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.

TABLE[Y]

SHOWING THE VALUE OF THE FRACTIONS A AND B FOR EVERY HALF DEGREE.

-------+-------------+-------------+ | A | B | Arc. |150 + [alpha]|150 - [alpha]| +-------------+-------------+ [alpha]|150 - [alpha]|150 + [alpha]| -------+-------------+-------------+ 145 | 59·00 | 0·017 | 144·5 | 53·54 | 0·019 | 144 | 49·00 | 0·020 | 143·5 | 45·15 | 0·022 | 143 | 41·86 | 0·024 | 142·5 | 39·00 | 0·026 | 142 | 36·50 | 0·028 | 141·5 | 34·29 | 0·029 | 141 | 32·33 | 0·031 | 140·5 | 30·58 | 0·033 | 140 | 29·00 | 0·035 | 139·5 | 27·57 | 0·036 | 139 | 26·27 | 0·038 | 138·5 | 25·09 | 0·040 | 138 | 24·00 | 0·042 | 137·5 | 23·00 | 0·044 | 137 | 22·08 | 0·045 | 136·5 | 21·22 | 0·047 | 136 | 20·43 | 0·049 | 135·5 | 19·69 | 0·051 | 135 | 19·00 | 0·052 | 134·5 | 18·35 | 0·054 | 134 | 17·75 | 0·056 | 133·5 | 17·18 | 0·058 | 133 | 16·65 | 0·060 | 132·5 | 16·14 | 0·062 | 132 | 15·67 | 0·064 | 131·5 | 15·22 | 0·066 | 131 | 14·79 | 0·068 | 130·5 | 14·38 | 0·070 | 130 | 14·00 | 0·071 | 129·5 | 13·63 | 0·073 | 129 | 13·28 | 0·075 | 128·5 | 12·95 | 0·077 | 128 | 12·64 | 0·079 | 127·5 | 12·33 | 0·081 | 127 | 12·04 | 0·083 | 126·5 | 11·76 | 0·085 | 126 | 11·50 | 0·087 | 125·5 | 11·24 | 0·089 | 125 | 11·00 | 0·091 | 124·5 | 10·76 | 0·093 | 124 | 10·54 | 0·095 | 123·5 | 10·32 | 0·097 | 123 | 10·11 | 0·099 | 122·5 | 9·91 | 0·101 | 122 | 9·72 | 0·103 | 121·5 | 9·53 | 0·105 | 121 | 9·35 | 0·107 | 120·5 | 9·17 | 0·109 | 120 | 9·00 | 0·111 | 119·5 | 8·84 | 0·113 | 119 | 8·68 | 0·115 | 118·5 | 8·52 | 0·117 | 118 | 8·37 | 0·119 | 117·5 | 8·23 | 0·121 | 117 | 8·09 | 0·123 | 116·5 | 7·96 | 0·126 | 116 | 7·82 | 0·128 | 115·5 | 7·69 | 0·130 | 115 | 7·57 | 0·132 | 114·5 | 7·45 | 0·134 | 114 | 7·33 | 0·136 | 113·5 | 7·22 | 0·139 | 113 | 7·11 | 0·141 | 112·5 | 7·00 | 0·143 | 112 | 6·89 | 0·145 | 111·5 | 6·79 | 0·147 | 111 | 6·69 | 0·150 | 110·5 | 6·59 | 0·152 | 110 | 6·50 | 0·154 | 109·5 | 6·41 | 0·156 | 109 | 6·32 | 0·158 | 108·5 | 6·23 | 0·160 | 108 | 6·14 | 0·163 | 107·5 | 6·06 | 0·165 | 107 | 5·97 | 0·168 | 106·5 | 5·89 | 0·170 | 106 | 5·82 | 0·172 | 105·5 | 5·74 | 0·174 | 105 | 5·67 | 0·176 | 104 | 5·52 | 0·182 | 103·5 | 5·45 | 0·183 | 103 | 5·38 | 0·186 | 102·5 | 5·31 | 0·188 | 102 | 5·25 | 0·190 | 101·5 | 5·18 | 0·193 | 101 | 5·12 | 0·195 | 100·5 | 5·06 | 0·198 | 100 | 5·00 | 0·200 | 99·5 | 4·94 | 0·202 | 99 | 4·88 | 0·205 | 98·5 | 4·82 | 0·207 | 98 | 4·77 | 0·209 | 97·5 | 4·71 | 0·212 | 97 | 4·66 | 0·215 | 96·5 | 4·61 | 0·217 | 96 | 4·55 | 0·220 | 95·5 | 4·50 | 0·222 | 95 | 4·45 | 0·224 | 94·5 | 4·40 | 0·227 | 94 | 4·36 | 0·230 | 93·5 | 4·31 | 0·232 | 93 | 4·26 | 0·235 | 92·5 | 4·22 | 0·237 | 92 | 4·17 | 0·240 | 91·5 | 4·13 | 0·242 | 91 | 4·08 | 0·245 | 90·5 | 4·04 | 0·247 | 90 | 4·00 | 0·250 | 89·5 | 3·96 | 0·253 | 89 | 3·92 | 0·255 | 88·5 | 3·88 | 0·258 | 88 | 3·84 | 0·260 | 87·5 | 3·80 | 0·263 | 87 | 3·76 | 0·266 | 86·5 | 3·72 | 0·269 | 86 | 3·69 | 0·271 | 85·5 | 3·65 | 0·274 | 85 | 3·62 | 0·276 | 84·5 | 3·58 | 0·279 | 84 | 3·54 | 0·282 | 81·5 | 3·38 | 0·296 | 81 | 3·35 | 0·299 | 80·5 | 3·31 | 0·302 | 80 | 3·28 | 0·304 | 79·5 | 3·25 | 0·307 | 79 | 3·22 | 0·310 | 78·5 | 3·19 | 0·313 | 78 | 3·17 | 0·316 | 77·5 | 3·14 | 0·319 | 77 | 3·11 | 0·322 | 76·5 | 3·08 | 0·325 | 76 | 3·05 | 0·327 | 75·5 | 3·03 | 0·330 | 75 | 3·00 | 0·333 | 74·5 | 2·973 | 0·336 | 74 | 2·947 | 0·339 | 73·5 | 2·921 | 0·342 | 73 | 2·896 | 0·345 | 72·5 | 2·871 | 0·348 | 72 | 2·846 | 0·351 | 71·5 | 2·822 | 0·354 | 71 | 2·797 | 0·357 | 70·5 | 2·773 | 0·360 | 70 | 2·750 | 0·364 | 69·5 | 2·726 | 0·367 | 69 | 2·703 | 0·370 | 68·5 | 2·680 | 0·373 | 68 | 2·658 | 0·376 | 67·5 | 2·636 | 0·379 | 67 | 2·614 | 0·382 | 66·5 | 2·592 | 0·386 | 66 | 2·571 | 0·389 | 65·5 | 2·550 | 0·392 | 65 | 2·529 | 0·395 | 64·5 | 2·509 | 0·398 | 64 | 2·488 | 0·402 | 63·5 | 2·468 | 0·405 | 63 | 2·448 | 0·408 | 62·5 | 2·428 | 0·412 | 62 | 2·409 | 0·415 | 61·5 | 2·389 | 0·418 | 59 | 2·296 | 0·435 | 58·5 | 2·278 | 0·439 | 58 | 2·261 | 0·442 | 57·5 | 2·243 | 0·446 | 57 | 2·226 | 0·449 | 56·5 | 2·208 | 0·453 | 56 | 2·191 | 0·456 | 55·5 | 2·174 | 0·460 | 55 | 2·158 | 0·463 | 54·5 | 2·141 | 0·467 | 54 | 2·125 | 0·471 | 53·5 | 2·109 | 0·474 | 53 | 2·093 | 0·478 | 52·5 | 2·077 | 0·481 | 52 | 2·061 | 0·485 | 51·5 | 2·045 | 0·489 | 51 | 2·030 | 0·492 | 50·5 | 2·015 | 0·496 | 50 | 2·000 | 0·500 | 49·5 | 1·985 | 0·504 | 49 | 1·970 | 0·508 | 48·5 | 1·955 | 0·511 | 48 | 1·941 | 0·515 | 47·5 | 1·926 | 0·519 | 47 | 1·913 | 0·523 | 46·5 | 1·898 | 0·527 | 46 | 1·884 | 0·531 | 45·5 | 1·870 | 0·535 | 45 | 1·857 | 0·538 | 44·5 | 1·843 | 0·542 | 44 | 1·830 | 0·546 | 43·5 | 1·816 | 0·550 | 43 | 1·803 | 0·554 | 42·5 | 1·790 | 0·558 | 42 | 1·777 | 0·562 | 41·5 | 1·765 | 0·567 | 41 | 1·752 | 0·571 | 40·5 | 1·739 | 0·575 | 40 | 1·727 | 0·579 | 39·5 | 1·714 | 0·583 | 39 | 1·702 | 0·587 | 36·5 | 1·643 | 0·609 | 36 | 1·631 | 0·613 | 35·5 | 1·620 | 0·617 | 35 | 1·608 | 0·622 | 34·5 | 1·597 | 0·626 | 34 | 1·586 | 0·630 | 33·5 | 1·575 | 0·635 | 33 | 1·564 | 0·639 | 32·5 | 1·553 | 0·644 | 32 | 1·542 | 0·648 | 31·5 | 1·531 | 0·653 | 31 | 1·521 | 0·657 | 30·5 | 1·510 | 0·662 | 30 | 1·500 | 0·667 | 29·5 | 1·489 | 0·671 | 29 | 1·479 | 0·676 | 28·5 | 1·469 | 0·681 | 28 | 1·459 | 0·685 | 27·5 | 1·449 | 0·690 | 27 | 1·439 | 0·695 | 26·5 | 1·429 | 0·700 | 26 | 1·419 | 0·705 | 25·5 | 1·409 | 0·709 | 25 | 1·400 | 0·714 | 24·5 | 1·390 | 0·719 | 24 | 1·380 | 0·724 | 23·5 | 1·371 | 0·729 | 23 | 1·362 | 0·734 | 22·5 | 1·352 | 0·739 | 22 | 1·343 | 0·744 | 21·5 | 1·334 | 0·749 | 21 | 1·325 | 0·754 | 20·5 | 1·316 | 0·760 | 20 | 1·307 | 0·765 | 19·5 | 1·298 | 0·770 | 19 | 1·290 | 0·775 | 18·5 | 1·281 | 0·780 | 18 | 1·272 | 0·786 | 17·5 | 1·264 | 0·791 | 17 | 1·255 | 0·796 | 16·5 | 1·247 | 0·802 | 16 | 1·238 | 0·807 | 15·5 | 1·230 | 0·813 | 15 | 1·222 | 0·818 | 14·5 | 1·214 | 0·823 | 14 | 1·206 | 0·829 | 13·5 | 1·198 | 0·835 | 13 | 1·189 | 0·841 | 12·5 | 1·181 | 0·847 | 12 | 1·173 | 0·852 | 11·5 | 1·166 | 0·858 | 11 | 1·158 | 0·863 | 10·5 | 1·150 | 0·869 | 10 | 1·143 | 0·875 | 9·5 | 1·135 | 0·881 | 9 | 1·127 | 0·887 | 8·5 | 1·120 | 0·893 | 8 | 1·112 | 0·899 | 7·5 | 1·105 | 0·905 | 7 | 1·097 | 0·911 | 6·5 | 1·090 | 0·917 | 6 | 1·083 | 0·923 | 5·5 | 1·076 | 0·929 | 5 | 1·068 | 0·935 | 4·5 | 1·061 | 0·942 | 4 | 1·054 | 0·948 | 3·5 | 1·047 | 0·954 | 3 | 1·040 | 0·960 | 2·5 | 1·033 | 0·967 | 2 | 1·027 | 0·974 | 1·5 | 1·020 | 0·980 | 1 | 1·013 | 0·987 | 0·5 | 1·006 | 0·993 | -------+-------------+-------------+

A SYNOPSIS OF THE PRINCIPAL EVENTS THAT HAVE OCCURRED IN CONNECTION WITH THE HISTORY OF THE TORPEDO.

---------+-------------+---------------------------+------------+--------------------------------- Date. |Operator, &c.| Event. | Place. | Remarks. ---------+-------------+---------------------------+------------+--------------------------------- 1585. | Italian | Attack on a bridge formed | Antwerp. |Bridge completely destroyed. | Engineer, | over the Scheldt. | | Vessels, each carrying a heavily | Zambelli. | | | charged magazine, fired by | | | | clockwork, were carried by the | | | | stream against the bridge. | | | | 1775. | Captain D. | Numerous small experiments| America. |By which he proved that a charge | Bushnell. | with gunpowder charges. | | of gunpowder could be fired | | | | under water. | | | | 1776. | " | Attack on the English | New York. |Boat managed by Sergeant E. Lee. | | frigate H.M.S. _Eagle_ by| | Attack failed, owing to his | | his submarine torpedo | | inexperience in manipulating | | boat. | | this novel kind of craft. | | | | 1777. | " | Attack on the English | New London.|Drifting torpedoes employed. | | man-of-war H.M.S. | | Crew of a prize schooner astern | | _Cerberus_ by his | | of the _Cerberus_ hauled one of | | drifting torpedoes. | | the torpedoes on board, which | | | | exploded, killing 3 men and | | | | destroying a boat. | | | | 1777. | " | Attack on English ships by| " |This failed, owing to the ships | | numerous floating | | having previously hauled into | | torpedoes. Known by the | | dock to avoid the ice, but it | | name of "Battle of Kegs."| | created a great amount of | | | | confusion and alarm among the | | | | crews of the vessels. | | | | 1797. | R. Fulton. | Experiments with torpedoes| France. |These first attempts were | | on the Seine. | | generally failures. | | | | July 3, | " | Experiments with his | Brest, |These experiments were successful 1801. | | submarine boat named the | France. | in so far as proving that with | | _Nautilus_. | | such a boat he could descend to | | | | any given depth and reascend to | | | | the surface at will, and that he | | | | could remain below for a | | | | considerable time. | | | | August | " | Attempted to sink a small | " |Completely successful. This is 1801. | | vessel by means of one of| | the first vessel known to be | | his torpedoes. | | destroyed by means of a torpedo. | | | | Charge of submarine mine 20 lbs. | | | | gunpowder. | | | | 1801. | " | Attempted to destroy one | Off |Owing to the ship altering her | | of the English channel | Boulogne, | position at the moment of | | fleet by means of his | France. | setting the torpedo adrift, this | | drifting torpedoes. | | attack failed. | | | | Oct. 3, | " |Catamarran expedition under| Boulogne, |Failed, owing to a mistake in the 1804. | | Lord Keith to destroy the| France. | construction of the torpedoes. | | French fleet. | | The mines exploded, but did no | | | | damage to the French ships. | | | | Oct. | " | Similar expedition. | " |Similar failure, owing to causes 1805. | | | | above mentioned. | | | | Oct. 15, | " |Attempted to destroy a brig| Dover, |The brig was completely 1805. | | _Dorothea_ with his | England. | demolished. Two torpedoes | | drifting torpedoes. | | employed, each charged with 180 | | | | lbs. gunpowder and fired by | | | | clockwork. | | | | July 20, | " | Experiment on a large hulk| New York, |Finally successful, several 1807. | | brig. | America. | attempts being necessary, owing | | | | to faulty construction. | | | | Oct. | " | Attack on the U.S. sloop | New York. |Failed, owing to the very 1810. | | _Argus_ for finally | | ingenious though elaborate | | testing the efficacy of | | defence of the vessel, carried | | his torpedo schemes. | | out under the directions of | | | | Commodore Rodgers. | | | | 1812. | Mr. Mix. | Attack on the English | Lynn, Haven|Complete failure, though six | | frigate H.M.S. | Bay, | different attempts were made. | | _Plantagenet_ with his | America. | | | drifting torpedoes. | | | | | | June 15, | " |Attack on H.M.S. _Ramilies_| New York. | An utter failure. 1813. | | by blowing up a schooner | | | | alongside. | | | | | | 1820. | Captain |Experiment with a submarine| Moulsford, |Idea was to fasten the torpedo by | Johnson. | boat carrying a torpedo | Berks, | means of screws to the bottom of | | on its back. | England. | the hostile vessel. Trial proved | | | | successful, but the English | | | | government refused to sanction | | | | the project as being too | | | | diabolical. | | | | July 4, | Colonel | Experiment on a raft with | Ware Pond, | Successful. 1829. | Samuel | his submarine battery. | America. | | Colt. | | | | | | | 1839. | General | Destruction of the wreck | Portsmouth,|He is stated to have employed | Paisley, | of the _Royal George_ by| England. | galvanic firing to explode the | R.E. | submarine mines. | | mines. | | | | 1840. | Captain | Experiment on the _John | England. | Successful. Details not known. | Warner. | O'Gaunt_. | | | | | | June 4, | Colonel S. | Experiment to explode a | New York. |Successful. The operator was at a 1842. | Colt. | submarine mine by | | great distance from the torpedo. | | electricity. | | | | | | July 4, | " | Experiment on the U.S. | Castle |Successful. The operator was on 1842. | | gunboat _Boxer_ with | Garden, | board U.S. man-of-war at some | | electric submarine mines.| New York. | distance from the place where | | | | the explosion occurred. | | | | Aug. 20, | Colonel S. | Similar experiment on a | Potomac |Successful, the operator being 1842. | Colt. | schooner. | River, | stationed at a distance of 5 | | | America. | miles from where the mine was | | | | placed. | | | | Oct. 18, | " | Similar experiment on the | New York. |Successful. The operator being on 1842. | | brig _Volta_, 300 tons. | | board the revenue cutter | | | | _Ewing_, at a considerable | | | | distance from the scene of the | | | | explosion. | | | | April 13,| " | Experiment to destroy a | Potomac |Successful. The vessel was, at 1843. | | vessel of 500 tons _under| River, | the time of the explosion, | | weigh_ by electric | America. | sailing at the rate of 5 knots | | submarine mines. | | per hour, and to prevent the | | | | possibility of any collusion | | | | between the operator and crew, | | | | they left the ship a few moments | | | | before the catastrophe. Operator | | | | 5 miles distant. Probably | | | | several mines were placed in the | | | | form of a circle. | | | | July, | Captain | Experiment with his | Brighton, | The vessel completely destroyed. 1844. | Warner. | invisible shell, on a | England. | | | barque of 450 tons. | | | | | | Jan. 1, | Colonel S. |Experiment with an electric| New York. |Successful. The operator being at 1845. | Colt. | submarine mine. | | a distance of 40 miles from | | | | where the explosion took place. | | | | 1846. | Professor | Discovered the explosive | .. |Brought into use for military | Schonbein.| agent "gun-cotton." | | purposes about 1863, by | | | | Professor Abel. | | | | 1846. | Sobrero. | Discovered the explosive | .. |Brought into use about 1863, for | | agent nitro-glycerine. | | blasting purposes by M. Alfred | | | | Nobel, a Swede. | | | | 1854. | Russians. | Attempted destruction of | Cronstadt. |Several torpedoes were exploded | | the English men-of-war | | near these ships, but with no | | _Merlin_ and _Firefly_, | | other results than a wetting to | | by stationary submarine | | some of their men. | | mines. | | | | | | Feb. 18, |Confederates.|Federal gunboats attempting| America. |Considerably delayed, caused by 1862. | | to force the Savannah | | the submarine mines, but no | | river. | | actual damage done. This was | | | | their first appearance in a | | | | practical form during the civil | | | | war. | | | | Dec. 13, | " | Destruction of the Federal|Yazoo River,|Two torpedoes exploded under her; 1862. | | ironclad _Cairo_, by | America. | vessel much shattered, and sunk | | stationary torpedoes. | | in 12 minutes. First vessel | | | | destroyed in this war. | | | | Feb. 28, | " | The Federal monitor | Ogeechee |She was saved from sinking by 1863. | | _Montauk_, severely | River, | being run on the mud, thus | | damaged by a submarine | Georgia. | enabling the hole to be | | mine. | | temporarily closed, and the | | | | vessel taken to Port Royal. | | | | July 22, | " | The Federal ironclad |Yazoo River.|The vessel went down in 15 1863. | | gunboat _Baron de Kalb_, | | minutes. As she was sinking a | | sunk by a submarine mine.| | second torpedo exploded under | | | | her stern. No lives were lost. | | | | Aug. 8, | " | The Federal gunboat |James River.|The ship was, at the time of the 1863. | | _Commodore Barney_ | | explosion, steaming 9 knots, and | | severely damaged. | | ran into it, losing 20 men, and | | | | being some what severely | | | | damaged. It was an electric | | | | submarine mine charged with 1750 | | | | lbs. gunpowder. | | | | Oct. 5, | " | Boat torpedo attack on the| Charleston.|Failed. It was made by a boat 1863. | | Federal ship _Ironsides_.| | armed with a spar torpedo with | | | | 60 lbs. gunpowder. | | | | 1863. | " | Confederate steamers | |Owing to the shifting of the | | _Marion_ and _Ettiwa_ | " | position of barrel torpedoes. | | destroyed by their own | | | | mines. | | | | | | 1863. | " | Confederate flag of truce |James River.| The same cause. | | boat _Shultz_. | | | | | | Feb. 17, | " | Boat torpedo attack on the|Charleston. |Successful, the ship being sunk. 1864. | | Federal frigate | | A submarine boat was employed on | | _Housatonic_. | | this occasion, and owing to her | | | | running into the hole made by | | | | her torpedo, went down with the | | | | ship. | | | | March 6, | " | Boat torpedo attack on the|North Edisto|Failed, owing to the torpedo spar 1864. | | Federal ship _Memphis_. |River, South| being broken by the vessel's | | | Carolina. | screw. | | | | April 1, | " | Destruction of the Federal| St. John's |This was effected by a floating 1864. | | transport _Maple Leaf_. | River, | torpedo. | | | Florida. | | | | | April 9, | " | Boat torpedo attack on the|James River.|The ship was severely damaged, 1864. | | Federal ship _Minnesota_.| | but not sunk. Spar torpedo, | | | | charge 53 lbs. gunpowder. | | | | April 19,| " | Boat torpedo attack on the|Charleston. |Failed, owing to the boat being 1864. | | Federal frigate _Wabash_.| | discovered. | | | | May 6, | " | Loss of the _Commodore |James River.|Completely demolished by an 1864. | | Jones_. | | electric torpedo, 1750 lbs. | | | | gunpowder. This part of the | | | | river having been carefully | | | | dragged. | | | | Aug. 5, |Confederates.|Loss of the Federal monitor| Mobile Bay.|This occurred during the Federal 1864. | | _Tecumseh_. | | attack on the defences of Mobile | | | | Bay, the ship disappearing | | | | almost instantaneously. The | | | | captain and 70 of the crew were | | | | killed. | | | | Oct. 27, | Federals. | Boat torpedo attack on the| Near |The only Federal torpedo success 1864. | | Confederate ironclad | Plymouth, | during the war. The boat was | | _Albemarle_. | America. | armed with the Wood and Lay | | | | disconnecting spar torpedo. The | | | | ship was sunk. | | | | Dec. 9, |Confederates.| Loss of the Federal | Roanoke |The latter vessel was proceeding 1864. | | steamers _Otsego_ and | River. | to the assistance of the former. | | _Bazeby_. | | Both were totally destroyed. | | | | 1864. | M. A. Nobel.| Introduction of dynamite. | .. |A modified form of the explosive | | | | nitro-glycerine. | | | | 1864. | Captain |First series of experiments| Fiume, |The idea of such a weapon | Lupuis and | with the fish torpedo. | Austria. | previously known, but not acted | Mr. | | | on. | Whitehead. | | | | | | | Jan. 15, |Confederates.|Loss of the Federal monitor|Charleston. |Completely destroyed by a barrel 1865. | | _Patapsco_. | | torpedo, sinking in a few | | | | minutes. Sixty-two officers and | | | | men drowned. | | | | March 1, | " |Loss of the Federal steamer|Near |The place where this catastrophe 1865. | | _Harvest Moon_. | Georgetown.| occurred had been previously | | | | swept for torpedoes. | | | | March 30 | " | Loss of two Federal |Mobile Bay. |These losses occurred in the to April,| | monitors, and three | | final attack on Mobile, at the 19 1865.| | gunboats. | | close of the war. | | | | Sept. 2, |Paraguayans. | Loss of the Brazilian war |Currupaity, |Completely destroyed by a 1866. | | steamer _Rio Janeiro_. | Paraguay. | stationary torpedo at the | | | | bombardment of Currupaity by the | | | | Brazilian fleet. | | | | 1874. | England. | Adoption of the electric | | | | light in the Navy. | | | | | | May 29, | English. | Torpedo attack by H.M.S. | .. |This is the first Whitehead fish 1877. | | _Shah_ on the Peruvian | | torpedo ever fired against an | | ironclad _Huascar_. | | hostile ship. It failed, owing | | | | to the _Huascar_ being at too | | | | great a distance. | | | | May 12, | Russians. |Russian torpedo boat attack| Batoum. |Failed. A Turkish ship was struck 1877. | | on several Turkish ships.| | by a towing torpedo, but it | | | | failed to explode. | | | | May 26, | " | Russian torpedo boat | Matchines, |Successful. A Turkish monitor, 1877. | | attack on the Turkish | River | _Duba Saife_, was sunk. | | ships _Fettu Islam_, | Danube. | | | _Duba Saife_, and _Kilidj| | | | Ali_. | | | | | | June 9, | " | Russian torpedo boat | Sulina, |Failed. The Russian torpedo boat 1877. | | attack on the Turkish | mouth of | No. 1 was sunk, and her | | ironclads _Feteh Bulend_,| the | commander, Lieutenant Poutschin, | | _Moocardemikhair_, and | Danube. | with his crew, taken prisoner. | | _Idglalieh_. | | The attack was made by six | | | | boats. | | | | June 20, | " | Turkish monitor attacked |Rutschuk, on|Failed. The officer in command of 1877. | | by the Russian spar | the Danube.| the boat being severely wounded, | | torpedo boat_Choutka_. | | and the torpedo wires cut. This | | | | attack was made in the daytime. | | | | June 23, | " | Two Russian torpedo boats |Mouth of the|Failed, owing to the spirited 1877. | | attacked a Turkish | Aluta, | defence on the part of the | | monitor. | Danube. | Turks. Another day affair. | | | | Aug. 22, | " | The Turkish ironclad | Soukoum |Failed. The captain of the 1877. | | _Assari Shefket_ attacked| Kaleh. | _Assari Shefket_ had placed | | by four Russian torpedo | | guard boats in advance of his | | boats. | | ship, by which he was warned of | | | | the approach of the torpedo | | | | boats, and so enabled to foil | | | | the attack by a well-directed, | | | | hot fire. | | | | Oct. 10, | " | Loss of Turkish gunboat | Sulina. |The gunboat was sunk by striking 1877. | | _Suna_ at the Russian | | an electro-contactmine, placed | | attack on Sulina. | | by the Russians about 3/4 mile | | | | above the Turkish defences. | | | | About fifteen officers and men | | | | killed and wounded. | | | | Dec. 27, | " | Turkish squadron attacked | Batoum. |Failed. The Russians fired two 1877. | | by four Russian torpedo | | Whitehead fish torpedoes (the | | boats, two being armed | | first attack of this nature | | with the Whitehead fish | | during the war), both of which | | torpedo. | | were picked up by the Turks. | | | | Jan. 25, | " |Attack on Turkish ships by | Batoum. |Successful. A Turkish revenue 1878. | | two Russian torpedo boats,| | steamer on guard being sunk. | | armed with the Whitehead | | Final torpedo attack made in the | | fish torpedo. | | Russo-Turkish war (1877-78). ---------+-------------+---------------------------+------------+---------------------------------

FOOTNOTES:

[Footnote Y: See page 92.]

ERRATA.

On Page 7 (line 11) insert words "could be destroyed" after "anchor."

On Page 284, (Middle of page) "Fig. 176" should be "Fig. 168."

On Page 285 (4th line from bottom) "e" should be "d."

INDEX.

A.

Abel, experiments by Professor, 207 Abel's detonation experiments, 216 ---- high tension fuzes, 37 ---- mechanical primer, 23 Action, chemical, 269 ---- ----, in a Daniell cell, 274 ---- ---- single fluid cell, 273 Adjustments of Whitehead's fish torpedo, the, 136 Admiral Porter's torpedo ship _Alarm_, 159 ---- ----, the armament of, 160 Adoption of the fish torpedo, the invention and, 131 Advantages of electrical submarine mines, the, 28 ---- ---- mechanical mines, the, 17 Agents, torpedo explosive, 217 Air pump, the, 260 _Alarm_, Admiral Porter's torpedo ship, 159 _Albemarle_, destruction of the, 191 Aluta, the Russian torpedo boat attack off the, 200 American Civil War, the, 189 ---- ----, mechanical mines in the, 16 ---- ----, torpedoes during the, 115 ---- ----, submarine mines during the, 27 ---- extempore drifting torpedoes, 119 Apparatus, directions for using the diving, 261 ----, firing keys and shutter, 80 ----, Siemens' electric light, 241 ---- ----, conducting wires for, 247 ---- ----, rotation of armatures in, 246 ---- ----, wear and tear of, 247 ----, the shutter, 82 ---- used with a circuit breaker, shutter, 83 Application of Ohm's law, the, 276 ---- ---- the electric light, the, 256 Arcs, firing by intersectional, 71 _Argus_, Fulton's attempt against the, 6 Armatures in Siemens' electric light apparatus, rotation of, 246 Armoured cables, single cored, 43 Armstrong's system of electrical testing, 107 Arrangement of earth plates, Brown's, 100 ---- ---- wires in McEvoy's spar torpedo, 155 Arrangements, Steward's safety cock, 25 Astatic galvanometer, the, 87 Attack with Harvey's torpedoes, methods of, 127 Attacks, boat torpedo, 191 ---- ----, methods of protecting ships against, 180 Austrian method of mooring, the, 56 ---- ---- testing, the, 109 ---- self-acting circuit closers, 64 ---- testing table, the, 108 ---- torpedo experiments, 220 ---- ---- launches, Thornycroft's, 165 ---- war, torpedo operations during the, 192 Austro-Italian war, torpedo operations during the, 188 Automatic arrangements, 10 ---- electric lamps, 248

B. Balance, Wheatstone's, 97 ---- ----, manipulation of, 99 ---- ----, measurement of resistances by, 98 Barrel torpedoes, 19 Batoum, Russian torpedo boat attack at, 195, 202 Batteries, bichromate, 77 ----, double fluid, 274 ----, firing, 75 Batteries, Leclanché's Voltaic, 77 ----, Menotti test, 79 ----, signalling, 78 ---- ----, Daniell's, 78 ----, single and double fluid, 272 ----, telegraph, 79 ----, Voltaic, 79 ----, Von Ebner's, 76 Battery test for electro-motive force, Voltaic, 105 ---- ---- internal resistance, Voltaic, 104 ---- ---- potential, Voltaic, 104 Beardslee's high tension fuze, 36 ---- joint, 46 Bearings, firing by cross, 70 Bichromate batteries, 77 Boat, Bushnell's submarine, 2, 184 ----, Confederate submarine, 185 ----, experiment at Cherbourg, torpedo, 170 ----, French submarine, a, 185 ----, Lay torpedo, the, 141 ---- ----, capabilities of the, 147 ---- ----, clearing obstructions with the, 151 ---- ----, improved form of the, 153 ---- ----, launching the, 147 ---- ----, method of sinking and raising the, 149 ---- ----, used as a tug, 150 ---- ---- to clear away mines, 152 ----, _Lightning_, Thornycroft's torpedo, 168 ----, torpedo, attack at Batoum, 195, 202 ---- ---- Rustchuk, 200 ---- ---- Soukoum Kaleh, 201 ---- ---- Soulina, 198 ---- ---- off Matchin, 196 ---- ---- the Aluta, 200 ---- ----, the final, 203 ---- ----, attacks, 180, 191 ---- ----, methods of protecting ships against, 180 ---- ----, protective, Fosberry's patent, 182 Boats, submarine, 183 ---- ----, qualifications essential to, 184 ----, torpedo, 162 ---- ----, English, 173 ---- ----, Herreshoff's, 178 ---- ----, ordinary type of, 179 ---- ----, Schibau's Russian, 178 ---- ----, Spanish, 175 ---- ----, Thornycroft's, 163 ---- ----, Yarrow's, 172 Booms, construction of, 110 ----, defence of harbours by, 110 Boots for divers, 261 Boxes, junction, 51 ---- ----, for multiple cables, 52 ---- ---- single cored cables, 52 ----, resistance, 97 Brakes for Harvey's torpedoes, 123 Breaker, the circuit, 62 Breast-plate for divers, 260 Brook's torpedoes, 19 Brown's arrangement of earth plates, 100 Buoys for Harvey's torpedoes, 122 Bushnell, the inventor of torpedoes, 2 Bushnell's drifting torpedoes, 2 ---- mode of ignition, 2 ---- submarine boat, 2, 184

C. Cable, Colt's electric, 7 ---- cutters, Fulton's, 5 Cables, circuit closer, 42 ----, creeping for electric, 112 ----, defects observed in the conductivity of, 103 ----, Hooper's, 41 ----, insulated electric, 38 ----, insulation test for electric, 102 ----, jointing electric, 44 ----, junction boxes for multiple, 52 ---- ---- single cored, 52 ----, land service, 43 ----, multiple, 42 ----, sea service, 43 ----, Siemens' electric, 40 ----, Silvertown electric, 41 ----, single cored armoured, 42 ---- ---- unarmoured, 43 ----, special, 43 ----, test of electrical resistance of, 104 _Cairo_, the loss of the, 189 Calland and Marié-Davy batteries, description of the, 275 Capabilities of Lay's torpedo boat, 147 ---- ---- Whitehead's fish torpedo, 134 Carlscrona, experiments with countermines at, 237 ----, torpedo experiments at, 220, 224, 232 Case, conical-shaped torpedo, 32 ----, cylindrical-shaped torpedo, 32 ----, form and construction of torpedo, 31 ----, spherical-shaped torpedo, 32 Cell, action in a single fluid, 273 ----, chemical action of a Daniell, 274 ----, definition and properties of a Voltaic, 269 ----, description of a Menotti, 78 ----, tests for insulation, sea, 106 ---- ----, sea, 100 Charges, size of torpedo, 218 Chatham, torpedo experiments at, 220 Chemical action, 269 ---- fuzes, 23 ---- ----, defects of, 24 Cherbourg, torpedo boat experiment at, 170 Circuit breakers, 62 ---- closer cables, 43 ---- closers, Austrian self-acting, 64 ---- ----, electro-contact mine, 63 ---- ----, Mathieson's inertia, 61 ---- ----, improvements in, 63 ---- ---- spiral spring, 63 ---- ----, McEvoy's mercury, 65 ---- ---- weight magneto, 66 ---- ----, the use of, 60 ----, closing the electric, 60 ---- resistances, 276 ----, short, 268 ----, the electric, 267 Civil war, torpedo operations during the American, 189 ----, torpedoes in the American, 115 Clearing a passage through torpedo defences, 111 Coil galvanometer, the three, 88 Colt, experiments by Colonel, 7 Colt's electric cable, 7 ---- reflector, 7 _Commodore Jones_, the loss of the, 189 Commutators or switch plates, 96 Comparing electro-motive forces, 94 Composition, Rain's detonating, 23 Compounds, explosive, 208 Concentration of the electric light, 251 Condenser, definition of a, 279 Conductivity of cables, defects observed in the, 103 ----, test of platinum wire fuze for, 101 Conductors, 266 Confederate submarine boat, 185 Connections of switch plates, 100 Construction of booms, 110 ---- ---- torpedo case, 31 Copenhagen, torpedo experiments at, 223 Countermining, 112 Countermines, experiments with, 235 ---- ---- at Carlscrona, 237 ---- ---- Stokes Bay, 236 ---- ---- in the Medway, 236 Coupling dynamo-electric machines, methods of, 254 Creeping for electric cables, 112 Crimean war, submarine mines during the, 27 ---- ----, torpedo operations during the, 187 Crinoline for divers, 261 Cross bearings, firing by, 70 Current, direction of, 272 ----, measuring the intensity of a, 95 ----, the Voltaic, 270

D. Daniell's signalling battery, 78 Defects observed in the conductivity of cables, 103 ---- of chemical fuses, 24 ---- electrical submarine mines, 29 Defence of harbours by booms, 110 ----, ship, 10 Defences, clearing a passage through torpedo, 111 Defensive purposes, Harvey's torpedo for, 129 ---- torpedo operations, Russian, 193 ---- ----, Turkish, 193 ---- ---- warfare, 13 Definition and properties of a Voltaic cell, 269 ---- of a condenser, 279 ---- potential, 270 ---- the ohm, 281 ---- ---- term explosion, 204 ---- ---- explosive force, 204 ---- ---- polarization, 273 Description of a frictional electric machine, 278 ---- ---- series of firing keys, 81 ---- ---- Yarrow's torpedo boat, 172 ---- ---- Calland's and Marié-Davy's batteries, 275 ---- ---- Siemens' electric light apparatus, 241 ---- ---- Whitehead's fish torpedo, 133 _Destroyer_, Ericsson's torpedo vessel, 160 Destruction of passive obstructions, the, 113 ---- ---- the _Albemarle_, 191 ---- ---- _Duba Saife_, 197 ---- ---- _Suna_, 194 Detector galvanometer, the, 88 Detonating composition, Rain's, 23 Detonation, 206 ---- experiments, Abel's, 216 ----, theory of, 206 Dielectric, gutta percha as a, 38 ----, meaning of, 279 Differential galvanometer, the, 88 Direction of current, 272 Directions for using the diving apparatus, 261 Discharge test, the, 103 Disconnector, the, 53 Diver, dressing the, 262 Divers, boots for, 261 ----, breast plate for, 260 ----, crinoline for, 261 ----, helmet for, 260 ----, ladder for, 260 Diving, 259 ---- dress, the, 260 ----, signals employed in, 263 _Dorothea_, Fulton's destruction of the, 4 Double fluid batteries, 274 ---- ----, single and, 272 Drifting torpedoes, 116 ---- ----, American extempore, 119 ---- ----, Bushnell's, 2 ---- ----, Fulton's, 5 ---- ----, Lewis's, 117 ---- ----, McEvoy's, 118 Dualin, 216 _Duba Saife_, destruction of the, 197 Duplex spar torpedo, McEvoy's, 154 ---- ----, arrangement of wires in, 155 Dutch torpedo launches, Thornycroft's, 168 ---- ----, Yarrow's, 172 Dynamite, 211 Dynamo-electric machines, methods of coupling, 254 ---- machine, Siemens' low tension, 75

E. Earth plates, Browne's arrangement of, 100 Effect compared, explosive force and, 204 Efficiency of Thornycroft's boat engines, 171 Electric cables, creeping for, 112 ---- ----, Hooper's, 41 ---- ----, insulated, 38 ---- ----, insulation test for, 102 ---- ----, jointing, 44 ---- ----, Siemens', 40 ---- ----, Silvertown, 41 ---- circuit, closing the, 60 Electric circuit, the, 267 ---- fuses, 33 ---- lamps, automatic, 248 ---- ----, Siemens' patent, 248 ---- light apparatus, Siemens', 241 ---- ----, conducting wires for, 247 ---- ----, light produced by, 244 ---- ----, rotation of armatures in, 246 ---- ----, wear and tear of, 247 ---- ----, application of the, 256 ---- ----, concentration of the, 251 ---- ----, precautions in manipulating, 252 ---- ----, self-acting shunt for Siemens', 245 ---- ----, the, 239 ---- machine, description of a frictional, 278 ---- machines, methods of coupling dynamo, 254 Electrical resistance of cables, test of the, 104 ---- resistances, measuring, 93 ---- submarine mines, 10, 27 ---- ----, advantages of, 28 ---- ----, defects of, 22 ---- ----, mooring, 54 ---- ----, rules for using, 29 ---- test of insulated joints, 104 ---- testing, Armstrong's system of, 107 ---- tests, 85 Electricity, frictional, 278 ----, methods of generating, 269 ----, theory of, 265 Electro-contact mines, circuit closers for, 63 Electrolytes, 271 Electro-positive and electro-negative, the terms, 271 Electro-magnet, the, 281 Electro-mechanical mines, Russian, 68 Electrometers, 86 ----, Thomson's quadrant, 86 Electro-motive force, 270 ---- ----, Voltaic battery test for, 105 ---- forces, comparing, 94 Employment of torpedo ships, the, 158 Engines, efficiency of Thornycroft's boat, 171 England, torpedo experiments in, 222 English service platinum wire fuse, the, 33 ---- torpedo boats, Yarrow's, 173 Ericsson's torpedo vessel _Destroyer_, 160 Experiment at Cherbourg, torpedo boat, 170 ---- with a torpedo boat, flotation, 171 Experiments, Abel's detonation, 216 ---- by Professor Abel, 207 ---- ---- Roux and Sarrau, 207 ----, Colt's torpedo, 7 ----, Fulton's practical, 5 ----, torpedo, at Carlscrona, 220, 224, 232 ---- ---- Chatham, 220 ---- ---- Copenhagen, 223 ---- ---- Kiel, 222 ---- ---- Pola, 231 ---- ---- Portsmouth, 229, 233 ---- ----, Fulton's French, 3 ---- ----, in Austria, 220 ---- ---- England, 222 ---- ---- Turkey, 232 ---- with countermines, 235 ---- ---- at Carlscrona, 237 ---- ---- Stokes Bay, 236 ---- ---- in the Medway, 236 Explosion, definition of the term, 204 Explosive agents, torpedo, 217 ---- compounds, 208 ---- force and effect compared, 204 ---- ----, definition of the term, 204 ---- mixtures, 208 ---- substance, physical state of the, 204 Explosions, illustrated torpedo, 218 Extempore drifting torpedoes, American, 119 ---- high tension fuzes, 37 ---- ----, Fisher's, 37 ---- mechanical mine, 21

F. Failure of offensive torpedoes, the, 8 Fastest vessel in the world, the, 177 Final Russian torpedo boat attack, the, 203 Firing batteries, 75 ---- by cross bearings, 70 ---- ---- intersectional arcs, 71 ---- ---- observation, 69 ---- ---- preconcerted signal, 71 ---- Harvey's torpedoes, mode of, 121 ---- keys, 80 ---- ----, description of a series of, 81 ---- ----, Morse, 81 ----, mode of, 205 ---- ----, in 1829, 6 ---- Whitehead torpedoes, Thornycroft's method of, 140 Fish torpedo, adjustments of Whitehead's, 136 ---- ----, description of the, 133 ---- ----, invention and adoption of the, 131 ---- ----, methods of projecting the, 138 ---- ----, the mode of ignition of the, 135 Fish torpedoes in war, employment of, 133 ---- ----, Thornycroft's method of firing, 140 ---- ----, Woolwich, 140 Fisher's extempore high tension fuze, 37 Floating torpedoes, 116 Flotation experiment with a torpedo boat, 171 Fluid batteries, double, 274 ---- ----, single and double, 272 Fluid cell, action in a single, 273 Force compared, explosive effect and, 204 ----, definition of the term explosive, 204 ----, electro-motive, 270 ----, Voltaic battery test for electro-motive, 105 Forces, comparing electro-motive, 94 Fore and aft mooring, 56 Form of Lay's torpedo boat, an improved, 153 ---- ---- torpedo case, 31 Fosberry's patent torpedo boat protective, 182 Frame torpedoes, 18 Frames, projecting, 111 Franco-German war, torpedo operations during the, 192 ---- ----, torpedoes in the, 13 French submarine boat _Plongeur_, 185 ---- torpedo launches, Thornycroft's, 165, 169 ---- towing torpedoes, 131 Frictional electric machine, description of a, 278 ---- electricity, 278 Fulminate of mercury, 215 Fulton, Robert, 2 Fulton's attempt against the _Argus_, 6 ---- block ship, 5 ---- cable cutters, 5 ---- destruction of the _Dorothea_, 4 ---- drifting torpedoes, 5 ---- failures, 2 ---- French torpedo experiments, 3 ---- harpoon torpedoes, 5 ---- practical experiments, 5 ---- return to America, 4 ---- spar torpedoes, 5 ---- stationary submarine mines, 5 Fuzes, Abel's, 37 ----, Beardslee's, 35 ----, chemical, 23 ----, defects of chemical, 24 ----, electric, 33 ----, extempore, 37 ----, extempore, Fisher's, 37 ---- for conductivity, test of platinum wire, 101 ----, high tension, 34 ----, improved form of Jacobi's, 24 ----, McEvoy's percussion, 24 ----, percussion, 23 ----, platinum wire, 33 ----, ----, English service, 33 ----, ----, McEvoy's, 34 ----, sensitive, 23 ----, Statham's, 35 ----, test of resistance of platinum wire, 101 ----, testing high tension, 102 ----, Von Ebner's, 36

G. Galvanometer, astatic, 87 ----, detector, 88 ----, differential, 88 ----, tables, Siemens' universal, 287 ----, thermo, 89 ----, Thomson's reflecting, 87 ----, three coil, 88 ----, universal, Siemens', 89 Generating electricity, methods of, 269 German torpedo vessel _Uhlan_, the, 158 Gun, the Nordenfelt torpedo, 257 ----, Hotchkiss torpedo, 259 Gun-cotton, 212 Gunpowder, 208 Guns, torpedo, 257 Gutta-percha as a dielectric, 38

H. Harbours by booms, defence of, 110 Harpoon torpedoes, Fulton's, 5 Harvey's towing torpedo, 119 ---- ----, brakes for, 123 ---- ----, buoys for, 122 ---- ----, for defensive purposes, 129 ---- ----, launching, 123 ---- ----, methods of attack with, 127 ---- ----, mode of firing, 121 ---- ----, tactics with, 127 ---- ----, the value of, 129 Helmet for divers, 260 Herreshoff's torpedo boats, 178 High tension fuzes, 102 Hooper's electric cables, 41 ---- material, 39 Horsley's powder, 216 Hotchkiss torpedo gun, the, 259

I. Ignition, Bushnell's mode of, 2 ---- of Whitehead's fish torpedo, mode of, 135 Illustrated torpedo explosions, 218 Improved form of Lay's torpedo, an, 153 India rubber tube joint, the, 45 Inertia circuit closer, Mathieson's, 61 ---- ----, improvements in, 63 Instrument and observing telescope, shutter, 84 Instruments used in testing, 85 Insulated electric cables, 38 ---- joints, electrical test of, 104 Insulation, sea cell tests for, 106 ---- test for electric cables, 102 Insulators, 268 Intensity of a current, measuring the, 95 Internal resistance, Voltaic battery test for, 104 Intersectional arcs, firing by, 71 Invention and adoption of the fish torpedo, the, 131 Italian torpedo launches, Thornycroft's, 168

J. Jacobi's fuze, improved form of, 24 Jar, the Leyden, 279 Jointing electric cables, 44 Joints, Beardslee's, 46 ----, electrical test of insulated, 104 ----, india rubber tube, 45 ----, Mathieson's, 45 ----, McEvoy's, 46 ----, Nicholl's metallic, 45 ----, rules to be observed in forming, 51 ----, Siemens' permanent, 47 _Jones_, the loss of the _Commodore_, 189 Junction boxes, 51 ---- ---- for multiple cables, 52 ---- ---- single cored cables, 52 ---- ----, T, 53

K. Keys, firing, 80 ---- ----, description of a series of, 81 ---- ----, Morse, 81 Kiel, torpedo experiments at, 222 Knowledge, theoretical, 8

L. Ladder for divers, 261 ---- mooring, 55 Lamps, automatic electric, 248 ----, Siemens' patent electric, 248 Land service cables, 43 Launch, description of a Yarrow torpedo, 172 ---- for placing moorings, steam, 58 Launches, Thornycroft's torpedo, 163 ---- ---- Austrian and French torpedo, 165 ---- ---- Dutch and Italian torpedo, 168 ---- ---- French torpedo, 169 ---- ---- Norwegian torpedo, 163 ---- ---- Swedish and Danish torpedo, 165 ----, Yarrow's Dutch torpedo, 173 ---- ---- Russian torpedo, 172 Launching Harvey's torpedo, mode of, 123 ---- Lay's torpedo boat, 147 Law, the application of Ohm's, 276 Lay's torpedo boat, 141 ---- ----, an improved form of, 153 ---- ----, capabilities of, 147 ---- ----, launching, 147 ---- ----, method of sinking and raising, 149 ---- ----, used as a tug, 150 ---- ----, in clearing obstructions, 151 ---- ----, to clear away mines, 152 Leclanché's Voltaic battery, 77 Lewis's drifting torpedo, 117 Leyden jar, the, 279 Light, Siemens' electric, 241 ---- ----, conducting wires for, 247 ---- ----, concentration of, 251 ---- ----, precautions in manipulating, 252 ---- ----, rotation of armatures in, 246 ---- ----, wear and tear of, 247 ----, the electric, 239 ---- ----, application of, 256 _Lightning_, Thornycroft's torpedo boat, 168 Lithofracteur, 216 Locomotive torpedoes, 131 Loss of the _Cairo_, 189 ---- ---- _Commodore Jones_, 189

M. Machine, description of a frictional electric, 278 ----, Siemens' low tension dynamo-electric, 75 Machines, methods of coupling dynamo-electric, 254 Magnet, the electro, 281 Magnetism, 279 Magneto circuit closer, McEvoy's weight, 66 Magnets, permanent, 280 Main system, McEvoy's single, 283 Manipulation of Wheatstone's balance, the, 98 Marié-Davy battery, description of the, 275 Matchin, Russian torpedo boat attack at, 196 Material, Hooper's insulating, 39 Mathieson's cement safety plug, 21 ---- circuit closer, inertia, 61 ---- ----, improvements in, 63 ---- ----, spiral spring, 63 ---- joint, 45 McEvoy's drifting torpedo, 118 ---- duplex spar torpedo, 154 ---- improved Singer's mine, 20 ---- joint, 46 ---- mechanical mine, 22 ---- ---- primer, 21 ---- ---- Turk's head, 53 ---- mercury circuit-closer, 65 ---- papier maché safety plug, 22 ---- percussion fuzes, 24 ---- platinum wire fuzes, 34 ---- single main system, 283 ---- weight magneto circuit-closer, 66 Measurement of resistance by Wheatstone's balance, 98 Measuring electrical resistances, 93 ---- the intensity of a current, 95 Mechanical mines, 10, 16 ---- ----, advantages of, 17 ---- ----, best kinds of, 17 ---- ----, extempore, 21 ---- ----, for coast defence, 16 ---- ----, in the American war, 16 ---- ----, McEvoy's, 22 ---- ---- improved Singer's, 20 ---- ----, mooring, 26 ---- ----, Russian electro, 68 ---- ----, Singer's, 19 Mechanical primer, Abel's, 23 ---- ----, McEvoy's, 21 ---- tests, 85 Medway, experiments with countermines in the, 236 Menotti cell, description of the, 78 ---- test batteries, 79 Menzing's towing torpedo, 130 Mercury circuit-closer, McEvoy's, 65 ----, fulminate of, 215 Metallic joint, Nicholl's, 45 Method of carrying fish torpedoes, Thornycroft's, 140 ---- ---- sinking and raising Lay's torpedo, 149 ---- ---- testing, the Austrian, 109 Methods of attack with Harvey's torpedoes, 121 ---- ---- coupling dynamo-electric machines, 254 ---- ---- generating electricity, 269 ---- ---- protecting ships against torpedo attacks, 180 ---- ---- projecting Whitehead's fish torpedo, 135 Mines, submarine, electrical, 10, 27 ---- ----, advantages of, 28 ---- ----, defects of, 29 ---- ----, mooring, 54 ---- ----, in the American war, 27 ---- ----, electro-contact, circuit-closers for, 63 ---- ----, Fulton's stationary, 5 ---- ----, mechanical, 10, 16 ---- ----, advantages of, 17 ---- ----, extempore, 21 ---- ----, McEvoy's, 22 ---- ----, improved Singer's, 20 ---- ----, mooring, 26 ---- ----, Russian electro, 68 ---- ----, Singer's, 19 ---- ----, rules to be observed in planting, 74 ---- ----, sweeping for, 112 Mixtures, explosive, 208 Mode of firing Harvey's torpedoes, 121 ---- ----, in 1829, 6 Monitor _Duba Saife_, destruction of the Turkish, 197 Mooring, Austrian method of, 56 ---- electrical submarine mines, 54 ----, fore and aft, 56 ----, ladder, 55 ----, launch for placing, 58 Mooring mechanical mines, 26 ----, single rope, 56 Morse firing keys, 81 Multiple cables, 43 ---- ----, junction boxes for, 52

N. Nicholl's metallic joint, 45 Nitro-glycerine, 209 Nordenfelt torpedo gun, the, 257 Norwegian torpedo launches, Thornycroft's, 163

O. Observation, firing by, 69 ---- ----, Prussian system of, 73 Observing telescope, shutter apparatus and, 84 Obstructions, destruction of passive, 113 ----, Lay's torpedo in clearing away, 151 Offensive torpedo operations, Russian and Turkish, 195 ---- ---- warfare still in its infancy, 115 ---- torpedoes, failure of, 8, 11 ---- ----, general remarks on, 156 Ohm, definition of the, 281 Ohm's law, application of, 276 Operations, torpedo, 187 ---- ----, during the American civil war, 189 ---- ---- Austrian war, 192 ---- ---- Austro-Italian war, 188 ---- ---- Crimean war, 187 ---- ---- Franco-German war, 192 ---- ---- Paraguayan war, 191 ---- ---- Russo-Turkish war, 192 ---- ---- defensive, Russian, 193 ---- ----, Turkish, 193 ---- ---- offensive, Turkish and Russian, 195 Ordinary type of torpedo boat, the, 179 Ottoman fleet, cause of failure of the, 14 Outrigger torpedoes, spar or, 154

P. Papier maché safety plug, McEvoy's, 22 Paraguayan war, torpedo operations during the, 191 Passage through torpedo defences, clearing a, 111 Passive obstructions, destruction of, 113 Patent electric lamp, Siemens', 248 ---- torpedo boat protective, Fosberry's, 182 Percussion fuzes, 23 ---- ----, McEvoy's, 24 Permanent joint, Siemens', 47 ---- magnets, 280 Physical state of the explosive substance, the, 204 Picric powder, 209 Planting submarine mines, rules to be observed in, 74 Plates, Brown's arrangement of earth, 100 ----, connections of switch, 100 Platinum wire fuze for conductivity, test of, 101 ---- ----, test of resistance of, 101 ---- ---- fuzes, 33 ---- ----, English service, 33 ---- ----, McEvoy's, 34 _Plongeur_, French submarine boat, 185 Plug, Mathieson's cement safety, 21 ----, McEvoy's papier maché safety, 22 Pola, torpedo experiments at, 231 Polarization, definition of the term, 273 Porter's torpedo ship _Alarm_, Admiral, 159 Portsmouth, torpedo experiments at, 229, 233 Potential, definition of, 270 ----, Voltaic battery test for, 104 Powder, Horsley's, 216 ----, picric, 209 Precautions in manipulating the electric light, 252 Primer, Abel's mechanical, 23 ----, McEvoy's, 21 Projecting frames for torpedo ship defence, 111 ---- Whitehead's fish torpedo, methods of, 138 Propeller, Thornycroft's screw, 170 Properties of a Voltaic cell, definition and, 269 Prussian system of firing by observation, the, 73

Q. Quadrant electrometers, Thomson's, 86 Qualifications essential to submarine boats, the, 184

R. Rain's detonating composition, 23 Reflecting galvanometer, Thomson's, 87 Reflector, Colt's, 7 Remarks on offensive torpedoes, general, 156 Resistance boxes, 97 ---- of cables, test of electrical, 104 ---- platinum wire fuze, test of, 101 ----, Voltaic battery test for internal, 104 Resistances by Wheatstone's balance, measurement of, 98 ----, circuit, 276 ----, measuring electrical, 93 Rheostat, the, 96 Rope mooring, single, 56 Rotation of armatures in Siemens' electric light apparatus, 246 Roux and Sarrau, experiments by, 207 Rules in connection with submarine mines, 29 ---- to be observed in forming cable joints, 51 ---- ---- planting mines, 74 Russian and Turkish offensive torpedo operations, 194 ---- defensive torpedo operations, 193 ---- electro-mechanical mines, 68 ---- torpedo boat attack at Batoum, 115, 202 ---- ---- Matchin, 196 ---- ---- Rustchuk, 200 ---- ---- Soukoum Kaleh, 201 ---- ---- Soulina, 198 ---- ---- off the Aluta, 200 ---- ----, the final, 203 ---- ---- boats, Schibau's, 178 ---- ---- launch, Yarrow's, 172 ---- torpedoes, 193 Russo-Turkish war, torpedo operations during the, 192 ---- ----, torpedoes during the, 14, 115 Rutschuk, Russian torpedo attack at, 200

S. Safety cock arrangement, Steward's, 25 ---- plug, Mathieson's cement, 21 ---- ---- McEvoy's papier maché, 22 Schibau's Russian torpedo boats, 178 Science of torpedo warfare, the, 15 Sea cell test for insulation, 106 ---- ---- tests, 100 ---- service cables, 43 Second class torpedo launches, Thornycroft's, 169 Self-acting circuit closer, the Austrian, 64 Sensitive fuzes, 23 Service cables, land, 43 ---- ----, sea, 43 ---- platinum wire fuze, English, 33 Ship _Alarm_, Admiral Porter's torpedo, 159 ---- defence, 10 ----, Fulton's block, 5 Ships against torpedo attacks, methods of protecting, 180 ----, employment of torpedo, 158 Shunt, definition of a, 95 ---- for Siemens' electric light, self-acting, 245 Shutter apparatus, firing keys and, 80 ---- ----, the, 82 ---- used with a circuit breaker, 83 ---- instrument and observing telescope, 84 Siemens' electric cables, 40 ---- ---- light apparatus, 241 ---- ----, conducting wires for, 247 ---- ----, description of, 241 ---- ----, power and light produced by, 244 ---- ----, rotation of armatures in, 246 ---- ----, self-acting shunt for, 245 ---- ----, wear and tear of, 247 ---- low tension dynamo machine, 75 ---- patent electric lamp, 248 ---- permanent joints, 47 ---- universal galvanometer, 89 ---- ---- tables, 287 Signal, firing by preconcerted, 71 Signals employed in diving, 263 Silvertown electric cables, 41 Singer's mechanical mine, 19 ---- ----, McEvoy's improved, 20 Single and double fluid batteries, 272 ---- cored armoured cables, 43 ---- ---- unarmoured cables, 43 ---- fluid cell, action in a, 273 ---- main system, McEvoy's, 283 ---- rope moorings, 56 Size of torpedo charges, 218 Soukoum Kaleh, Russian torpedo attack at, 201 Soulina, Russian torpedo attack at, 198 Spanish torpedo boats, Yarrow's, 175 Spar or outrigger torpedoes, 154 ---- torpedo, McEvoy's duplex, 154 ---- torpedoes, Fulton's, 5 Special cables, 43 Spherical shaped torpedo case, the, 32 Spiral spring circuit closer, Mathieson's, 63 Stake torpedoes, 18 State of the explosive substance, the physical, 204 Statham's high tension fuze, 35 Stationary mines, Fulton's, 5 Steward's safety cock arrangement, 25 Stokes Bay, experiments with countermines at, 236 Submarine boat, Bushnell's, 2, 184 ---- ----, Confederate, 185 ---- ----, French, 185 ---- boats, 183 ---- ----, qualifications essential to, 184 ---- mines 13 ---- ----, during the Crimean and American wars, 27 ---- ----, rules for using, 29 ---- ----, sweeping for, 112 ---- ----, electrical, 27 ---- ----, advantages of, 28 ---- ----, defects of, 29 ---- ----, mooring, 54 Submersion, tests after, 106 Success in torpedo warfare, elements of, 16 _Suna_, destruction of the Turkish vessel, 194 Swedish torpedo launch, Thornycroft's, 165 Sweeping for submarine mines, 112 Switch plates, commutators or, 96 ---- ----, connections of, 100 Synopsis, 290 System, McEvoy's single main, 283 ---- of electrical testing, Armstrong's, 107 ---- ---- firing by observation, Prussian, 73 ---- ---- tests, object of, 84

T. T junction box, the, 53 Table, the Austrian testing, 108 Tables, Siemens' universal galvanometer, 287 ----, test, 99 Tactics with Harvey's torpedoes, 127 Telegraph batteries, 79 Telescope, shutter instrument and observing, 84 Tension dynamo machines, Siemens' low, 75 ---- fuses, testing high, 102 Term torpedo, definition of the, 115 Terms electro-positive and electro-negative, the, 271 Test battery, the Menotti, 79 ----, discharge, 103 ---- for electrical cables, insulation, 102 ---- of electrical resistance of cables, 104 ---- ---- insulated joints, electrical, 104 ---- ---- platinum wire fuze for conductivity, 101 ---- ---- resistance, 101 ---- tables, 99 Testing, Armstrong's system of electrical, 107 ----, Austrian method of, 109 ---- high tension fuzes, 102 ----, instruments used in, 85 ---- table, Austrian, 108 Tests after submersion, 106 ----, electrical, 85 ---- for insulation, sea cell, 106 ----, mechanical, 85 ----, object of a system, 84 ----, sea cell, 100 Theoretical knowledge of torpedoes, 8 Theory of detonation, the, 206 ---- ---- electricity, the, 265 Thermo galvanometer, the, 89 Thomson's quadrant electrometer, 86 ---- reflecting galvanometer, 87 Thornycroft's boat engines, efficiency of, 171 ---- method of carrying fish torpedoes, 140 ---- propeller, 170 ---- torpedo launches, 163 ---- ----, Austrian and French, 165 ---- ----, Danish and Swedish, 165 ---- ----, Dutch and Italian, 168 ---- ----, French, 169 ---- ----, Norwegian, 163 ---- ----, second class, 169 Three coil galvanometer, 88 Torpedo attacks, boat, 180, 191 ---- ----, methods of protecting ships against, 180 ---- boat, Lay's, 141 ---- ----, capabilities of, 147 ---- ----, an improved form of, 153 ---- ---- attack, Russian, at Batoum, 195, 202 ---- ---- ---- ---- Matchin, 196 ---- ---- ---- ---- Rustchuk, 200 ---- ---- ---- ---- Soukoum Kaleh, 201 ---- ---- ---- ---- Soulina, 198 ---- ---- ----, off the Aluta, 200 ---- ---- ----, the final, 203 ---- ---- experiment at Cherbourg, 170 ---- ---- for flotation, 171 ---- ---- _Lightning_, Thornycroft's, 168 ---- ---- protective, Fosberry's patent, 182 ---- boats, 162 ---- ----, Herreshoff's, 178 ---- ----, ordinary type of, 179 ---- ----, Schibau's Russian, 178 ---- ----, Yarrow's, 172 ---- ----, description of a, 172 ---- ---- Dutch, 172 ---- ---- English, 173 ---- ---- Russian, 172 ---- ---- Spanish, 175 ---- case, form and construction of, 31 ---- ----, conical shaped, 32 ---- ----, cylindrical shaped, 32 ---- ----, spherical shaped, 32 ---- charges, size of, 218 ---- defences, clearing a passage through, 111 ---- experiments at Carlscrona, 220, 224, 232 ---- ---- Chatham, 220 ---- ---- Copenhagen, 223 ---- ---- Kiel, 222 ---- ---- Pola, 231 ---- ---- Portsmouth, 229, 233 ---- ---- in Austria, 220 ---- ---- England, 222 ---- ---- Turkey, 232 ---- explosive agents, 217 Torpedo guns, 257 ---- ----, Hotchkiss, 259 ---- ----, Nordenfelt, 257 ---- invention and adoption of the fish, 131 ---- launches, Thornycroft's, 163 ---- operations, 187 ---- ---- during the Austro-Italian war, 188 ---- ---- Crimean war, 187 ---- ---- Franco-German war, 192 ---- ---- Paraguayan war, 191 ---- ---- Russo-Turkish war, 192 ---- ----, Russian defensive, 193 ---- ----, Turkish defensive, 193 ---- ---- and Russian offensive, 195 ---- ship _Alarm_, Admiral Porter's, 159 ---- ---- _Destroyer_, Ericsson's, 160 ---- ---- _Uhlan_, the German, 158 ---- ships, employment of, 158 ---- spar, McEvoy's duplex, 154 ---- ---- or outrigger, 154 ----, the term, 115 ---- warfare, defensive, 13 ---- ----, elements of success, 16 ---- ----, science of, 15 ---- ---- still in its infancy, offensive, 115 ----, Whitehead's fish, 133 ---- ----, adjustments of, 136 ---- ----, capabilities of, 134 ---- ----, methods of projecting, 138 ----, Woolwich fish, the, 140 ----, American extempore drifting, 119 ----, barrel, 19 ----, Brook's, 19 ----, Bushnell's drifting, 2 ---- ----, invention of, 2 ----, drifting, 116 ----, floating, 116 ----, frame, 18 ----, Fulton's drifting, 5 ---- ---- harpoon, 5 ---- ---- spar, 5 ----, general remarks on offensive, 156 ---- in war, the employment of fish, 133 ----, Lewis's drifting, 117 ----, locomotive, 131 ----, McEvoy's drifting, 118 ----, moral effect of, 9 ----, offensive, 11 ---- ----, failure of 8 ----, stake 18 ----, towing 119 ---- ----, French, 131 ---- ----, Harvey's, 119 ---- ----, methods of attack with, 127 ---- ----, the value of, 129 ---- ----, Mensing's, 130 ----, turtle 19 Turkey, torpedo experiments in, 232 Turkish defensive torpedo operations, 193 ---- monitor _Duba Saife_, destruction of the, 197 ---- offensive torpedo operations, 195 ---- ship _Suna_, loss of the, 194 ---- torpedoes, 193 ---- war, torpedoes during the Russo-, 115 Turk's head, McEvoy's mechanical, 53 Turtle torpedoes, 19

U. _Uhlan_, the German torpedo vessel, 158 Unarmoured cables, single cored, 43 Universal galvanometer, Siemens', 89 ---- ----, tables, 287 Use of circuit closers, the, 60

V. Vessel _Destroyer_, Ericsson's torpedo, 160 ---- in the world, the fastest, 177 ---- _Uhlan_, the German torpedo, 158 Voltaic batteries, 79 ---- battery, Leclanché's, 77 ---- ----, Von Ebner's, 76 ---- ----, test for electro-motive force, 105 ---- ---- internal resistance, 104 ---- ---- potential, 104 ---- cell, definition and properties of a, 269 ---- current, the, 70 Von Ebner's high tension fuze, 36 ---- ---- Voltaic battery, 6

W. War, employment of fish torpedoes in, 133 ----, torpedo operations during the American civil, 189 ---- ---- Austrian, 192 ---- ---- Austro-Italian, 188 ---- ---- Crimean, 187 ---- ---- Franco-German, 192 ---- ---- Paraguayan, 191 ---- ---- Russo-Turkish, 192 ----, torpedoes during the American civil, 115 ---- ----, Russo-Turkish, 115 Warfare, defensive torpedo, 13 ----, elements of success in torpedo, 16 ----, science of torpedo, 15 ---- still in its infancy, offensive torpedo, 115 Wars, submarine mines in the Crimean and American, 27 Wear and tear of Siemens' electric light apparatus, 247 Welden railway saved by torpedoes, the, 190 Wheatstone's balance, 97 ---- ----, manipulation of, 99 ---- ----, measurement of resistances by, 98 Whitehead's fish torpedo, 133 ---- ----, adjustments of, 136 ---- ----, capabilities of, 134 ---- ----, methods of projecting, 138 ---- ----, mode of ignition of, 135 Wire fuze for conductivity, test of platinum, 101 ---- ----, test of resistance of platinum, 101 Wire fuzes, platinum, 33 ---- ----, English service, 33 ---- ----, McEvoy's, 34 Wires in McEvoy's spar torpedo, arrangement of, 155 Woolwich fish torpedo, the, 140

Y. Yarrow's torpedo boats, 172 ---- ----, English, 173 ---- ----, Spanish, 175 ---- ---- launch, description of a, 172 ---- ---- launches, Dutch, 172 ---- ----, Russian, 172

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