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_.
[Illustration: M^{c.}EVOY'S SINGLE MAIN SYSTEM
PLATE LIV.]
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