for the reception of an unusually lengthy communication. Instead of a
wire coil on a cylinder, a ribbon of very thin flat steel spring is
wound from one reel on to another across the poles of _two_
electro-magnets, which touch the lower side only of the strip. The
first magnet is traversed by a continuous current to efface the
previous record; the second magnetises the strip in obedience to
impulses from the telephone wires. The message complete, the strip is
run back, and the magnets connected with receivers, which give out
loud and intelligent speech as the strip again traverses them. The
Poulsen machine makes the transmission of the same message
simultaneously through several telephones an easy matter, as the strip
can be passed over a series of electro-magnets each connected with a
telephone.
THE TELAUTOGRAPH.
It is a curious experience to watch for the first time the movements
of a tiny Telautograph pen as it works behind a glass window in a
japanned case. The pen, though connected only with two delicate wires,
appears instinct with human reason. It writes in a flowing hand, just
as a man writes. At the end of a word it crosses the t’s and dots the
i’s. At the end of a line it dips itself in an inkpot. It punctuates
its sentences correctly. It illustrates its words with sketches. It
uses shorthand as readily as longhand. It can form letters of all
shapes and sizes.
And yet there is no visible reason why it should do what it does. The
japanned case hides the guiding agency, whatever it may be. Our ears
cannot detect any mechanical motion. The writing seems at first sight
as mysterious as that which appeared on the wall to warn King
Belshazzar.
In reality it is the outcome of a vast amount of patience and
mechanical ingenuity culminating in a wonderful instrument called the
Telautograph. The Telautograph is so named because by its aid we can
send our autographs, _i.e._ our own particular handwriting,
electrically over an indefinite length of wire, as easily as a
telegraph clerk transmits messages in the Morse alphabet. Whatever
the human hand does on one telautograph at one end of the wires, that
will be reproduced by a similar machine at the other end, though the
latter be hundreds of miles away.
[Illustration: _By kind permission of The Telautograph Co._
_The Telautograph. The upper portion is the Receiver, the lower (with
cover removed) is the Transmitter._]
The instrument stands about eighteen inches high, and its base is as
many inches square. It falls into two parts, the receiver and the
transmitter. The receiver is vertical and forms the upright and back
portion of the telautograph. At one side of it hangs an ordinary
telephone attachment. The transmitter, a sloping desk placed
conveniently for the hand, is the front and horizontal portion. The
receiver of one station is connected with the transmitter of another
station; there being ordinarily no direct communication between the
two parts of the same instrument.
An attempt will be made to explain, with the help of a simple diagram,
the manner in which the telautograph performs its duties.
These duties are threefold. In the first place, it must reproduce
whatever is written on the transmitter. Secondly, it must reproduce
only what is _written_, not all the movements of the hand. Thirdly, it
must supply the recording pen with fresh paper to write on, and with
fresh ink to write with.
In our diagram we must imagine that all the coverings of the
telautograph have been cleared away to lay bare the most essential
parts of the mechanism. For the sake of simplicity not all the coils,
wires, and magnets having functions of their own are represented, and
the drawing is not to scale. But what is shown will enable the reader
to grasp the general principles which work the machine.
Turning first of all to the transmitter, we have P, a little platform
hinged at the back end, and moving up and down very slightly in front,
according as pressure is put on to or taken off it by the pencil.
Across it a roll of paper is shifted by means of the lever S, which
has other uses as well. To the right of P is an electric bell-push, E,
and on the left K, another small button.
The pencil is at the junction of two small bars CC’, which are hinged
at their other end to the levers AA’. Any motion of the pencil is
transmitted by CC’ to AA’, and by them to the arms LL’, the
extremities of which, two very small brushes ZZ’, sweep along the
quadrants RR’. This is the first point to observe, that the position
of the pencil decides on which sections of the quadrants these little
brushes rest, and consequently how much current is to be sent to the
distant station. The quadrants are known technically as rheostats, or
current-controllers. Each quadrant is divided into 496 parts,
separated from each other by insulating materials, so that current can
pass from one to the other only by means of some connecting wire. In
our illustration only thirteen divisions are given, for the sake of
clearness. The dark lines represent the insulation. WW’ are the very
fine wire loops connecting each division of the quadrant with its
neighbours. If then a current from the battery B enters the rheostat
at division 1 it will have to pass through all these wires before it
can reach division 13. The current always enters at 1, but the point
of departure from the rheostat depends entirely upon the position of
the brushes Z or Z’. If Z happens to be on No. 6 the current will pass
through five loops of wire, along the arm L, and so through the main
wire to the receiving station; if on No. 13, through twelve loops.
[Illustration: THE TELAUTOGRAPH]
Before going any further we must have clear ideas on the subject of
electrical resistance, upon which the whole system of the telautograph
is built up. Electricity resembles water in its objection to flow
through small passages. It is much harder to pump water through a
half-inch pipe than through a one-inch pipe, and the longer the pipe
is, whatever its bore, the more work is required. So then, two things
affect resistance--_size_ of pipe or wire, and _length_ of pipe or
wire.
The wires WW’ are very fine, and offer very high resistance to a
current; so high that by the time the current from battery B has
passed through all the wire loops only one-fifteenth or less of the
original force is left to traverse the long-distance wire.
The rheostats act independently of one another. As the pencil moves
over the transmitting paper, a succession of currents of varying
intensity is sent off by each rheostat to the receiving station.
The receiver, to which we must now pay attention, has two arms DD’,
and two rods FF’, corresponding in size with AA’ and CC’ of the
transmitter. The arms DD’ are moved up and down by the coils TT’ which
turn on centres in circular spaces at the bend of the magnets MM’. The
position of these coils relatively to the magnets depend on the
strength of the currents coming from the transmitting station. Each
coil strains at a small spiral spring until it has reached the
position in which its electric force is balanced by the retarding
influence of the spring. One of the cleverest things in the
telautograph is the adjustment of these coils so that they shall
follow faithfully the motions of the rods LL’ in the transmitter.
[Illustration: _By kind permission of_] [_The Telautograph Co._
_An example of the work done by the Telautograph. The upper sketch
shows a design drawn on the transmitter; the lower is the same design
as reproduced by the receiving instrument, many miles distant._]
We are now able to trace the actions of sending a message. The sender
first presses the button E to call the attention of some one at the
receiving station to the fact that a message is coming, either on the
telephone or on the paper. It should be remarked, by-the-bye, that the
same wires serve for both telephone and telautograph, the unhooking of
the telephone throwing the telautograph out of connection for the
time.
He then presses the lever S towards the left, bringing his transmitter
into connection with the distant receiver, and also moving a fresh
length of paper on to the platform P. With his pencil he writes his
message, pressing firmly on the paper, so that the platform may bear
down against an electric contact, X. As the pencil moves about the
paper the arms CC’ are constantly changing their angles, and the
brushes ZZ’ are passing along the segments of the rheostats.
Currents flow in varying intensity away to the coils TT’ and work the
arms DD’, the wires FF’, and the pen, a tiny glass tube.
In the perfectly regulated telautograph the arms AA’ and the arms DD’
will move in unison, and consequently the position of the pen must be
the same from moment to moment as that of the pencil.
Mr. Foster Ritchie, the clever inventor of this telautograph, had to
provide for many things besides mere slavish imitation of movement. As
has been stated above, the pen must record only those movements of the
pencil which are essential. Evidently, if while the pencil returns to
dot an _i_ a long line were registered by the pen corresponding to the
path of the pencil, confusion would soon ensue on the receiver; and
instead of a neatly-written message we should have an illegible and
puzzling maze of lines. Mr. Ritchie has therefore taken ingenious
precautions against any such mishap. The platen P on being depressed
by the pencil touches a contact, X, which closes an electric circuit
through the long-distance wires and excites a magnet at the receiving
end. That attracts a little arm and breaks another circuit, allowing
the bar Y to fall close to the paper. The wires FF’ and the pen are
now able to rest on the paper and trace characters. But as soon as the
platen P rises, on the removal of the pencil from the transmitting
paper, the contact at X is broken, the magnet at the receiver ceases
to act, the arm it attracted falls back and sets up a circuit which
causes the bar to spring up again and lift the pen. So that unless
you are actually pressing the paper with your pencil, the pen is not
marking, though it may be moving.
As soon as a line is finished a fresh surface of paper is required at
both ends. The operator pushes the lever S sideways, and effects the
change mechanically at his end. At the same time a circuit is formed
which excites certain magnets at the receiver and causes the shifting
forward there also of the paper, and also breaks the _writing_
current, so that the pen returns for a moment to its normal position
of rest in the inkpot.
It may be asked: If the wires are passing currents to work the writing
apparatus, how can they simultaneously affect the lifting-bar, Y? The
answer is that currents of two different kinds are used, a direct
current for writing, a vibratory current for depressing the
lifting-bar. The _direct_ current passes from the battery B through
the rheostats RR’ along the wires, through the coils working the arms
DD’ and into the earth at the far end; but the _vibratory_ current,
changing its direction many times a second and so neutralising itself,
passes up one wire and back down the other through the lifting-bar
connection without interfering with the direct current.
The message finished, the operator depresses with the point of his
pencil the little push-key, K, and connects his receiver with the
distant transmitter in readiness for an answer.
The working speed of the telautograph is that of the writer. If
shorthand be employed, messages can be transmitted at the rate of over
100 words per minute. As regards the range of transmission, successful
tests have been made by the postal authorities between Paris and
London, and also between Paris and Lyons. In the latter case the
messages were sent from Paris to Lyons and back directly to Paris, the
lines being connected at Lyons, to give a total distance of over 650
miles. There is no reason why much greater length of line should not
be employed.
The telautograph in its earlier and imperfect form was the work of
Professor Elisha Gray, who invented the telephone almost
simultaneously with Professor Graham Bell. His telautograph worked on
what is known as the step-by-step principle, and was defective in that
its speed was very limited. If the operator wrote too fast the
receiving pen lagged behind the transmitting pencil, and confusion
resulted. Accordingly this method, though ingenious, was abandoned,
and Mr. Ritchie in his experiments looked about for some preferable
system, which should be simpler and at the same time much speedier in
its action. After four years of hard work he has brought the rheostat
system, explained above, to a pitch of perfection which will be at
once appreciated by any one who has seen the writing done by the
instrument.
The advantages of the Telautograph over the ordinary telegraphy may be
briefly summed up as follows:--
Anybody who can write can use it; the need of skilled operators is
abolished.
A record is automatically kept of every message sent.
The person to whom the message is sent need not be present at the
receiver. He will find the message written out on his return.
The instrument is silent and so insures secrecy. An ordinary telegraph
may be read by sound; but not the telautograph.
It is impossible to tap the wires unless, as is most unlikely, the
intercepting party has an instrument in exact accord with the
transmitter.
It can be used on the same wires as the ordinary telephone, and since
a telephone is combined with it, the subscriber has a double means of
communication. For some items of business the telephone may be used as
preferable; but in certain cases, the telautograph. A telephone
message may be heard by other subscribers; it is impossible to prove
the authenticity of such a message unless witnesses have been present
at the transmitting end; and the message itself may be misunderstood
by reason of bad articulation. But the telautograph preserves secrecy
while preventing any misunderstanding. Anything written by it is for
all practical purposes as valid as a letter.
We must not forget its extreme usefulness for transmitting sketches. A
very simple diagram often explains a thing better than pages of
letter-press. The telautograph may help in the detection of criminals,
a pictorial presentment of whom can by its means be despatched all
over the country in a very short time. And in warfare an instrument
flashing back from the advance-guard plans of the country and of the
enemy’s positions might on occasion prove of the greatest importance.
MODERN ARTILLERY.
The vast subject of artillery in its modern form, including under this
head for convenience’ sake not only heavy ordnance but machine-guns
and small-arms, can of necessity only be dealt with most briefly in
this chapter.
It may therefore be well to take a general survey and to define
beforehand any words or phrases which are used technically in
describing the various operations.
The employment of firearms dates from a long-distant past, and it is
interesting to note that many an improvement introduced during the
last century is but the revival of a former invention which only lack
of accuracy in tools and appliances had hitherto prevented from being
brought into practical usage.
So far back as 1498 the art of _rifling_ cannon in straight grooves
was known, and a British patent was taken out in 1635 by Rotsipan. The
grooves were first made spiral or screwed by Koster of Birmingham
about 1620. Berlin possesses a rifled cannon with thirteen grooves
dated 1664. But the first recorded uses of such weapons in actual
warfare was during Louis Napoleon’s Italian campaign in 1859, and two
years later by General James of the United States Army.
The system of _breech-loading_, again, is as old as the sixteenth
century, and we find a British patent of 1741; while the first United
States patent was given in 1811 for a flint-lock weapon.
_Magazine_ guns of American production appeared in 1849 and 1860, but
these were really an adaptation of the old matchlock revolvers, said
to belong to the period 1480-1500. There is one in the Tower of London
credited to the fifteenth century, and a British patent of 1718
describes a well-constructed revolver carried on a tripod and of the
dimensions of a modern machine-gun. The inventor gravely explains that
he has provided round chambers for round bullets to shoot Christians,
and square chambers with square missiles for use against the Turks!
The word “ordnance” is applied to heavy guns of all kinds, and
includes guns mounted on fortresses, naval guns, siege artillery, and
that for use in the field. These guns are all mounted on stands or
carriages, and may be divided into three classes:--
(i.) _Cannon_, or heavy guns.
(ii.) _Howitzers_, for field, mountain, or siege use, which are
lighter and shorter than cannon, and designed to throw hollow
projectiles with comparatively small charges.
(iii.) _Mortars_, for throwing shells at a great elevation.
The modern long-range guns and improved howitzers have, however,
virtually superseded mortars. _Machine-guns_ of various forms are
comparatively small and light, transportable by hand, and filling a
place between cannon and small-arms, the latter term embracing the
soldier’s personal armament of rifle and pistol or revolver, which are
carried in the hand.
A group of guns of the like design are generally given the name of
their first inventor, or the place of manufacture: such as the
Armstrong gun, the Vickers-Maxim, the Martini-Henry rifle, or the
Enfield.
The indifferent use of several expressions in describing the same
weapon is, however, rather confusing. One particular gun may be thus
referred to:--by its _weight_ in tons or cwt., as “the 35-ton gun”; by
the weight of its _projectile_, as “a 68-pounder”; by its _calibre_,
that is, size of bore, as “the 4-inch gun.” Of these the heavier
breech-loading (B.-L.) and quick-firing (Q.-F.) guns are generally
known by the size of bore; small Q.-F.’s, field-guns, &c., by the
weight of projectile. It is therefore desirable to enter these
particulars together when making any list of service ordnance for
future reference.
No individual gun, whether large or small, is a single whole, but
consists of several pieces fastened together by many clever devices.
The principal parts of a cannon are:--
(1) The _chase_, or main tube into which the projectile is
loaded; terminating at one end in the muzzle.
(2) The _breech-piece_, consisting of (_a_) the chamber, which
is bored out for a larger diameter than the chase to contain
the firing-charge. (_b_) The _breech-plug_, which is closed
before the charge is exploded and screwed tightly into place,
sealing every aperture by means of a special device called the
“obturator,” in order to prevent any gases passing out round it
instead of helping to force the projectile forwards towards the
muzzle.
The whole length of inside tube is termed the _barrel_, as in a
machine-gun, rifle, or sporting-piece, but in the two latter weapons
the breech-opening is closed by sliding or springing back the
breech-block or bolt into firing position.
Old weapons as a rule were smooth-bored (S.-B.), firing a round
missile between which and the barrel a considerable amount of the
gases generated by the explosion escaped and caused loss of power,
this escape of gas being known as _windage_.
In all modern weapons we use conical projectiles, fitted near the base
with a soft copper driving-band, the diameter of which is somewhat
larger than that of the bore of the gun, and cut a number of spiral
grooves in the barrel. The enormous pressure generated by the
explosion of the charge forces the projectile down the bore of the gun
and out of the muzzle. The body of the projectile, made of steel or
iron, being smaller in diameter than the bore, easily passes through,
but the driving-band being of greater diameter, and being composed of
soft copper, can only pass down the bore with the projectile by
flowing into the grooves, thus preventing any escape of gas, and being
forced to follow their twist. It therefore rotates rapidly upon its
own longitudinal axis while passing down the barrel, and on leaving
the muzzle two kinds of velocity have been imparted to it;--first, a
velocity of motion through the air; secondly, a velocity of rotation
round its axis which causes it to fly steadily onward in the required
direction, _i.e._ a prolongation of the axis of the gun. Thus extreme
velocity and penetrating power, as well as correctness of aim, are
acquired.
The path of a projectile through the air is called its _trajectory_,
and if uninterrupted its flight would continue on indefinitely in a
perfectly straight line. But immediately a shot has been hurled from
the gun by the explosion in its rear two other natural forces begin to
act upon it:--
Gravitation, which tends to bring it to earth.
Air-resistance, which gradually checks its speed.
(Theoretically, a bullet dropped perpendicularly from the muzzle of a
perfectly horizontal rifle would reach the ground at the same moment
as another bullet fired from the muzzle horizontally, the action of
gravity being the same in both cases.)
Its direct, even course is therefore deflected till it forms a curve,
and sooner or later it returns to earth, still retaining a part of its
velocity. To counteract the attraction of gravity the shot is thrown
upwards by elevating the muzzle, care being taken to direct the gun’s
action to the same height above the object as the force of gravitation
would draw the projectile down during the time of flight. The gunner
is enabled to give the proper inclination to his piece by means of the
_sights_; one of these, near the muzzle, being generally fixed, while
that next the breech is adjustable by sliding up an upright bar which
is so graduated that the proper _elevation_ for any required range is
given.
The greater the velocity the flatter is the trajectory, and the more
dangerous to the enemy. Assuming the average height of a man to be six
feet, all the distance intervening between the point where a bullet
has dropped to within six feet of the earth, and the point where it
actually strikes is dangerous to any one in that interval, which is
called the “danger zone.” A higher initial velocity is gained by using
stronger firing charges, and a more extended flight by making the
projectile longer in proportion to its diameter. The reason why a
shell from a cannon travels further than a rifle bullet, both having
the same muzzle velocity, is easily explained.
A rifle bullet is, let us assume, three times as long as it is thick;
a cannon shell the same. If the shell have ten times the diameter of
the bullet, its “nose” will have 10 × 10 = 100 times the area of the
bullet’s nose; but its _mass_ will be 10 × 10 × 10 = 1000 times that of
the bullet.
In other words, when two bodies are proportional in all their
dimensions their air-resistance varies as the square of their
diameters, but their mass and consequently their momentum varies as
the _cube_ of their diameters. The shell therefore starts with a great
advantage over the bullet, and may be compared to a “crew” of cyclists
on a multicycle all cutting the same path through the air; whereas the
bullet resembles a single rider, who has to overcome as much
air-resistance as the front man of the “crew” but has not the weight
of other riders behind to help him.
As regards the effect of rifling, it is to keep the bullet from
turning head over heels as it flies through the air, and to maintain
it always point forwards. Every boy knows that a top “sleeps” best
when it is spinning fast. Its horizontal rotation overcomes a tendency
to vertical movement towards the ground. In like manner a rifle
bullet, spinning vertically, overcomes an inclination of its atoms to
move out of their horizontal path. Professor John Perry, F.R.S., has
illustrated this gyroscopic effect, as it is called, of a whirling
body with a heavy flywheel in a case, held by a man standing on a
pivoted table. However much the man may try to turn the top from its
original direction he will fail as long as its velocity of rotation is
high. He may move the top relatively to his body, but the table will
turn so as to keep the centre line of the top always pointing in the
same direction.
RIFLES.