followed by attempts to apply it to the production of signals at a
distance. Ampère first pointed out the possibility of making an electric
telegraph with needles surrounded by wires; but he proposed to have a
separate needle and wire for each signal to be transmitted. If Ampère
had but thought of producing signals by different combinations of two
movements, as Schweigger had before suggested for Sömmering’s telegraph,
thus making two wires and two needles suffice, the practical
introduction of the electric telegraph would have dated some twenty
years earlier than it actually did. In 1835 Baron Schilling exhibited an
electric telegraph with five magnetic needles, and he afterwards
improved upon it so far as to reduce the number of needles and
conductors to one—for to him the happy thought seems first to have
occurred that one needle could be made to produce many signals by
different combinations of its movements—sometimes to the right,
sometimes to the left. Thus two movements to the left might stand for A,
three for B, four for C, one to left followed by one to left for D, and
so on. Schilling’s apparatus does not appear to have had the requisite
qualities for practical working on the large scale. From this time,
however, telegraphic inventions succeeded each other rapidly, and we
meet with the names of Gauss, Weber, Steinheil, and others, as inventors
and discoverers in the region of practical science which was now fairly
opened, The first two used the magneto-electric machine to give motion
to the needle; and the thought of using the metals of the railway line
as conductors having occurred to Gauss, he found, on making the attempt,
that the insulation was imperfect, but he perceived that the great
apparent conductibility of the earth would allow of its being
substituted for one of the metallic communicators.
But the first who succeeded, after long and persevering effort, in
giving a practical character to the electric telegraph, was undoubtedly
Professor Wheatstone. He had for some years been engaged in electrical
researches before, in 1837–-a memorable year for telegraphic
inventions—he took out a patent in conjunction with Mr. W. Fothergill
Cooke. In their telegraph there were five magnetic needles, arranged in
a horizontal row, each needle being in a vertical position, and the
various letters of the alphabet were indicated by the convergence of the
needles towards the point at which the letter was marked on the dial.
The first electric telegraph constructed in England was made on this
system on the London and Blackwall Railway. In 1838, Messrs. Wheatstone
and Cooke had reduced the number of needles to two, and many other
improvements were effected in the apparatus for signalling, it being
made possible for any number of intermediate stations to receive the
messages. Several great railway companies erected lines with five lines
of wire, but the expense of so many conductors was found to be
considerable, and Messrs. Cooke and Wheatstone, after reducing the
number of needles and conductors to two, ultimately (1845) patented an
instrument with a single needle. It was about this time that an incident
occurred which strongly drew the attention of the general public to the
electric telegraph, which had, up to that time, been considered as the
more immediate concern of the railway companies. A foul crime had been
committed at Salthill, by the murder of a woman named Hart; and Tawell,
the suspected murderer, was traced to Slough station, and there it was
found he had taken the train to London; a description of his person was
telegraphed, with instructions to the police to watch his movements on
his arrival at Paddington. He was accordingly followed, apprehended,
tried, convicted, and executed. This incident has been graphically and
circumstantially described by Sir Francis B. Head, in connection with an
anecdote recording a curiously expressed recognition of the value of the
telegraph in furthering the ends of justice. We give the passage in
full:
“Whatever may have been his fears, his hopes, his fancies, or his
thoughts, there suddenly flashed along the wires of the electric
telegraph, which were stretched close beside him, the following words:
‘A murder has just been committed at Salthill, and the suspected
murderer was seen to take a first-class ticket for London by the train
which left Slough at 7·42 p.m. He is in the garb of a Quaker, with a
brown great-coat on, which reaches nearly down to his feet. He is in the
last compartment of the second first-class carriage.’ And yet, fast as
these words flew like lightning past him, the information they
contained, with all its details, as well as every secret thought that
had preceded them, had already consecutively flown millions of times
faster; indeed, at the very instant that, within the walls of the little
cottage at Slough, there had been uttered that dreadful scream, it had
simultaneously reached the judgment-seat of Heaven! On arriving at the
Paddington Station, after mingling for some moments with the crowd, he
got into an omnibus, and as it rumbled along he probably felt that his
identity was every minute becoming confounded and confused by the
exchange of fellow-passengers for strangers, that was constantly taking
place. But all the time he was thinking, the cad of the omnibus—a
policeman in disguise—knew that he held his victim like a rat in a cage.
Without, however, apparently taking the slightest notice of him, he took
one sixpence, gave change for a shilling, handed out this lady, stuffed
in that one, until, arriving at the Bank, the guilty man, stooping as he
walked towards the carriage door, descended the steps, paid his fare,
crossed over to the Duke of Wellington’s statue, where, pausing for a
few moments, anxiously to gaze around him, he proceeded to the Jerusalem
Coffee-house, thence over London Bridge to the Leopard Coffee-house in
the Borough, and, finally, to a lodging-house in Scott’s Yard, Cannon
Street. He probably fancied that, by making so many turns and doubles,
he had not only effectually puzzled all pursuit, but that his appearance
at so many coffee-houses would assist him, if necessary, in proving an
_alibi_; but, whatever may have been his motives or his thoughts, he had
scarcely entered the lodging when the policeman—who, like a wolf, had
followed him every step of the way—opening his door, very calmly said to
him—the words, no doubt, were infinitely more appalling to him even than
the scream that had been haunting him—‘Haven’t you just come from
Slough?’ The monosyllable, ‘No,’ confusedly uttered in reply,
substantiated his guilt. The policeman made him his prisoner; he was
thrown into jail, tried, found guilty of wilful murder, and hanged. A
few months afterwards, we happened to be travelling by rail from
Paddington to Slough, in a carriage filled with people all strangers to
one another. Like English travellers, they were mute. For nearly fifteen
miles no one had uttered a single word, until a short-bodied,
short-necked, short-nosed, exceedingly respectable-looking man in the
corner, fixing his eyes on the apparently fleeting posts and rails of
the electric telegraph, significantly nodded to us as he muttered aloud,
‘Them’s the cords that hung John Tawell!’”
So far we have followed Wheatstone and Cooke, because these gentlemen
were the first who in any country made the electric telegraph a success
on the great scale. Elsewhere than in England, laboratories and
observatories had been connected by experimental lines, and models had
been exhibited to Emperors, but these two Englishmen were the first to
construct a telegraph for practical use. It must not, however, be
supposed that they are entitled to be considered the exclusive inventors
of the electric telegraph, for we have already named other distinguished
investigators who contributed their share to this remarkable invention.
And some years before Wheatstone and Cooke had patented their first
needle telegraph, the first ideas of a system which has largely
superseded the needles for ordinary telegraphic purposes, had presented
themselves to a mind capable of developing them into the most efficient
form of telegraphic apparatus which we possess. In October, 1832, among
the passengers on board the steamship _Sully_, bound from France to the
United States, was a talented American artist who had gained some
reputation in his profession. A casual conversation with his
fellow-passengers on electricity, and the plan by which Franklin drew it
from the clouds along a slender wire, suggested to the artist the
possibility of thus communicating intelligence by signals at a distance.
He named his notion to a fellow-passenger, Dr. Jackson, an American
professor, who had devoted some attention to electrical science, and
this gentleman suggested several possible (and impossible) methods in
which the thing might, as he thought, be accomplished. None of these
suggestions, however, indicated the direction in which the idea
afterwards took practical form in Morse’s hands. Jackson had among his
baggage in the hold, and therefore inaccessible on the voyage, a
galvanic battery and an electro-magnet, and these he described to the
painter by the aid of rough sketches. When, some years afterwards, Morse
had realized his ideas of electric communication, and success was
bringing him the favour of fortune, Jackson advanced a claim to a share
in the invention, and a famous lawsuit, Jackson _v._ Morse, was ended by
a verdict in favour of Morse, which public and scientific opinion has
unanimously endorsed. In reference to this matter, Mr. R. Sabine, the
author of an excellent little treatise on “The History and Progress of
the Electric Telegraph,” has thus placed the subject in its true light:
“Two men came together. A seed-word, sown, perhaps, by some purposeless
remark, took root in fertile soil. The one, profiting by that which he
had seen and read of, made suggestions, and gave explanations of
phenomena and constructions only imperfectly understood by himself, and
entirely new to the other. The theme interested both, and became a
subject of daily conversation. When they parted, the one forgot or was
indifferent to the matter, whilst the other, more in earnest, followed
it up with diligence, toiling and scheming ways and means to realize
what had only been a dream common to both. His labours brought him to
the adoption of a method not discussed between them, and Morse became
the acknowledged inventor of a great system. Fame and fortune smiling
upon the inventor, it was natural enough that Jackson, awakening from
his unfortunate indolence, should remember his share in their earlier
interchange of ideas, that had, perhaps, first directed Morse’s
attention to the subject of telegraphy. And, although we are compelled
to pronounce dishonest those attempts which Jackson made to claim the
later and proper invention of Morse—that of the _electro-magnetic
recorder_—and strong as is our confidence in the spotless integrity of
our friend, we cannot entirely ignore Jackson—little as he has done—nor
deny him an inferior place amongst those men whose names are associated
with the history and progress of the electric telegraph in America.”
From the time of this chance conversation with Dr. Jackson, Morse
devoted his mind entirely to the subject of telegraphic communication,
and although then more than forty years of age, he abandoned the
profession in which he had already gained some distinction, and with the
energy and elastic power of adaptability which characterize the American
mind, he gave himself up to this new pursuit to such good purpose, that
a few years afterwards saw his telegraph system completely established
in the United States, where the lines now exceed 20,000 miles in length.
At the instigation of the late Emperor of the French, the Governments of
France, Belgium, Holland, Austria, Sweden, Russia, Turkey, and the Papal
States, combined to award to Professor Morse, in recognition of his
services to practical science, the sum of £16,000. It was in 1836 that
Morse had first brought his notions into a practical form, but his
apparatus has since received many improvements at his own hands, or by
the useful modifications of it which have been proposed by others. The
transmitting key invented by Morse has proved a valuable piece of
apparatus, and its simplicity has contributed much to the success of his
invention. Telegraphs on this system were erected in America in 1837,
and the Morse apparatus is now more extensively used than any other in
every country.
In 1840 Professor Wheatstone had succeeded in most ingeniously applying
electro-magnetism in such a manner as actually to realize Strada’s
sympathetic needles, by having the letters of the alphabet arranged
round the circumference of a circle, and pointed at by a revolving hand.
Such a dial is provided at each end of the line, and the sender of the
message has only to make the index of his own dial pause for an instant
at any letter; the hand of his correspondent’s dial will also pause at
the same letter. These dial telegraphs are particularly convenient for
many purposes, as they do not require a trained telegraphist to read or
send the messages. Wheatstone’s plan has been greatly simplified by
Breguet, of Paris, and others, and it is much used in mercantile and
public establishments. From the foregoing discursive historical
indication of the progress of the electric telegraph we shall now
proceed to describe the systems most commonly employed in practical
telegraphy, with a brief reference to some other interesting forms; and
in following these descriptions, the reader will find the advantage of
an acquaintance with the electrical facts discussed in the last article,
with which facts we shall presume he has become to a certain extent
familiar.
In every telegraphic system there are three distinct portions of the
apparatus, which may be separately considered, as they may be variously
combined. We have—
1º. The apparatus for producing the electricity, such as batteries,
magneto-electric machines, &c.
2º. The conductors, or wires, which convey the electricity.
3º. The apparatus for sending and for receiving the messages.
Of the first we shall have little to add to what has been said in the
last article; and before entering upon the description of the second, it
will be better to discuss the third division.
_TELEGRAPHIC INSTRUMENTS._
Telegraphs may conveniently be classed according to the mode in which
the actions of the sender produce their effect at the point where the
message is received. A first class may include those in which the
current is made to deflect magnetized needles; a second may comprise
those in which the current, by magnetizing soft iron, causes an index to
travel along a dial and point to the letter intended; a third may
embrace those in which the same action on soft iron is made to print the
despatches, either in ordinary type or in conventional signs; while in a
fourth class we may put the instruments which give their indications by
sounds only. It is obvious that in some of these systems signs only are
used, and a special training and acquaintance with the symbols is
necessary, while in the rest the ordinary alphabetic letters are shown
or recorded. In the former case the apparatus is simpler, and therefore
for the general business of public telegraphy it is almost exclusively
employed; while for private purposes, where it is often required that
the messages should be dispatched and received by persons not acquainted
with the symbolic language, the dial telegraph, or that which prints the
message in ordinary characters, will continue to be employed, in spite
of the greater complexity and greater liability to derangement of the
apparatus.
In the needle telegraphs the essential part of the apparatus is a
multiplier (page 493), having its needle mounted vertically on a
horizontal axis, to which is also attached an indicator, visible on the
face of the instrument, and formed either of a light strip of wood, or
of another magnetized needle, having its poles placed in the reverse
position to those of the needle within the coil. When the current is
sent through the latter, the index is deflected to the right or left,
according to the direction in which the current passes. Fig. 282
represents the exterior of one of Wheatstone and Cooke’s double-needle
instruments, now almost entirely superseded, where needles are used at
all, by the single-needle instrument. The face of the instrument is
marked with letters and signs, which were supposed to aid the memory of
the telegraphist, and the movements of the needles were chosen rather
with that view than any other. We need not here give the code of
signals, as the double instrument is now obsolete, and the code for the
single-needle instrument, which was devised by Wheatstone and Cooke, has
been in most cases superseded by one corresponding with the Morse code,
a deflection to the right representing a dot, and a deflection to the
left a dash.
[Illustration:
FIG. 282.—_The Double-Needle Instrument._
]
The smaller case surmounting the instrument, Fig. 282, contains a bell
or alarum, which serves to call the attention of the clerk at the
receiving station. The first electric bell-alarum was invented by
Wheatstone and Cooke. It was simply a clock alarum, put in motion by a
wound-up spring. The spring was released at the proper moment by a
detent, which was removed by the attraction of a soft iron armature to
the core of a small electro-magnet, formed by the line wire itself; but
when the current, on account of the length of the line, was too weak to
produce a sufficiently strong electro-magnet, Wheatstone caused it to
close the circuit of a local battery. The electric alarum has been
modified in a thousand ways, and as electric alarums or bells are now
coming into common use in hotels, and even private houses, we give in
Fig. 283 a representation of one of the simplest forms, in which the
bell is rung continuously by the electric current so long as the circuit
is closed. The action is very simple: a soft iron armature, A, is
attached to the steel spring, B, and prolonged into a hammer, C, which
strikes the bell, D, every time the armature is attracted to the
electro-magnet. The armature and the spring, E, form part of the
circuit, which is continued by connectors to F, and through the coils to
G. The spring, E, does not follow the armature in its motion towards the
electro-magnet, and consequently the circuit is broken before the
armature touches the magnet; but the hammer strikes the bell, and the
elasticity of the spring, B, brings the armature back into contact with
E, the circuit is closed, and the motions are repeated, so that the bell
is struck a rapid succession of blows. This _make-and-break_ movement is
precisely similar to that with which Ruhmkorff’s coils are usually
provided.
[Illustration:
FIG. 283.—_Electro-Magnetic Bells._
]
Below the dial of the instrument, in Fig. 282, may be seen two handles.
Each of these is connected with an arrangement constituting the
transmitting apparatus, by which the metallic contacts are varied
according to the position of the handles. When the handle is vertical,
all communication with the battery in connection with the instrument is
cut off, but the coils are ready to receive any current from the
line-wires. When the handle is turned to the right or left, the contacts
are such that the battery current flows into the line, and deflects to
the right or left the needles of both receiving and transmitting
instruments. The single-needle instrument as now made is of a very
simple and inexpensive construction, and it is the form principally used
in connection with the working of lines of railway. One may see at every
station in the United Kingdom the little vertical needle, mounted in the
centre of a small perfectly plain green dial-plate; for the letters and
signs with which it was formerly the practice to cover the dial have
been found to distract the eye more than they aid the memory. A boy will
after a few weeks’ practice learn to read the signals and to transmit
messages with considerable rapidity.
[Illustration:
FIG. 284.—_Portable Single-Needle Instrument._
]
The field telegraph lines, which are used in actual warfare to enable
the commander of an army to communicate with every part of his forces,
require as the essential condition for their construction rapidity of
erection and removal, and the greatest possible simplicity and
portability in the sending and receiving instruments. The wires are
fastened to trees, or other fixed supports, where such are available,
but artificial supports are provided in light poles which admit of being
readily planted in the ground and removed. In cases where it is
inexpedient or impossible to use these, the conductor may be laid along
the ground, but must then be well insulated with some non-conducting
material, which is capable of withstanding the action of the weather. A
kind of cable is usually employed, in which is the conductor, made of
copper, protected and strengthened by hemp fibres and covered with some
non-conducting material. No form of needle telegraph instrument could be
simpler than that represented in Fig. 284, which has been designed for
military purposes. The communicator, or transmitting apparatus, here
shows an arrangement very compact, and not easily deranged. The springs,
A B, press against the piece of metal marked C, with which good contact
is insured by providing the springs with several projecting steel
points. D, E are finger-keys of ebonite or ivory; underneath are two
points of a metallic conductor on which the springs can be pressed down
by a touch of the finger. This conductor is in communication with the
binding-screw, F, from which a wire proceeds to the negative or zinc end
of the battery, while the piece, C, is in metallic connection with G, to
which a wire proceeding to the positive or copper end of the battery is
attached. From B a wire, H, communicates through the hinge with one end
of the coil, the upper end of which is connected through the upper hinge
with a binding-screw not visible in the figure, and to this the end of
the line conductor is attached. From A a wire K passes to another
binding-screw, by which the earth connection is made. A current arriving
by the line traverses the coils and passes through H and B into C, hence
by A into the earth through K. When D is depressed the current from the
battery passing from G through C, A, and K, into the earth, and thus to
the distant station, returns through the coils of the instrument there
and along the line wire, through the coils, L L, and by H, B, D and F,
to the negative pole of the battery. The reader will have little
difficulty in tracing the course of the reverse currents, whether sent
or received, which deflect the needles in the opposite direction.