THE ELECTRIC TELEGRAPH.
THE VOLTAIC PILE--DANIELL’S BATTERY--USE OF CONDUCTING WIRE BY
WEBER--STEINHEIL EMPLOYS EARTH AS RETURN CIRCUIT--PROF. HENRY’S
ELECTRO MAGNET, AND FIRST TELEGRAPHIC EXPERIMENT--PROF. MORSE’S
TELEGRAPHIC CODE AND REGISTER--FIRST LINE BETWEEN WASHINGTON
AND BALTIMORE--BAIN’S CHEMICAL TELEGRAPH--GINTL’S DUPLEX
TELEGRAPH--EDISON’S QUADRUPLEX--HOUSE’S PRINTING TELEGRAPH--FAC
SIMILE TELEGRAPHS--CHANNING AND FARMER FIRE ALARM--TELEGRAPHING BY
INDUCTION--WIRELESS TELEGRAPHY BY MARCONI--STATISTICS.
In the effort to lengthen out the limited span of life into a greater
record of results, time becomes an object of economy. To save time is to
live long, and this in a pre-eminent degree is accomplished by the
telegraph. Of all the inventions which man has called into existence to
aid him in the fulfillment of his destiny, none so closely resembles man
himself in his dual quality of body and soul as the telegraph. It too
has a body and soul. We see the wire and the electro-magnet, but not the
vital principle which animates it. Without its subtile, pulsating,
intangible spirit, it is but dead matter. But vitalized with its
immortal soul it assumes the quality of animated existence, and through
its agency thought is extended beyond the limitations of time and space,
and flashes through air and sea around the world. Its moving principle
flows more silently than a summer’s zephyr, and yet it rises at times to
an angry and deadly crash in the lightning stroke. At once powerful and
elusive, it remained for Professor Morse to capture this wild steed,
and, taming it, place it in the permanent service of man. On May 24,
1844, there went over the wires between Washington and Baltimore the
first message--“What hath God wrought?” This was both prayer and praise,
and no more lofty recognition of the divine power and beneficence could
have been made. It was indeed the work of God made manifest in the hands
of His children.
Popular estimation has always credited Prof. Morse with the invention of
the telegraph, but to ascribe to him all the praise would do great
injustice to many other worthy workers in this field, some of whom are
regarded by the best judges to be entitled to equal praise.
The practical telegraph as originally used is resolvable into four
essential elements, viz., the battery, the conducting wire, the
electro-magnet, and the receiving and transmitting instruments.
The development of the battery began with Galvani in 1790, and Volta in
1800. Galvani discovered that a frog’s legs would exhibit violent
muscular contraction when its exposed nerves were touched with one metal
and its muscles were touched with another metal, the two metals being
connected. The effect was due to an electric current generated and
acting with contractile effect on the muscles of the frog’s legs.
[Illustration: FIG. 1.]
From this phenomenon, the chemical action of acids upon metals and the
production of an electric current were observed, and the voltaic pile
was invented. This consisted of alternate discs of copper and zinc,
separated by layers of cloth steeped in an acidulated solution. This was
the invention of Volta. From this grew the Daniell battery, invented in
1836 by Prof. Daniell of London, quickly followed by those of Grove,
Smee, and others. These batteries were more constant or uniform in the
production of electricity, were free from odors, and did not require
frequent cleaning, as did the plates of the voltaic pile, which were
important results for telegraphic purposes. The Daniell battery in its
original form employed an acidulated solution of sulphate of copper in a
copper cell containing a porous cup, and a cylinder of amalgamated zinc
in the porous cup and surrounded by a weak acid solution. In the
illustration, which shows a slightly modified form, a cruciform rod of
zinc within a porous cup is surrounded by a copper cell, the whole being
enclosed within a glass jar.
[Illustration: FIG. 2.--DANIELL’S BATTERY.]
The second element of the telegraph--the conducting wire--was scarcely
an invention in itself, and the fact that electricity would act at a
distance through a metal conductor had been observed many years before
the Morse telegraph was invented. In 1823, however, Weber discovered
that a copper wire which he had carried over the houses and church
steeples of Göttingen from the observatory to the cabinet of Natural
Philosophy, required no special insulation. This was an important
observation in the practical construction of telegraph lines. One of
even greater importance, however, was that of Prof. Steinheil, of
Munich, who, in 1837, made the discovery of the practicability of using
the earth as one-half, or the return section, of the electric conductor.
[Illustration: FIG. 3.--PROF. HENRY’S INTENSITY MAGNET.]
The third element of the telegraph is the electro-magnet. This, and its
arrangement as a relay in a local circuit, was a most important
invention, and contributed quite as much to the success of the telegraph
as did the inventions of Prof. Morse. It may be well to say that an
electro-magnet is a magnet which attracts an iron armature when an
electric current is sent through its coil of wire, and loses its
attractive force when the circuit is cut off, thereby rendering it
possible to produce mechanical effects at a distance through the agency
of electrical impulses only. For the electro-magnet the world is chiefly
indebted to Prof. Joseph Henry, formerly of Princeton, N. J., but later
of the Smithsonian Institution. In 1828 he invented the energetic modern
form of electro-magnet with silk covered wire wound in a series of
crossed layers to form a helix of multiple layers around a central soft
iron core, and in 1831 succeeded in making practical the production of
mechanical effects at a distance, by the tapping of a bell by a rod
deflected by one of his electro-magnets. This experiment may be
considered the pioneer step of the telegraph.
[Illustration: FIG. 4.
HENRY.
STURGEON.
]
Great as was the work of Prof. Henry, he must share the honors with a
number of prior inventors who made the electro-magnet possible.
Electro-magnetism, the underlying principle of the electro-magnet, was
first discovered in 1819 by Prof. Oersted, of Copenhagen. In 1820
Schweigger added the multiplier. Arago in the same year discovered that
a steel rod was magnetized when placed across a wire carrying an
electric current, and that iron filings adhered to a wire carrying a
voltaic current and dropped off when the current was broken. M. Ampere
substituted a helix for the straight wire, and Sturgeon, of England, in
1825 made the real prototype of the electro-magnet by winding a piece of
bare copper wire in a single coil around a varnished and insulated iron
core of a horse shoe form, but the powerful and effective electro-magnet
of Prof. Henry is to-day an essential part of the telegraph, is in
universal use, and is the foundation of the entire electrical art. It is
unfortunate that Prof. Henry did not perpetuate the records of his
inventions in patents, to which he was opposed, for there is good reason
to believe that he was also the original inventor of the important
arrangement of the electro-magnet as a relay in local circuit, and other
features, which have been claimed by other parties upon more enduring
evidence, but perhaps with less right of priority.
[Illustration: FIG. 5.--MORSE’S FIRST MODEL PENDULUM INSTRUMENT.]
The fourth and great final addition to the telegraph which crowned it
with success was the Morse register and alphabetical code, the invention
of Prof. Samuel F. B. Morse, of Massachusetts. Prof. Morse’s invention
was made in 1832, while on board ship returning from Europe. He set up
an experimental line in 1835, and got his French patent October 30,
1838, and his first United States patent June 20, 1840, No. 1647. In
1844 the United States Congress appropriated $30,000 to build a line
from Baltimore to Washington, and on May 24, 1844, the notable message,
“What Hath God wrought?” went over the wires.
[Illustration: FIG. 6.--THE MORSE CODE.]
Morse’s first model, his pendulum instrument of 1837, is illustrated in
Fig. 5. A pendulum carrying a pencil was in constant contact with a
strip of paper drawn beneath the pencil. As long as inactive the pencil
made a straight line. The pendulum carried also an armature, and an
electro-magnet was placed near the armature. A current passed through
the magnet would draw the pendulum to one side. On being released the
pendulum would return, and in this way zigzag markings, as shown at 4
and 5, would be produced on the strip of paper, which formed the
alphabet. A different alphabet, known as the Morse Code, was
subsequently adopted by Morse, and in 1844 the receiving register shown
at Fig. 7 was adopted, which finally assumed the form shown at Fig. 8.
The alphabet consisted simply of an arrangement of dots and dashes in
varying sequence. The register is an apparatus operated by the combined
effects of a clock mechanism and electro-magnet. Under a roll, see Fig.
8, a ribbon of paper is drawn by the clockwork. A lever having an
armature on one end arranged over the poles of an electro-magnet,
carries on the other end a point or stylus. When an electric impulse is
sent over the line the electro-magnet attracts the armature, and the
stylus on the other end of the lever is brought into contact with the
paper strip, and makes an indented impression. A short impulse gives a
dot, and a long impulse holds the stylus against the paper long enough
to allow the clock mechanism to pull the paper under the stylus and make
a dash. By the manipulation of a key for closing the electric circuit
the short or long impulse may be sent, at the pleasure of the operator.
[Illustration: FIG. 7.--MORSE RECEIVER.]
This constituted the completed invention of the telegraph, and on
comparing the work of Profs. Henry and Morse, it is only fair to say
that Prof. Henry’s contribution to the telegraph is still in active use,
while the Morse register has been practically abandoned, as no expert
telegrapher requires the visible evidence of the code, but all rely now
entirely upon the sound click of the electro-magnet placed in the local
circuit and known as a sounder, the varying time lengths of gaps between
the clicks serving every purpose of rapid and intelligent communication.
The invention of the telegraph has been claimed for Steinheil, of
Munich, and also for Cooke and Wheatstone, in England, but few will
deny that it is to Prof. Morse’s indefatigable energy and inventive
skill, with the preliminary work of Prof. Henry, that the world to-day
owes its great gift of the electric telegraph, and with this gift the
world’s great nervous forces have been brought into an intimate and
sensitive sympathy.
[Illustration: FIG. 8.--PERFECTED MORSE REGISTER.]
Whenever an invention receives the advertisement of public approval and
commercial exploitation, the development of that invention along various
lines follows rapidly, and so when practical telegraphic communication
was solved by Henry, Morse, and others, further advances in various
directions were made. Efforts to increase the rapidity in sending
messages soon grew into practical success, and in 1848 _Bain’s Chemical
Telegraph_ was brought out. (U. S. Pats. No. 5,957, Dec. 5, 1848, and
No. 6,328, April 17, 1849.) This employed perforated strips of paper to
effect automatic transmission by contact made through the perforations
in place of the key, while a chemically prepared paper at the opposite
end of the line was discolored by the electric impulses to form the
record. This was the pioneer of the automatic system which by later
improvements is able to send over a thousand words a minute.
[Illustration: FIG. 9.--HOUSE PRINTING TELEGRAPH.]
[Illustration: FIG. 10.--STOCK BROKER’S “TICKER,” WITH GLASS COVER
REMOVED.]
In line with other efforts to increase the capacity of the wires, the
_duplex telegraph_ was invented by Dr. William Gintl, of Austria, in
1853, and was afterwards improved by Carl Frischen, of Hanover, and by
Joseph B. Stearns, of Boston, Mass, who in 1872 perfected the duplex (U.
S. Pats. No. 126,847, May 14, 1872, and No. 132,933, Nov. 12, 1872).
This system doubles the capacity of the telegraphic wire, and its
principle of action permits messages sent from the home station to the
distant station to have no effect on the home station, but full effect
on the distant station, so that the operators at the opposite ends of
the line may both telegraph over the same wire, at the same time, in
opposite directions. This system has been further enlarged by the
quadruplex system of Edison, which was brought out in 1874 (and
subsequently developed in U. S. Pat. No. 209,241, Oct. 22, 1878). This
enabled four messages to be sent over the same wire at the same time,
and is said to have increased the value of the Western Union wires
$15,000,000.
In 1846 Royal C. House invented the _printing telegraph_, which printed
the message automatically on a strip of paper, something after the
manner of the typewriter (U. S. Pat. No. 4,464, April 18, 1846). The
ingenious mechanism involved in this was somewhat complicated, but its
results in printing the message plainly were very satisfactory. This was
the prototype of the familiar “_ticker_” of the stock broker’s office,
seen in Figs. 10 and 11. In 1856 the Hughes printing telegraph was
brought out (U. S. Pat. No. 14,917, May 20, 1856), and in 1858 G. M.
Phelps combined the valuable features of the Hughes and House systems
(U. S. Pat. No. 26,003, Nov. 1, 1859).
[Illustration: FIG. 11.--RECEIVING MESSAGE ON STOCK BROKER’S “TICKER.”]
_Fac Simile_ telegraphs constitute another, although less important
branch of the art. These accomplished the striking result of reproducing
the message at the end of the line in the exact handwriting of the
sender, and not only writing, but exact reproductions of all outlines,
such as maps, pictures, and so forth, may be sent. The fac simile
telegraph originated with F. C. Bakewell, of England, in 1848 (Br. Pat.
No. 12,352, of 1848).
The Dial Telegraph is still another modification of the telegraph. In
this the letters are arranged in a circular series, and a light needle
or pointer, concentrically pivoted, is carried back and forth over the
letters, and is made to successively point to the desired letters.
Among other useful applications of the telegraph is the _fire alarm
system_. In 1852 Channing and Farmer, of Boston, Mass., devised a
system of telegraphic fire alarms, which was adopted in the city of
Boston (U. S. Pat. No. 17,355, May 19, 1857), and which in varying
modifications has spread through all the cities of the world,
introducing that most important element of time economy in the
extinguishment of fires. Hundreds of cities and millions of dollars have
been thus saved from destruction.
Similar applications of local alarms in great numbers have been extended
into various departments of life, such as _District Messenger Service_,
_Burglar Alarms_, _Railroad-Signal Systems_, _Hotel-Annunciators_, and
so on.
[Illustration: FIG. 12.--TELEGRAPHING BY INDUCTION.]
For furnishing current for telegraphic purposes the dynamo, and
especially the storage battery, have in late years found useful
application. In fact, in the leading telegraph offices the storage
battery has practically superseded the old voltaic cells.
_Telegraphing by induction_, _i. e._, without the mechanical connection
of a conducting wire, is another of the developments of telegraphy in
recent years, and finds application to telegraphing to moving railway
trains. When an electric current flows over a telegraph line, objects
along its length are charged at the beginning and end of the current
impulse with a secondary charge, which flows to the earth if connection
is afforded. It is the discharge of this secondary current from the
metal car roof to the ground which, on the moving train, is made the
means of telegraphing without any mechanical connection with the
telegraph lines along the track. As, however, this secondary circuit
occurs only at the making and breaking of the telegraphic impulse, the
length of the impulse affords no means of differentiation into an
alphabet, and so a rapid series of impulses, caused by the vibrator of
an induction coil, is made to produce buzzing tones of various duration
representing the alphabet, and these tones are received upon a telephone
instead of a Morse register. The diagram, Fig. 12,[1] illustrates the
operation.
[1] From “Electricity in Daily Life,” by courtesy of Charles
Scribner’s Sons.
To receive messages on a car, electric impulses on the telegraph wire W,
sent from the vibrator of an induction coil, cause induced currents as
follows: Car roof R, wire _a_, key K, telephone _b c_, car wheel and
earth. In sending messages closure of key K works induction coil I C,
and vibrator V, through battery B, and primary circuit _d_, _c_, _f_,
_g_, and the secondary circuit _a_, _h_, _i_, charges the car roof and
influences by induction the telegraph wire W and the telephone at the
receiving station.
In 1881 William W. Smith proposed the plan of communicating between
moving cars and a stationary wire by induction (U. S. Pat. No. 247,127,
Sept. 13, 1881). Thomas A. Edison, L. J. Phelps, and others have further
improved the means for carrying it out. In 1888 the principle was
successfully employed on 200 miles of the Lehigh Valley Railroad.
[Illustration: FIG. 13.--WIRELESS TELEGRAPHY, INTERNATIONAL YACHT RACES,
OCTOBER, 1899.]
_Wireless Telegraphy_, or telegraphing without any wires at all, from
one point to another point through space, is the most modern and
startling development in telegraphy. To the average mind this is highly
suggestive of scientific imposition, so intangible and unknown are the
physical forces by which it is rendered possible, and yet this is one of
the late achievements of the Nineteenth Century. Many scientists have
contributed data on this subject, but the principles and theories have
only begun to crystallize into an art during the first part of the last
decade of the Nineteenth Century. Heinrich Hertz, the German scientist,
was perhaps the real pioneer in this line in his studies and
observations of the nature of the electric undulations which have taken
his name, and are known as “Hertzian” waves, rays, or oscillations.
Tesla in the United States, Branly and Ducretet in France, Righi in
Italy, the Russian savant, Popoff, and Professor Lodge, of England, have
all made contributions to this art. It will aid the understanding to
say, in a preliminary way, that electric undulations are generated and
emitted from a plate or conductor a hundred feet or more high in the
air, are thence transmitted through space to a remote point, which may
be many miles away, and there influencing a similar plate high in the
air give, through a special form of receiving device known as a
“coherer,” a telegraphic record. The “coherer,” invented by Branly in
1891, is a glass tube containing metal filings between two circuit
terminals. The electric waves cause these filings to cohere, and so vary
the resistance to the passage of the current as to give a basis for
transformation into a record.
In March, 1899, Signor Guglielmo Marconi, an Italian student, then
residing in England, successfully communicated between South Foreland,
County of Kent, and Boulogne-sur-mer, in France, a distance of
thirty-two miles across the English Channel. Signor Marconi used the
vertical conductors and the Hertz-oscillation principle, and his system
is described in his United States patent. No. 586,193, July 13, 1897.
His patent comprehends many claims, a leading feature of which is the
means for automatically shaking the “coherer” to break up the cohesion
of the metal filings as embodied in his first claim, as follows:
“In a receiver for electrical oscillations, the combination of an
imperfect electrical contact, a circuit through the contact, and
means actuated by the circuit for shaking the contact.”
The Marconi system of wireless telegraphy was practically employed with
useful effect April 28, 1899, on the “Goodwin Sands” light-ship to
telegraph for assistance when in collision twelve miles from land and in
danger of sinking. It was also used in October, 1899, on board the
“Grande Duchesse” to report the international yacht race between the
“Columbia” and the “Shamrock” at Sandy Hook, as seen in Fig. 13. Lord
Roberts also made good use of it in his South African campaign against
the Boers. According to Signor Marconi its present range is limited to
eighty-six miles, but it is expected that this will be soon extended to
150 miles.
[Illustration: FIG. 13A.--THE COHERER.]
Marconi’s receiving apparatus is shown in Fig. 13A, and consists of a
small glass tube called the coherer, about 1½ inches in length, into the
ends of which are inserted two silver pole pieces, which fit the tube,
but whose ends are 1/50 inch apart. The space between the ends is filled
with a mixture composed of fine nickel and silver filings and a mere
trace of mercury, and the other ends of the pole pieces are attached to
the wires of a local circuit. In the normal condition the metallic
filings have an enormous resistance, and constitute a practical
insulator, preventing the flow of the local current; but if they are
influenced by electric waves, coherence takes place and the resistance
falls, allowing the local current to pass. The coherence will continue
until the filings are mechanically shaken, when they will at once fall
apart, as it were, insulation will be established, and the current will
be broken. If, then, a coherer be brought within the influence of the
electric waves thrown out from a transmitter, coherence will occur
whenever the key of the transmitter at the distant station is depressed.
Mr. Marconi has devised an ingenious arrangement, which is the subject
of his patent referred to, in which a small hammer is made to rap
continuously upon the coherer by the action of the local circuit, which
is closed when the Hertzian waves pass through the metal filings. As
soon as the waves cease, the hammer gives its last rap, and the tube is
left in the decohered condition ready for the next transmission of
waves. It is evident that by making the local circuit operate a relay,
in the circuit of which is a standard recording instrument, the messages
may be recorded on a tape in the usual way.
[Illustration: FIG. 13B.--DIAGRAM OF THE TRANSMITTER AND RECEIVER.]
In Fig. 13B is shown the diagram of circuits. The letters _d d_ indicate
the spheres of the transmitter, which are connected, one to the vertical
wire w, the other to earth, and both by wires _c′ c′_, to the terminals
of the secondary winding of induction coil, c. In the primary circuit is
the key _b_. The coherer _j_ has two metal pole pieces, _j¹ j²_,
separated by silver and nickel filings. One end of the tube is connected
to earth, the other to the vertical wire _w_, and the coherer itself
forms part of a circuit containing the local cell _g_, and a sensitive
telegraph relay actuating another circuit, which circuit works a
trembler _p_, of which _o_ is the decohering tapper, or hammer. When the
electric waves pass from _w_ to _j¹ j²_ the resistance falls, and the
current from _g_ actuates the relay _n_, the choking coils _k k′_, lying
between the coherer and the relay, compelling the electric waves to
traverse the coherer instead of flowing through the relay. The relay _n_
in its turn causes the more powerful battery _r_ to pass a current
through the tapper, and also through the electro-magnet of the
recording instrument _h_.
The alternate cohering by the waves and decohering by the tapper
continue uninterruptedly as long as the transmitting key at the distant
station is depressed. The armature of the recording instrument, however,
because of its inertia, cannot rise and fall in unison with the rapid
coherence and decoherence of the receiver, and hence it remains down and
makes a stroke upon the tape as long as the sending key is depressed.
The principal applications of wireless telegraphy so far have been at
sea, where the absence of intervening obstacles gives a free path to the
electrical oscillations. The system is also applicable on land, however,
and no one can doubt that if the Ministers of the Legations shut up in
Pekin had been supplied with a wireless telegraphy outfit, neither the
walls of Pekin nor the strongest cordon of its Chinese hordes could have
prevented the long sought communication. The full story of mystery and
massacre would have been promptly made known, and the civilized world
have been spared its anxiety, and earlier and effective measures of
relief supplied.
As the art of telegraphy grows apace toward the end of the Nineteenth
Century, individuality of invention becomes lost in the great maze of
modifications, ramifications, and combinations. Inventions become merged
into systems, and systems become swallowed up by companies. In the
promises of living inventors the wish is too often father to the
thought, and the conservative man sees the child of promise rise in
great expectation, flourish for a few years, and then subside to quiet
rest in the dusty archives of the Patent Office. They all contribute
their quota of value, but it is so difficult to single out as
pre-eminent any one of those which as yet are on probation, that we must
leave to the coming generation the task of making meritorious selection.
To-day the telegraph is the great nerve system of the nation’s body, and
it ramifies and vitalizes every part with sensitive force. In 1899 the
Western Union Telegraph Company alone had 22,285 offices, 904,633 miles
of wire, sent 61,398,157 messages, received in money $23,954,312, and
enjoyed a profit of $5,868,733. Add to this the business of the Postal
Telegraph Company and other companies, and it becomes well nigh
impossible to grasp the magnitude of this tremendous factor of
Nineteenth Century progress. Figures fail to become impressive after
they reach the higher denominations, and it may not add much to either
the reader’s conception or his knowledge to say that the statistics for
the _whole world_ for the year 1898 show: 103,832 telegraph offices,
2,989,803 miles of wire, and 365,453,526 messages sent during that year.
This wire would extend around the earth about 120 times, and the
messages amounted to one million a day for every day in that year. This
is for land telegraphs only, and does not include cable messages.
What saving has accrued to the world in the matter of time, and what
development in values in the various departments of life, and what
contributions to human comfort and happiness the telegraph has brought
about, is beyond human estimate, and is too impressive a thought for
speculation.