great submarine lines which unite the Old and New Worlds. Morse and
Wheatstone about the same time (1843) independently experimented with
sub-aqueous insulated wires, and their success gave rise to numerous
projects for submarine lines. How far any of these might have been
practical need not here be discussed, but it fortunately happened that
some years after this, the electrical properties of gutta-percha were
recognized, and this material, so admirably adapted for forming the
insulating covering of wires, was taken advantage of by Brett and Co.,
who obtained the right of establishing an electric telegraph between
France and England, and they succeeded in laying down the first
submarine cable. This cable extended from Dover to Cape Grisnez near
Calais, and the experiment proved successful; but, unfortunately, the
cable was severed within a week by the sharp rocks on which it rested
near the French coast. It proved, however, the excellent insulating
property of the new material, and demonstrated the possibility of
submarine telegraphic communication. Another cable was manufactured, in
which the gutta-percha core was protected by a covering of iron wires
laid specially on the exterior, and thus combining greater security with
a far larger amount of tenacity. A view and section of this—the first
practically successful submarine cable—are given in Fig. 297 of the real
size. It has four separate copper wires, each insulated with a covering
of gutta-percha, and the whole was spun with tarred hemp into the form
of a rope, and protected with an outer covering of ten of the thickest
iron wires wound spirally upon it. The cable when complete was 27 miles
in length, and each mile weighed 7 tons. This cable was laid in 1851,
and from that time it has been in constant use, with the exception of a
few interruptions from accidental ruptures. Its success immediately led
to the construction of other cables connecting England with Ireland,
Belgium, Holland, &c. In 1855 the practicability of an Atlantic cable
was no longer doubted, and £350,000 were soon subscribed by the public
for the project. A cable was manufactured weighing 10 tons to the mile,
and in August, 1857, 338 miles of it had been successfully paid out by
the ships when the cable parted. Better paying-out apparatus was now
devised—self-releasing brakes were constructed, so that the cable should
not be exposed to too great a strain; and in 1858 another cable,
requiring a strain of 3 tons to break it, was manufactured, and the
laying of it commenced in mid-ocean—the _Mægera_ and _Agamemnon_ going
in opposite directions, and paying out as they proceeded. Twice the
cable was severed, twice the ships met and repaired the injury; but the
third time, when they were 200 miles apart, the cable again broke. But
again the attempt was repeated, and this time success crowned the
effort; for on the 5th of August the two continents were telegraphically
connected. Unfortunately the electric continuity failed after the cable
had been a month in use.
Seven years elapsed before another endeavour was made; but the
experience gained in the unsuccessful attempt was not lost; and in 1865
another cable had been constructed, and the _Great Eastern_ was employed
in laying it. In this the conductor was composed of seven copper wires
twisted into one strand, covered with several layers of insulating
material, and covered externally with eleven stout iron wires, each of
which was itself protected by a covering of hemp and tar. This cable was
2,600 miles long, and contained 25,000 miles of copper wire, 35,000
miles of iron wire, and 400,000 miles of hempen strands, or more than
sufficient to go twenty-four times round the world. It was carefully
made, mile by mile, formed into lengths of 800 miles, and shipped on
board the _Great Eastern_ in enormous iron tanks, which weighed, with
their contents, more than 5,800 tons. This cable was manufactured by
Messrs. Glass and Elliot, at Greenwich, to whom the iron wire for the
outer covering was furnished by Messrs. Webster and Horsfall, of
Birmingham. Fig. 298 represents the workshops with the iron wire in
process of making. The great ship sailed from Valentia on the 23rd of
July, 1865, and the paying out commenced. Constant communication was
kept up with the shore, and signals exchanged with the instrument-room
at Valentia, which is represented in Fig. 299, where, among various
instruments invented by Sir W. Thompson, may be seen his mirror
galvanometer. After several mishaps, which required the cable to be
raised for repairs after it had been laid in deep water, the _Great
Eastern_ had paid out about 1,186 miles of cable, and was 1,062 miles
from Valentia, when a loss of insulation in the cable was discovered by
the electricians on board. This indicated some defect in the portion
paid out, and the usual work of raising up again had to be once more
resorted to. During this process the cable parted, and Fig. 300 shows
the scene on board the _Great Eastern_ produced by this occurrence, as
represented by an artist of the “Illustrated London News” who
accompanied the expedition. The broken cable was caught several times by
grapnels, and raised a mile or more from the bottom, but the tackle
proved unable to resist the strain, and four times it broke; and after
the spot had been marked by buoys, the _Great Eastern_ steamed home to
announce the failure of the great enterprise. For this 5,500 miles of
cable had altogether been made, and 4,000 miles of it lay uselessly at
the bottom of the ocean, after a million and a quarter sterling had been
swallowed up in these attempts.
[Illustration:
FIG. 298.—_Making Wires for Atlantic Telegraph Cable._
]
[Illustration:
FIG. 299.—_The Instrument-Room at Valentia._
]
But these disasters did not crush the hopes of the promoters of the
great enterprise, and in the following year the _Great Eastern_ again
sailed with a new cable, the construction of which is shown of the
actual size, in Fig. 301. In this there is a strand of seven twisted
copper wires, as before, forming the electric conductor; round this are
four coatings of gutta-percha; and surrounding these is a layer of jute,
which is protected by ten iron wires (No 10, B.W.G) of Webster and
Horsfall’s homogeneous metal, twisted spirally about the cable; and each
wire is enveloped in spiral strands of Manilla hemp. The _Great Eastern_
sailed on the 13th of July, and on the 28th the American end of the
cable was spliced to the shore section in Newfoundland, and the two
continents were again electrically connected. They have since been even
more so, for the cable of 1865 was eventually fished up, and its
electrical condition was found to be improved rather than injured by its
sojourn at the bottom of the Atlantic. It was spliced to a new length of
cable, which was successfully laid by the _Great Eastern_, and was soon
joined to a Newfoundland shore cable. There were now two cables
connecting England and America, and one connecting America and France
has since been laid. At the present time upwards of 20,000 miles of
submerged wires are in constant use in various parts of the world.
[Illustration:
FIG. 300.—_The Breaking of the Cable._
]
Certain interesting phenomena have been observed in connection with
submarine cables, and some of the notions which were formerly
entertained as to the speed of electricity have been abandoned, for it
has been ascertained that electricity cannot properly be said to have a
velocity, since the same quantity of electricity can be made to traverse
the same distance with extremely different speeds. No effect can be
perceived in the most delicate instruments in Newfoundland for one-fifth
of a second after contact has been made at Valentia; after the lapse of
another fifth of a second the received current has attained about seven
per cent. of its greatest permanent strength, and in three seconds will
have reached it. During the whole of this time the current is flowing
into the cable at Valentia with its maximum intensity. Fig. 302
expresses these facts by a mode of representation which is extremely
convenient. Along the line O X the regular intervals of time in tenths
of seconds are marked, commencing from O, and the intensity of the
current at each instant is expressed by the length of the upright line
which can be drawn between O X and the curve. The curve therefore
exhibits to the eye the state of the current throughout the whole time.
If after nearly a second’s contact with the battery the cable be
connected with the earth at the distant end, the rising intensity of the
current will be checked and then immediately begin to decline somewhat
more gradually than it rose, as indicated by the descending branch of
the curve in Fig. 302. A little reflection will show the unsuitability
for such currents of instruments which require a fixed strength to work
them. We may remark that, supposing a receiving instrument were in
connection with the Atlantic Cable which required the maximum strength
of the received current to work it, the sending clerk would have to
maintain contact for three seconds before this intensity would be
reached, and then, after putting the cable to earth, he would have to
wait some seconds before the current had flowed out. Several seconds
would, therefore, be taken up in the transmission of one signal, whereas
by means of the mirror galvanometer about one-fourteenth of this time
suffices, and the syphon recorder will write the messages twelve times
as fast as the Morse instrument. The cause of the gradual rise of the
current at the distant end of a submarine cable must be sought for in
the fact that the coated wire plays the part of a Leyden jar, and the
electricity which pours into it is partly held by an inductive action in
the surrounding water. The importance of Sir W. Thomson’s inventions as
regards rapidity of signalling, upon which the commercial success of the
Atlantic Cable greatly depends, will now be understood.
[Illustration:
FIG. 301.—_Atlantic Telegraph Cable, 1866._
]
[Illustration:
FIG. 302.
]
By furnishing the means of almost instantaneous communication between
distant places, the electric telegraph has enabled feats to be performed
which appear strangely paradoxical when expressed in ordinary language.
When it is mentioned as a sober fact that intelligence of an event may
actually reach a place before the time of its occurrence, a very
extraordinary and startling statement appears to be made, on account of
the ambiguous sense of the word _time_. Thus it appears very marvellous
that details of events which may happen in England in 1876 can be known
in America in 1875, but it is certainly true; for, on account of the
difference of longitude between London and New York, the hour of the day
at the latter place is about six hours behind the time at the former. It
might, therefore, well happen that an event occurring in London on the
morning of the 1st of January, 1876, might be discussed in New York on
the night of the 31st of December, 1875. There are on record many
wonderful instances of the celerity with which, thanks to electricity,
important speeches delivered at a distant place are placed before the
public by the newspapers. And there are stories in circulation
concerning incidents of a more romantic character in connection with the
telegraph. The American journals not long ago reported that a wealthy
Boston merchant, having urged his daughter to marry an unwelcome suitor,
the young lady resolved upon at once uniting herself to the man of her
choice, who was then in New York, _en route_ for England. The electric
wires were put in requisition; she took her place in the telegraph
office in Boston, and he in the office in New York, each accompanied by
a magistrate; consent was exchanged by electric currents, and the pair
were married by telegraph! It is said that the merchant threatened to
dispute the validity of the marriage, but he did not carry this threat
into execution. The following _jeu d’esprit_ appeared a short time ago
in “Nature,” and, we strongly suspect, has been penned by the same hand
as the lines quoted from “Blackwood,” on page 508.
ELECTRIC VALENTINE.
(_Telegraph Clerk_ ♂ _to Telegraph Clerk_ ♀.)
“‘The tendrils of my soul are twined
With thine, though many a mile apart;
And thine in close-coiled circuits wind
Around the magnet of my heart.
“‘Constant as Daniell, strong as Grove;
Seething through all its depths like Smee;
My heart pours forth its tide of love,
And all its circuits close in thee.
“‘Oh tell me, when along the line
From my full heart the message flows,
What currents are induced in thine?
One click from thee will end my woes!’
“Through many an Ohm the Weber flew,
And clicked this answer back to me—
‘I am thy Farad, staunch and true,
Charged to a Volt with love for thee.’”
[NOTE BY THE EDITOR.—_Ohm_, standard of electric resistance; _Weber_,
electric current; _Volt_, electro-motive force; _Farad_, capacity (of a
condenser).]
_THE TELEPHONE._
Of more recent invention than any of the classes of instruments already
mentioned for electrical communication at a distance is the telephone,
which differs widely from the rest in many notable particulars. Though
the telephone completely realized what had for years before been the
dream of physicists, the first announcement of its capabilities was
received, even by the scientific world, with some pause of incredulity;
but when its powers were demonstrated, it created no small sensation. It
has now, within a few years afterwards, become so familiar as an
appliance of ordinary life and business, that people in general are less
impressed by the wonder of it than were their fathers half a century ago
by the electric telegraphs of Wheatstone and of Morse. Like all other
inventions, it was led up to by preceding discoveries and tentative
efforts. It will be unnecessary here to trace those successive steps
with minuteness, or to attempt to adjust the claims of merit or priority
that have been put forward for different inventors, but a notice of some
of the stages in the evolution of this wonderful contrivance may be of
interest. If the reader has no previous knowledge of the physical nature
of sounds in relation to music, and especially to articulate speech, he
should now refer to the brief explanation given in a subsequent chapter,
at the commencement of the section on the Phonograph. He should,
however, bear in mind that in that explanation are included some
acoustical discoveries of a later date than some of the inventions we
are here to speak of, or, at least, the real causes of which give other
qualities than pitch to sound, had not been fully demonstrated when the
notion of the electric telephone was conceived.
When the electric telegraph came into use and it was found possible to
use it for communication of intelligence to great distances, it is not
surprising that the further problem of transmitting by electricity, not
signals merely, but audible speech, should be suggested. Perhaps the
first scientific person who avowed a belief in the possibility of doing
this, and even indicated the direction in which the solution of the
problem was to be sought, was a Frenchman of science, M. Charles
Bourseul. In 1854, he pointed out that sounds are caused by vibrations,
and reach the ear by like vibrations of the intervening medium, and,
although he could not say what took place in the modifications of the
organs of speech by which syllables are produced, he inferred that these
syllables could reach the ear only by vibrations of the medium, and that
if these vibrations could be reproduced the syllables would be
reproduced. He suggests that a man might speak near a flexible disc,
which the vibrations of his voice would throw into oscillatory movements
that could be caused to make and break a battery circuit, and that, at a
distance, the currents might be arranged to produce the like vibrations
in another disc. The weak point of this scheme was the want of any
suggestion as to the mode in which this last effect was to be produced.
Even when this part of the problem was solved in a few years afterwards,
as we shall presently see, it was musical—and not articulate—sound that
could be transmitted by an arrangement, using make and break contacts.
The reader, who has understood what has been said of electrical
currents, and also the account of the compounded vibrations in
articulate sounds introduced into our section on the phonograph, should
have little difficulty in seeing this must necessarily be the case, for
the contacts could only give the succession of the vibrations by
currents of equal intensity, and could not, like the yielding wax of the
phonograph cylinder, correspond with their relative intensities. M.
Bourseul pointed out advantages which would arise from the transmission
of speech by electricity, such as simplicity of apparatus and facility
in use—for, unlike the telegraph, no skilled operators would be
needed—to signal messages, or time spent in spelling out the words
letter by letter. He says that he had made some experiments, which
promised a favourable result, but demanded time and patience, and that
he is certain that, in a more or less distant future, speech will be
transmitted by electricity, so that what is spoken in Vienna may be
heard in Paris. One cannot help thinking that if M. Bourseul had but
pursued his experiments a little longer, he would not improbably have
achieved the invention of the speaking telephone, for which the world
had to wait twenty years longer. As it is, we cannot but admire his
scientific foresight and his confidence in the ultimate realization of
his idea.
But before this came to pass, an intermediate stage was reached in the
apparatus contrived by M. Reiss, a schoolmaster of Friedrichsdorf, who,
in 1860, solved the problem of electrically transmitting musical tones.
So far as concerned the reproduction of the sounds, this telephone was
founded upon a discovery, made in 1837, by an American physicist, named
Page, which was this: At the moment a bar of iron is magnetized, by
sending a current through a coil surrounding it, as shown in Fig. 265, a
slight but sharp click is heard. The transmitting apparatus was, in
principle, Mr. Scott’s phono-autograph (described in the section on the
phonograph), which had been invented in 1855. The tracing style of this
was replaced in Reiss’ apparatus by a small disc of platinum, connected
by a very light spring of the same metal with a binding-screw for the
battery connection. Nearly in contact with the little disc was a
platinum point, so arranged that the slightest oscillation of the
membrane would bring them into actual contact and thus close the
circuit. Worthy of remark is the very primitive nature of the materials
with which Reiss made his first experimental apparatus. The receptacle
for the voice was simply a large bung hollowed out into a conical
cavity, and the membrane was supplied by the skin of a German sausage,
while the clicking bar of the receiver was a stout knitting needle,
surrounded by a coil of covered copper wire and stuck into the bridge of
a violin, which, by acting as a sounding board, made the clicks produced
in the needle distinctly audible. M. Reiss finally produced his
telephone in the form shown in Fig. 302_a_, where _I_ is the receiver;
_B_, the voltaic battery; _I I_, the receiver; _c c_ is a coil of
insulated wire, surrounding a slender iron rod, mounted on the supports,
_f f_, which rest on the sounding board, _g g_. The transmitter consists
of the hollow box, _A_, provided with a trumpet-mouthed opening in one
side and having at the top a circular piece cut out, across which is
stretched a membrane with the little disc of platinum, _n_, fixed in its
centre. When a person applying his mouth to A sings into the box, the
membrane is thrown into vibrations corresponding with the notes, and at
each vibration a contact is made and a click is emitted from the distant
sounding box. The tones are concentrated by covering this box with the
perforated lid. It was afterwards found that a trumpet mouth fitted into
the receiver was still more effective. Reiss tried to use his
arrangement for transmitting speech, but without success, although
occasionally a syllable could be very indistinctly heard. An instrument,
with springs so nicely adjusted that slight vibrations did not separate
the platinum from actual contact, but merely caused change of pressure,
has indeed been made to convey articulate sounds, although the
arrangement was not essentially different from that of M. Reiss. This
mode of action is, however, a different thing, and we shall presently
see that very effective speech transmitters have been constructed by
applying it in a more refined way. This musical telephone could give the
pitch of the sounds in the song but not their quality (_timbre_), and
the receiver added to the main system of vibration other sets that
belonged to itself, the result being a shrill and by no means pleasing
tone, recalling that of a penny trumpet. Messrs. C. and L. Wray
afterwards effected some considerable improvements in M. Reiss’s
telephone, with the object of intensifying the effects and producing
better tones.
[Illustration:
FIG. 302_a_.—_Reiss’ Musical Telephone._
]
[Illustration:
FIG. 302_b_.—_Bell’s Musical Telephone._
]