Discoveries and Inventions of the Nineteenth Century

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 580instruments 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 581regards rapidity of signalling, upon which the commercial success of the Atlantic Cable greatly depends, will now be understood. Fig. 301.—Atlantic Telegraph Cable, 1866. 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 582when 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, 583in 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. 302a, 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