JUST mentioning en passant the sympathetic needle and sympathetic flesh telegraphs of the sixteenth and seventeenth centuries, a full account of which will be found in my 'History of Electric Telegraphy to 1837, (chap. i.), 1 we come to the year 1795 for the first glimmerings of telegraphy without wires. Salvá, who was an eminent Spanish physicist, and the inventor of the first electro-chemical telegraph, has the following bizarre passage in his paper "On the Application of Electricity to Telegraphy," read before the Academy of Sciences, Barcelona, December 16, 1795.
After showing how insulated wires may be laid under the seas, and the water used instead of return wires, he goes on to say: "If earthquakes be caused by electricity going from one point charged positively to another point charged negatively, as Bertolon has shown in his 'Électricité des Météores' (vol. i. p. 273), one does not even want a cable to send across the sea a signal arranged beforehand. One could, for example, arrange at Mallorca an area of earth charged with electricity, and at Alicante a similar space charged with the opposite electricity, with a wire going to, and dipping into, the sea, On leading another wire from the sea-shore to the electrified spot at Mallorca, the communication between the two charged surfaces would be complete, for the electric fluid would traverse the sea, which is an excellent conductor, and indicate by the spark the desired signal." 2 Another early telegraph inventor and eminent physiologist, Sömmerring of Munich, has an experiment which, under more favourable conditions of observation, might easily have resulted in the suggestion at this early date of signalling through and by water alone. Dr Hamel 3 tells us that Sömmerring, on the 5th of June 1811, and at the suggestion of his friend, Baron Schilling, tried the action of his telegraph whilst the two conducting cords were each interrupted by water contained in wooden tubs. The signals appeared just as well as if no water had been interposed, but they ceased as soon as the water in the tubs was connected by a wire, the current then returning by this shorter way.
Now here we have, in petto, all the conditions necessary for an experiment of the kind with which we are dealing, and had it been possible for Sömmerring to have employed a more delicate indicator than his water-decomposing apparatus he would probably have noticed that, notwithstanding the shorter way, some portion of the current still went the longer way; and this fact could hardly have failed to suggest to his acute and observant mind further experiments, which, as I have just said, might easily have resulted in his recognition of the possibility of wireless telegraphy.
Leaving the curious suggestion of Salvá, which, though seriously meant, cannot be regarded as more than a jeu d'esprit--a happy inspiration of genius--and the what-might-have-come-of-it experiment of Sömmerring, we come to the year 1838, when the first intelligent suggestion of a wireless telegraph was made by Steinheil of Munich, one of the great pioneers of electric telegraphy on the Continent.
The possibility of signalling without wires was in a manner forced upon him. While he was engaged in establishing his beautiful system of telegraphy in Bavaria, Gauss, the celebrated German philosopher, and himself a telegraph to him inventor, suggested that the two rails of a railway might be utilised as telegraphic conductors. In July 1838 Steinheil tried the experiment on the Nürmberg-Fürth railway, but was unable to obtain an insulation of the rails sufficiently good for the current to reach from one station to the other. The great conductibility with which he found that the earth was endowed led him to presume that it would be possible to employ it instead of the return wire or wires hitherto used. The trials that he made in order to prove the accuracy of this conclusion were followed by complete success; and he then introduced into electric telegraphy one of its greatest improvements--the earth circuit. 4 Steinheil then goes on to say: "The inquiry into the laws of dispersion, according to which the ground, whose mass is unlimited, is acted upon by the passage of the galvanic current, appeared to be a subject replete with interest. The gavanic excitation cannot be confined to the portions of earth situated between the two ends of the wire; on the contrary, it cannot but extend itself indefinitely, and it therefore only depends on the law that obtains in this excitation of the ground, and the distance of the exciting terminations of the wire, whether it is necessary or not to have any metallic communication at all for carrying on telegraphic intercourse. "An apparatus can, it is true, be constructed in which the inductor, having no other metallic connection with the multiplier than the excitation transmitted through the ground, shall produce galvanic currents in that multiplier sufficient to cause a visible deflection of the bar. This is a hitherto unobserved fact, and may be classed amongst the most extraordinary phenomena that science has revealed to us. It only holds good, however, for small distances; and it must be left to the future to decide whether we shall ever succeed in telegraphing at great distances without any metallic communication at all. My experiments prove that such a thing is possible up to distances of 50 feet. For greater distances we can only conceive it feasible by augmenting the power of the galvanic induction, or by appropriate multipliers constructed for the purpose, or, in conclusion, by increasing the surface of contact presented by the ends of the multipliers. At all events, the phenomenon merits our best attention, and its influence will not perhaps be altogether overlooked in the theoretic views we may form with regard to galvanism itself." 5 In another place, discussing the same subject, Steinheil says: "We cannot conjure up gnomes at will to convey our thoughts through the earth. Nature has prevented this. The spreading of the galvanic effect is proportional, not to the distance of the point of excitation, but to the square of this distance; so that, at the distance of 50 feet, only exceedingly small effects can be produced by the most powerful electrical effect at the point of excitation. Had we means which could stand in the same relation to electricity that the eye stands to light, nothing would prevent our telegraphing through the earth without conducting wires; but it is not probable that we shall ever attain this end." 6 Steinheil proposed another means of signalling without wires, which is curiously àpropos of Professor Graham Bell's photophone. In his classic paper on "Telegraphic Communication, especially by Means of Galvanism," he says: "Another possible method of bringing about transient movements at great distances, without any intervening artificial conductor, is furnished by radiant heat, when directed by means of condensing mirrors upon a thermo-electric pile. A galvanic current is called into play, which in its turn is employed to produce declinations of a magnetic needle. The difficulties attending the construction of such an instrument, though certainly considerable, are not in themselves insuperable. Such a telegraph, however, would only have this advantage over those [semaphores] based on optical principles--namely, that it does not require the constant attention of the observer but, like the optical one, it would cease to act during cloudy weather, and hence partakes of the intrinsic defects of all semaphoric methods." 7 Acting on this suggestion, in June 1880 the present writer, while stationed at Teheran, Persia, and while yet ignorant of Professor Bell's method, worked out for himself a photophone, or rather a tele-photophone, which will be found described in the 'Electrician,' February 26, 1881. On my temporary return to England in 1882, I found that as early as 1878 Mr A. C. Brown, of the Eastern Telegraph Company, was working at the photophone. In September of that year he submitted his plans to Prof. Bell, who afterwards said of them: "To Mr Brown is undoubtedly due the honour of having distinctly and independently formulated the conception of using an undulatory beam of light, in contradistinction to a merely intermittent one, in connection with selenium and a telephone, and of having devised apparatus, though of a crude nature, for carrying it into execution" ('Jour. Inst. Elec. Engs.,' vol. ix. p. 404). Indeed the photophone is as much the invention of Mr Brown as of Prof. Bell, who, however, has all the credit for it in popular estimation.
1 E. & F. N. Spon, London, 1884.
2 Later on (infra) we shall see that Salvá's idea is after all not so extravagant as it seems. We now know that large spaces of the earth can be electrified, giving rise to the phenomenon of "bad earth," so well known to telegraph officials.
3 'Historical Account of the Introduction of the Galvanic and Electro-magnetic Telegraph into England,' Cooke's Reprint, p. 17.
4 For the use of the earth circuit before Steinheil's accidental discovery, see my 'History of Electric Telegraphy,' pp. 343-345.
5 Sturgeon's 'Annals of Electricity,' vol. iii. p. 450.
6 'Die Anwendung des Electromagnetismus,' 1873, p. 172. We now have these means in "the electric eye" of Hertz! See pp. 180, 270 infra.
7 'Sturgeon's Annals of Electricity,' March 1839.
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