The New Physics and Its Evolution Part 12

It is right to add that Sir William Preece had himself utilised induction phenomena in his experiments, and had begun researches with the aid of electric waves. Much is due to him for the welcome he gave to Marconi; it is certainly thanks to the advice and the material support he found in Sir William that the young scholar succeeded in effecting his sensational experiments.

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The starting-point of the experiments based on the properties of the luminous ether, and having for their object the transmission of signals, is very remote; and it would be a very laborious task to hunt up all the work accomplished in that direction, even if we were to confine ourselves to those in which electrical reactions play a part.

An electric reaction, an electrostatic influence, or an electromagnetic phenomenon, is transmitted at a distance through the air by the intermediary of the luminous ether. But electric influence can hardly be used, as the distances it would allow us to traverse would be much too restricted, and electrostatic actions are often very erratic. The phenomena of induction, which are very regular and insensible to the variations of the atmosphere, have, on the other hand, for a long time appeared serviceable for telegraphic purposes.

We might find, in a certain number of the attempts just mentioned, a partial employment of these phenomena. Lindsay, for instance, in his project of communication across the sea, attributed to them a considerable role. These phenomena even permitted a true telegraphy without intermediary wire between the transmitter and the receiver, at very restricted distances, it is true, but in peculiarly interesting conditions. It is, in fact, owing to them that C. Brown, and later Edison and Gilliland, succeeded in establis.h.i.+ng communications with trains in motion.

Mr Willoughby S. Smith and Mr Charles A. Stevenson also undertook experiments during the last twenty years, in which they used induction, but the most remarkable attempts are perhaps those of Professor Emile Rathenau. With the a.s.sistance of Professor Rubens and of Herr W. Rathenau, this physicist effected, at the request of the German Ministry of Marine, a series of researches which enabled him, by means of a compound system of conduction and induction by alternating currents, to obtain clear and regular communications at a distance of four kilometres. Among the precursors also should be mentioned Graham Bell; the inventor of the telephone thought of employing his admirable apparatus as a receiver of induction phenomena transmitted from a distance; Edison, Herr Sacher of Vienna, M. Henry Dufour of Lausanne, and Professor Trowbridge of Boston, also made interesting attempts in the same direction.

In all these experiments occurs the idea of employing an oscillating current. Moreover, it was known for a long time--since, in 1842, the great American physicist Henry proved that the discharges from a Leyden jar in the attic of his house caused sparks in a metallic circuit on the ground floor--that a flux which varies rapidly and periodically is much more efficacious than a simple flux, which latter can only produce at a distance a phenomenon of slight intensity. This idea of the oscillating current was closely akin to that which was at last to lead to an entirely satisfactory solution: that is, to a solution which is founded on the properties of electric waves.

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Having thus got to the threshold of the definitive edifice, the historian, who has conducted his readers over the two parallel routes which have just been marked out, will be brought to ask himself whether he has been a sufficiently faithful guide and has not omitted to draw attention to all essential points in the regions pa.s.sed through.

Ought we not to place by the side, or perhaps in front, of the authors who have devised the practical appliances, those scholars who have constructed the theories and realised the laboratory experiments of which, after all, the apparatus are only the immediate applications?

If we speak of the propagation of a current in a material medium, can one forget the names of Fourier and of Ohm, who established by theoretical considerations the laws which preside over this propagation? When one looks at the phenomena of induction, would it not be just to remember that Arago foresaw them, and that Michael Faraday discovered them? It would be a delicate, and also a rather puerile task, to cla.s.s men of genius in order of merit. The merit of an inventor like Edison and that of a theorist like Clerk Maxwell have no common measure, and mankind is indebted for its great progress to the one as much as to the other.

Before relating how success attended the efforts to utilise electric waves for the transmission of signals, we cannot without ingrat.i.tude pa.s.s over in silence the theoretical speculations and the work of pure science which led to the knowledge of these waves. It would therefore be just, without going further back than Faraday, to say how that ill.u.s.trious physicist drew attention to the part taken by insulating media in electrical phenomena, and to insist also on the admirable memoirs in which for the first time Clerk Maxwell made a solid bridge between those two great chapters of Physics, optics and electricity, which till then had been independent of each other. And no doubt it would be impossible not to evoke the memory of those who, by establis.h.i.+ng, on the other hand, the solid and magnificent structure of physical optics, and proving by their immortal works the undulatory nature of light, prepared from the opposite direction the future unity. In the history of the applications of electrical undulations, the names of Young, Fresnel, Fizeau, and Foucault must be inscribed; without these scholars, the a.s.similation between electrical and luminous phenomena which they discovered and studied would evidently have been impossible.

Since there is an absolute ident.i.ty of nature between the electric and the luminous waves, we should, in all justice, also consider as precursors those who devised the first luminous telegraphs. Claude Chappe incontestably effected wireless telegraphy, thanks to the luminous ether, and the learned men, such as Colonel Mangin, who perfected optical telegraphy, indirectly suggested certain improvements lately introduced into the present method.

But the physicist whose work should most of all be put in evidence is, without fear of contradiction, Heinrich Hertz. It was he who demonstrated irrefutably, by experiments now cla.s.sic, that an electric discharge produces an undulatory disturbance in the ether contained in the insulating media in its neighbourhood; it was he who, as a profound theorist, a clever mathematician, and an experimenter of prodigious dexterity, made known the mechanism of the production, and fully elucidated that of the propagation of these electromagnetic waves.

He must naturally himself have thought that his discoveries might be applied to the transmission of signals. It would appear, however, that when interrogated by a Munich engineer named Huber as to the possibility of utilising the waves for transmissions by telephone, he answered in the negative, and dwelt on certain considerations relative to the difference between the periods of sounds and those of electrical vibrations. This answer does not allow us to judge what might have happened, had not a cruel death carried off in 1894, at the age of thirty-five, the great and unfortunate physicist.

We might also find in certain works earlier than the experiments of Hertz attempts at transmission in which, unconsciously no doubt, phenomena were already set in operation which would, at this day, be cla.s.sed as electric oscillations. It is allowable no doubt, not to speak of an American quack, Mahlon Loomis, who, according to Mr Story, patented in 1870 a project of communication in which he utilised the Rocky Mountains on one side and Mont Blanc on the other, as gigantic antennae to establish communication across the Atlantic; but we cannot pa.s.s over in silence the very remarkable researches of the American Professor Dolbear, who showed, at the electrical exhibition of Philadelphia in 1884, a set of apparatus enabling signals to be transmitted at a distance, which he described as "an exceptional application of the principles of electrostatic induction." This apparatus comprised groups of coils and condensers by means of which he obtained, as we cannot now doubt, effects due to true electric waves.

Place should also be made for a well-known inventor, D.E. Hughes, who from 1879 to 1886 followed up some very curious experiments in which also these oscillations certainly played a considerable part. It was this physicist who invented the microphone, and thus, in another way, drew attention to the variations of contact resistance, a phenomenon not far from that produced in the radio-conductors of Branly, which are important organs in the Marconi system. Unfortunately, fatigued and in ill-health, Hughes ceased his researches at the moment perhaps when they would have given him final results.

In an order of ideas different in appearance, but closely linked at bottom with the one just mentioned, must be recalled the discovery of radiophony in 1880 by Graham Bell, which was foreshadowed in 1875 by C.A. Brown. A luminous ray falling on a selenium cell produces a variation of electric resistance, thanks to which a sound signal can be transmitted by light. That delicate instrument the radiophone, constructed on this principle, has wide a.n.a.logies with the apparatus of to-day.

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Starting from the experiments of Hertz, the history of wireless telegraphy almost merges into that of the researches on electrical waves. All the progress realised in the manner of producing and receiving these waves necessarily helped to give rise to the application already indicated. The experiments of Hertz, after being checked in every laboratory, and having entered into the strong domain of our most certain knowledge, were about to yield the expected fruit.

Experimenters like Sir Oliver Lodge in England, Righi in Italy, Sarrazin and de la Rive in Switzerland, Blondlot in France, Lecher in Germany, Bose in India, Lebedeff in Russia, and theorists like M.H.

Poincare and Professor Bjerknes, who devised ingenious arrangements or elucidated certain points left dark, are among the artisans of the work which followed its natural evolution.

It was Professor R. Threlfall who seems to have been the first to clearly propose, in 1890, the application of the Hertzian waves to telegraphy, but it was certainly Sir W. Crookes who, in a very remarkable article in the _Fortnightly Review_ of February 1892, pointed out very clearly the road to be followed. He even showed in what conditions the Morse receiver might be applied to the new system of telegraphy.

About the same period an American physicist, well known by his celebrated experiments on high frequency currents--experiments, too, which are not unconnected with those on electric oscillations,--M.

Tesla, demonstrated that these oscillations could be transmitted to more considerable distances by making use of two vertical antennae, terminated by large conductors.

A little later, Sir Oliver Lodge succeeded, by the aid of the coherer, in detecting waves at relatively long distances, and Mr Rutherford obtained similar results with a magnetic indicator of his own invention.

An important question of meteorology, the study of atmospheric discharges, at this date led a few scholars, and more particularly the Russian, M. Popoff, to set up apparatus very a.n.a.logous to the receiving apparatus of the present wireless telegraphy. This comprised a long antenna and filings-tube, and M. Popoff even pointed out that his apparatus might well serve for the transmission of signals as soon as a generator of waves powerful enough had been discovered.

Finally, on the 2nd June 1896, a young Italian, born in Bologna on the 25th April 1874, Guglielmo Marconi, patented a system of wireless telegraphy destined to become rapidly popular. Brought up in the laboratory of Professor Righi, one of the physicists who had done most to confirm and extend the experiments of Hertz, Marconi had long been familiar with the properties of electric waves, and was well used to their manipulation. He afterwards had the good fortune to meet Sir William (then Mr) Preece, who was to him an adviser of the highest authority.

It has sometimes been said that the Marconi system contains nothing original; that the apparatus for producing the waves was the oscillator of Righi, that the receiver was that employed for some two or three years by Professor Lodge and Mr Bose, and was founded on an earlier discovery by a French scholar, M. Branly; and, finally, that the general arrangement was that established by M. Popoff.

The persons who thus rather summarily judge the work of M. Marconi show a severity approaching injustice. It cannot, in truth, be denied that the young scholar has brought a strictly personal contribution to the solution of the problem he proposed to himself. Apart from his forerunners, and when their attempts were almost unknown, he had the very great merit of adroitly arranging the most favourable combination, and he was the first to succeed in obtaining practical results, while he showed that the electric waves could be transmitted and received at distances enormous compared to those attained before his day. Alluding to a well-known anecdote relating to Christopher Columbus, Sir W. Preece very justly said: "The forerunners and rivals of Marconi no doubt knew of the eggs, but he it was who taught them to make them stand on end." This judgment will, without any doubt, be the one that history will definitely p.r.o.nounce on the Italian scholar.

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The apparatus which enables the electric waves to be revealed, the detector or indicator, is the most delicate organ in wireless telegraphy. It is not necessary to employ as an indicator a filings-tube or radio-conductor. One can, in principle, for the purpose of constructing a receiver, think of any one of the multiple effects produced by the Hertzian waves. In many systems in use, and in the new one of Marconi himself, the use of these tubes has been abandoned and replaced by magnetic detectors.

Nevertheless, the first and the still most frequent successes are due to radio-conductors, and public opinion has not erred in attributing to the inventor of this ingenious apparatus a considerable and almost preponderant part in the invention of wave telegraphy.

The history of the discovery of radio-conductors is short, but it deserves, from its importance, a chapter to itself in the history of wireless telegraphy. From a theoretical point of view, the phenomena produced in those tubes should be set by the side of those studied by Graham Bell, C.A. Brown, and Summer Tainter, from the year 1878 onward. The variations to which luminous waves give rise in the resistance of selenium and other substances are, doubtless, not unconnected with those which the electric waves produce in filings. A connection can also be established between this effect of the waves and the variations of contact resistance which enabled Hughes to construct the microphone, that admirable instrument which is one of the essential organs of telephony.

More directly, as an antecedent to the discovery, should be quoted the remark made by Varley in 1870, that coal-dust changes in conductivity when the electromotive force of the current which pa.s.ses through it is made to vary. But it was in 1884 that an Italian professor, Signor Calzecchi-Onesti, demonstrated in a series of remarkable experiments that the metallic filings contained in a tube of insulating material, into which two metallic electrodes are inserted, acquire a notable conductivity under different influences such as extra currents, induced currents, sonorous vibrations, etc., and that this conductivity is easily destroyed; as, for instance, by turning the tube over and over.

In several memoirs published in 1890 and 1891, M. Ed. Branly independently pointed out similar phenomena, and made a much more complete and systematic study of the question. He was the first to note very clearly that the action described could be obtained by simply making sparks pa.s.s in the neighbourhood of the radio-conductor, and that their great resistance could be restored to the filings by giving a slight shake to the tube or to its supports.

The idea of utilising such a very interesting phenomenon as an indicator in the study of the Hertzian waves seems to have occurred simultaneously to several physicists, among whom should be especially mentioned M. Ed. Branly himself, Sir Oliver Lodge, and MM. Le Royer and Van Beschem, and its use in laboratories rapidly became quite common.

The action of the waves on metallic powders has, however, remained some what mysterious; for ten years it has been the subject of important researches by Professor Lodge, M. Branly, and a very great number of the most distinguished physicists. It is impossible to notice here all these researches, but from a recent and very interesting work of M. Blanc, it would seem that the phenomenon is allied to that of ionisation.

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The history of wireless telegraphy does not end with the first experiments of Marconi; but from the moment their success was announced in the public press, the question left the domain of pure science to enter into that of commerce. The historian's task here becomes different, but even more delicate; and he will encounter difficulties which can be only known to one about to write the history of a commercial invention.

The actual improvements effected in the system are kept secret by the rival companies, and the most important results are patriotically left in darkness by the learned officers who operate discreetly in view of the national defence. Meanwhile, men of business desirous of bringing out a company proclaim, with great nourish of advertis.e.m.e.nts, that they are about to exploit a process superior to all others.

On this slippery ground the impartial historian must nevertheless venture; and he may not refuse to relate the progress accomplished, which is considerable. Therefore, after having described the experiments carried out for nearly ten years by Marconi himself, first across the Bristol Channel, then at Spezzia, between the coast and the ironclad _San Bartolommeo_, and finally by means of gigantic apparatus between America and England, he must give the names of those who, in the different civilised countries, have contributed to the improvement of the system of communication by waves; while he must describe what precious services this system has already rendered to the art of war, and happily also to peaceful navigation.

From the point of view of the theory of the phenomena, very remarkable results have been obtained by various physicists, among whom should be particularly mentioned M. Tissot, whose brilliant studies have thrown a bright light on different interesting points, such as the role of the antennae. It would be equally impossible to pa.s.s over in silence other recent attempts in a slightly different groove. Marconi's system, however improved it may be to-day, has one grave defect. The synchronism of the two pieces of apparatus, the transmitter and the receiver, is not perfect, so that a message sent off by one station may be captured by some other station. The fact that the phenomena of resonance are not utilised, further prevents the quant.i.ty of energy received by the receiver from being considerable, and hence the effects reaped are very weak, so that the system remains somewhat fitful and the communications are often disturbed by atmospheric phenomena. Causes which render the air a momentary conductor, such as electrical discharges, ionisation, etc., moreover naturally prevent the waves from pa.s.sing, the ether thus losing its elasticity.

Professor Ferdinand Braun of Strasburg has conceived the idea of employing a mixed system, in which the earth and the water, which, as we have seen, have often been utilised to conduct a current for transmitting a signal, will serve as a sort of guide to the waves themselves. The now well-known theory of the propagation of waves guided by a conductor enables it to be foreseen that, according to their periods, these waves will penetrate more or less deeply into the natural medium, from which fact has been devised a method of separating them according to their frequency. By applying this theory, M. Braun has carried out, first in the fortifications of Strasburg, and then between the island of Heligoland and the mainland, experiments which have given remarkable results. We might mention also the researches, in a somewhat a.n.a.logous order of ideas, by an English engineer, Mr Armstrong, by Dr Lee de Forest, and also by Professor Fessenden.

Having thus arrived at the end of this long journey, which has taken him from the first attempts down to the most recent experiments, the historian can yet set up no other claim but that of having written the commencement of a history which others must continue in the future.

Progress does not stop, and it is never permissible to say that an invention has reached its final form.

Should the historian desire to give a conclusion to his labour and answer the question the reader would doubtless not fail to put to him, "To whom, in short, should the invention of wireless telegraphy more particularly be attributed?" he should certainly first give the name of Hertz, the genius who discovered the waves, then that of Marconi, who was the first to transmit signals by the use of Hertzian undulations, and should add those of the scholars who, like Morse, Popoff, Sir W. Preece, Lodge, and, above all, Branly, have devised the arrangements necessary for their transmission. But he might then recall what Voltaire wrote in the _Philosophical Dictionary_:

"What! We wish to know what was the exact theology of Thot, of Zerdust, of Sanchuniathon, of the first Brahmins, and we are ignorant of the inventor of the shuttle! The first weaver, the first mason, the first smith, were no doubt great geniuses, but they were disregarded.

Why? Because none of them invented a perfected art. The one who hollowed out an oak to cross a river never made a galley; those who piled up rough stones with girders of wood did not plan the Pyramids.

Everything is made by degrees and the glory belongs to no one."

To-day, more than ever, the words of Voltaire are true: science becomes more and more impersonal, and she teaches us that progress is nearly always due to the united efforts of a crowd of workers, and is thus the best school of social solidarity.