The New Physics and Its Evolution

by Lucien Poincaré

§ 2

The first, and not the least difficulty, is to clearly define the subject. The words "wireless telegraphy," which at first seem to correspond to a simple and perfectly clear idea, may in reality apply to two series of questions, very different in the mind of a physicist, between which it is important to distinguish. The transmission of signals demands three organs which all appear indispensable: the transmitter, the receiver, and, between the two, an intermediary establishing the communication. This intermediary is generally the most costly part of the installation and the most difficult to set up, while it is here that the sensible losses of energy at the expense of good output occur. And yet our present ideas cause us to consider this intermediary as more than ever impossible to suppress; since, if we are definitely quit of the conception of action at a distance, it becomes inconceivable to us that energy can be communicated from one point to another without being carried by some intervening medium. But, practically, the line will be suppressed if, instead of constructing it artificially, we use to replace it one of the natural media which separate two points on the earth. These natural media are divided into two very distinct categories, and from this classification arise two series of questions to be examined.

Between the two points in question there are, first, the material media such as the air, the earth, and the water. For a long time we have used for transmissions to a distance the elastic properties of the air, and more recently the electric conductivity of the soil and of water, particularly that of the sea.

Modern physics leads us on the other hand, as we have seen, to consider that there exists throughout the whole of the universe another and more subtle medium which penetrates everywhere, is endowed with elasticity in vacuo, and retains its elasticity when it penetrates into a great number of bodies, such as the air. This medium is the luminous ether which possesses, as we cannot doubt, the property of being able to transmit energy, since it itself brings to us by far the larger part of the energy which we possess on earth and which we find in the movements of the atmosphere, or of waterfalls, and in the coal mines proceeding from the decomposition of carbon compounds under the influence of the solar energy. For a long time also before the existence of the ether was known, the duty of transmitting signals was entrusted to it. Thus through the ages a double evolution is unfolded which has to be followed by the historian who is ambitious of completeness.

§ 3

If such an historian were to examine from the beginning the first order of questions, he might, no doubt, speak only briefly of the attempts earlier than electric telegraphy. Without seeking to be paradoxical, he certainly ought to mention the invention of the speaking-trumpet and other similar inventions which for a long time have enabled mankind, by the ingenious use of the elastic properties of the natural media, to communicate at greater distances than they could have attained without the aid of art. After this in some sort prehistoric period had been rapidly run through, he would have to follow very closely the development of electric telegraphy. Almost from the outset, and shortly after Ampère had made public the idea of constructing a telegraph, and the day after Gauss and Weber set up between their houses in Göttingen the first line really used, it was thought that the conducting properties of the earth and water might be made of service.

The history of these trials is very long, and is closely mixed up with the history of ordinary telegraphy; long chapters for some time past have been devoted to it in telegraphic treatises. It was in 1838, however, that Professor C.A. Steinheil of Munich expressed, for the first time, the clear idea of suppressing the return wire and replacing it by a connection of the line wire to the earth. He thus at one step covered half the way, the easiest, it is true, which was to lead to the final goal, since he saved the use of one-half of the line of wire. Steinheil, advised, perhaps, by Gauss, had, moreover, a very exact conception of the part taken by the earth considered as a conducting body. He seems to have well understood that, in certain conditions, the resistance of such a conductor, though supposed to be unlimited, might be independent of the distance apart of the electrodes which carry the current and allow it to go forth. He likewise thought of using the railway lines to transmit telegraphic signals.

Several scholars who from the first had turned their minds to telegraphy, had analogous ideas. It was thus that S.F.B. Morse, superintendent of the Government telegraphs in the United States, whose name is universally known in connection with the very simple apparatus invented by him, made experiments in the autumn of 1842 before a special commission in New York and a numerous public audience, to show how surely and how easily his apparatus worked. In the very midst of his experiments a very happy idea occurred to him of replacing by the water of a canal, the length of about a mile of wire which had been suddenly and accidentally destroyed. This accident, which for a moment compromised the legitimate success the celebrated engineer expected, thus suggested to him a fruitful idea which he did not forget. He subsequently repeated attempts to thus utilise the earth and water, and obtained some very remarkable results.

It is not possible to quote here all the researches undertaken with the same purpose, to which are more particularly attached the names of S.W. Wilkins, Wheatstone, and H. Highton, in England; of Bonetti in Italy, Gintl in Austria, Bouchot and Donat in France; but there are some which cannot be recalled without emotion.

On the 17th December 1870, a physicist who has left in the University of Paris a lasting name, M. d'Almeida, at that time Professor at the Lycée Henri IV. and later Inspector-General of Public Instruction, quitted Paris, then besieged, in a balloon, and descended in the midst of the German lines. He succeeded, after a perilous journey, in gaining Havre by way of Bordeaux and Lyons; and after procuring the necessary apparatus in England, he descended the Seine as far as Poissy, which he reached on the 14th January 1871. After his departure, two other scholars, MM. Desains and Bourbouze, relieving each other day and night, waited at Paris, in a wherry on the Seine, ready to receive the signal which they awaited with patriotic anxiety. It was a question of working a process devised by the last-named pair, in which the water of the river acted the part of the line wire. On the 23rd January the communication at last seemed to be established, but unfortunately, first the armistice and then the surrender of Paris rendered useless the valuable result of this noble effort.