LINDSAY'S LAST EXPERIMENT.

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immersed sheets; (3) by increasing the coil that moves the receiving needle; and (4) by increasing the lateral distance of the sheets. In cases where lateral distance could be got he recommended increasing it, as then a smaller battery power would suffice. In telegraphing by this method to Ireland or France abundance of lateral distance could be got, but for America the lateral distance in Britain was much less than the distance across."

This devoted investigator's latest experiment with wireless telegraphy took place in 1860, when he again succeeded in strongly moving a telegraphic needle across the Tay at a point where it is more than a mile wide. Two years later he died, perfectly convinced to the last, as we are told, of the correctness of his views and of the ultimate triumph of his method of telegraphy.

CHAPTER III

Highton and his suggestions-Other experimenters in Wireless Telegraphy-A proposal to communicate with besieged Paris by telegraphy through the waterIts necessity obviated by the armistice-Wireless telegraphy in India-An American dentist's conception and experiments.

WHILE Lindsay thus occupied himself in Britain Bonelli was busy with similar investigations in Italy, just as Gint (first inventor of duplex telegraph) was in Austria, and Bouchot and Donat in France. So little, however, is known about their experiments that it must suffice here simply to mention their names, going to show, as they do, that the idea of wireless telegraphy was, as we say, very much "in the air.”

Of another investigator, who was at work at the same time, and whose researches, begun in 1852, extended over a period of twenty years, it is necessary to speak at greater length. This was Henry Highton, who, basing his suggestions upon numberless experiments designed with the view of finding out the best means of telegraphing between two places separated by water, described in a paper on Telegraphy without Insulation, read before the Society of Arts (May

HIGHTON'S PLANS.

41

I, 1872), three plans by which that end could be attained. The first is practically the same as the plan adopted by Morse. In the water near one bank are placed the copper plates A B (Fig. 5), which are connected by a wire, including the battery P. Near the opposite bank are submerged similar plates, C D, connected by a wire, in the circuit whereof is placed the galvanometer G. Between A and B

the current will pass by every possible route, in quantities inversely proportional to their resistances; parts passing direct by A B, and

FIG. 5.

other portions by A, C, D, B, and by A, C, G, D, B. If the plates be large, and A C and B D respectively comparatively near to each other, an appreciable current will pass from A C, through G, back to D B; but if the plates be small, the battery power small, and the distance from A to B, and from C to D, comparatively short, no appreciable amount will pass through the galvanometer circuit.

Mr. Highton held that it was possible, by erecting a very thick line wire from the Hebrides to Cornwall, by the use of enormous plates at each extremity, and by an enormous amount of battery power (as regards quantity) to transmit

a current which would be sensibly perceived in a similar line, with equally large plates, on the other side of the Atlantic. "But," adds Mr. Highton, "the trouble and expense would probably be much greater than that of laying a wire. across the ocean."

Highton's second plan was to lay across the water two wires kept from metallic contact with each other, and to work with that portion of the current which preferred to pass through this metallic circuit instead of passing through the liquid conductor, having currents of low tension from batteries of large surface. In certain cases, finally, this double line across the water might be dispensed with and a single imperfectly insulated wire used in its place, when the water itself would serve for the return current. Of these three plans Highton held the second to be the simplest and, on the whole, the most workable. It was, as a matter of fact, the one largely made use of by telegraph engineers in India for crossing large rivers, for which purpose it was found specially adapted, provided the two wires sunk in the water were a sufficient distance from each other.

There were many other workers in the same field in these mid-nineteenth century years, and a large number of patent specifications are to be seen at the office for that purpose in Chancery Lane, London, in which the subject of electric

FRENCH EXPERIMENTS.

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signaling is dealt with, chiefly on the lines laid down by one or other of the investigators whose experiments have been described. Their methods need not be described; but there was one projected plan of signaling which, both on account of its historical interest and its striking originality, is well worthy of a place in these pages. I refer to the method proposed by M. Bourbouze, a noted French electrician, for establishing telegraphic communications between Paris during the time it was invested by the German army and the French forces operating in the provinces. Bourbouze's proposal was, from a suitable place outside the German lines, to discharge a strong current into the river Seine, and to receive the same, or such portion of it as could be picked up by a metal plate sunk in the river and connected with a delicate galvanometer. Some preliminary experiments between the Hotel de Ville and the works of M. Claparède at St. Denis having proved successful, it was decided to put the plan in operation. With this object in view M. d'Almeida, on December 17, 1870, quitted Paris by balloon, and, after some perilous experiences, descended outside the German lines, and made his way by Lyons and Bordeaux to Havre. From that place the apparatus necessary for the experiment were ordered from England, and on January 14, 1871, M. d'Almeida arrived at Poissy on the Seine, where the contemplated