EXPERIMENTS AT MENAI STRAITS.

97

far earth conduction could be utilized. He had the satisfaction of getting results at the distance of seventeen kilometers; but the cost at which they were obtained rendered his method practically inoperative. He had not, of course, hit upon the right principle, which appears to have been reserved for Messrs. Orling and Armstrong (whose system we shall presently have to discuss) to discover.

While on this subject of communication with lighthouses and lightships it may be well to refer to two or three other experiments of the kind, although they take us a little too far ahead as regards date. In 1896 Mr. Evershed made trial of a method of using coils which he had patented several years before on the North Sand Head (Goodwin) lightship. One end of a cable was coiled in a ring on the sea-bottom, enclosing the entire area covered by the ship in swinging to and fro with the tide, the other end being connected with the shore. The ship itself was encircled by another coil above the water-line. The two coils were only about 200 fathoms apart; but for various reasons—the influence of the vessel's iron hull and the screening effect of the seawater-effective signaling was out of the ques

tion.

A year or two later (1899) Preece conducted some careful experiments on the Menai Straits "which determined the fact that the maximum

effects with telephones are produced when the parallel wires are terminated by earth-plates in the sea itself." It became desirable to establish communication between the lighthouse on the rocks known as the Skerries and the coastguard station at Cemlyn on the mainland of Anglesea,

and it was decided to do this by means of wireless telephony. A wire 750 yards in length was stretched along the Skerries, and on the mainland one of 3 miles from a point opposite the Skerries to Cemyln, the average distance between the two being 2.8 miles. Each line terminates by an earth-plate in the sea. The connections used are shown in the diagram (Fig. 20). Telephonic communication is easily maintained and the service is said to be excellent.

COMMUNICATION WITH RATHLIN ISLAND. 99

The same system was subsequently adopted for communication between Rathlin Island on the north coast of Ireland, and the mainland. The east and west portions of the island of Rathlin are about eight miles from the mainland, but a tongue of land projects southward to within a

distance of four miles (Fig. 21). Communication was required between the lighthouse near the northeastern corner of the island and the mainland, and it was a question whether an overhead line across the neck of the southern peninsula would be sufficient. This proved to be the case, and thus wireless communication, both telegraphic and telephonic, was established across the sea.

At this time Preece seemed to hold these experiments as conclusive that earth conduction had nothing to do with the results obtained. Other authorities, however, such as Sir Oliver Lodge, Charles A. Stevenson, Professor Rathenau, of Berlin (cognate researches by whom we shall shortly have to describe), and others, inclined to the opinion that the effect is partly inductive and partly conductive.

As the result of his many experiments Preece came to the conclusion that "although communication across space has thus been proved to be practical in certain conditions, those conditions do not exist in the case of isolated lighthouses and lightships, cases which it was specially desired to provide for." But after seeing what was subsequently done at the Fastnet Lighthouse, Sir William no doubt changed his opinion in this respect.

CHAPTER VII

Hertz's great discovery of electromagnetic waves-His apparatus-Clerk Maxwell's hypothesis-Sir Oliver Lodge on Maxwell and Hertz-The identity of electricity with light-Professor Hughes and his researches -Sir William Crookes's prediction-Hughes's account of his experiments-His wireless telegraphy-Discouragement by scientific experts.

THESE later installations of Sir William Preece -for the establishment of permanent communications at the Skerries, Rathlin Island, and Lavernock had gone beyond the experimental stage-did not at the time attract the attention they deserved, and would otherwise have excited, because of the sensation awakened, not only in 1897, when the new discovery first became known, but since, by Marconi's application of Hertzian waves to telegraphy. Up to this time, although Hertz's epoch-making researches were nearly ten years old, they were almost wholly unknown to the general public. Nor in all probability would the German professor's famous discovery, whereby Clerk Maxwell's mathematical deduction as to the existence of electromagnetic waves was lifted into the clear region of established fact, have become generally appreciated had not the foundation thus laid suddenly found

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