Page:The New International Encyclopædia 1st ed. v. 19.djvu/124

* TELEGRAPHY. the line. This idea, originated by C. F. Varley, was embodied in a patent in 1S62 and put in practice in 1866. Wlien first used at the receiv- ing end it was foimd that the speed was consider- ably increased, and when placeil at both ends the erticiency of the cable was practically doubled. Greater" distinctness in the transmission of the sigiuils was obtained as well as increased rapid- ity. The operation of a simple cable circuit will be seen from the preceding diagram of the con- nections.' The cable connected with a condenser at either end is shown above. From the opposite plates of the condenser connection is made with a switch through which the current may pass either to the earth tlirough a galvanometer or recorder or to a transmitting key, K, and then to the battery and earth, depending on whether signals are be- ing sent or received at the particular station. At K and K' either pole of the battery can be con- nected at will to the line, or rather to the con- denser, and the cable charged inductively. The corresponding signals are produced at the distant station, the galvanometer being connected to the line by the switch. Cables can also be worked du- plex with facility and an increased speed of 90 per cent, attained, but as yet it is not possible to employ the quadruples method in use on land lines. The duplex system was devised in 1875 and 1876 by Muirhead and Taylor and was first used on the Atlantic cable in 1878. Previously in 1873 experiments in this field had been car- ried on by J. B. Stearns. History and St.vtistics. The feasibility oT laying a line for the transmission of signals along the bottom of the ocean seems to have been first suggested in 1795 by a Spaniard named Salvia. Eight years later a nephew of the famous electrician Galvani performed ex- periments of a similar nature in the deep sea off Calais. The first really important experiments, however, bearing directly upon this subject are believed to have been those of Summering and Schilling, who in 1811 applied a soluble insulat- ing material to a conductor which was laid across the river Isar near Munich, These investigators also used a submarine conductor to explode gun- powder by an electric current. In 1813 an Eng- lishman named John Sharpe transmitted signals through seven miles of insulated copper wire laid on the bottpm of a pond, but the first practical attempt to use such a conductor to transmit telegraphic signals was by Colonel Paisley of the Eoyal Engineers at Chatham. England, in 1838. He surrounded his conductor with strands of tarred rope and wrapped the whole with pitched yarn. In 1839 Dr. W. O'Shaughnessy at Cal- cutta laid across the Hugli River copper wire cov- ered with bamboo and then coated with cotton and tar. In 1840 Wheatstone proposed a scheme similar to those of the last two inventors, and later .suggested the use of gutta-percha as a cov- ering for the wire, but was imable to put his idea into practice. Prof. S. F. B. Morse, of New York, laid an insulated cable between Castle Garden and Governor's Island, and as a result of his experiments came to the conclusion '"that a tele- graphic communication on his plan might with certainty be established across the Atlantic." The idea that submarine conductors for tele- graphic purposes could be constructed was rapid- ly taking root, and in 1845 the Messrs. Brett, 98 TELEGRAPHY. who were active in the construction of the first telegraphic lines across the English Channel and the first Atlantic cable, registered a "General Oceanic Telegraphic Company' for the purpose of establishing telegraphic communication between England and America. In 1850 an experimental line was laid across the English Channel by the Messrs. Brett, and this was lollowed in 1851 by a permanent cable of such excellent construction that it survived for a number of years. Several longer lengths of submarine cable were laid within tlie next few years, Italy was connected with Corsica and Sardinia, and Sardinia with Africa. A Black Sea cable was laid in 1855, but operated onl}' a short time. Thus far attempts to lay submarine tele- graph lines had been confined to comparatively short distances. In 1858, after repeated un- successful experiments, telegraphic communi- cation was established across the Atlantic, After something over a hundred messages had been sent back and forth, the cable ceased to work. Al- though this cable was a comparative failure, yet its brief success proved two things: (1) That a cable could be laid through 3000 miles of deep sea; (2) that the electric current could be transmitted through a wire of that length. It was not until 1866 that a permanent cable was laid across the Atlantic. (The detailed history of this undertaking is described ruider Atl. tic Telegkaph.) a second .tlantic cable was in- augurated immediately after, the one which had broken in the la^'ing in 1865 having been re- paired. In 1859, after the first Atlantic cable had ceased to work, the Red Sea and East Indian Telegraph was laid, over a route 3043 miles long, but this also proved a dismal failure and was finally abandoned. The Malta-Alexandria cable was laid in 1801, and was in use till 1872, when, from repeated breakages in shallow water, its use was discontinued. The core consisted of a strand of seven copper wires, covered by tliree layers of gutta-percha; outside of this was a serving of tarred yarn ; and, finally, IS iron wires constituted the sheathing. This was the first long cable suc- cessfull.v laid (its total length, in three sections, being 1331 miles) ; and it was also the first properly tested under water before being laid, and carefully constructed with constant watch- fulness as to its electrical and mechanical con- ditions. In 1869 a cable 2328 miles long was laid from Brest, France, to the island of Saint-Pierre, south of Newfoundland; in 1873, one from Lisbon to Pernambueo, Brazil. In 1874 a third British Atlantic cable was laid, from Ireland to New- foundland, and in 1875 a fourth, from Ireland to New Hampshire. In 1903 there were 19 cables across the Atlantic, of which three were no longer in use. Of these, two distinct lines, one of which is duplicated, connect Europe with South America. In 1902 the British Pacific Cable between Australia and British Columbia, 7800 nautical miles in len,cth. was completed, and in 1003 the first American cable was laid across the Pacific, with a length of 7846 nautical miles, by the Commercial Cable Company, between San Francisco and the Philippines, touching at Ha- waii, Midway Island, and Guam, In 1903 the total length of submarine cable was estimated at over 250,000 miles, representing an outlay of over $300,000,000.