Page:The American Cyclopædia (1879) Volume XV.djvu/645

 TELEGRAPH 617 DO

W< d many of them have soon proved failures through imperfection in the insulation. The wires are best insulated by coating them with gutta percha, and they are protected from in- jury by laying them in pipes of lead or of earth- enware, or in wooden boxes preserved by sat- urating the wood with a solution of sulphate of copper or chloride of zinc. Some of these lines have worked perfectly for many years, but when they fail it is a matter of great ex- pense and difficulty to discover their defective points. In the extent of its telegraphic lines " e United States has exceeded every other omtry. In 1860 it was estimated that there ere over 50,000 m. in operation, and at pres- ent there is not less than 150,000 m. of wire. In the aggregate, 700,000 m. of wire spread their network over the earth for telegraphic purposes, including lines in Australia, India, China, and Siberia. Russia is engaged in ex- tending an important line from Moscow to the Pacific so as to connect eastern Asia with Europe, and possibly hereafter with America by the way of Behring strait. This line was completed to Perm, on the borders of Siberia, and from that place across the Ural mountains to Omsk on the Irtish, in 1861. Thence it is continued to Tomsk, and S. E. to Irkutsk; next it passes the Altai mountains to Kiakhta on the Chinese frontier, thence to Cheta on the Amoor, and thence to Nertchinsk. From Orum, or some other point on the Amoor, one branch will go down the river and another southward to a Russian port on the Japan sea. The project of extending these lines to Beh- ring's strait, and across to Alaska, Oregon, and California, which had been partially car- ried into effect on the American side, was abandoned after the Atlantic cables had been brought into working condition. Submarine Telegraphs. The idea of a submarine tele- graph appears to have been conceived by sev- eral of the earlier electricians. Salva is said to have proposed one as early as 1797 be- tween Barcelona and Palma in the island of Majorca. Experiments were made in India by Dr. O'Shaughnessy in 1839 with this ob- ject, and he insulated his wires by covering them with tarred yarn, enclosing them in split rattan, and covering this again with tarred yarn. Wheatstone in 1840 gave it as his opin- ion before a committee of the house of com- mons that a submarine communication between England and France was practicable. Morse, on Oct. 18, 1842, laid a copper wire, insulated by means of a hempen strand coated with tar, pitch, and India rubber, from Governor's island to the Battery in New York, and the next morning was beginning to receive communica- tions through it, when the wire was caught in the anchor of a vessel getting under way, and being hauled on board was stolen by the sailors. Samuel Colt laid a submarine cable in 1843 from Coney island and Fire island, at the mouth of New York harbor, up to the city, and operated it successfully. The first subma- rine telegraph wire laid in Europe was across the Rhine from Deutz to Cologne, about half a mile ; it was insulated with gutta percha, and laid by Lieut. Siemens of the royal Prussian artillery. This appears to have been the first application of gutta percha to this purpose, the substance about that time first beginning to attract attention. In 1850 a copper wire cov- ered with gutta percha was laid between Dover and Calais by Brett, but its success was short- lived. The next year it was replaced by a cable of four wires, which has given complete satisfaction. In 1853 six cables (the longest of which, between England and Scotland, was about 100 m.) were successfully laid. In 1854 five other cables went into operation, the longest being only about 64 m. In 1855-'6 two more were added, that from Varna to Constantinople being about 160 m. Besides these, two cables had been laid in deeper wa- ters: one from Newfoundland to Cape Bre- ton, and another from Spezia to Corsica. The grand attempts to connect the European and American continents by a cable across the At- lantic, commenced in 1857 and perfected Aug. 5, 1858, have been noticed in the article FIELD, CYRUS WEST. Before these were undertaken great encouragement was given to the enter- S'ise by the successful experiments made on ct. 9, 1856, in transmitting distinct signals at the rate of 210, 241, and even 270 a minute through a number of connected coils of wires, insulated with gutta percha, and making a total length of about 2,000 m., increased to a virtual circuit of 2,300 m. by the interposition of fine wires at the joinings of the coils. The wires were excited by the magneto-electric coils of Whitehouse, and the signals were re- ceived upon the ordinary recording apparatus of Morse. But a great difference was after- ward experienced in the working of the wires when submerged. Before the cable was laid it was ascertained that insulated wires acquire a new character when submerged, and that instead of transmitting the current as simple conductors, they are of the nature of the Ley- den jar, the gutta percha corresponding to the glass, the inner wire to the interior coating, and the iron covering or the water itself to the exterior coating; and that consequently the cable must be charged throughout the en- tire length before any current is produced. Among other interesting phenomena, it was observed that the voltaic current is not trans- mitted so rapidly through such a conductor as the magneto-electric current; and that al- ternating positive and negative signals are transmitted more rapidly than successive sig- nals of the same character. After being laid, the wires were first worked by the Ruhm- korff induction coils and a Smee battery, and afterward by a Daniell battery ; but the cur- rent was for the most part so weak as scarcely to operate the most delicate relay, though sus- ceptible to a current that can hardly be per- ceived on the tongue. The effect was indicated