=369. Submarine telegraph lines.=—The telegraph, which soon became of national and international importance, was still of restricted influence so long as it was confined to the land lines. Experiments on a modest scale, about the middle of the century, had shown the possibility of conducting the electric current through an insulated cable under water, and the world waited only for men of faith and energy to connect continents by submarine lines. A group of prominent Americans, of whom Cyrus W. Field was the leader, took up the project of an Atlantic cable, failed twice in their attempts to lay it, and succeeded in 1858 only to find, after a few days of successful operation, that the cable had ceased to work. The project rested during the Civil War, but in 1866 was finally accomplished. The extension of submarine cables since that time may be followed in the statistics of the preceding chapter. Cables now unite the peoples of all civilized nations, and form an indispensable part of the modern world of thought, politics, and commerce. =370. Wireless telegraphy.=—To the men who were struggling to unite continents by electrical conductors the idea that connection for the purposes of communication could be established without any conductors whatever would have seemed an idle dream. Yet this result has been attained by wireless telegraphy. Electrical waves sent broadcast from a transmitting station affect delicate instruments “tuned” to receive them at a distance of thousands of miles, and enable messages to be sent across unsounded seas or untraversed deserts with equal facility. Wireless telegraphy has not displaced the older form, which still is and probably always will be more reliable in operation. For many purposes, however, it is a useful supplement, and for one important use it is an indispensable substitute. Wireless instruments can be established as readily on board ship as on land, and so permit ships to communicate with each other and with the shore. Ships can summon aid in time of emergency, and can regularly keep in touch with their agents so that their movements can be directed to suit the need of markets. In 1914 over 500 wireless stations had been established on land, and nearly ten-fold that number on board ship. QUESTIONS AND TOPICS 1. American clippers. [Marvin, Amer. merchant marine, chap. 12; Clark, in Harper’s Magazine, 1908, vol. 117, p. 92 ff.] 2. Is it probable that steamers will drive sailing vessels entirely from the seas? People once thought that railroads would cause a decline in the demand for draft-horses; has that been the case? 3. The life of the merchant sailor. [W. Clark Russell, Scribner’s Magazine, July, 1893, 14: 3-19.] 4. Early voyages by steam across the Atlantic. [Fry, 33-42.] 5. Improvement of marine engines. [Thurston, chap. 5: Maginnis, chap. 11 (technical, good plates and pictures); Chadwick in Ocean steamships, pp. 1-56.]