Page:The American Cyclopædia (1879) Volume XV.djvu/646

 G18 TELEGRAPH at the Newfoundland station by the deflection of a delicate galvanometer, and at Valentia in Ireland by that of the reflecting galvanometer of Thomson, in which a delicate magnet carries a small mirror from which a beam of light is reflected. This ray being thrown upon a sur- face at some distance, a movement of the mag- net that is not directly perceptible may be even measured upon a graduated scale. The transmitted current was, much of the time that the cable continued in action, so weak that every expedient of this kind was necessary to render the signals perceptible. From the first there was a defect in the part of the cable laid toward the Irish shore, which caused a tem- porary interruption of communications between the ships. Between Aug. 13 and Sept. 1 there were 129 messages of 1,474 words sent from Valentia to Newfoundland, and 271 of 2,885 words in the other direction. The message from Queen Victoria to the president of the United States, 99 words, occupied in its trans- mission 67 minutes. The rate of reception was very variable, the signals being often un- intelligible and requiring several repetitions. Electricians were sent to Valentia, and the most powerful batteries, as well as the great magneto- electric machine of W. T. Henley, were applied to test the condition of the cable. The power thus employed was more than 1,000 times what would be required in an ordinarily well insulated conductor to give perfect signals to the mirror galvanometer. To the end of the cable a voltaic battery was connected by one of its poles, a galvanometer was placed in the circuit, the other pole was connected with the earth, and by these means the location of the defect in the cable was ascertained ; but all attempts to recover it were unsuccessful. The cost of the cable was as follows : for 2,500 m. at $485 per mile, $1,212,500; for 10 m. at $1,250 per mile, $12,500 ; and for 25 m. shore ends at the same price, $31,250 ; making alto- gether $1,256,250. The expenditures of the company up to Dec. 1, 1858, had amounted to $1,834,500. After the failure of this great enterprise attention was directed to the prac- ticability of extending a cable across the At- lantic from Labrador to Scotland, by way of Greenland, Iceland, and the Faroe islands. The route is about 1,800 m. long, and presents no continuous length of submarine cable for a greater distance than that between Labrador and Greenland, which is about 600 m. Mr. T. P. Shaffner, of the United States, had obtained in 1854 from the king of Denmark a conces- sion of exclusive rights in Greenland, Iceland, and the Faroe islands for this purpose. He sailed from Boston, Aug. 29, 1859, and made the preliminary surveys at his own expense, and he induced the British government to send a steam vessel to take the deep-sea soundings ; but the project was not consummated. The failure of other deep-sea cables, as that between Sardinia, Malta, and Corfu, and the long cable from the Red sea to India, increased the dis- trust occasioned by the failure of the Atlantic cable of 1858. The result was that a commit- tee, consisting of the most eminent electrical engineers, was appointed by the English cham- ber of commerce and the " Transatlantic Tele- graph Company," to whom the duty was as- signed of inquiring into the causes of these dis- astrous failures, and providing instructions for the future in regard to the manufacture, tests, and placing of cables. It appeared that the mechanical department of the subject was in a more advanced state than the electrical. The committee, after 18 months of hard work, published an elaborate report in 1863. More- over, the theoretical researches of Thomson, Jenkins, and others, had thrown much light on the electrical requirements of submarine lines. Meanwhile, a cable was laid successfully be- tween Malta and Alexandria in 1861, and the Persian gulf cable (about 1,330 m. long) in 1864. When Mr. Field visited England in 1862, to urge on a second attempt to establish tele- graphic communications across the Atlantic, he found that the manufacturers, Messrs. Glass, Elliott, and co., were confident of their ability to make and place a good and durable cable between Great Britain and America, and were willing to incur a part of the risk. The second Atlantic cable, made by the " Telegraph Con- struction and Maintenance Company," was tested with every precaution, and found to be unexceptionable in its electrical conditions, and was shipped on board the Great Eastern in 1865. This cable (2,186 m. long) consists of seven copper wires (No. 18) twisted into a spiral, covered with four coats of gutta percha, between which are thin layers of Chatterton's compound. The external protection is made of ten iron wires, each surrounded by rnanila yarn. After about half of the cable had been paid out it broke, and the expedition was abandoned for the season. The total expendi- ture of money had been about $3,000,000. In 1866 a third cable, of similar construction to the second, but stronger, lighter, and more flexible, was placed on board the Great East- ern and successfully laid. The length between Trinity bay and Valentia is 2,134 m. Its first duty was to transmit a message of peace, viz., that a treaty had been signed by Prussia and Austria. Capt. Anderson returned with the Great Eastern to the place where the cable of 1865 had parted, and succeeded in splicing it and completing the line. In 1869 the French Atlantic line went into operation between Brest and St. Pierre, and between St. Pierre and Duxbury, Mass., the total length being 3,857 m. In 1870 more than 15,000 m. of cable were laid, including the Indian cables (from Suez to Aden, from Aden to Bombay, and from Penang to Singapore), the China cable, and the North China from Hong Kong to Shanghai and from Shanghai to Posiet in the Littoral prov- ince of Siberia. In 1874 the work was begun by the "Direct Cable Company " of laying the new Atlantic line between Ballinskilligs bay,