Submarine Telegraph

—A device whereby me ages are electrically transmitted through copper wires laid at the bottom of the sea. The wires are insulated in gutta perch a, tarred manila, and gutta perch a again; those cables near the shore, which are subject to chafing on the rocks, bein further protected by an armoring of plaited stee wires, Fhe conductor is usually of purest copper wire, weighing from 70 to 400 lbs. per nautical mile, made in a sevenfold strand to Je en risk of - breaking. In the Atlantic cable, which is of the usual type of cable for long lines, the core is protected first by a stout layer of gutta-perch a, then by woven coating of jute, and outside all an external sheath made of ten iron wires, each covered with hemp. The shore ends are even more strongly protected by external wires. Culley states that when a current is sent through an Atlantic cable from Ireland to Newfoundland no effect is produced on the most delicate instrument at the receiving end for two tenths of a second, and that it requires three seconds for the current to gain its full strength, rising in an electric wave which travels forward through the cable. The strength of the current falls gradually also when the circuit is broken.