as follows:—
1842.—Professor Morse sent aërial messages across the Susquehanna River. A line containing a battery and transmitter was carried on posts along one bank and "earthed" in the river at each end. On the other bank was a second wire attached to a receiver and similarly earthed. Whenever contact was made and broken on the battery side, the receiver on the other was affected. Distance about 1 mile.
1859.—James Bowman Lindsay transmitted messages across the Tay at Glencarse in a somewhat similar way. Distance about ½ mile.
1885.—Sir William Preece signalled from Lavernock Point, near Cardiff, to Steep Holm, an island in the Bristol Channel. Distance about 5½ miles.
In all these electrical induction of current was employed.
1886.—Hertzian waves discovered.
1895.—Professor A. Popoff sent Hertzian wave messages over a distance of 3 miles.
1897.—Marconi signalled from the Needles Hotel, Isle of Wight, to Swanage; 17½ miles.
1901.—Messages sent at sea for 380 miles.
1901, Dec. 17.—Messages transmitted from Poldhu, Cornwall, to Hospital Point, Newfoundland; 2,099 miles.
Mr. Marconi has so perfected tuning devices that his transatlantic messages do not affect receivers placed on board ships crossing the ocean, unless they are purposely tuned. Atlantic liners now publish daily small newspapers containing the latest news, flashed through space from land stations. In the United States the De Forest and Fessenden systems are being rapidly extended to embrace the most out-of-the-way districts. Every navy of importance has adopted wireless telegraphy, which, as was proved during the Russo-Japanese War, can be of the greatest help in directing operations.
Chapter VIII.
THE TELEPHONE.
The Bell telephone—The Edison transmitter—The granular carbon transmitter—General arrangement of a telephone circuit—Double-line circuits—Telephone exchanges—Submarine telephony.
For the purposes of everyday life the telephone is even more useful than the telegraph. Telephones now connect one room of a