The history of wireless telegraphy may be summed up 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.