In 1879 Hughes discovered the phenomena on which depends the action of coherer. In 1883 Fitzgerald suggested a method of producing electromagnetic waves in space by the discharge of a conductor. In 1887 Hertz showed that electromagnetic waves are in complete accordance with the waves of light and heat, and founded the theory upon which all modern radio signalling de vices are based. In 1896 Marconi lodged his application for the first British patent for wireless telegraphy. He conducted experi ments in communicating over a distance of I miles successfully. On Dec. 6, 1897, signals were transmitted from shore to a ship at sea, 18 miles distant. On Dec. 17, 1897, the first floating wireless station was completed. On June 3, 1898, the first paid radiogram was transmitted (from the Needles [Isle of Wight] station).
On March 3o, 1903, the first transoceanic radiogram was pub lished in The Times, London. In 1906 Dr. DeForest was granted a patent (Jan. 18) for a vacuum rectifier, commercially known as the audion. In the same year Gen. H. N. C. Dunwoody discovered the rectifying proportions of carborundum crystals, and Pickard discovered the similar properties of silicon crystals. These discoveries formed the basis of the widely used crystal detectors. In 1912 Frederick August Kolster, of the U.S. Bureau of Stand ards invented and developed the Kolster decremeter, which is used to make direct measurements of wave length and logarithmic decrement. In 1912 the first practical trials with wireless ap paratus on trains were made on a train belonging to the Dela ware, Lackawanna and Western Railroad.
In Oct. 1914, E. H. Armstrong was issued a patent covering the regenerative circuit, also known as the feed-back and the self heterodyne circuit. On July 28, 1915, the American Telephone and Telegraph Co., working in conjunction with the Western Electric Co., succeeded in telephoning by wireless from Arlington, Va., to Hawaii, a distance of nearly 5,000 miles. On Oct. 26, 1915, the wireless telephone experiments were continued, communication being effected across the Atlantic from Arlington to the Eiffel Tower, Paris.
In 1919 the successful trans-Atlantic flights of the American "NC4" and of Alcock and Brown, and of the British dirigible "R34" focused attention upon the great value of radio for aviation purposes. On March z, 1923, Louis Alton Hazeltine, of Stevens Institute of Technology, presented a paper before the Radio Club of America on tuned radio-frequency amplification with the neu tralization of capacity coupling. Professor Hazeltine was granted a patent for the non-radiating neutrodyne receiver. In 1925 radio compass (direction finder) came into greater use on board vessels. In 1926 directional or beam transmission developed to a point where it is considered practical for commercial usage. In 1927-28 Bell laboratories experiments effected successful transmission by wire and radio of television signals. In 1927-28 extension of radio-telegraphy to the principal countries of the world was accomplished.