§ 5. Forerunners of ether telegraphy: Clerk Maxwell
and Hertz--Dolbear, Hughes, and Graham Bell.

§ 6. Telegraphy by Hertzian waves first suggested
by Threlfall--Crookes', Tesla's, Lodge's,
Rutherford's, and Popoff's contributions--Marconi
first makes it practicable.

§ 7. The receiver in wireless telegraphy--Varley's,
Calzecchi--Onesti's, and Branly's researches--
Explanation of coherer still obscure.

§ 8. Wireless telegraphy enters the commercial stage--
Defect of Marconi's system--Braun's, Armstrong's, Lee de
Forest's, and Fessenden's systems make use of earth--
Hertz and Marconi entitled to foremost place among
discoverers.


CHAPTER VIII

THE CONDUCTIVITY OF GASES AND THE IONS

§ 1. The Conductivity of Gases: Relations of matter to
ether cardinal problem--Conductivity of gases at first
misapprehended--Erman's forgotten researches--Giese
first notices phenomenon--Experiment with X-rays--
J.J. Thomson's interpretation--Ionized gas not obedient
to Ohm's law--Discharge of charged conductors by
ionized gas.