CHAPTER VII
WIRELESS TELEGRAPHY
Sec. 1. Histories of wireless telegraphy already written,
and difficulties of the subject.
Sec. 2. Two systems: that which uses the material media (earth,
air, or water), and that which employs ether only.
Sec. 3. Use of earth as return wire by Steinheil
--Morse's experiments with water of canal--Seine used as
return wire during siege of Paris--Johnson and Melhuish's
Indian experiments--Preece's telegraph over Bristol
Channel--He welcomes Marconi.
Sec. 4. Early attempts at transmission of messages through
ether--Experiments of Rathenau and others.
Sec. 5. Forerunners of ether telegraphy: Clerk Maxwell
and Hertz--Dolbear, Hughes, and Graham Bell.
Sec. 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.
Sec. 7. The receiver in wireless telegraphy--Varley's,
Calzecchi--Onesti's, and Branly's researches--
Explanation of coherer still obscure.
Sec. 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.
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