CHAPTER VI

THE ETHER

Sec. 1.  The Luminiferous Ether:  First idea of Ether due to Descartes—­Ether must be imponderable—­Fresnel shows light vibrations to be transverse—­Transverse vibrations cannot exist in fluid—­Ether must be discontinuous.

Sec. 2.  Radiations:  Wave-lengths and their measurements—­Rubens’ and Lenard’s researches—­ Stationary waves and colour-photography—­Fresnel’s hypothesis opposed by Neumann—­Wiener’s and Cotton’s experiments.

Sec. 3.  The Electromagnetic Ether:  Ampere’s advocacy of mathematical expression—­Faraday first shows influence of medium in electricity—­Maxwell’s proof that light-waves electromagnetic—­His unintelligibility—­Required confirmation of theory by Hertz.

Sec. 4.  Electrical Oscillations:  Hertz’s experiments—­ Blondlot proves electromagnetic disturbance propagated with speed of light—­Discovery of ether waves intermediate between Hertzian and visible ones—­Rubens’ and Nichols’ experiments—­Hertzian and light rays contrasted—­Pressure of light.

Sec. 5.  The X-Rays:  Roentgen’s discovery—­Properties of X-rays—­Not homogeneous—­Rutherford and M’Clung’s experiments on energy corresponding to—­Barkla’s experiments on polarisation of—­Their speed that of light—­Are they merely ultra-violet?—­Stokes and Wiechert’s theory of independent pulsations generally preferred—­J.J.  Thomson’s idea of their formation—­ Sutherland’s and Le Bon’s theories—­The N-Rays—­ Blondlot’s discovery—­Experiments cannot be repeated outside France—­Gutton and Mascart’s confirmation—­ Negative experiments prove nothing—­Supposed wave-length of N-rays.

Sec. 6.  The Ether and Gravitation:  Descartes’ and Newton’s ideas on gravitation—­Its speed and other extraordinary characteristics—­Lesage’s hypothesis—­Cremieux’ experiments with drops of liquids—­Hypothesis of ether insufficient.

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.