cannot exist in fluid--Ether must be discontinuous.

§ 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.

§ 3. The Electromagnetic Ether: Ampère'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.

§ 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.

§ 5. The X-Rays: Röntgen'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