ity--
Spring's analogies of solids and liquids--Crystallization
--Lehmann's liquid crystals--Their existence doubted
--Tamman's view of discontinuity between crystalline
and liquid states.

Sec. 4. The Deformation of Solids: Elasticity--
Hoocke's, Bach's, and Bouasse's researches--Voigt
on the elasticity of crystals--Elastic and permanent
deformations--Brillouin's states of unstable
equilibria--Duhem and the thermodynamic postulates--
Experimental confirmation--Guillaume's researches
on nickel steel--Alloys.

CHAPTER V

SOLUTIONS AND ELECTROLYTIC DISSOCIATION

Sec. 1. Solution: Kirchhoff's, Gibb's, Duhem's and Van
t'Hoff's researches.

Sec. 2. Osmosis: History of phenomenon--Traube and
biologists establish existence of semi-permeable
walls--Villard's experiments with gases--Pfeffer
shows osmotic pressure proportional to concentration--
Disagreement as to cause of phenomenon.

Sec. 3. Osmosis applied to Solution: Van t'Hoff's
discoveries--Analogy between dissolved body and
perfect gas--Faults in analogy.

Sec. 4. Electrolytic Dissociation: Van t'Hoff's and
Arrhenius' researches--Ionic hypothesis of--Fierce
opposition to at first--Arrhenius' ideas now triumphant
--Advantages of Arrhenius' hypothesis--"The ions
which react"--Ostwald's conclusions from this--Nernst's
theory of Electrolysis--Electrolysis of gases makes
electronic theory probable--Faraday's two laws--Valency--
Helmholtz's consequences from Faraday's laws.

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