Contents. ix 



Page 



Young proposes a dynamical theory of light in crystals, . . 110 



Researches of Malus on polarization, .... Ill 



Recognition of biaxal crystals, ... . 113 



Fresnel successfully explains diffraction, . . . 114 



His theory of the relative motion of aether and matter, . . 115 



Young suggests the transversality of the vibrations of light, . 121 



Fresnel discusses the dynamics of transverse vibrations, . . 123 



Fresnel's theory of the propagation of light in crystals, . . 125 



Hamilton predicts conical refraction, . . . ] 31 



Fresnel's theory of reflexion, ..... 133 



CHAPTER V. 

 I ,THE AETHER AS AN ELASTIC SOLID. 



Astronomical objection to the elastic-solid theory : Stokes' 



hypothesis. . . . . . . .137 



Navier and Cauchy discover the equation of vibration of an elastic 



solid, 139 



Poisson distinguishes condensational and distortional waves, . 141 



Cauchy's first and second theories of light iq, crystals, . . 143 



Cauchy's first theory of reflexion, ..... 145 



His second theory of reflexion, ..... 147 



The theory of reflexion of MacCullagh and Neumann, . . 148 



Green discovers the correct conditions at the boundaries, . . 151 



Green's theory of reflexion : objections to it, . . . 152 



MacCullagh introduces a new type of elastic solid, . . . 154 



W. Thomson's model of a rotationally-elastic body, . . 157 



Cauchy's third theory of reflexion : the contractile aether, . . 158 



Later work of W. Thomson and others on the contractile aether, . 159 



Green's first and second theories of light in crystals, . . 161 



Influence of Green, ....... 167 



Researches of Stokes on the relation of the direction of vibration of 



light to its plane of polarization, .... 168 



The hypothesis of aeolotropic inertia, .... 171 



Rotation of the plane of polarization of light by active bodies, . 173 



MacCullagh's theory of natural rotatory power, . . 175 



MacCullagh's and Cauchy's theory of metallic reflexion, . . 177 



Extension of the elastic -solid theory to metals, . . 179 



Lord Rayleigh's objection, .... . 181 



Cauchy's theory of dispersion, . . 182 



Boussinesq's elastic-solid theory, ..... 185 



