CONTENTS 



law of the conservation of energy, p. 266 Mayer and Helmholtz, 

 p. 267 Joule's paper of 1843, P- 2 ^9 Joule or Mayer, p. 272 Lord 

 Kelvin and the dissipation of energy, p. 274 The final unification, 

 p. 279. 



CHAPTER IX 



THE ETHER AND PONDERABLE MATTBR 



James Clerk- Maxwell's conception of ether, p. 283 Thomas Young 

 and " Luminiferous ether," p. 285 Young's and Fresnel's concep- 

 tion of transverse luminiferous undulations, p. 285 Faraday's ex- 

 periments pointing to the existence of ether, p. 287 Professor 

 Lodge's suggestion of two ethers, p. 288 Lord Kelvin's calcula- 

 tion of the probable density of ether, p. 289 The vortex theory of 

 atoms, p. 290 Helmholtz's calculations in vortex motions, p. 290 

 Professor Tait's apparatus for creating vortex rings in the air, p. 

 291 The ultimate constitution of matter as conceived by Bosco- 

 vich, p. 293 Davy's speculations as to the changes that occur in 

 the substance of matter at different temperatures, p. 294 Clau- 

 sius's and Maxwell's investigations of the kinetic theory of gases, 

 p. 295 Lord Kelvin's estimate of the size of the molecule, p. 299 

 Studies of the potential energy of molecules, p. 300 Action of 

 gases at low temperatures, p. 304. 



APPENDIX 307 



