418 The Theory of Aether and Electrons in the 



A sequel to the experiment of Michelson and Morley was 

 performed in 1897, when Michelson* attempted to determine 

 by experiment whether the relative motion of earth and aether 

 varies with the vertical height above the terrestrial surface. 

 No result, however, could be obtained to indicate that the 

 velocity of light depends on the distance from the centre of 

 the earth ; and Michelson concluded that if there were no choice 

 <"but between the theories of Fresnel and Stokes, it would be 

 necessary to adopt the latter, and to suppose that the earth's 

 influence on the aether exends to many thousand kilometres 

 above its surface. By this time, however, as will subsequently 

 appear, a different explanation was at hand. 



Meanwhile the perplexity of the subject was increased by 

 experimental results which pointed in the opposite direction 

 to that of Michelson. In 1892 Sir Oliver Lodgef observed the 

 interference between the two portions of a bifurcated beam of 

 light, which were made to travel in opposite directions round 

 a closed path in the space * between two rapidly rotating steel 

 disks. The observations showed that the velocity of light is 

 not affected by the motion of adjacent matter to the extent of 

 (l/200)th part of the velocity of the matter. Continuing his 

 investigations, Lodge} strongly magnetized the moving matter 

 (iron in this experiment), so that the light was propagated 

 across a moving magnetic field ; and electrified it so that the 

 path of the beams lay in a moving electrostatic field ; but in 

 no case was the velocity of the light appreciably affected. 



We must now trace the steps by which theoretical physicists 

 not only arrived at a solution of the apparent contradictions 

 furnished by experiments with moving bodies, but so extended 

 the domain of electrical science that it became necessary to 

 enlarge the boundaries of space and time to contain it. 



The first memoir in which the new conceptions were 

 unfolded-j was published by H. A. Lorentzg in 1892. The 



* Amer. Journ. Sci. (4) iii (1897), p. 475. 



t Phil. Trans, clxxxiv (1893), p. 727. J Ibid., clxxxix (1897), p. 149. 



Archives Neerl. xxv (1892), p. 363 : the theory is given in eh. iv, pp. 432 

 et sqq. 



