432 The Theory of Aether and Electrons in the 



where E denotes the electric force on a charge at rest, which is 

 zero in the present case. Thus, according to Lorentz' theory, 

 the charges on the faces would have only (e - l)/e of the values 

 which they would have in Hertz' theory ; that is, they would be 

 practically zero. The result of Blondlot's experiment was in 

 favour of the theory of Lorentz. 



An experiment of a similar character was performed in 

 1905 by H. A. Wilson.* In this, the space between the inner 

 and outer coatings of a cylindrical condenser was filled with 

 the dielectric ebonite. When the coatings of such a con- 

 denser are maintained at a definite difference of potential, 

 charges are induced on them ; and if the condenser be rotated 

 on its axis in a magnetic field whose lines of force are parallel 

 to the axis, these charges will be altered, owing to the 

 additional polarization which is produced in the dielectric 

 molecules by their motion in the magnetic field. As before, 

 the value of the additional charge according to the theory of 

 Lorentz is (e - l)/e times its value as calculated by the theory 

 of Hertz. The result of Wilson's experiments was, like that of 

 Blondlot's, in favour of Lorentz. 



The reconciliation of the electromagnetic theory with 

 Fresnel's law of the propagation of light in moving bodies was 

 a distinct advance. But the theory of the motionless aether 

 was hampered by one difficulty : it was, in its original form, 

 incompetent to explain the negative result of the experiment 

 of Michelson and Morley.f The adjustment of theory to 

 observation in this particular was achieved by means of a 

 remarkable hypothesis which must now be introduced. 



In the issue of " Nature" for June 16th, 1892,J Lodge 



mentioned that Fitz Gerald had communicated to him a new 







suggestion for overcoming the difficulty. This was, to suppose 

 that the dimensions of material bodies are slightly altered 

 when they are in motion relative to the aether. Five months 

 afterwards, this hypothesis of Fitz Gerald's was adopted by 



*Phii. Trans, cciv (1905), p. 121. 



t Cf. p 417. J Nature, xlvi (1892), p. 165, 



