Earth and the Luminiferous Ether. 



335 



The discusssion of this oversight and of the entire experiment 

 forms the subject of a very searching analysis by H. A. Lo- 

 rentz,* who finds that this effect can by no means be disregarded. 

 In consequence, the quantity to be measured had in fact but 

 one-half the value supposed, and as it was already barely be- 

 yond the limits of errors of experiment, the conclusion drawn 

 from the result of the experiment might well be questioned ; 

 since, however, the main portion of the theory remains un- 

 questioned, it was decided to repeat the experiment with such 

 modifications as would insure a theoretical result much too 

 large to be masked by experimental errors. The theory of the 

 method may be briefly stated as follows : 



Let sa, fig. 1, be a ray of light which is partly reflected 

 in ab, and partly transmitted in ac, being returned by the mir- 

 rors b and c, along ba and ca. ba is partly transmitted along ad, 



1. 



and ca is partly reflected along ad. If then the paths ab and ac 

 are equal, the two rays interfere along ad. Suppose now, the 

 ether being at rest, that the whole apparatus moves in the di- 

 rection sc, with the velocity of the earth in its orbit, the direc- 



* De l'lnfluence du Mouvement de la Terre sur les Phen. Lum. Archives Neer- 

 landaises, xxi, 2 me livr., 1886. 



