( 438 ) 



at CijHal local limes. If theiefore, we should meet with plienomen.a, 

 ill which the difference of the local times for mutually acting- par- 

 ticles might have a sensible influence, and in which yet observation 

 showed the above theonnn to be true, this would indicate a modifi- 

 catiou, like the one we have just specified, of the molecular forces 

 by the influeuce of a translation. Of course, such a modification 

 would only be possible, if the molecular forces were no direct actions 

 at a distance, but were i)ropagated by the aether in a similar w^ay 

 as the electromagnetic actions. Perhaps the rotation of tiie plane of 

 polarization in the so-called active bodies will be found to be a 

 phenomenon of the kind, just mentioned. 



§ 9. Hitherto all quantities of the order pV^'~ ^^'^^ been ne- 

 glected. As is well known, these must be taken into account in 

 the discussion of Michelson's experiment, in which two rays of 

 light interfered after having traversed rather long paths, the one 

 parallel to the direction of the earth's motion, and the other 

 perpendicular to it. In order to explain the negative result of this 

 experiment Fitzgerald and myself have supposed that, in consequence 

 of the translation, the dimensions of the solid bodies serving to 

 support the optical apparatus, are altered in a certain ratio. 



Some time ago, M. Liénard^) has emitted the opinion that, ac- 

 cording to my theory, the experiment should have a positive result, 

 if it were modified in so far, that the rays had to pass through a 

 solid or a liqtiid dielectric. 



It is impossible to say with certainty what would be observed in 

 such a case, for, if the explication of Michelson's lesult which I 

 have proposed is accepted, we must also assume that the mutual 

 distances of the molecules of transparent media are altered by the 

 translation. 



Besides, we must keep in view the possibility of an influence, be 

 it of the second order, of the translation (tn the molecular forces. 



In what follows I shall shew, not that the result of the experi- 

 ment must necessarily be negative, but that this might very well 

 be the case. At the same time it will appear what would be the 

 theoretical meaning of such a result. 



Let us return again to the equations (Ic)— (Vc). This time we 

 shall not put in them i-=l, but the other simplifications of which 

 we have spoken in § 6 will again be introduced. We shall now 

 have to distinguish between the vectors ^ and 5', the former alone 



^) L'Eclairage Electi-i(|ue, 20 et 27 aout 18 '.)i 



