THE ZEEMAN EFFECT AND DISPERSION. 429 



any gyrostatic action postulated ? Apparently nowhere. 

 When, however, we look further into the matter, we find 

 that even in Mr. Larmor's theory a gyrostatic effect is 

 introduced in order to explain the properties of his ether 

 upon ordinary dynamical principles. His ether is supposed 

 capable of elastic reaction to absolute twist. This is only 

 to be explained on ordinary dynamical principles by attribut- 

 ing to the ether gyrostatic properties due to some of its 

 parts being in rapid rotation. It would appear, then, that, 

 if not directly, at all events, indirectly, the phenomenon 

 of the rotation of the plane of polarisation of light by 

 magnetised media is rightly considered as involving gyro- 

 static properties in the ether and so far tends to confirm 

 the hypothesis that the properties of the ether may be 

 due to the rapid rotation of the parts of a fluid. 



Geo. Fras. Fitzgerard. 



