Recent Progress of Theoretical Physics. 261 



the components of the strength of an ordinary vortex, but the 

 components of magnetic force. 



The components of the angular velocity of an element of the 

 medium are 



1(77 "dzi 



, d Idq dC\ \ 



dt \ dy 



dt ^ dz dx 



-, d / d-/i d$ \ 



Wg = ^ — I — ^ — — )• 



dt \ dx dy I 



The next step in our hypothesis is the assumption that the 

 kinetic energy of the medium contains a term of the form : 



2 C (awi + ^co.^ + jcoi). (8) 



This is equivalent to supposing that the angular velocity ac- 

 quired by the element of the medium during the propagation of 

 light is a quantity which maj^ enter into combination with that 

 motion by which magnetic phenomena are explained. 



In order to form the equations of motion of the medium, we 

 must express its kinetic energy in terms of the velocity of its 



parts, the components of which are — , _?-, -A.. We therefore 



dt di di 



integrate by parts, and find 



2 G J J J {p.o\ + ^co-i + j'Wg) dx dy dz 



^ (^/(^_^. ^ d^,dl_da^\ ) .^^^^ ^^_ ^^^ 



dt ^ dz dx J dt \ dx dy I ) 



The double integrals refer to the bounding surface, which may 

 be supposed at an infinite distance. We may, therefore, while 

 investigating what takes p'ace in the interior of the medium, con- 

 fine oar attention to the triple integral. 



