On Material Molecules and the Etherial Medium. 261 



y the symmetry of the arrangement of the etheria 

 articles. 



Hence from (12), (13), (14), and (15) 



dz 2 



= (3R + S )g + (B + S )5 + ( K + S) 



dx \dy dz ) 



Now, if the vibrations of the ether be transversal to the 

 direction of propagation, 



du do dw _ ^ 

 dx dy dz 



Hence in this case 



dhi 



dx 2 



/o-n o\ d 2 U d /dv dw\ /-p. a\d 2 U 



(3E + S) ; + + 7fe ) = (K + S)^ 



Hence putting E + S = A we have 



a + v + + ap* 



ofic rf?/ as 



. r c? 2 w ^ 2 /t d 2 ^ ) /1/1X 



= A {^t^ + 3? } • • • • < 16 > 



Again, if m' be the mass of one of the material molecules, 

 and r fr the law of the action of the molecules on the ether, 



cr r = w! 2 {fr (x — x) } 

 = ni 2// . say 



- ml {\,fr'li 2 + // \ . . . (17) 



d* x 



dx 



d* x 

 dy 



- ml | p /V # | . . . . (18) 



d* x | 1 



da 



- w'2 ^ v/v^ V\ • . . . (18*; 



Now, let us take a.s the typica] case of a biaxaJ crystal 



