On Material Molecules and the Etherial Medium. 267 
u-^u^', Uc^u^, '^i^i'' ^2^^V' ^^") ^® ^^^^ corresponding values 
of uu\ vv', &c. 
Then, from (28) 
A 
v^^ - A ~ 
^ A72 + B'?7i2 4- C'w^ 
A 
(29) 
(30) 
Now, in order that the two rays may be polarised in planes 
at right angles to each other, we must have for all values 
of Z, m, n, 
Multiplying the expressions (29) and (30), and substituting 
for the values of v-^ and from (27), we easily find 
u^ u^ _ k'^-k^ A7^ + B-m^ + C^n ^ 
In order that this may become of the form g for all 
values of m, we must have 
A^ = B' = C 0 
F =: a =r H = 0 
and then from (27) 
v^^ = A , 
that is, one of the rays in every biaxal crystal follows the 
ordinary law of refraction, which is known not to be the case. 
Hence the particular manner in which we have above 
attempted to take into account the action of the material 
molecules, although being remarkable as leading 'to a quad- 
ratic equation for the determination of the velocity of pro- 
pagation of plane waves through crystallised media, fails 
when developed further. 
VOL. III. 2 M 
