( 148 ) 
Physics. — Mr. Frep. Scrum on: “Plane waves of light in an 
homogeneous, electrically and magnetically anisotropic dielectric.” 
(254 part). 
10. Before examining the wave surface more closely, I shall first 
show that the ray of light is normal to the electric and the mag- 
netic force, and therefore to the ray-plane. For this purpose we first 
show that the ray is electrically conjugate to D and magnetically 
to %, properties which continue to exist after a transformation 
such as we have used. From equation (59) follows by (56), (57) 
and (58), 
gb dy me! ge aan! v' 
“9 — =, 
° 9 We ares 1 
(Blip (HS —— by Oj UP ae ae a. ve —s 2 
from which by (50), (51) and (52) 
aaf M+ ag tt Hach v' —=0, 
which expresses that D' and the transformed ray are conjugate dia- 
meters of the transformed electric ellipsoid. 
If we take (50) into account, we derive from (56), 
a s" (o"? = s''2) Ni 
a. 
ae a’ == ii ‘A a! mn 
v g" v2 (ay fi + ay ui’ g +azn' lh’) 
Adding to this the corresponding equations for w'b and ve, 
we find: 
i! a! al u We at p' a 0, 
which means that 3’ and the transformed ray are conjugate diameters 
of the transformed magnetic ellipsoid (sphere with radius 1). 
11. The electric force being normal to the magnetic induction 
and to the ray, we get: 
P Q R 1 
vee deve pu 
