Polarization in perfectly transparent Media. 465 
another (p,) the components 4,, f,, 7, These will belong to 
conjugate diameters, each being parallel to the tangent at the 
extremity of the other. The area of the ellipse will therefore 
be equal to the decir Sa of which p,, and p, are oh o sides, 
oR ak by Now it is evident that f;7.—71 8,, —a Tw 
which the wave-normal is drawn, it follows that 0 is positive 
or negative according as the combination of displacements has 
the character of a right-handed or a left-handed screw 
e kinetic energy of the medium, which is to be esti- 
mated for an instant of no displacement, may be shown as in 
§ 7 of the former paper (page 266 of this volume) to ¢ 
sist of two parts, of which one relates to the aschiges! Ras 
G, 1, o> and the other to the irregular flux ¢ i 2’). The 
rst, in the notation of that paper, is represented 
4/(é Pot & +n Pot +2 Pot 2) dv, 
which reduces to 
Us en ae 
gad +9° +6 ) dw. 
By substitution of the values given by equations (1), we obtain 
for the kinetic energy due to the regular flux in a unit of vol- 
ume 
=a + PB; +y +al+ B+ y,)- (10) 
11. The kinetic energy of the irregular part of the flux is 
represented by the volume-integra 
sae’ Pot &’ +77 Pot n +2! Pot 2!) dy. 
Now, since &,. 7, C' are everywhere linear functions of &, y, ¢ 
and diff. cob tees § 4), and since the integrations implied 
in the notation Pe may be confined toa sphere of which the 
