THE ELECTRIC AND LUMINIFEROUS MEDIUM. 
785 
Recapitulation of the Vibrational Qualities of the uRither. 
91. On the present extension of MacCullagh’s scheme, the properties of the 
sether in a ponderable medium, as regards those averaged undulations which constitute 
radiation, are to be derived from the following functions; 
its kinetic energy 
T = 
+ 
cl^ 
clh 
th 
its potential energy 
W = 1 |(ay 2 ^ cIt, where {f g, h) = curl (^, 77 , Q, 
its dissipation function, representing decay of the regularity of the motion, 
We may add as subsidiary terms the magneto-optic energy 
T' {( z OZ ^0 , 3 cm\ 
T = J! MMJt) 
where 
d _ d r/ a 
dd 
dz 
(“o> /^O’ To) being the intensity of the imposed magnetic field; 
and the optical rotational energy 
W' = -f -f yRiVK) dr. 
And there are also to be included the terms in W of higher orders, that produce 
regular {i.e. sensibly non-selective) dispersion of various kinds, of which the chief is 
W, = f't {(/. 9, l>). vm ff. h)} dr, 
where the symbol in the integral denotes a llneo-linear function. 
Throughout these equations, the elastic properties of the adher retain their purely 
rotational character; its internal elastic energy, its dissipation, and its connexions 
with other interlinked motions, depend on the rotation of its elements and not on their 
distortion or compression. A partial exception occurs in the magneto-optic terms. 
MDCCCXCIV.—A. 5 H 
