236 Dr. Faraday on Magnetic and Diamagnetic Action. 
2427. Asalready stated, the magnetic force is so strikingly dis- 
tinct in its action upon bodies of the magnetic and the diamagnetic 
class, that when it causes the attraction of the one it produces 
the repulsion of the other; and this we cannot help referring, in 
some way, to an action upon the molecules or the mass of the 
substances acted upon, by which they are thrown into different 
conditions and affected accordingly. In that point of view it is 
very striking to compare the results with those which are pre- 
sented to us by a polarized ray, especially as then a remarkable 
difference comes into view; for if transparent bodies be taken 
from the two classes, as for instanton, heavy glass or water from 
the diamagnetic, and a piece of green glass or a solution of green 
vitriol from the magnetic class, then a given line of magnetic 
force will cause the repulsion of one and the attraction of the 
other; but this same line of force which thus affects the parti- 
cles so differently, affects the polarized ray when passing through 
them precisely in the same manner in — cases; for the two 
bodies cause its rotation: in the same directio 
2428. Thi important when we 
connect it with the carotene and the optical properties of bodies 
which rotate a polarized ray. ‘Thus the iron solution and a piece 
of quartz, having the power to rotate a ray, point by the influ- 
ence of the same line of magnetic force, the one axially and the _ 4 
other equatorially ; but the rotation which is impressed on a ray 
of light by these two bodies, as far as they are under the influ- — 
ence of the same magnetic force, is the same for both. Further, 
this rotation is quite independent of, and quite unlike that of the 
quartz in a most important point; for the quartz by itself can 
only rotate the ray in one direction, but under the influence of 
the magnetic force it can rotate it both to the right and left, ac- 
cording to the course of the ray. Or, if two pieces of quartz (oF 
two tubes of oil of turpentine) be taken which can rotate the ray 
different ways, the further rotative force manifested by them 
when under the dominion of the magnetism is always the same 
way; and the direction of that way may be made either to the 
right or left in either crystal of quartz. All this time the con- 
trast between the quartz asa diamagnitic, and the solution.of 
iron as a magnetic body remains undisturbed. Certain consider- 
ations regarding the character of a ray, arising from. these con- 
‘ote, press strongly 0 on Toy mares which, when I have had time 
