16 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XIX.) 
non-action of a vacuum, of air or gases ; and it is also further shown by the special 
degree in which different matters possess the property. That magnetic force acts 
upon the ray of light always with the same character of manner and in the same di- 
rection, independent of the different varieties of substance, or their states of solid or 
liquid, or their specific rotative force (2232.), shows that the magnetic force and the 
light have a direct relation: but that substances are necessary, and that these act 
in different degrees, shows that the magnetism and the light act on each other 
through the intervention of the matter. 
2225. Recognizing or perceiving matter only by its powers, and knowing nothing 
of any imaginary nucleus, abstract from the idea of these powers, the phenomena 
described in this paper much strengthen my inclination to trust in the views I have 
on a former occasion advanced in reference to its nature*. 
2226. It cannot be doubted that the magnetic forces act upon and affect the in- 
ternal constitution of the diamagnetic, just as freely in the dark as when a ray of light 
is passing through it ; though the phenomena produced by light seem, as yet, to pre- 
sent the only means of observing this constitution and the change. Further, any 
such change as this must belong to opake bodies, such as wood, stone, and metal ; 
for as diamagnetics, there is no distinction between them and those which are trans- 
parent. The degree of transparency can at the utmost, in this respect, only make a 
distinction between the individuals of a class. 
222/. If the magnetic forces had made these bodies magnets, we could, by light, 
have examined a transparent magnet; and that would have been a great help to our 
investigation of the forces of matter. But it does not make them magnets (2171-)? 
and therefore the molecular condition of these bodies, when in the state described, 
must be specifically distinct from that of magnetized iron, or other such matter, and 
must be a new magnetic condition ; and as the condition is a state of tension (ma- 
nifested by its instantaneous return to the normal state when the magnetic induction 
is removed), so the force which the matter in this state possesses and its mode of ac- 
tion, must be to us a new magnetic force or mode of action of matter. 
2228. For it is impossible, I think, to observe and see the action of magnetic forces, 
rising in intensity, upon a piece of heavy glass or a tube of water, without also per- 
ceiving that the latter acquire properties which are not only new to the substance, 
but are also in subjection to very definite and precise laws (2160. 2199.), and are 
equivalent in proportion to the magnetic forces producing them. 
2229. Perhaps this state is a state of electric tension tending to a current ; as in mag- 
nets, according to Ampere’s theory, the state is a state of current . When a core of 
iron is put into a helix, every thing leads us to believe that currents of electricity are 
produced within it, which rotate or move in a plane perpendicular to the axis of the 
helix. If a diamagnetic be placed in the same position, it acquires power to make 
light rotate in the same plane. The state it has received is a state of tension, but it 
* A speculation, &c. Philosophical Magazine, 1844, vol. xxiv. p. 136. 
