36 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXII.) 
and there is a still greater difference in this, that the heavy glass takes up its state 
only for a time by constraint and under induction, whilst the crystal possesses it 
freely, naturally and permanently. In both cases, however, whether natural or in- 
duced, it is a state of the particles ; and comparing the effect on light of the glass 
under constraint with that of the crystal at liberty, it indicates a power in the mag- 
net of inducing something like that condition in the particles of matter whieh is 
necessary for crystallization ; and that even in the partieles of fluids (2184.). 
2612. If there be any weight in these considerations, and if the forces manifested 
in the crystals of bismuth and Iceland spar be the same (2607.), then there is further 
reason for believing that, in the case of bismuth and the other metals named, there is, 
when they are subjected to the power of the magnet, both an induced condition of 
force (2584.), and also a pre-existing force (2577*) • The latter may be distinguished 
as the crystalline force, and is shown, first, by such bodies exhibiting optic axes and 
lines of foree when not under induetion ; by the symmetric condition of the whole 
mass, produced under circumstances of ordinary occurrence ; and by the fixity of 
the line of magnecrystallic force in the bodies shown experimentally to possess it. 
2613. Though I have spoken of the magnecrystallic axis as a given line or direc- 
tion, yet I would not wish to be understood as supposing that the force decreases, 
or state changes, in an equal ratio all round from it. It is more probable that the 
variation is different in degree in different directions, dependent on the powers whieh 
give difference of form to the crystals. The knowledge of the disposition of the force 
can be ascertained minutely hereafter, by the use of good crystals, an unchangeable 
ordinary magnet (2485. 2528.), or a regulated electro-magnet, flat-faced poles (2463.), 
and torsion (2500. 2530.). 
2614. I cannot conclude this series of researches without remarking how rapidly 
the knowledge of molecular forces grows upon us, and how strikingly every investi- 
gation tends to develope more and more their importance, and their extreme attrac- 
tion as an object of study. A few years ago magnetism was to us an occult power, 
affecting only a few bodies ; now it is found to influence all bodies, and to possess 
the most intimate relations with electricity, heat, chemical action, light, crystalliza- 
tion, and, through it, with the forces concerned in cohesion ; and we may, in the 
present state of things, well feel urged to continue in our labours, encouraged by the 
hope of bringing it into a bond of union with gravity itself. 
Royal Institution, 
October 20, 1848. 
