4 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXII.) 
g-ether, and tends to acquire no motion but what is due to torsion of the suspending 
fibre, or currents of air : but a piece of regularly crystallized bismuth is, in the same 
situation, very powerfully affected by virtue of its magnecrystallic condition. 
2465. Hence the great value of a magnetic field of uniform force; and, if, here- 
after, in the extension of these investigations to bodies having only a small degree of 
crystalline power, a perfectly uniform field should be required, it could easily be 
given by making the form of the pole face somewhat convex, and rounded at the 
edges more or less. The required shape could be ascertained by calculation, or 
perhaps better in practice, by the use of a little test cylinder of bismuth in the gra- 
nular or amorphous state, or of phosphorus. 
2466. In addition to these observations it may be remarked, that small crystals, 
or masses of crystals, and such as approach in their general shape to that of a cube 
or a sphere, are better than large or elongated pieces ; inasmuch, as if there be irre- 
gularities in the force of a magnetic field, such pieces are less likely to be affected by 
them. 
2467- When the crystal of bismuth is* in a magnetic field of equal strength, it is 
equally affected whether- it be in the middle of the field or close up to one or the 
other magnetic pole ; i. e. the number of vibrations in equal times appears to be equal. 
Much care, however, is required in estimating it by such means, because, from the 
occurrence of two positions of unstable equilibrium in the equatorial direction, the 
vibrations in large arcs are much Slower than those in small arcs ; and it is difficult 
in different eases to adjust them to the same extent of vibration. 
2468. Whether the bismuth be in a field of intense magnetic force or one of feeble 
powers ; whether the magnetic poles are close up to the piece, or are opened out until 
they are five or six inches or even a foot asunder; whether the bismuth be in the 
line of maximum force, or raised above, or lowered beneath it; whether the electric 
current be strong or weak, and the magnetic force, therefore, more or less in that 
respect ; if the bismuth be affected at all it is always affected in the same manner. 
2469. The results are, altogether, very different from those produced by diamag- 
netic action (2418). They are equally distinct from those dependent on ordinary 
magnetic action. They are also distinct from those discovered and described by 
Plucker, in his beautifid researches into the relation of the optic axis to magnetic 
action ; for there the force is equatorial, whereas here it is axial. So they appear to 
present to us a new force, or a new form of force in the molecules of matter, which, 
for convenience sake, I will conventionally designate by a new word, as the magne- 
crystallic force. 
2470. The direction of tliis force is, in relation to the magnetic field, axial and not 
equatorial-, this is proved by several considerations. Thus, when a piece of re- 
gularly crystallized bismuth was suspended in the magnetic field, it pointed ; keep- 
ing it in this position, the point of suspension was removed 90° in the equatorial 
plane (2252.), so that when again freely suspended, the line through the crystal. 
