160 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXX.) 
the name of magnecrystallic action. Early experiments (2499-2501.) showed that, 
with respect to bismuth, the relation between the magnetic force in the axial and 
equatorial directions, was unchanged by varying the surrounding medium from water 
to a solution of sulphate of iron. This equality has, perhaps, been confirmed by 
other philosophers, and, it may be, with other substances ; but not being aware of 
any strict investigation, I found it needful in relation to my own views, which 
required just now proofs more certain than those quoted, to enlarge and extend the 
experimental results. 
3366. The method I have employed to compare the possible variations of force 
produced by different circumstances, has been to suspend the object, a magnecrystal 
for instance, by a torsion fibre or wire ; — to place it in the magnetic field ; — to adjust 
the torsion index so that it should be at zero when the crystal had taken its position 
of stable equilibrium ; — then to put on right-handed torsion until the crystal had 
attained the point of unstable equilibrium, or the upsetting point, on that side ; and 
after having noted the torsion required, to reverse the motion and put on left-handed 
force until the upsetting point on the opposite side was attained. Either of these 
forces, minus the deflection, is the measure of the upsetting force; and therefore the 
sum of these two observations, minus the number of degrees through which the 
crystal has moved in passing from one upsetting point to the other, may be con- 
sidered as expressing the force which solicits the crystal to retain its stable position 
of rest. By thus making the observations on both sides of zero, the effect of set in 
the suspending torsion thread could be included in a regular and compensatory 
manner ; — two definite starting-points (the upsetting positions) were ensured ; — and 
also a large, i. e. a sensitive expression of the force to be measured was obtained. 
3367. It is evident, that, when a magnecrystal is suspended in the magnetic field, 
and torsion force is gradually applied to deflect it from its position of rest, that force 
will grow up and carry the crystal round, until at last the latter will attain a position 
at which the setting forces of the crystal are equal to the torsion force, but beyond 
Avhich the former will, by further motion of the crystal, fall more rapidly than the 
latter, so that the least additional torsion force will carry the crystal past that posi- 
tion and cause it to revolve through many degrees. This position (the upsetting' 
point) being one of unstable equilibrium, is easily observed experimentally; and, by 
careful manipulation with the torsion index, it is also easily attained. When the two 
upsetting points are observed, the whole number of degrees of torsion required to 
proceed from one to the other, is an excellent measure of the setting force of the 
object. When the crystal is in the form of a cube or sphere and suspended between 
flat-faced poles, the two upsetting points are nearly at an angle of 45° with the axial 
line, and tlie angle between them is near upon 90°. I have found this angle to vary 
for the different objects employed ; but, whilst the position of the poles, &c. remained 
the same, not for the same object, however the force might vary. It has therefore to 
be ascertained, experimentally, for each object, in any one series of observations where 
