MAGNECRYSTALLIC FORCE — NOT ATTRACTIVE NOR REPULSIVE. 
23 
silkj consisting of two bundles of seven filaments each^ four inches long and one- 
twelfth of an inch apart ; and suspended a crystal of bismuth (2457.) ffom one end of 
the lever, so that it might be fixed and retained in any position. This balance was 
protected by a glass case, outside of which the conical terminal of one pole of the 
great electro-magnet (2247.) was adjusted, so as to be horizontal, at right angles to 
the lever of the torsion-balance, and in such a position that the bismuth crystal was 
in the prolongation of the axis of the pole, and about half an inch from its extremity 
when all was at rest. The other pole, four inches off, was left large so that the lines 
of magnetic force should diverge, as it were, and rapidly diminish in strength from 
the end of the conical pole. The object was to observe the degree of repulsion ex- 
erted by the magnet on the bismuth, as a diamagnetic body, either by the distance 
to which it was repelled, or by the torsion required to bring it back to its first posi- 
tion ; and to do this with the bismuth, having its magnecrystallic axis at one time 
axial or parallel to the lines of magnetic force, at another equatorial, observing whether 
any difference was produced. 
2552. The crystal was therefore placed with its magnecrystallic axis first parallel 
to the lines of magnetic force, and then turned four times in succession 90° in a 
horizontal plane, so as to observe it under all positions of the magnecrystallic axis ; 
but in no case could any difference in the amount of the repulsion be observed. In 
other experiments the axis was placed oblique, but still with the same result. If 
there be therefore any difference it must be exceedingly small. 
2553. A corresponding experiment was made, hanging the crystal as a pendulum 
by a bifilar suspension of cocoon silk thirty feet in length, with the same result. 
2554. Another very striking series of proofs that the effect is not due to attraction 
or repulsion, was obtained in the following manner. A skein of fifteen filaments of 
cocoon silk, about fourteen inches long, was made fast above, and then a weight of 
an ounce or more hung to the lower end ; the middle of this skein was about the 
middle of the magnetic field of the electro-magnet, and the square weight below 
rested against the side of a block of wood, so as to give a steady, silken, vertical axis, 
without swing or revolution. A small strip of card, about half an inch long, and 
the tenth of an inch broad, was fastened across the middle of this axis by cement ; 
and then a small prismatic crystal of sulphate of iron about 0‘3 of an inch long, and 
0*1 in thickness, was attached to the card, so that the length, and also the magne- 
crystallic axis, were in the horizontal plane ; all the length was on one side of the 
silken axis, so that as the crystal swung round, the length was radius to the circle 
described, and the magnecrystallic axis parallel to the tangent. 
2555. This crystal took a position of rest due to the torsion force of the suspending 
skein of silk ; and the position could be made any one that was desired, by turning 
the weight below. The torsion force was such, that, when the crystal was made to 
vibrate on its silken axis, forty complete (or to and fro) vibrations were performed 
in a minute. 
