MAGNECRYSTALLIC FORCE — AFFECTED BY HEAT. 
27 
action ; but in a few seconds, as the temperature fell, it resumed its power of point- 
ing; and, apparently, in an instant and with full force, and the pointing was pre- 
cisely in the same direction as at first. On examining the crystal carefully, its ex- 
ternal shape and its cleavage showed that, as a crystal, it was unchanged ; but the 
appearance of a minute globule of bismuth, which had exuded upon the surface in 
one place, showed that the temperature had been close upon the point of fusion. 
2571. The same result occurred in the oil-bath, except that as removing the lamp 
from the oil-bath did not immediately stop the addition of heat to the bismuth, so 
more of the latter was melted; and about one-fourth of the metal appeared as a drop 
hanging at the lower part. Still the whole mass lost its power at the high tempera- 
ture, and the power was regained in the same direction, but in a less degree on cool- 
ing. The diminished force was accounted for on breaking up the crystal ; for the 
parts which had been liquefied were now crystallized irregularly, and therefore, 
though active at the beginning of the experiment, were neutral at the end. 
2572. As heat has this effect, the expectation entertained (2502.) of crystallizing 
bismuth regularly in the magnetic Jield is of course unfounded ; for the metal must 
acquire the solid state, and be lowered through several degrees probably, before it 
can exhibit the magnecrystallic phenomena. If heat has the same effect on all bodies 
prior to their liquefaction, then, of course, such a process can be applied to none of 
them. 
2573. A crystallized piece of antimony was subjected to the same experiment, and 
it also lost its magnecrystallic power below a dull red heat, and just as it was soften- 
ing so as to take the impression of the copper loop in which it was hung. On being 
cooled it did not resume its former state, but then became ordinarily magnetic and 
pointed. This I conclude arose from iron affected by the flame and heat of the spirit- 
lamp ; for, as the heat was high enough to burn off part of the antimony and make it 
rise in fumes of oxide of antimony, so this might set a certain portion of iron free which 
the carbon and hydrogen of the flame would leave in a very magnetic state (2608.). 
2574. In further elucidation of the mutual action of the bismuth and the magnet, 
the bismuth was suspended, as already described (2551.), on the bifilar balance, but 
so turned that its magnecrystallic axis, being horizontal, was not parallel or perpen- 
dicular to the arm of the lever, but a little inclined, as in the 
figure (5.), where 1 represents the crystal of bismuth attached 
to the balance arm h, the axis of which is so placed that the 
crystal can swing through the various positions 1, 2, 3, 4 ; S 
is the pole of the magnet separated only by the glass of the 
shade. It is manifest that in position 1 the magnecrystallic 
axes and the lines of magnetic force are parallel to each other ; 
whereas in the positions 2, 3, 4, they are oblique. When the apparatus was so 
arranged that the crystal of bismuth rested at 1, the superinduction of the full mag- 
netic force sent it towards 4 ; a result of diamagnetic action. When however the 
E 2 
Fig. 5. 
