AIAGNECRYSTALLIC FORCE — INDUCED OR INHERENT? 
29 
fact. A jar containing about a quart of solution of sulphate of soda, of such strength 
as to crystallize when cold by the touch of a crystal of the salt or an extraneous body, 
was left, accidentally, for a week or more unattended to and undisturbed. The solution 
remained fluid ; but on the jar being touched, crystallization took place throughout 
the whole mass at once, producing clear, distinet, transparent plates, which were an 
inch or more in length, up to half an ineh in breadth ; and very thin, perhaps about 
the one-fiftieth or one-sixtieth of an inch. These were all horizontal, and of course 
parallel to each other ; and I think, if I remember rightly, had their length in the same 
direction ; and they were alike in character, and, apparently, in quantity in every 
part of the jar. They almost held the fluid in its place when the jar was tilted ; and 
when the liquid was poured off presented a beautiful and uniform assemblage of 
crystals. The result persuaded me, at the time, that, though the influence of a pai- 
ticle in solution and about to crystallize, must be immediately and essentially upon 
its neighbours, yet that it could exert an influence beyond these, without which in- 
fluence, the whole mass of solution could hardly have been brought into such a uni- 
form crystallizing state. Whether the horizontality of the plates can have any rela- 
tion to the almost vertical lines of magnetic force, which from the earth’s magnetism 
was pervading the solution during the whole time of its rest, is more than I will ven- 
ture to say. 
2579 . The following are considerations which bear upon this great question (2576.) 
of an original or an induced state. 
2580. In the first place, the bismuth carries off no power or particular state from 
the magnetic field, able to make it affect a magnet (2504.) ; so that if the condition 
acquired by the crystal be an induced condition, it is probably a transient one, and 
continues only v/hilst under induction. The fact therefore, though negative in its 
evidence, agrees, as far as it tells, with that supposition. 
2581. In the next place, if the effect were wholly due, as far as the crystal is con- 
cerned, to an original power inherent in the mass, we might expect to find the earth’s 
magnetism, or any weak magnet, affecting the crystal. It is true that a weak mag- 
netie force ought to induce any given condition in a crystal of bismuth just as well 
as a stronger, only proportionally. But if the given condition were inherent in the 
crystal, and did not change in its amount by the degree of magnetic force to which 
it was subjected, then a weak magnetic force ought to act more decidedly on the 
bismuth than it would do if the condition were induced in the bismuth, and only in 
proportion to its own force. Whatever the value of the argument, I was induced to 
repeat the experiment of the earth’s influence (2505.) very carefully, and by shelter- 
ing the suspended crystals in small flasks or jar contained within the larger covering 
jar, and making the experiment in an underground plaee of uniform and constant 
temperature, I was able to exclude every effect of currents of air, so that the crystals 
obeyed the slightest degree of torsion given to the suspending fibre by the index 
above. Under these circumstances I could obtain no indications of pointing by 
