LAW OF MAGNECRYSTALLIC ACTION. 
7 
give a more important indication in relation to the essential and real crystalline 
structure of the mass than its form can do. 
24/9. I have already stated that the magnecrystaUic force does not manifest itself 
by attraction or repulsion, or, at least, does not cause approach or recession, but 
gives position only. The law of action appears to be, that, the line or axis of magne- 
CRVSTALLic fovce (being the resultant of the action of all the molecules), tends to place 
itself parallel, or as a tangent, to the magnetic curve or line of magnetic force, passing 
through the place where the crystal is situated. 
2480. I now broke up masses of bismuth which had been melted and solidified in 
the ordinary way, and, selecting those fragments which appeared to be most regularly 
crystallized, submitted them to experiment. It was almost impossible to take a small 
piece which did not obey the magnet and point more or less readily. By selecting 
the thin plates with perfect cleavage planes, I readily obtained specimens which cor- 
responded in all respects with the crystals ; but thicker plates or angular pieces often 
proved complicated in the results, though apparently simple and regular as to form. 
Occasionally, the cleavage plane, which I have beforehand taken for that perpendi- 
cular to the line of force (2475.), has proved not to be the plane supposed; but, after 
observing experimentally the direction of the magnecrystaUic power, I have always 
either found, or else obtained by cleavage, a plane corresponding to it, possessing 
the appearance and character before described (2475.). Bismuth plates from the 
one-twentieth to the one-tenth of an inch in thickness, and bounded by parallel and 
similar planes, when broken up often proved, upon ocular examination, to be com- 
pounded and irregular. 
2481. When a well-selected plate of bismuth (mine are about 0-3 of an inch in 
length and breadth, and 0‘05, more or less, in thickness) is hung up by the edge in the 
magnetic field, it vibrates and points, presenting its faces to the magnetic poles, and 
setting diametrally (2461.). By whatever part of the edge it is suspended, the 
same results follow. But if it be suspended horizontally, the cleavage planes of the 
fragment and of the magnetic axis being parallel to the plane of motion of the plate, 
then it is perfectly indifferent ; for then the line of magnecrystaUic force is perpen- 
dicular to the line of magnetic force in every position that it can take. 
2482. But if the plate be inclined only a very small quantity from this position, it 
points, and that with more force as the planes become more nearly vertical (2475.) ; 
and the phenomena before described with a crystal (2476.), can here be obtained 
with a fragment from a mass, and any part of the edge of the plate made to point 
axially, by elevating or depressing it above or below the horizontal plane. 
2483. If a number of these crystalline plates be selected at the magnet, they may 
afterwards be built up together, with a little good cement (2458.), into a mass which 
has perfectly regular magnecrystaUic action ; and in that respect resembles the 
