Al4 Scientific Intelligence. 
SCIENTIFIC INTELLIGENCE. 
I. CHEMISTRY AND Puysics. 
1. On the Deportment of Crystalline Bodies between the poles of @ 
Magnet ; by Joun Tynpatt and Hermann Knosravcn; (Phil. Mag., 
xxxvi, 178, March, 1850.)—The results obtained by Professor Pliicker of 
Bonn, in his investigations upon crystals, induced us early in the month 
of November last to commence a series of researches in connection 
with this subject. Our inquiries, so far as they at present reach, form 
the subject of this paper. 
After a long series of trials, not necessary to be recapitulated here, 
we arrived at the persuasion that no safe inference could be drawn from 
experiments made with full crystals. It appeared necessary to examine 
the forces attributed to crystalline bodies in detail, one at a time, re- 
moving as far as possible all influences likely to interfere with the sim- 
ple action of this one. 
o attain this object we experimented with cubes: we had one cut 
from tourmaline, in such a manner that the optical axis of the crystal 
ran parallel to four sides of the cube ; on suspending it between the 
poles and closing the circuit, the optical axis set itself strongly equato- 
rial; thus corroborating the law of Plicker, which affirms that the op- 
tical axes of negative crystals are repelled. When, however, the same 
cube was hung with the optical axis vertical, the influence of that axis 
destroyed, a preference was shown to one of the diagonals 
onal chanced to lie from pole to pole, the latter seemed to experience 
a repulsive shock, sufficient to make the cube spin several times round 
upon its axis. 
We do not see any possibility of referring this election of a partic- 
ular diagonal to the influence exerted by the optical axis, at least in the 
case of beryl. 
To ascertain the exact nature of this influence, we had recourse to 
discs, cut so that the optical axis of the crystal lay as a diameter in the 
plane of each. In this way the influence of mere form was totally an- 
nulled, and the pure action of the optical axis, if such existed, might 
be observed. 
O t discs, five in number, were taken from a semi-transparent 
crystal of Iceland spar, and lay at various angles to the sides thereof. 
In all these cases the law of Pliicker was strictly verified, the optical 
axis being always repelled. 
