fe 
Chemistry and Physics. 273 
the results following from it), with respect to an ellipsoid of finite dimen- 
sions influence by an infinitely distant pole. By means of a beautiful 
Periment, by observations made on two carefully worked ellipsoids. of soft 
ton, executed by M. Fessel of Cologne. 
cnitacterized by the property that if a crystal be suspended along any 
of them, the two others set, one axially, and the other equatorially. 
there are two optic axes, situated in the plane of the axes of greatest 
and least elasticity, so there are two magnetic axes, characterized by the 
Property already mentioned. 
 “Yanid of iron, sulphate of zine, and formiate of copper. The first is 
Patamagnetic, the second diamagnetic, and in both cases the principal 
- 8Xes of Magnetic induction are determined by the planes of crystalline 
and short cylinders or circular plates, cut in various selected directions 
fom the crystals, is described in detail. The use of both cylinders and 
;acular plates, cut with their axes in the same direction, obviated any ob- 
San ae might be raised attributing the setting to the external form, 
? ar as fa) 
Would Set with their axes in rectangular directions. : 
ommiate of copper differs from the former erystals in having but one 
ra. axis of magnetic induction determined by the crystalline form. 
“tistence of three principal magnetic axes, having the property already 
2 : determined, 
 theip 2UClusion, the author gives a list of erystals, ¢ 
‘ie 
“oned, was demonstrated experimentally, and the directions of those 
ide of the magnetic inductions in the direction of their principal axes. 
orphous substances, 
