276 Scientific Intelligence. 
as well as the film itself, ha egular axes of double refraction, as if 
they were regularly crystallized portions of the substance under exam- 
ination. Th treaks and capillary lines, which were often of ex 
there is the appearance of a polished surface on the compressed oh 
stance. In general, I have used both the smooth and the rough een 
and have frequently obtained results with the one which were not da 
he other. 
of yellow reflected light, the phenomena are peculiarly splendid ; of 
natural colors of the substance, which vary greatly with Ce 
of the streaks and films, being combined with the different tints ey 
- 
by traction ; and the superficial colors which they reflect vary with os 
azimuth which the plane of incidence forms with the plane pass!P& 
through the axis of the prism. “ey 
The remarkable property which Ihave now described I have found, 
in a greater or a less degree, in the following crystals :— 
Chrysammate of magnesia. Palmic acid. 
" of potash, Amygdaline. 
1ydro-chrysammid, - Tannin, pure, 
Murexide. Quinine, pure. 
Aloetinate of potash. “ acetate of. 
Aloetinic acid. «sulphate of. 
Oxamide. + muriate of. 
Palmine. “ phosphate of. 
