492 
MEASUREMENTS OF CRYSTALS. 
CORUNDUM. (Continued.) 
Fig. 254, a secondary form. 
SPINELLE. Figs. 255 to 264 inclusive. Page 315. 
Fig. 255. The primary, a regular octa¬ 
hedron. 
P on P' . 109°28'16" 
Figs. 256 and 257. 
P on o .. 144°48'8" 
o on o . 120 0 0 
Figs. 260 and 261. Groups of crystals, 
Orange county. 
Fig. 262. A twin consisting of two equal 
and similar portions of a crystal 
similar to 256. 
Fig. 263. A twin composed of about 
equal parts of the primary octahe¬ 
dron, of which one half is turned 
round. 
SPINELLE. 
Fig. 264. Three nearly equal parts of the 
same crystal variously turned upon 
each other. The faces of composi¬ 
tion in the latter case project. 
AUTOMOLITE. Fig. 265. Page 319. 
Fig. 265. The primary, a regular octahe¬ 
dron. 
P on P' .. 109°28T6" 
IDOCRASE. Figs. 266 to 269 inclusive. Page 321. 
Fig. 266. The primary, a right square 
prism. 
Figs. 267 and 268. 
Monc . 115° 15' 
M on d . 135 0 
P one . 142 54 
c on d .. 127 6 
i 
