1896.] Mineralogy. 573 
General Notes. 
MINERALOGY. 
Contact Goniometer with two Graduated Circles.—In pur- 
suance of the idea already applied to the reflection goniometer (ref. in 
this journal, 1895, p. 266) Goldschmidt? has designed a contact gonio- 
meter with two graduated circles. The horizontal circle carries the 
support for the crystal, which can thus be rotated about a vertical axis. 
The vertical circle is a metallic band carrying a moyeable block. 
Through the block asmall metal rod passes radially toward the center, 
and on the inner end of the rod a small plate is fixed. By movement 
of the crystal about its vertical axis and of the block on its arc, the 
plate may be brought to parallelism with any face on the upper side of 
the crystal, Actual contact of the plate with the crystal face is effected 
by sliding the rod through its block. Readings on the two circles give 
data for computing the position of a plane, exactly as in the case of the 
reflection goniometer to which reference was above made. 
Crystallographic Properties of the Sulphonic Acid Deri- 
vatives of Camphor.—A bout 17 of these compounds are mentioned 
by Kipping and Pope? with much detailed information concerning the 
erystallograpy of several of them. As might be expected from the 
fact that the solutions of many of these substances exhibit the phenom- 
enon of circular polarization, the crystals furnish examples of a num- 
ber of the Jess common low symmetry grades, Among these are hemi- 
morphism in the monoclinic system (sphenoidal class of Groth), sphen- 
oidal hemihedrism in the orthorhombic system (bisphenoidal class), 
and probably hemihedrism in the triclinic system (pedial class). Such 
crystallographic studies must be of great value to stereo-chemistry. 
Optical Properties of Lithiophilite and Triphilite.—On 
these two minerals Penfield and Pratt‘ have based an interesting in- 
vestigation of the change of optical properties due to the mutual re- 
placement of manganese and iron in isomorphous mixture. It is found 
1 Edited by A. C. Gill, Cornell University, Ithaca, N. Y. 
* Zeitschr. f. Kryst., XXV, p. 321, 1 
* Zeitschr. f. Kryst., XXV, pp. 225-256, 1895. 
t Am, Jour. Sci., L, pp. 387-390, Nov., 1895. 
