616 The American Naturalist. [July, 
granular mass, in the neighborhood of solfataras. The soluble sub- 
stance extracted from this mass by Hof? gave: 
SO, AlO, FeO, FeO CaO MgO Na,O H,O 
38.62 13.96 94 .66 22 04 2.37 42.01 
The form of the crystals as determined by Becke’ is tabular parallel 
to © Pa. They have a weak negative double refraction. The axis 
of mean elasticity is inclined 48° to œ Po, and that of the least elas- 
ticity 13° to +Po. The crystallization is ‘inbnndlinis with a: b:¢= 
? : 825 2 = 97° 34’——In the druses of a massive garnet used as 
a flux in the copper smelters at Kedobek, Caucasia, are found crystals 
of garnet that rival in beauty the famous Tyrol varieties. They are 
bounded by the forms 202, œ O and occasionally 303, and all the 
faces are brilliant. Their color is wine to honey-yellow and their com- 
position? is represented by : 
SiO, CaO AlO, FeO, Loss : 
39.12 85.84 2273 1.76 15 Ca Al,(i0,), 
—— According to Branner* inexhaustible beds of beauxite occur near 
Little Rock and Benton, Ark., that are supposed to be genetically 
related in some way with eruptive granites. The material is pisolitic 
in structure. The composition of one variety as shown by a partial 
analysis is: 
ALO, SiO, FeO, TiO, Loss 
55.64 10.38 195 3.50 27.62 
The handsome calcite’ twins from Guanajuato, Mexico, that have 
been known for some time, are usually the scalenohedron R°, twinned 
parallel to —?R. Corresponding pairs of faces on each individual are 
so developed that their combination has a monoclinic habit, resembling 
strongly the swallow-tailed twins of gypsum. The forms recognized in 
the crystals are mentioned in the paper and six figures accompany it. 
1Min. u. Petrog., Mitth. xii, p. 39. 
*Ib., p. 45. 
3Müller : Neues. Jahrb. f. Min., etc., 1891, i, p. 272. 
4Amer. Geologist, vii, 1891, p. 181. 
5Pirsson: Amer. Jour. Sci., Jan., 1891, p. 61. 
