514 The American Naturalist. [June, 



Anatase and brookite are described 1 as occurring in French rocks, 

 the former in the mica porphyrites of Pranal, Puy-de-Dom, and the 

 latter in the chloritized mica of the limestone of Ville-es-Martin, in 

 the Loire-Inferieure, and in the mica of a mica porphyrite from Pou- 

 chon, in Cercie, and in the granite of Lacourt, Ariege. 



The same author 2 announces the discovery of octahedra of cristo- 

 balite associated with tridymite in a piece of quartz inclusion from the 

 basalt of Mayen in Rhenish Prussia. . 



Nova Scotian Gmelinite.— A careful analysis of gmelinite from 

 the Five Islands, Nova Scotia, has been made by Pirsson, 3 and the 

 properties of the mineral have been investigated. The mineral occurs 

 in seams in a decomposed trap. In thin sections its crystals are found 

 to be composed of a colorless compact outer zone enclosing a flesh- 

 colored, friable inner nucleus. Their habit is short pyramidal, and 

 their axial ratio a : c = 1 : .7345. Two methods of twinning were 

 observed, viz., interpenetration twinning with oP the twinnino- plane, 

 and contact twinning parallel to f R. The double refraction is weak 

 and negative, with o>~ for sodium light = .0033. Density = 2.037, 

 and composition : 



The author regards the mineral as a sodium-chabazite, in which 

 Na : Ca = 8 : 1. The sodium is thought to exert a marked morpho- 

 tropic action, since the crystallographic planes of the gmelinite can- 

 not be conveniently referred to the axes of chabazite. It may, there- 

 fore, be considered as a distinct mineral species. 



Crystallography of Cerussite, etc.— Pirsson 4 also contributes 

 a few crystallographic notes on cerussite, gypsum and krammerite. 

 Twinned crystals of the first-named mineral from the Red Cloud Mine, 

 Ariz., are arrow-shaped, with the plane oo P3 the twinning plane. The 

 gypsums are from Girgenti, Sicily. They are twinned according to 

 the usual law, but JPoo so largely predominates over other forms that 

 they resemble basal planes and cause the twinned crystals to resemble 

 in symmetry an orthorhombic form. The krammerite studied is from 



»Lacroix. lb., xiv p. 191. 



2 Ib., xiv, p. 185. 



