358 The American Naturalist. [April, 
MINERALOGY. 
Symmetry of Nepheline and Davyne.—Baumhauer’s studies 
of the etched figures of nepheline produced by hydrofluoric and hy- 
drochloric acids, have shown that the mineral belongs in that division 
of the hexagonal system in which trapezohedral or pyramidal hemi- 
hedrism is combined with hemimorphism—the first hemimorphic 
tetartohedrism of Liebisch—and that apparently simple individuals 
are usually compound twins, the twinning planes being the base and 
the second order prism. As more recent studies of Tenne seemed to 
lead to a different conclusion, Traube? has repeated Baumhauer’s 
studies on excellent material from Vesuvius, with the result of con- 
firming the latter in every particular. He has also obtained excellent 
figures on the prism planes by use of concentrated or warm dilute hydro- 
chloric acid, the figures having the same symmetry but not the same 
form as those produced by hydrofluoric acid. He has observed one 
twinning law in addition to the two described by Baumhauer. The 
examination of a twinned section 5 mm. in thickness cut normal to 
the principal axis gave no evidence of circular polarization. He has 
investigated for the first time the etched figures of the closely related 
mineral Davyne, which may be easily etched with nitric acid. On 
the prism planes these figures possess two lines of symmetry, normal to 
one another, showing that the mineral is holohedral hexagonal. As 
nepheline is not attacked by nitric acid this affords a ready means of 
distinguishing the two minerals from one another. It is especially 
valuable because Traube finds that Davyne is not always optically 
positive as has been supposed. 
The Minerals of the Emery Deposits of Naxos.—Except 
for a paper by Smith on the paragenesis of these deposits and one by 
Zirkel on the two chief minerals (corundum and magnetite), no scien- 
tific mineralogical study of the deposits has heretofore been made. 
Tschermak® contributes to the Mittheilungen the results of a detailed 
study of a large number of specimens from the locality. The island 
of Naxos is composed of fine grained gneisses and marbles resting On 
a basement of coarse grained gneisses. The emery occurs in numerous 
1 Edited by Dr. Wm. H. Hobbs, University of Wisconsin, Madison, Wis. 
2 Neues Jahrb. f. Min. etc., Beil. Bd. ix, pp. 466-479, 1894. 
3 Min. u. petrog. Mittheil., xiv, pp. 311-342, 1894. 
