928 | General Notes. 
teeth. The full paper will appear in the next number of the 
NATURALIST. In the meantime I will be glad to receive sugges- 
tions or criticisms upon the above terms.— Henry F. Osborn. 
MINERALOGY AND PETROGRAPHY.! 
PETROGRAPHICAL News.—The basaltic rocks of Alsace, accord- 
ing to Linck}? embrace feldspathic and non-feldspathic varieties. 
Of the latter a limburgite from Reichenweiler contains a glassy 
base, which deports itself towards reagents like nepheline, a fact 
which would cause the rock strictly to be classed among the nepheline 
basalts. Its olivine yields upon analysis :— 
SiO, AO; . Fe; 0, FeO MgO Na,O 
41.53 2.33 0.58 10.27 43.60 1.69, 
indicating a replacement of part of the magnesium of the typical 
molecule by aluminium and sodium. Olivine concretions occurring 
in this rock consist of olivine, bronzite and a bottle-green augite 
containing 2.64 per cent. of K,O and 2.41 per cent. of Na,O.— 
rief notes on the rocks of Fernando Noronha, an island in the 
Atlantic about two hundred miles north-east of Cape St. Roque, 
Brazil, are communicated from the laboratory of the Johns Hop- 
kins University by Mr. Gill? The rocks described are phonolites, 
from conical hills similar to those in the Hegau in Baden, nephe- ` 
ine-basanites and basalts, nephelinite, and finally basalt glass. A 
extended petrographical study of these in all their different varie- 
ties will be published later.— Although the rocks of the Bohemian 
Mittelgebirge have been made the subjects of study by several pet- 
rographers, Hibsch‘ finds something new to say of them in a late 
article in T'schermak’s Mittheilungen. The trachytes of the region 
are younger than the phonolites or the basalts and occur in but a 
few localities. Their porphyritic sanidines possess a rounded out- 
line and are fringed with a rim of newly formed secondary feld- 
spathic substance. Many of the phonolites contain a large amount 
of plagioclase, and have besides a trachytic habit. In their cavi- 
ties is often noticed quite an interesting development of secondary 
albite. Little crystals of this mineral extend out from the sides of 
the cavity and penetrate into a mass of analcite, which, together 
' Edi . W.E. iversi aterville, Me. 
EE Paci a er, ee a 
P Johns Hopkins Univ. Circulars, No. 65, April, 1888, p. 71. 
* Min. u. Petrog. Mitth., 1887, p. 282. 
