576 The American Naturalist. [July, 
found calculated for 
-m Ca, Fe, Si,O,, 
SiO, 35.45 35.43 
Fe,O, 32.33 32.11 31.50 
CaO 32.58 33.07 
— Foote” gives some details concerning a new mineral which he pro- 
poses to name Northupite. It was found by Mr. Northup in the “ tail- 
ings” from a boring made at Borax Lake, Cal. The crystals are reg- 
ular octahedrons reaching rarely 1 cm. in diameter. The substance 
seems to be a double chloride and carbonate of sodium and magnesium. 
Cleavage imperfect, H = 3.5 to 
PETROGRAPHY.’ 
Volcanic Rocks and Tuffs in Prussia.—In the hills east of 
_Ebsdorf, near Marburg, Prussia, are large areas covered by basalt flows, 
flows of dolerite, and others of rocks intermediate in character between — 
these two, both of which are pre-Tertiary in age, or at any rate are 
older than the Tertiary beds with which they are associated. The vol- 
canic rocks are cut by dykes of very basic rock resembling limburgite. 
The little hill west of Wittelsberg, near the northern edge of the basalt 
area, and the flank of the hill near Kehrenberg, are composed largely 
of basalt tuff. 
The basalt consists of phenocrysts of augite and olivine in a dense 
felt of augite microlites, biotite and magnetite, in the spaces between 
which is a colorless glass containing xenomorphic feldspar, leucite and 
nepheline. Inclusions in the basalt are very common. They comprise 
besides fragments of Foreign rocky; concretions of olivine and of augite. 
The olivine con more or less bronzite, and usually 
they are surrounded by a violet-brown rim similar to the rims found 
surrounding the augite phenocrysts in the basalt. Even those concre- 
tions that are composed almost exclusively of bronzite are surrounded 
by rims of this character. The principal component of this rim is a 
monoclinic augite, so that it appears here that the bronzite, which must 
have been one of the earliest separations from the magma, was, after 
its crystallization, changed into augite. Other concretions show the 
1 Am. Jour. Sci., L, pp. 480-488, Dec., 1895. 
1 Edited by Dr. W. 8. Boi Colby Univesity, Waterville, Me. 
