1895.] Petrography. 659 
“ netrographical province,” the paper closes with the statement that 
although the lavas of the region under discussion are so similar to those 
of the Andes, nevertheless, the original undifferentiated magmas of the 
two districts were quite dissimilar. 
Maryland Granites.—The granite and associated rocks on the 
east side of the Susquehanna River in Cecil County, Maryland, have 
been made the subject of study by Grimsley.’ In the northern portion 
of the area investigated, the granite is but little sheared, while in its 
southern portion the rock is very gneissic. The two portions of the 
area are separated from each other by a band of staurolite-schist. 
Though the rocks of both areas were originally the same in composi- 
tion, it is thought that the northern granite may be the younger, since 
it is intruded by dykes of what appears to be a dynamically meta- 
morphosed gabbro, while, on the other hand, the southern granite in- 
trudes a basic rock that apparently grades into gabbro. Both granites 
are biotitic varieties, and both are eruptive in origin. The northern 
granite is remarkable for the epidotization of its feldspar, which is pre- 
dominantly plagioclastic, and for the occurrence in it of numerous 
dark basic segregations. Many rare minerals, such as zircon, magne- 
tite, tourmaline, cubical garnets and sphene were found in large quan- 
tities in the soil produced by its decomposition. The northern contact 
of the northern granite is somewhat abnormal in its characters. The 
granite appears to become more basic toward the contact, and the 
basic phases are cut by apophyses of the normal acid rock. 
An analyses of the granite follows : 
SiO, TiO, Al,O, Fe,0, Feo MnO CaO SrO BaO MgO 1e 20 Li,O Hio P,O, Total 
66.68 .50 14.93 1.58 3.23 .10 4.89 tr. .08 219 tr. 19 = 100.32 
Alabama Cherts.—Hovey’ has recently examined a series of 
cherts sent him from Alabama. Those from the Lower Magnesian 
series consist almost entirely of chalcedony, with the addition of a little 
quartz and opal. The rocks are fine-grained mosaics that are mottled 
by reason of variations in the fineness of their grains. The quartz 
appears to be secondary, as it fills cavities in the chalcedony. A few 
scales of limonites and dust particles are present in almost all sections. 
No well-defined organic remains were detected in any. The cherts 
from the Lower Carboniferous, on the other hand, contain numerous 
$ Jour. Cin. Soc, Nat. Hist., Apr.—July, 1894. 
7 Amer. Jour. Sci., 1894, xlviii, p. 401. 
