968 THE AMERICAN NATURALIST. 
County, N. Y., are brought out by C. H. Smyth, Jr.,! in a recent 
paper. The term “gneiss ” is made to cover all the gneissoid rocks of 
the district studied, whether they be acid or basic. All the gneisses 
are not of the same age ; some are younger than the limestone with 
which they are associated. As to origin, it is definitely shown that a 
large portion of them are igneous. It is also inferred by the author 
that, “the gneisses constitute a complex series of rocks, differing 
somewhat in age, and largely, if not wholly, of igneous origin; parts 
of this series are clearly younger than the limestones, and while other 
parts may be older than the latter formation, there is nothing as yet 
to prove that this is the case. An exception to the latter statement 
is probably afforded by certain laminated gneisses of limited extent, 
which appear to underlie the limestone, perhaps marking the base of 
the series.” 
Notes. — Derby ? has separated the constituents of the itacolumite 
of the Minas Geraes district, of Goyaz, and of Bahia, Brazil. The 
quartz grains show no evidence of clastic origin. The micaceous 
component is usually some form of muscovite, though occasionally 
it is some brittle mica. Magnetite, hematite, and pyrite are quite 
common. Rutile or anatase is frequently met with, and zircon is so 
abundant that it must be regarded as a concentration in a sediment. 
It moreover bears evidence of having been transported by water. A 
few of the specimens contain clastic grains of dark tourmaline that 
have been secondarily enlarged by the deposition of light-colored 
tourmaline around the dark nuclei. The result of the study leads 
the author to conclude that the itacolumite is a metamorphosed 
sandstone. 
A list of dykes found by Cushing? in Clinton County, N. Y., is 
reported in a paper on the geology of Clinton County. The material 
of the dykes embraces diabase, olivine-diabase, bostonite, fourchite, 
camptonite, monchiquite, and fourchite. 
1 Fifteenth Annual Report State Geologist. Geol. Sur., State of N. Y., 1895, 
481. 
pa 
2 Amer. Journ. of Sci., vol. v (1898), p. 187. 
8 Fifteenth Annual Report State Geologist. Geol. Sur., State of N. Y., 1895 
P- 503. 
