454 THE AMERICAN NATURALIST. |. [Vor. XXXIV. 
geologists have recently carefully examined them. Coleman ! describes 
an exposure on the New York branch of Madawaska River, in Dun- 
gannon township, as a light and gray banded rock cut by a pegma- 
tite dike composed of large crystals of nepheline and muscovite. 
In the syenite are nepheline, albite, oligoclase, labradorite, orthoclase 
microcline-biotite, scapolite, calcite, muscovite, and occasionally 
augite and apatite. Corundum is also present, as small grains and 
large crystals usually associated with muscovite. Specimens obtained 
from exposures in other portions of Dungannon and neighboring 
townships present variations from the rock referred to above, but 
they are not of special significance. 
In one case, however, a medium-grained white rock from Methuen, 
Peterboro County, consists essentially of a plagioclase, more acid than 
the plagioclase of the anorthosites. 
The corundum in these rocks is thought to represent the excess of 
A10; that existed in a magma supersaturated with alumina, but not 
saturated with silica. 
Miller? outlines the situation of three belts of the corundiferous 
rocks. These rocks, like those referred to by Coleman, are syenites, 
nepheline-syenites, and an anorthosite. The last-named rock was 
analyzed, with this result : : 
SiO, AlO; FeO; FeO CaO MO NaO KO CO, Tot. 
26.24 29.85 1.30 2.12 16.24 2.41 1.98 MT 1.00 = 101.35 
Its feldspar has the formula Ab,, Any, ze, it is a bytownite. The 
rock is from the Seine River. 
Another occurrence of nepheline syenite in New Jersey is added 
by Ransome ° to those already known in the State. The rock forms a 
portion of the trap mass of Mt. Gilboa, near Brookville, which is 
intrusive in Triassic beds. The constituents of the syenite are: 
orthoclase, anorthoclase, and other feldspars, nepheline, hornblende, 
sgirine, biotite, cancrinite, muscovite, analcite, natrolite, apatite, 
fluorite, and calcite, the last six named, with the exception of apatite, 
being secondary. An analysis gave: 
SiO, TiO, Al,O; Fe,0, FeO CaO BaO MgO K,O Na,O H,O F 
54.68 -79 21.63 2.22 2.00 2. 105 A 4.58 7.03 2.15 .22 
SOs, P405 Total Less O —F 
07 .28 99.81 — .09 = 99.72- 
1 Journ. of Geol., vol. vii, 1899, p. 437. 
2 Amer. Geol., vol. xxiv, 1899, p. 276. - 
3 Amer. Journ. Sci., vol. viii, p. 417. 
