530 Go, JLIR Tal 
which is flanked on the east side by mica-schist, locally pegmatized. 
Beyond the mica-schist on the Ravenswood shore is a massive horn- 
blende-gneiss or granite, which is thought to be intrusive. 
Merrill,* in connection with a report on the mineral resources of 
New York, publishes a geological map of the entire state and a large 
scale geological map of the southeastern part of the state. These maps 
embody information available to date concerning the distribution of 
the pre-Cambrian rocks of New York. 
Merrill,? in connection with a report on road materials of New 
York, publishes a map of the state showing distribution of pre- 
Cambrian rocks. 
Bascom? describes and maps pre-Cambrian volcanic rocks of South 
Mountain, Pennsylvania. The volcanic rocks are both basic and acid. 
The acid rocks comprise quartz-porphyries, devitrified rhyolites or 
aporhyolites, with accompanying pyroclastics, and sericite-schists, the 
last being the metamorphosed forms of the quartz-porphyries and 
aporhyolites. The basicrocks comprise melaphyres, augite-porphyrites, 
slates, and pyroclastics. Lithologically the volcanic rocks resemble 
the Keweenawan copper-bearing rocks of Lake Superior. 
There is not sufficient evidence to decide the comparative age of 
the basic and acid rocks, but field observations in the Monterey district 
indicate that the acid rocks are the older. ‘The volcanics are overlain, 
with stratigraphical unconformity, but with structural conformity, by 
sedimentary rocks of Lower Cambrian age. Both volcanics and sedi- 
mentaries have been subjected to strong dynamic action, whereby the 
igneous rocks have been cleaved and sheared, and the sedimentary 
rocks thrust over them from the east. 
Kemp‘ describes the ore deposits at Franklin Furnace and Ogdens- 
burg, N. J., and briefly sketches the general geology of the area. ‘The 
Mineral resources of New York State, by F. J. H. MERRILL: Bull. N. Y. State 
Museum, Vol. 3, No. 15, 1895, pp. 365-595. 
2Bull. N. Y. State Museum, Vol. 4, No. 17, 1897, pp. 90-134. With maps. 
3The ancient volcanic rocks of South Mountain, Pa., by FLORENCE BASCOM: 
Bull. U. S. Geol. Surv., No. 136, 1896, pp. 124. With geol. map. 
4The ore deposits at Franklin Furnace and Ogdensburg, N. J., by J. F. KEMP: 
Trans. N. Y. Acad. Sci., Vol. 13, 1893, pp. 76-98. 
