SUMMARIES OF CURRENT NORTH AMERICAN PRE- 
CAMBRIAN LITERATURE.’ 
Davis,? in connection with an account of the Triassic formation of 
Connecticut, maps the boundary between the Triassic and crystalline 
rocks to the east and west. ‘The prevailing monoclinal faulted struc- 
ture in the Triassic involves a similar structure in the crystallines below, 
and it is believed that the structure observed in the Triassic is due to 
the slipping of large slabs of the crystalline rocks and the overlying 
Triassic rocks, in such way that each slab was elevated with reference 
to the slab next to the west, or, lowered with reference to the one next 
to the east. The explanation of the cause of the faulted structure is 
the same as that offered in a previous paper.? 
Merrill* gives a general account of the geology of the crystalline 
rocks of southeastern New York. 
The crystalline rocks lie on the east of the Hudson River, in 
New York, Westchester, Putnam, and Dutchess counties, whence they 
extend into Connecticut; and on the west of the river, in Orange and 
Rockland counties, whence they extend southwesterly into New Jersey. 
The lowest member is a coarse hornblende-granite which forms the 
central mass of the range of mountains known as the Highlands of the 
Hudson, and, in their highest peak, Breakneck Mountain, is exposed 
through a vertical height of nearly 1200 feet. Other granites, nearly 
free from hornblende, occur in subordinate masses. ‘The granites are 
probably igneous and of great age. On their flanks are banded 
gneisses, the Fordham Gneiss, consisting chiefly of quartz and ortho- 
clase, with biotite and hornblende, and containing numerous beds of 
magnetic iron-ore. The gneisses on the south side of the Highlands 
extend through Westchester county in a series of folds with south- 
westerly trend, and on the northern slope of the Highlands, at several 
t Continued from p. 425, Vol. VII, Jour. GEOL. 
2The Triassic formation of Connecticut, by Wm. M. Davis: Eighteenth Ann. 
Rept. U.S. Geol. Surv., Part II, 1898, pp. 1-192. With geological map. 
3The Structure of the Triassic Formation of the Connecticut Valley, by Wm. 
Morris Davis: Seventh Ann. Rept. U.S. Geol. Survey, 1888. 
4The geology of the crystalline rocks of southeastern New York, by F. J. H. 
MERRILL: Report of the New York State Museum, 1896, pp. 21-44. 
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