hobbs.] STRUCTURAL GEOLOGICAL STUDIES. 
Peet.— In a recent extended report on the Glacial and post-Glacial 
history of the Hudson Valley, Peet" favors the view that the Hudson 
water body was in post-Glacial time a lake impounded by the moraine, 
the inlet now existing through the moraine having been formed by 
the cutting down of the lake outlet to the present narrows. He says: 
In conclusion it may be stated that, while no single argument seems to be fatal to 
the salt-water hypothesis accounting for the Hudson water body, unless those drawn 
from the phenomena on the outside of the moraine be such, it is likewise true that 
the facts are not fatal to the lake hypothesis, unless the sponge spicules reported 
from Croton represent salt-water species. Aside from these sponge spicules, the 
weight of the evidence seems to be in favor of the lake hypothesis. 
Hobbs. — Still more recently the writer 6 has made a study of the 
channels surrounding Manhattan Island, and has shown that limestone 
has been but seldom encountered in them, except along Harlem River, 
where for a portion of its length, between Kingsbridge and McComb\s 
dam, the stream flows in a fault gorge, and where in another por- 
tion it cuts diagonally across belts of gneiss and limestone south of 
McComb's dam. In this latter section of the river there is no rock 
channel corresponding to the present river and the rock floor is with- 
out uniform slope in either direction, but is characterized by marked 
irregularit} r . Stevens's view that the location of the channels has 
been largely conditioned by a set of fractures is adopted as the most 
probable one. 
AREA WEST OF THE HUDSON. 
It will not be necessary here to review the voluminous literature 
descriptive of the type area of the Newark series. The rocks of this 
series, which are represented in the New York area, as here limited, 
comprise sandstones and shales with intrusive sills and dikes of basalt 
or diabase, all of which, except the dikes, dip at a low angle (10°-15°) 
to the northwest. All recent writers on this area have regarded the, 
system as a faulted monocline with the main faults trending in a north- 
northeast direction. All are in accord in stating that the number of 
faults which must be present is in excess of those which have been 
described. The more important papers upon the area are the following: 
Russell, I. C. Physical history of the Triassic formation in New Jersey and the 
Connecticut Valley: Annals New York Acad. Sci., vol. 1, 1878, pp. 220-256. 
Cook, G. H. Red sandstone or Triassic formation: Ann. Rept. State Geologist New 
Jersey, 1879, pp. 18-35. (Contains colored map.) 
Russell, I. C. Geology of Hudson County, N. J.: Annals New York Acad. Sci., 
vol. 2, 1882, pp. 27-80. 
Davis, Wm. M. Relations of the Triassic traps and sandstones of the eastern United 
States: Bull. Mus. Comp. Zool. Harv. Coll., vol. 7, 1883, pp. 250-309. 
a Peet, C.E., Glacial and post-Glacial history of the Hudson and Champlain valleys: Jour. Geol., 
vol. 12, 1904, pp. 415-469, 617-660. 
& Hobbs, W. H., Origin of the channels surrounding Manhattan Island: Bull. Geol.Soc. America, 
vol. 16, 1905, pp. 157-182, pi. 35. 
