HOBBS.] 
STRUCTURAL GEOLOGICAL STUDIES. 
15 
theory of the origin of the Manhattanville val- 
Drift 
Referring to Dana 
ley, he says: 
Professor Dana has noted 
evidence tending to show that 
the Manhattanville depression 
is due to an oblique wrenching 
and faulting of the rocks, and 
it is possible that the same 
movement may have caused 
the breaks at Inwood and 
Spuyten Duyvil. 
The paper contains a 
geological map which has 
the excellent but un- 
usual peculiarity that the 
larger drift-covered 
areas are represented. 
In the alluvial flats of 
Harlem three parallel 
tongues of limestone or 
dolomite are represented 
trending with the ave- 
nues and extending from 
Harlem River southward 
for distances averaging 1 
mile. (See fig. 2.) 
Merrill.— Dr. F. J. H. 
Merrill, recently the 
State geologist of New 
York, has published a 
number of brief notes" 
on the geology of New 
York Island, and re- 
cently a more extended 
report in the New York 
City folio. * He follows 
Dana in believing the 
structure of the island 
to be conditioned largely 
as a result of a system 
of longitudinal and transverse flexures, the trend of the former being 
in the general direction of the long axis of the island or of its avenues. 
a Merrill, F. J. H., (1) Metamorphic strata of southeastern New York: Am. Jour. Sci., 3d ser., vol. 
39, 1890, pp. 383-392. (2) New York State Museum, 1896. (3) Geology of Greater New York: Trans. 
New York Acad. Sci., vol. 16, 1897, p. 371. (4) Note on the colored clays recently exposed in rail- 
road cuttings near Morrisania, N. Y.: Trans. New York Acad. Sci., vol. 9, 1889, pp. 45-46. 
b Geologic Atlas U. S., folio 83, U. S. Geol. Survey, 1902, pp. 3-5. 
Fig. 2.— Sketch map of Manhattan Island. (After Kemp. 
