14 EOCK FLOOR OF GREATER NEW YORK. [bull. 270. 
epoch, and the local scouring out of channels during Champlain time, 
were all well brought out in this paper. Newberry regarded East 
River as the last reach of Housatonic River of Connecticut before 
discharging into the Hudson, which was then carrying the waters from 
the Laurentian system of lakes/' 
Dana.— h\ an excellent paper on the Geology of Northern Man- 
hattan and the Bronx, 6 J. D. Dana printed a geological map cover- 
ing the areas of the present boroughs of Manhattan and the Bronx 
north of Central Park, on a scale of 2 inches to the mile. This 
map. by reason of the numerous dip and strike symbols entered upon 
it, is pract ically an outcrop map. The position and the attitudes of the 
rock masses upon the island Dana accounted for through a system of 
folds which strike with the avenues. His sections show three synclines 
and two intervening anticlines between Tnwood on the northwest 
and East River upon the east. The gorge at Manliattanville, which 
crosses the direction of tin' strike. Dana thought "probably had its 
initiation in an oblique wrenching and faulting of the rocks." He 
noted the offset between the gneiss upland which lies north of the 
Manhattanville valley and that to the south. Referring in his resume 
to the fundamental features of New York Island, he says: 
Finally, we may conclude that the predeterminations of the fundamental features 
of New York [sland date back to the era of the Lower Silurian, and to the epoch of 
mountain making at its close. No other rocks that now remain have been added by 
subsequent geological operations excepting the loose or unconsolidated material of 
the surface. Fissures and faults may have occurred through subterranean move- 
ments, hut the work of separating its ledges has gone forward chiefly by the action 
of the sun, atmosphere, ocean, rivers, and ice. and the present condition, barring 
human encroachments, is the final result. 
Russell. — In his paper on the Geology of Hudson County, N. J., c 
Russell has furnished many important data from borings upon Man- 
hattan Island, which reveal both the depth of rock from the surface 
and the nature of the rock encountered. 
Kemp. — In a paper published in L887 Kemp d gives a general sum- 
mary of the rock distribution upon Manhattan Island and adopts 
Dana's view of the structure. Reviewing the sections of Stevens, he 
objects to the four or live synclines suggested. He argues: 
But this docs not seem to me to be warranted by the facts. If the original stratum 
has been doubled up so many times, it could only have been very thin when hori- 
zontal. It docs not seem reasonable that so broadly extended and so thin 
a stratum could by any possible convulsion be doubled up together so as to give 
these results. The synclinal mapped seems beyond dispute; as for dividing up the 
strata each side of it, 1 do not feel justified in doing it. 
a Newberry, J. S., Techn. Quart., vol. 13,1900, p. 121; als... Bull. Geol. Soc. America, vol. L3, L901,p.24. 
fcDana, J. 1).. Geological relations of the limestone belts <>f Westchester County and northern New- 
York Island: Am. Jour. Sci., vol.21, 1881, pp. 125 143, and vol.22, L881, pp.313 315. 
'•Russell. LC, Geology of Hudson County, N.J.: Annals New Vorl< Acad. Sci., vol. 2. L882, pp. 66 79. 
'/Kemp, J. P., Geology of Manhattan [sland: Iran-. New York Acad. Sci., vol. 7. L887, pp. 19 65. 
