20 EOCK FLOOK OF GREATER NEW YORK. [bull.270. 
Darton, N. H. Relations of the traps of the Newark system in the New Jersey 
region: Bull. U. S. Geol. Survey No. 67, 1890, pp. 1-82, 6 pis. 
Russell, I. C. Correlation papers — the Newark system: Bull. U. S. Geol. Survey 
No. 85, 1892, pp. 1-344, 13 pis. (Especially pp. 83-95.) 
KtiMMEL, H. B. The Newark system, report of progress: Ann. Rept. State Geolo- 
gist New Jersey, 1896-97, pp. 25-88; 1897-98, pp. 25-159. 
Darton, N. H. Geologic Atlas V. S., folio 83, IT. S. Geol. Survey, 1902, pp. 6-10. 
COMMENT. 
In the opinion of the writer too little weight has been accorded by 
recent observers to the importance of normal faulting in determining 
the structure of Manhattan Island. Particularly, in view of the prox- 
imity of the much-faulted Newark area across Hudson River, the 
markedly rectilinear boundaries of the island uplands, and the known 
zones of discontinuity discovered by engineers in subterranean work- 
ings. Stevens, among the earlier writers, and Julien and the present 
writer among the later ones have accorded greater weight to this 
consideration. Dana assumed a cross fault at Manhattan ville, and this 
has been accepted by Kemp, who suggests also that there may be 
similar cross breaks at Enwood and Spuyten DuyviJ. Merrill has 
entered upon his map. in addition to the fault at Man hat tan ville, two 
additional cross faults, one between Hell Gate and Blackwells Island, 
and another between Randall Island and the mainland, in order to 
account for the present positions and attitudes of the formations in 
those localities. Julien has described among others an additional 
cross fault accompanied by friction breccia at 138th street and St. 
Nicholas avenue, and has called attention to the shattering and brecci- 
ation at Spuyten Duyvil. The writer has described a number of addi- 
tional fault planes which have been recently located. 
SCOPE OF THE PRESENT STUDY. 
An attempt has here been made to determine the depth and the 
nature of bed rock beneath Greater New York, by means of wells and 
borings, the numerous bridge and tunnel sections, the Government 
dredgings, the reefs in mid-channel, etc., in the belief that it will con- 
tribute not only toward the solution of the geological problems of the 
area, but will greatly aid the engineers who are carrying out the enter- 
prises previously referred to, as well as architects, contractors, and 
man} r others. 
The investigation has been conducted by personal interviews and 
correspondence with engineers who have been in charge of public 
works, by examination of drill cores, by study of municipal and other 
reports, and by kindred methods, rather than by attack on the rocks 
themselves, though this has so far as possible been undertaken. Tin 
writer takes this opportunity to acknowledge his obligation to tin 1 
