434 J. D. Dana—On Southern Westchester County 
The schist east of the limestone along the west side of Fleet- 
wood Park is nearly vertical in its bedding. That on the west 
side has, north of 167th Street, a high dip to the eastward, like 
the prevailing dip of the limestone; but south of this it becomes 
nearly vertical, and then westerly, and, within a fourth of a 
mile of McComb’s bridge, the beds have widely varying dip 
with large contortions in the bedding, though westerly dips pre- 
vail; yet on the Harlem River side, the beds have greater regu- 
larity and stand nearly vertical. As shown below, they here 
face the Harlem River band of limestone. 
B. On New York Island.—In New York, the limestone band 
to the east or west of this locality. 
How far this Cromwell Valley belt extends south of 181st 
Street is uncertain. The surface continues low to 124th Street, 
where rise the rocky ledges of Mt. Morris Park, and this may 
well be its southern limit. It is a question, however, whether 
it does not narrow and pass by the west side of the park, and, 
continuing southward, enter the low northeast corner of Cen- 
tral Park; in which case 103d Street would be its farthest pos- 
sible limit since on 102d the schists of Central Park spread 
eastward across 5th Avenue, and so bring to an end the low 
valley: like area. 
* This Journal, xx, 362 (Nov., 1880), where I cite a remark respecting it from 
R. P. Stevens in Ann. Lyc. Nat. Hist., N. Y., viii, 116. 
