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THE BOROUGH OF THE BRONX
The Borough
of the Bronx embraces a region that stretches eastward to the Sound and
encloses the low winding valley of the Bronx—a picturesque but shrunken
stream which only in spring exhibits the congruous features of a river.
This borough otherwise continues the geological features of Manhattan,
and in the main is a group of north and south ridges with a strike
approximating that of New York (N. 400 E. magnetic),
declining eastward to the waters of the Sound from the high bluffs of
Fordham and Van Cortlandt Park, and separated by valleys, or lower
areas, with a drainage to the southeast, and more directly south
between Fordham and the highland on the Hudson.
It
has not been so much opened as the region of Manhattan Island, though
in its general aspects of gneiss rock and granite veins, surmounted
here and there, as formerly, at Mott Haven, by prominences of
limestone, it displays the features familiar to all observers on
Manhattan itself, and promising the same mineral disclosures when more
thoroughly explored. The glaciation is marked and significant and, in
this respect, it forms only a pendant to the identical features of
Manhattan Island.
The
gneiss ridges seen on the north side of Westchester 'Avenue, the gneiss
rock of Fordham Heights, the gneiss in the Bronx gorge—all present and
duplicate* the familiar features of Manhattan Island; but the gneiss
typically shown at Fordham has received an interpretation somewhat at
variance with the assumption of their complete identity.
Professor
F. J. H. Merrill has called attention to the rock character of the
Highlands far north of Manhattan Island as being composed of fragmental
rocks, chiefly feldspar and quartz, and mainly designated under the
term granulite. He
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