but
the thickness of ice which surmounted the highest land was so slight
that it advanced but little beyond the summit, and at its position of
maximum advance its edge rested on a descending slope." This is
ingenious if not altogether convincing.
There is also a small area south of Tottenville, at the angle of the island, on which the moraine does not encroach.
South
of the morainal region on Staten Island toward the sea the washed and
distributed material of the drift is found on the surface, ending in a
swampy and uneven tract, from which again develop the beach ridges of
sand.
On
Long Island the moraine is well developed, reaching almost to a height
of 200 feet. It forms some of the rolling landscape of Prospect Park,
the irregular topography of Greenwood Cemetery, and north of Jamaica
and Hollis forms an abrupt and commanding bench. From it extends
southward the flat plane, whose surface soils, loams, or clays have
been derived from it, overlying earlier formations beneath, whose
extent and depth are as yet unknown, but which will be progressively
better understood as the present survey of water-bearing levels on Long
Island proceeds. At Ridgewood odd-shaped polyhedral nodules have been
found in the drift, and mistaken for human handiwork. They are
limonitic concretions.
Morainal accumulations were formed or left on Manhattan Island, often against the stoss, " push " side, of the slopes of higher ground. Such a deposit occurs at 128th Street and Broadway (Fig. 52), where there was a till bed
or bank, some twenty feet thick, with superimposed sand in slightly
undulating lines—for the most part horizontal and laid down by water.
This had its counterpart on the north side of the Manhattanville
depression in morainal banks which could be seen formerly from the Fort
Lee ferry dock (Fig. 53), and in which very considerable admixtures of
dolomite sands occurred, and where, at 135th Street, between Broadway
and Riverside Drive, large red sandstone boulders were emplaced.
