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204 GEOLOGY OF NEW YORK CITY
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of
the ground, or buried deeply in the morainal mass. Mr. J. A. Grenzig,
who has recently paid considerable attention to the mineral contents of
the drift in Brooklyn, remarks upon the rapid disappearance of the
boulders by blasting and breaking, since they furnished useful building
material. He says: " The places which formerly had many large boulders
on the surface were mostly on the west or northwest of the ridge or
highland running from Prospect Park northeast along what is now the
Boulevard to East New York, and then on to Jamaica, also on the ocean
side of this highland, where it disappears in the plains." West of
Prospect Park the highland follows a more southerly course toward Fort
Hamilton, and, as Mr. Grenzig indicates the large boulders west again
of this ridge were numerous.
A
very picturesque and almost startling example of a boulder can be seen
to-day on the shore road running from New Rochelle to Bartow (Fig. 47).
It is a huge granite mass perched attractively on a low knoll, forming
a natural foil to a neighboring villa.
The
boulders on Staten Island are innumerable, though their former
conspicuous display has sensibly contracted. The building of stone
walls and especially the construction of the Rapid Transit Railroad
along the north shore of the island has both buried them out of sight
and turned them to use as well. Formerly the shores of the Kill van
Kull on its south side, quite contrasting with the far less encumbered
north shore of the same channel, were thickly strewn with boulders of
all sizes. Above them rose a terrace as at present, and from its summit
backward over the island, with the center of their distribution rather
nearer the shore, these boulders appeared over field and hillside. They
were plainly foreign. Unless dropped from the skies, they never could
have reached their positions except by transportation. The great
majority of these boulders were trap, many were hornblende gneiss, a
few sandstones, granite, slates, and occasionally a limestone or
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