These
pebbles are, as might have been expected, quite irregularly lined, the
movement of the pebble itself exposing it to abrasions in many
directions, quite unlike the immovable rock surfaces over which the
glaciers have swept in one but slightly deviating path. The likelihood
to mistake is far more increased in the case of these scratched
pebbles than even in the grooved rocks, as the creases of decay
simulate the glacial striae. The indications are unmistakable when the
stone presents its face or faces scored by a series of parallel cuts
that resemble the incision of a gouge or stone pick. The hardness of
the stones, and even their shapes, have considerable influence on the
retention of these cuts. The softer or more friable stones, as the
sandstones, lose these scratches more quickly than the harder, denser
rocks, and the long, flatter stones are more usually engraved than the
rounder forms.
The
teacher will also find plentiful evidences of the ice sheet in the
neighboring highlands of the Palisades, where the uncovered surfaces
display the immemorial etchings of the continental glacier. Professor
I. C. Russell, in his " Geology of Hudson County, New Jersey," says: "
Wherever the superficial material is removed from above the trap rock
in Hudson County, we invariably find the surface of the hard
crystalline rock smoothed and polished and all the projecting ledges
worn and rounded off. This smoothed surface is also scratched and
grooved in parallel lines, bearing usually N. io° 15" W. Upon this
polished and striated surface rests an irregular confused accumulation
of earth and stones from ten to twenty-five feet or more in thickness.
This sheet of drift is spread over all the highlands, and, covering the
hillsides, dips beneath the more recent sand dunes and salt marshes
along the Newark Bay on the west, and bordering the New York Bay on the
east. This drift consists mainly of broken and disintegrated red
sandstone and shales derived from the Triassic area to the westward,
and gives the prevailing reddish color to the soil. It also contains
numerous boulders, frequently four or five feet in diameter; some of
these are of
