udson is bordered for nearly forty miles by a great
ridge of columnar rock, lying upon sandstone. When this is surveyed with
an eye to its analogy to volcanic action, it appears as if it were the
outpourings of a crater, whose basin is now occupied by the lake in
which the Hackensack river takes its rise, and whence a great stream of
lava has run over the sandstone rock, as far as the strait that
separates Staten Island from the main land. The two Newark mountains are
ridges of the same description, of even greater extent; other smaller
ridges of the same kind are also distinctly visible, and the whole of
this last system appears to have proceeded from a crater now filled by
the alluvion of the Passaic, but which is bordered by a ridge still
occupying two-thirds of a circle, and showing conclusive marks of
igneous action, that goes by the name of the Hook mountain. The
phenomenon of a dyke of trap is well exhibited in the quarries near
Hartford in Connecticut, where this rock has been laid bare for a
considerable depth, as it rises through a sandstone rock, instead of
overlying it, as it is seen to do on the Hudson.

The trap-rocks, which are, generally speaking, of the character called
by mineralogists greenstone, vary in this district of New-Jersey, from a
compact basalt of homogeneous structure, to one of regular and distinct
crystallization, not distinguishable in hand specimens from primitive
syenite. A rock of this last character is to be found in the mountain
that extends from Morristown to Mount Kemble, which is columnar in its
structure, but almost identical, in mere external characters, with
stratified rocks of gneiss containing hornblende, that are found in the
primitive ridges within a few miles.

Thus then the older volcanic rocks gradually pass in character into
those which, under the general name of granitic, form the apparent
nucleus of gneiss and mica slate mountains, and penetrate them, and the
primitive limestones, in veins. One of the best instances of veins of
granite with which we are acquainted, are those which occur in the
quarries of white marble at Kingsbridge, which are traversed in every
direction by thin veins of a rock, principally composed of a white fetid
felspar, mixed with spangles of silvery mica, and small grains of
quartz, interspersed with occasional masses of tourmaline. The famous
locality of chrysoberyl, beryl, and other interesting minerals, at
Haddam, in Connecticut, is said t