In addition to various geological references
scattered through these pages the following facts from an
American Geological Railway Guide, by James Macfarlane,
Ph.D., will be of interest.
"The State of New York is to the geologist what the Holy
Land is to the Christian, and the works of her
Palæontologist are the Old Testament Scriptures of the
science. It is a Laurentian, Cambrian, Silurian and Devonian
State, containing all the groups and all the formations of
these long ages, beautifully developed in belts running
nearly across the State in an east and west direction, lying
undisturbed as originally laid down.
"The rock of New York Island is gneiss, except a portion of
the north end, which is limestone. The south portion is
covered with deep alluvial deposits, which in some places
are more than 100 feet in depth. The natural outcroppings of
the gneiss appeared on the surface about 16th Street, on the
east side of the city, and run diagonally across to 31st
Street on 10th Avenue. North of this, much of the surface
was naked rock. It contains a large proportion of mica, a
small proportion of quartz and still less feldspar, but
generally an abundance of iron pyrites in very minute
crystals, which, on exposure, are decomposed. In consequence
of these ingredients it soon disintegrates on exposure,
rendering it unfit for the purposes of building. The
erection of a great city, for which this island furnishes a
noble site, has very greatly changed its natural condition.
The geological age of the New York gneiss is undoubtedly
very old, not the Laurentian or oldest, nor the Huronian,
but it belongs to the third or White Mountain series, named
by Dr. Hunt the Montalban. It is the same range which is the
basis rock of nearly all the great cities of the Atlantic
coast. It crosses New Jersey where it is turned to clay,
until it appears under Trenton, and it extends to
Philadelphia, Baltimore, Washington and Richmond, Va., and
probably Boston, Massachusetts, is founded on this same
formation.
"On the opposite side of the river may here be seen for many
miles the Palisades, a long, rough mountain ridge close to
the water's edge. Its upper half is a perpendicular
precipice of bare rock of a columnar structure from 100 to
200 feet in height, the whole height of the mountain being
generally from 400 to 600 feet, and the highest point in the
range opposite Sing Sing 800 feet above the Hudson, and
known as the High Torn. The width of the mountain is from a
half mile to a mile and a half, the western slope being
quite gentle. In length it extends from Bergen Point below
Jersey City to Haverstraw, and then westward in all 48
miles, the middle portion being merely a low ridge. The
lower half of the ridge on the river side is a sloping mound
of detritus, of loose stones which has accumulated at the
base of the cliff, from its weathered and wasted surface.
"Viewed from the railroad or from a steamboat on the river,
this lofty mural precipice with its huge weathered masses of
upright columns of bare rock, presenting a long, straight
unbroken ridge overlooking the beautiful Hudson River, is
certainly extremely picturesque. Thousands of travelers gaze
at it daily without knowing what it is. This entire ridge
consists of no other rock than trap traversing the Triassic
formation in a huge vertical dike. The red sandstone
formation of New Jersey is intersected by numerous dikes of
this kind, but this is much the finest. The materials of
this mountain have undoubtedly burst through a great rent or
fissure in the strata, overflowing while in a melted or
plastic condition the red sand-stone, not with the violence
of a volcano, for the adjoining strata are but little
disturbed in position, although often greatly altered by the
heat, but forced up very slowly and gradually, and probably
under pressure. Subsequent denudation has laid bare the part
of the mountain now exposed along the river. The rock is
columnar basalt, sometimes called greenstone, and is solid,
not stratified like water-formed rocks, but cracked in
cooling and of a crystalline structure. Here is a remarkable
but not uncommon instance of a great geological blank. On
the east side of this river the formations belong to the
first or oldest series of Primary or Crystalline rocks,
while on the west side they are all Triassic, the
intermediate Cambrian, Silurian, Devonian and Carboniferous
formations being wanting. This state of things continues all
along the Atlantic coast to Georgia, the Cretaceous or
Jurassic taking the place of the Triassic farther south.
"Montrose to Cornwall. This celebrated passage of the Hudson
through the Highlands, is a gorge nearly 20 miles long from
3 miles south of Peekskill to Fishkill, and is worn out of
the Laurentian rocks far below mean tide water. The hills on
its sides rise in some instances as much as 1,800 feet, and
in many places the walls are very precipitous. The rock is
gneiss, of a kind that is not easily disintegrated or
eroded, nor is there any evidence of any convulsive
movement. It is clearly a case of erosion, but not by the
present river, which has no fall, for tide water extends 100
miles up the river beyond the Highlands. This therefore was
probably a work mainly performed in some past period when
the continent was at a higher level. Most likely it is a
valley of great antiquity.
"Opposite Fishkill is Newburgh, which is in the great valley
of Lower Silurian or Cambrian limestone and slate. North of
that, on the west side of the river, the formations occur in
their usual order, their outcrops running northeast and
southwest. On the N. Y. C. & H. R. R. R., on the east side,
the same valley crosses, and the slates from Fishkill to
Rhinebeck are about the same place in the series; but being
destitute of fossils and very much faulted, tilted and
disturbed, their precise geology is uncertain. See the
exposures in the cuts at Poughkeepsie. The high ground to
the east is commonly called the Quebec group.
"A series of great dislocations with upthrows on the east
side traverse eastern North America from Canada to Alabama.
One of these great faults has been traced from near the
mouth of the St. Lawrence River, keeping mostly under the
water up to Quebec just north of the fortress, thence by a
gently curving line to Lake Champlain or through western
Vermont across Washington County, N. Y., to near Albany. It
crosses the river near Rhinebeck 15 miles north of
Poughkeepsie and continues on southward into New Jersey and
runs into another series of faults probably of a later date,
which extends as far as Alabama. It brings up the rocks of
the so called Quebec group on the east side of the fracture
to the level of the Hudson River and Trenton.
"Catskill Mountains. For many miles on this railroad are
beautiful views of the Catskill Mountains, 3,800 feet high,
several miles distant on the opposite or west side of the
river, and which furnish the name for the Catskill
formation. The wide valley between them and the river is
composed of Chemung, Hamilton, Lower Helderberg and Hudson
River. The geology on the east or railroad side is entirely
different.
"Albany. The clay beds at Albany are more than 100 feet
thick, and between that city and Schenectady they are
underlaid by a bed of sand that is in some places more than
50 feet thick. There is an old glacial clay and boulder
drift below the gravel at Albany, but Professor Hall says it
is not the estuary stratified clay."
The Hudson
Tide
(Condensed from article by permission
of writer.)
The tide in the Hudson River is the
continuation of the tide-wave, which comes
up from the ocean through New York Bay, and
is carried by its own momentum one hundred
and sixty miles, growing, of course,
constantly smaller, until it is finally
stopped by the dam at Troy. The crest of
this wave, or top high water, is ten hours
going from New York to Troy. A steamer
employing the same time (ten hours) for the
journey, and starting at high water in New
York, would carry a flood tide and highest
water all the way, and have an up-river
current of about three miles an hour helping
her. On the other hand, the same steamer
starting six hours later, or at low tide,
would have dead low water and an ebb tide
current of about three miles against her the
entire way. The average rise and fall of the
tides in New York is five and one-half feet,
and in Troy, about two feet.
Flood tide may carry salt water, under the
most favorable circumstances, so that it can
be detected at Poughkeepsie; ordinarily the
water is fresh at Newburgh.
To those who have not studied the tides the
following will also be of interest.
The tides are the semi-diurnal oscillations
of the ocean, caused by the attraction of
the moon and sun.
The influence of the moon's attraction is
the preponderating one in the tide rising
force, while that of the sun is about
two-fifths as much as that of the moon. The
tides therefore follow the motion of the
moon, and the average interval between the
times of high water is the half length of
the lunar day, or about twelve hours and
twenty-five minutes.