Слике страница
PDF
ePub

NATURAL HISTORY OF NEW YORK.

I. GEOLOGY AND MINERALOGY.

Geology may be defined as that science which treats of the structure of the earth, and the substances which compose it.

An examination of the banks of rivers, the sides of precipices, &c., shows that there are two kinds, or classes of rocks; the one being deposited in layers, or strata, of variable thickness, are called stratified rocks, and bear evidence of having been, at some remote period, deposited as a sediment, from water; the other irregular in shape, containing numerous crystals, and most of the metals in common use, and forming the basis of the lofty mountain chains, are termed unstratified rocks, and were undoubtedly brought into their present form by the action of fire, which then existed, and probably still exists, in the interior of the earth.

Granite is the principal constituent of the unstratified rocks, and probably formed the original crust of the earth. It still exists below all the other rocks. Owing, however, to violent convulsions of nature, (such as earthquakes, volcanic eruptions, &c.,) which have occurred since the layers above it were deposited, it has in many places been forced up through fissures in these layers, so as to appear on the surface, or has raised them up, so as to form mountains or hills. If these were still covered with water, or became again submerged by a subsequent convulsion, new layers were again deposited, frequently at considerable angles with the first deposit.

The figure represents such an occurrence.

с

a, represents the unstratified rock upon which the layers b, b, had been deposited in a horizontal position; but by a convulsion of nature, the whole mass had been upheaved, and the granite had forced its way to the surface; being however still submerged, new layers C, C, were deposited, at an angle of nearly 450 with the first.

Hypersthene and primitive limestone also occur among the unstratified rocks.

THE STRATIFIED Rocks are divided into six orders or systems, as they are called; viz.,-beginning at the lowest strata, or those next succeeding the unstratified rocks, we have,

I, THE PRIMARY, OR PRIMITIVE System, consisting of disintegrated granite, deposited by the waters; and probably again modified by the action of the subterranean heat.

The rocks, composing this system, are known as gneiss, mica schist, and hornblende. There is no evidence of the existence of either animal or vegetable life, during the period while this strata were depositing. Nearly all the metals, used in the arts, are found in these rocks, and in the granite on which they rest.

II. THE TRANSITION System. This system embraces a great variety of formations, and occupies a large portion of the crust of the earth. Its lower strata consist of limestones, sandstones, and shales or slaty rocks. Above these, is a layer of sandstone, known as the old red sandstone, which is succeeded by a limestone, forming the bed of the vast coal formations, which furnish so large an amount of fuel to the world. Over these is deposited a magnesian limestone, and another layer of red sandstone, distinguished as the new red sandstone.

The period, when these deposits were made, was characterized by extraordinary luxuriance of vegetable life. The coal deposits are all of vegetable origin, and were reduced to their present form, by the influence of heat, decay and pressure. In the rocks belonging to this system are also found, in immense quantities, the lower orders of animals, shell fish, snails, and a few fishes, and amphibious reptiles. None of them, however, belong to species now known to be in existence.

III. THE SECONDARY SYSTEM, composed of colitic limestone, greensand, and chalk. This system contains a large number of fog. sils, both animal and vegetable. Among the former are those gigantic amphibious animals, mostly belonging to the lizard and crocodile tribes, whose skeletons, found both on this continent and in Europe, have excited so much attention. There are also many shells, fishes, insects, and a few quadrupeds. Several hundreds of species of plants have been found in the secondary rocks. These fossils, vegetable and animal, with scarcely an exception, belong to extinct species.

IV. THE TERTIARY SYSTEM. This consists of deposits of clay, sand and gravel, in some instances hardened into rock, but generally containing evidence of the comparative recentness of its deposition. It contains an immense number of fossils, both animal and vegetable; of these about 12 per cent. have been identified as belonging to ex. isting species, and the remainder generally bear a marked resemblance to plants and animals now in existence, which the fossils of the earlier periods do not.

V. THE DILUVIAL DEPOSITS, called also the erratic block group. In thi system are included the boulders, scattered so abundantly over many sections of the earth's surface, and many of the more extensive deposits of sand, gravel and clay, which are evidently the result of the resistless action of an overwhelming deluge. These deposits contain numerous animal and vegetable forms, the greater part of which belong to existing species, although occasionally extinct races are found.

VI. THE ALLUVIAL Deposits, including the deltas, or earthy deposits at the mouths of rivers, the beds of lakes which have become drained, the valleys of rivers subject to periodical inundations, the shores of oceans, seas, &c.

These also contain, in untold quantities, relics of animal and vegetable existence, but, with very few exceptions belonging to races now known. The gigantic mastodon has been found in these deposits.

We have been thus particular in noticing the fossils belonging to each system, because they serve as way-marks, by the aid of which, even the most unlettered may read the progress of the earth's history, from the period, when it was first set in motion, a vast mass of molten granite, devoid of vegetable or animal life, to the present time, when its green fields, and its innumerable hosts of living and moving beings, attest with myriad voices, the power and wisdom of the great Creator.

The whole of these formations do not exist in every part of the world; but wherever geological explorations have been made, it has been found that the same order is observed; and, that, although some one, or more, of these systems are absent, those which are present follow the arrangement we have described.

In the state of New York the secondary formation is wanting.* as well as the upper members of the transition system,* and in most parts of the state the tertiary system.

It will be seen, by the following table, that coal is not laid down among the formations of the state. All the formations of New York, except the alluvial and diluvial deposits, and the beds of tertiary, on the St. Lawrence, are below the coal measures; the Catskill group, which is the highest member of the transition system in New York, being the layer immediately beneath it.

It is true that there are layers of Anthracite, an inch or two in thickness, and extending over a few feet of surface, between the strata of rocks of an earlier era, in various parts of the state ; but coal does not exist in the state, in sufficient quantities to be of any practical value. This deficiency, however, is abundantly made up by the vast coal fields of Pennsylvania and Ohio, which, by means of the extended systems of internal improvement, are rendered so easily accessible.

The prevalence of limestone in nearly all the formations is worthy of notice, affording, as it does, the basis rock best adapted to yield the. materials for fertilizing the soil.

The table exhibits the geological formations of the state, accord.' ing to the arrangement adopted by the state geologists in their late survey.

III., IV. and V. of this arrangement are comprised under the general head of the Transition system, heretofore described.

* The existence of a small bed of oolite in Saratoga county, and the somewhat doubtful era of the red sandstone of Rockland county, can scarcely be considered as exceptions to this statement.

TABULAR VIEW OF THE ROCKS OF NEW YORK, ARRANGED IN

SYSTEMS, GROUPS AND FORMATIONS.

[ocr errors][merged small][ocr errors][ocr errors][merged small]

Systems.
Groups.

Formations.
I. Aluvial.

Aluvial.

Diluvial, including 11. Diluvial.

boulders, &c.

Clays and sands. III. Old Red sand Old Red sandstone, Conglomerate, stone system. or Catskill group.

Old Red sandstone.

Chemung sandstones and flagstones,
Erie group

Ludlowville shales.
Helderberg limestone,
Schoharie grit,

Brown argillaceous sandstone,
Helderberg series, Encrinal limestone,

Oriskany sandstone,
Green shaly limestone,
Pentamerus limestone.

Onondaga salt and gypseous rocks,
IV. New York tran-

Limestone and green shales,
sition system.
Ontario group,

Argillaceous iron ore,
Medina sandstone, soft, green and va-

riegated.
Grey sandstone and conglomerate,
Lorraine shales and roofing slates,
Utica slate,

Trenton limestone,
Champlain group, Birdseye limestone,

Chazy limestone,
Calciferous sandrock,
Potsdam sandstone.

Light green shales, sometimes dark and
V. Taghkanic, or Ta-

plumbaginous. conic system.

Grey and clouded limestone,

Brown sandstone. VI. Gneiss, or Primary

Gneiss, hornblende, and mica slate, system.

Talcose slate and steatite. VII. Superincumbent

Greenstone, trap and porphyry. rocks.

Granite, Hypersthene rock. VIII. Unstratified

Primary limestone, serpentine, rocks.

Magnetic iron ore. There are in the state two tracts of primary and unstratified rocks. The first is nearly circular in form, and occupies the counties of Essex, Warren and Hamilton, and portions of Saratoga, Fulton, Herkimer, Oneida, Lewis, Jefferson, St. Lawrence, Franklin and Clinton. The Black river forms its southwestern boundary, from Wilna, in Jefferson, to Remsen, in Oneida county.

The second is in the southeastern part of the state, of a somewhat triangular form, and comprises Putnam and Westchester, together with the larger part of New York, and part of Rockland, Orange and Dutchess counties.

These two sections together occupy nearly one third of the state.

They contain extensive and valuable mines of iron, lead and plumbago, both in the northeastern and southeastern portions of the state. Their surface is generally broken and elevated, towering up to the height of more than a mile above tide water, in the A lirondack group, and attaining a considerable, though less lofty altitude in the beetling cliffs which overlook the waters of the Hudson.

The soil is less arable and fertile than in the lands of the limestone formations, but is covered, except in the older counties, with a gigantic growth of oak, pine and hemlock timber.

The gneiss of this system furnishes a fine building material, and under the name of granite, is abundantly quarried for that purpose. The serpentine, primitive limestone, and steatite, are also largely quarried for the purposes of the arts.

These rocks abound in minerals of great interest to the mineralogist. Garnet, beryl, chrysoberyl, pyroxene, sphene, tourmaline, apatite, colophonite, scapolite, Labradorite, epidote, &c. &c.

Geologists differ in opinion, on the question, whether the Taghkanic, or Taconic system should be ranked with the Primary, or the Transition system. It is composed of brown sandstone, limestone and green shales, or slaty rocks. It contains some minerals, and furnishes a fine limestone for building, but has few, or no fossils. The soil which overlays this system is generally good, and often highly fertile. Its

range is quite extensive, although frequently of no great width. It comprises nearly the whole of the counties of Washington, Rensselaer and Columbia, part of Dutchess, Ulster, Greene, Albany and Saratoga, and trending westward occupies a narrow tract in Schenectady, Montgomery, Herkimer and Oneida, and expands more widely in Oswego and Jefferson counties.

We next come to the New York system, as it has been appropriately named, comprising, according to the table, four distinct groups. We commence with the lowest of these, the Champlain Group. The constituents of this group are various kinds of sandstone and limestone, slate, conglomerate, and a peculiar stone, compounded of Jime and sandstone, and hence called calciferous (or limebearing) sandrock.

Of these the Potsdam sandstone furnishes a beautiful and durable building material, and is also used in the manufacture of glass, and the preparation of sand paper. The Trenton and birdseye* limestones are used for the purposes of the arts. The Lorraine shales, and the Utica slate are employed for roofing, and to some extent for writing slates. The grey sandstone and conglomerate furnish stone suitable for grindstones.

The rocks of this group, and particularly the limestones and slates, abound in fossils of the earlier periods ; encrinites, trilobites and numerous others, unlike any of the crustaceous animals now in exist.

The soil, throughout the territory occupied by this group, is gener, ally good, and much of it is highly fertile, being constantly enriched by the decomposition of the limestone, slate and sandstone, which is

This limestone receives its name from the abundance of encrinites which it contains, which give it, when polished, an appearance somewhat resembling birdseye maple.

ence.

« ПретходнаНастави »