The land, therefore, occupies rather more than three tenths of the whole surface, and consequently the water covers nearly seven tenths; and as the total area is about 16,370,200 square leagues, if the preceding numbers be multiplied by this we shall obtain a near approximation to the quantity of land in each zone, as well as in the whole surface. The great preponderance of land in the northern hemisphere over that on the southern side of the equator cannot escape the most superficial observer. The former contains more than three times the quantity in the latter. The principal mass, particularly of the Old World, is situated on the north side of the equator; and, indeed, nearly two thirds of the whole is north of the tropic of Cancer, while scarcely one tenth lies south of that of Capricorn. No regularity can be observed in the arrangement of the solid parts of this surface; for the only appearance of symmetry is, that nearly all the great promontories are directed towards the south. The general direction of the land in the two continents is different. In the New World, it is from pole to pole; in the Old, including Africa, it is nearly parallel to the equator. The longest line that can be drawn is from the Cape of Good Hope to the north east part of Africa, which is about 2,960 leagues; while in the New World a line from the mouth of the River la Plate to Bhering's Strait is nearly 2,640 leagues: a resemblance, however, is perceptible between the Old and New Worlds, so far as the approaching seas almost divide each into two parts; the Isthmus of Suez joining Asia and Africa, and that of Panama con necting North and South America.

The surface of the land in both hemispheres is moulded into all possible varieties of declivity, from the horizontal plane to the perpendicular rock. In reference to the declivities themselves, they may be divided into two great classes, those which descend towards the exterior, and those which face the inte

rior; and which may be readily traced on the map by the directions of the rivers, which always rise in the most elevated parts, and descend to the lowest, A careful examination of the globe leads to the following division of the solid part of the Earth's surface.

1. Mountains, separated from each other by deep vallies, and presenting only plateaux and other small plains.

2. Extensive plains nearly covered with herbaceous vegetables; as steppes, savannas, ilanos, pampas, &c.

3. Sandy deserts; which are extensive in many parts of the globe.

4. Regions which are intersected by hills, and watered by rivers, in which rocks and sand bear but a small proportion to the whole surface. It is those which are best adapted for the residence, and most capable of supplying the wants of man.

Though it would be foreign to the present purpose to enter into any lengthened geological delineations, it would, perhaps, be equally inconsistent with the nature of this essay to omit the subject altogether. We shall, however, notice it as briefly as possible, referring to the Introduction to TIME'S TELESCOPE for 1818, which contains Outlines of Geology and Mineralogy.'

Nothing can be known respecting the central nucleus of the Earth, beyond a few shadowy conceptions, deduced by inference from what is more obvious to our senses, The outer crust is more exposed to view, and more subject to our examination. As far as human experience has yet proceeded, the materials of which this exterior is composed may also be arranged under four classes:

1. Those rocks which neither contain any animal or vegetable remains, nor are mixed with others in which they are enclosed. These are called pri mitive rocks, as having been formed before the existence of organized beings. Some of the most

abundant of this class are granite, gneiss, mica slate, and clay slate; with quartz, serpentine, granular limestone, &c. which are more sparingly distributed over the surface of the globe. These rocks are not only free from all kinds of organic remains, but generally lie beneath those in which they are found.

2. Such rocks as contain these remains have been formed since the existence of organized beings, and are denominated secondary rocks. The principal of these are greywacke, sandstone, limestone, gypsum, slate clay, and a certain kind of trap, all which are usually found resting upon the primitive rocks.

3. The preceding class of substances is again covered with gravel, sand, earth, and moss, which are termed alluvial formations; and constitute the general and outward coating of the continental and insular parts of the globe.

4. In addition to the preceding classes, certain places on the Earth's surface exhibit beds of lava, scoriæ, and other substances, ejected by means of subterranean fire: these are known by the name of volcanic formations. The metallic substances are found in too small and insulated portions to form any exceptions to this general classification of the exterior parts of the Earth.

To an inexperienced eye, the outer crust of the Earth presents a confused appearance of different substances, but, on a closer examination, a distinct arrangement may be traced. When the primary and secondary rocks are exposed to view together, it is usually found that the latter are incumbent on the former. The granite is almost invariably found under all the others, and yet it occupies the highest summits of the Earth's surface. The gneiss, which is only a stratified granite, lies next it, and this is succeeded by mica slate, which is followed by clay slate. The greywacke and other secondary rocks are then incumbent on these. When the primary rocks appear through the others, as they frequently

do in the higher parts of the globe, they often seem as if they stood on edge, and are seldom inclined to the horizon in a less angle than 45°. The secondary rocks have more the appearance of mechanical deposits, occupying a lower level than the former, and are placed more horizontally. Many phenomena in geology show, that the formation of rocks has been accompanied, nearly in all stages, by the process of waste, decay, and recomposition. The primary rocks being acted upon by air, water, and other agents, become disintegrated, and, being afterwards united by a cement, constitute the first species of the secondary class; while the debris of this class, when aggregated in the same manner, form the third. But the most interesting memorials of the past history of the globe are supplied by the myriads of organical remains which are contained in its exterior crust: these present traces of numerous orders of beings which appear to have succeeded each other at different times, and under different circumstances. Not only every age, but every region, climate, and element, seem to have been rendered tributary to some of the principal of these deposits of organic remains. As a specimen of these singular collections we may refer to Mount Bolca, in Italy, about 20 miles north-east of Verona. The surrounding districts bear evident marks of former volcanic action, as well as of having once been covered with the sea; though now wholly destitute of those active energies of nature, and at least 50 miles from the nearest shore. Plants, shells, land and marine animals, leaves, birds, and insects, are found deposited in this mountain, in almost every direction, sometimes in separate beds, and at others combined with productions obviously volcanic. What is still more extraordinary, most of the rivers, seas, and climates of the globe appear to have contributed to the stores of Bolca. The petrified fishes of Europe, Asia, Africa, and America, are found embedded in

large masses of rock on the side of this mountain, more than 1000 feet above the present level of the

sea.

Simple or detached mountains are not frequently met with except in volcanic districts, or those in which trap rock abounds. Mountains usually exist in extended bands, either in one central chain, with ramifications running off nearly at right angles to the main ridge, or of several ranges almost parallel to each other. In both these cases, they are often accompanied by subordinate chains, or inferior elevations; and the lengths of these ridges are commonly great in proportion to their breadths. These remarks may be readily exemplified by examining a good map of the Alps, the Andes, or other of the great ridges, in either hemisphere. The highest points of the main chains are usually about the middle, as Mont Blanc in the Alps, Chimborazo in the Andes, &c.; but the most elevated parts of those which branch from the main ridges, are at the points where they join the parent stem. Cols, or necks, are the lowest parts of these ranges, and those over which passages are generally effected. The Col de Brenner is the least elevated tract of the great Alpine range of Europe, and is about 4680 feet above the level of the sea. There are four other principal passes over this chain, which vary in height, from 6500 to 8000 feet. The lowest passage over the Pyrenees is about 3400 feet in elevation, and that of the Andes 12,000 feet. The summits of these chains sometimes constitute a series of peaks, and at others form extensive plains, denominated plateaux, like those in Mexico and central Asia. It has also been observed, that mountains, which surround lakes or seas, have their steepest sides towards the water. The form and arrangement of vallies must necessarily depend upon those of the mountains. Those which separate the main ridges are denominated principal or lateral vallies, and those which divide the branches are called