PART III.

PHYSICAL GEOGRAPHY.

87. PHYSICAL geography is a description of the general features of the earth's surface, the organized beings placed upon it, and the operations of the atmosphere by which it is universally surrounded.

88. Definitions.-The terrestrial surface comprises an area of about 196,806,658 square miles, and consists of two natural divisions,-land and water. An extensive continuous mass of land is termed a continent, (derived from a Latin word, signifying "connexion," or "holding together.") A small portion of land surrounded by water is called an island; but as the continents are encircled by the same element, there is no real distinction between them and islands, except that of size. A projecting tract of land of some extent, nearly surrounded by water, is denominated a peninsula, (almost an island,) as the peninsulas of Scandinavia and Spain, Yucatan and Jutland. Comparatively small points of land, protruding into the sea, are styled capes and headlands, or promontories, -as the northern and southern extremities of Europe, North Cape and Cape Tarifa, Beachy Head and Flamborough Head. A narrow neck of land connecting two great masses, is termed an isthmus,—as the Isthmus of Suez, joining Asia and Africa; of Panama, joining North and South America; and of Corinth, connecting the Morea with northern Greece, where the Greeks celebrated one of their national festivals, called on that account the Isthmian Games. An extensive uninterrupted expanse of water is called an ocean, -as the Atlantic Ocean, which separates Europe and Africa from America; the Pacific Ocean, between America and Asia. A considerable

branch of an ocean is denominated a sea,-of which the Mediterranean, Baltic, and White Seas, are familiar examples. A bend of the sea into the land forms a bay or gulf,-as the Bay of Biscay, the Gulf of narrow connecting piece of sea, a strait or Strait of Gibraltar, the English Channel. water constitute lakes.

1. THE LAND.

Bothnia; and a channel,-as the Inland sheets of

89. Extent and distribution.-The extent of the solid surface of the globe cannot be accurately ascertained, owing to its north and south polar regions not having been explored; but it is vastly inferior to the area occupied by the waters. It may be approximately stated as amounting to rather more than one-fourth of the entire superficies, distributed through the different latitudinal zones as follows:

The unequal distribution of the land is apparent from the above Table, by far the greater portion being in the northern hemisphere. If we suppose the whole space included in each zone represented by 1, the proportionate amount of land will stand thus:

Let the quantity of land, therefore, in the northern hemisphere be represented by 16, and the quantity in the southern will be scarcely equal to 5. The result is similar, if we consider the globe to be divided, not in the line of the equator, but in the direction of the meridian of 20° W., the one usually selected for the projection of maps of the world in eastern and western hemispheres. The western hemisphere will contain the least land, and the eastern comprise a much larger portion. But the unequal distribution of the land is most strikingly exhibited by adopting another

division of the surface. It is possible so to constitute it into hemispheres, that one shall embrace such a large proportion of the solid surface, and the other of the fluid, as to be appropriately styled terrestrial and oceanic hemispheres. Thus take London and its antipodes, near Antipodes Island, to the south-east of New Zealand, for the respective centres, and the hemisphere which has London for its centre will contain nearly all the land, the other being almost entirely sea. This may be readily exhibited by adjusting an artificial globe, so as to have New Zealand at the highest or zenith point. Above the wooden horizon there will be seen some narrow lines of coast, with islands in the midst of an immense ocean, the great continental masses being below it.

90. Continents.-There are two continents, the Eastern or the Old World, including Europe, Asia, and Africa; and the Western or New World, comprising North and South America. The denominational phrases refer to their relative position, east and west of the meridian of the Ferro Isles, from which longitude was formerly reckoned; and to the modern discovery of America to Europeans. The extreme limits of the eastern continent are-Cape Taimura, otherwise called Severo Vostochni-noss, or North-East Cape, in Siberia, lat. 78° 16' N.; Cape Lagullus, east of the Cape of Good Hope, lat. 34° 50' s.; Cape Verde, the most westerly point of Africa, long. 17° 33' w.; and Tschuktschi-noss, or East Cape, the most easterly point of Asia, long. 190° E. Its area is computed at about 33,000,000 of square miles. Its maritime coast-line has a linear extent of upwards of 60,000 miles. The greatest elevation of the surface is 28,178 feet above the level of the sea, attained by one of the Himalaya mountains: the greatest depression is at the south extremity of the valley of the Jordan, which is upwards of 1300 feet below the level of the Mediterranean. The extreme limits of the western continent are-] -Point Barrow, in the Arctic Ocean, lat. 72° N.; Strait of Magellan, lat. 54° s.; Cape St. Augustin, the most easterly projection of South America, in Brazil, long. 35° w.; and Cape Prince of Wales, the most westerly projection of North America, long. 168° w. Its area is estimated at about 14,000,000 of square miles. The maritime coast-line has an extent of 32,000 miles. The greatest

But

elevation of the surface above the sea level at present known is 23,200 feet, attained by the volcano of Aconcagua, one of the Chilian Andes. Comparing the two continents together, the following general features of similarity and discordance are presented:-1. Their southern extremities correspond in shape, offering a rude resemblance to an inverted pyramid. Compare Africa and South America. 2. Both attain their greatest breadth about the parallel of 50° N.; and are cut off by the ocean on the north with no great difference as to their latitudinal limits. 3. Each has a large portion of its area nearly detached; Africa being appended to Asia by an isthmus about seventy-five miles broad, and North and South America being joined by an isthmus which narrows to little more than eighteen miles. 4. The peninsulas of both continents follow a southerly direction, as Scandinavia, Spain, Italy, Greece, Africa, Arabia, India, Malacca, Cambodia, Korea, and Kamschatka in the one, and South America, California, Florida, and Alaska in the other. each continent has one important exception to this rule, the peninsula of Yucatan, in central America, and of Jutland, in Europe, projecting towards the north. 5. Both have a remarkable local development of island formations, of fiords or crevices in the shore, and a deeply indented coast: examples, the West Indies and the Asiatic Archipelago; the Norwegian and Patagonian Firths; the west coast of Europe and the east coast of North America. The great point of difference between the continents is in the prevailing direction of the land, which follows the course of the parallels in the eastern, and of the meridians in the western. The coast of the Old World is also much more broken by the ocean than that of the New, Europe and Asia being deeply indented by it, and America scarcely at all, except the northeastern sea-board. In this respect, Europe possesses more maritime advantages than any other of the great divisions of the globe, as appears from the annexed comparison of their areas and extent of coast:

Hence, while Europe has only 229 square miles of surface

to one mile of coast, America has 437; Asia 500; and Africa 741.

91. Islands.-Islands differ vastly in size, from miniature continents, with systems of mountains, rivers, and lakes, to mere banks of sand or points of rock just raised above the surface of the waves. Australia, the largest island, is 2,400 miles from east to west, by 1,700 miles from north to south. Rockal, in the Atlantic, is simply a block of granite, 100 yards in circumference, by 70 feet in height, remarkable for its solitariness, being 290 miles away from the mainland of Scotland, 260 from the north coast of Ireland, and 180 from any other land; an example of isolation in a spot so small probably without a parallel on the face of the globe. Semi-islands are portions of land insulated by the advancing tide, and connected with an adjoining shore at low water. St. Michael's Mount, in the bay opposite the town of Marazion, in Cornwall, comprehending about seventy acres of surface, is connected with the mainland by the sands when the tide is out, but is insulated when it is high water; and Holy Island, the Lindisfarne of the Saxons, off the coast of Northumberland, is another example. Islands occur under various conditions, in chains, clusters, archipelagos. or singly. 1. Continental islands, or those which are adjacent to some main shore, have frequently the elongated arrangement; as the Aleutian Isles, which form a chain between North America and Asia, the Kurile and Japan Isles, stretching along the eastern Asiatic coast. 2. Oceanic islands, or those which occur at a distance from continents, often form clusters, one or two principal members being sometimes centrally situated with reference to others of smaller size, as the Marquesas and Society groups. 3. Islands contiguous to each other without definite arrangement, whether continental or oceanic, are usually classed as an archipelago; a term of doubtful origin, but clearly including the word pelagus, the " sea.' Where the term occurs without a distinguishing prefix, those islands are meant which lie between the shores of Greece and Asia Minor. The principal archipelagos are the Caribbean, or Antilles, in the West Indies; the Chagos, Maldive, and Laccadive, in the Indian ocean; the Dangerous, Louisiade, and Great Cyclades, in the Pacific Ocean. 4. Single islands remote from any shore are of rare occurrence. St. Helena, 1,800 miles from the coast of Brazil, 1,200 from the coast of Africa,