(3) A singular parallelism exists between the two sides of the Atlantic, the form of which is thus that of a great curving valley. (4) The European and North American shores of the Atlantic are both irregular-the South American side and opposite African coast are, on the other hand, both regular and almost unbroken. (5) The irregular southern coast of Europe has its counterpart in the broken southern coast of Asia, and each of them projects southward in three great peninsulas-the Spanish, Italian and Balkan peninsulas of Europe, answering to the Arabian, Indian and Indo-Chinese peninsulas of Asia. (6) North and South America are united by an isthmus, so are Africa and Eurasia. (7) An archipelago or island-cluster is found to lie to the south-east of all the great land. masses, e.g., the West Indies to the south-east of North America, the Falkland Islands to the south-east of South America, the Ægean Islands to the south-east of Europe, the East Indian Archipelago to the south-east of Asia, and the New Zealand group to the southeast of Australia. ...These and other resemblances which the student may readily find out by careful examination of the map or globe, are too general and constant to be merely accidental; they must, therefore, be due to the same producing causes. But the contrasts in form and structure are no less striking and important, and an attentive study and comparison of these similarities and contrasts will give the student a clear and definite conception of the configuration, relative position, and general structure of the great land-masses. Contrasts: The great land-masses exhibit numerous striking contrasts in form and structure. (1.) The greatest extension of the Old World is from east to west; that of the New World from north to south. (2.) Europe, Asia, and Australia extend most from east to west; Africa and the two Americas from north to south.1 (3.) The eastern and western continents stretch out towards the north and terminate in long lines of coast which approach each other so as almost to encircle the whole North Polar Sea; but, towards the south, the great land-masses terminate in promontories widely apart from each other. (4.) But the most striking and important contrast is in variety of contour and development of coast-line : Africa is simple in form-a trunk without limbs-a vast continent without any great peninsula or considerable inlet—“a land which seems to close itself against any influence from without." The coast-line, for a surface of 12,000,000 square miles, is only 16,000 miles, or 1 mile of coast for every 750 square miles of area a proportion less than that of any other continent. Asia is a vast body with few limbs-three great peninsulas on the south, one on the west, and another on the east, and a coast-line more than double that of Africa, and in spite of its great area (17,500,000 square miles) relatively much longer, the ratio being I unile of coast to every 500 square miles of area. Europe is the most richly articulated of all the continents, for not only is the mainland deeply indented in all parts, but its peninsulas and projections are themselves cut up by innumerable inlets, thus greatly extending the coast-line, which has a total length of 19,500 miles, or 1 mile of coast to every 190 square miles of area—a proportion exceed. ing that of any other continent. 1. Eurasia and North America attain their greatest dimensions from east to west along the same parallel (50 N.). 2. Guyot thus compares the three continents of the Old World in this respect:-" Africa is the most simple: it is a body without members, a tree with out branches. Asia is a mighty trunk, the numer ous members of which however make only a fifth of its mass. In Europe, the members overrule the principal body, the branches cover the trunk; the peninsulas form almost a third of its entire surface. Africa is closed to the ocean; Asia opens only its margins; Europe surrenders entirely to it, and is the most accessible of all the continents." North America is more deeply indented than South America, but there is not the same difference as between Europe and Africa. Still, the great inland seas and inlets extend the coast-line to a total length of 24,500 miles, or 1 mile of coast to every 350 square miles of area-a proportion of coast-line to surface about half that of Europe, but more than twice that of Africa. South America, like Africa, has a re..arkably regular and almost unbroken coastline. Its total length is 15,000 miles, equivalent to an average of 1 mile of coast to every 480 square miles of area, thus closely approximating Asia in this respect. Australia resembles Africa and South America in regularity of coast-line, which extends to only about 10,000 miles, or 1 mile of coast to every 300 square miles of area. ... These results are summarised in the following Table, showing the PROPORTION OF COAST-LINE TO AREA. Relief of the land: By the relief of the land we mean the alternate elevation and depression of its surface. The relief or vertical form of the land, like its contour or horizontal configuration, is infinitely varied, and this variation of form is due to the slow but unceasing action through untold ages of two opposing forces, that of upheaval, by which large areas have been raised, and that of erosion, by which the raised land is "planed" down again. The gradual elevation or upheaval of parts of the earth's crust, and the accompanying subsidence of other parts, is evidently the result of the slow cooling and consequent contraction of the heated interior; the outer crust cooling so much more rapidly, and being too rigid to contract evenly, becomes in consequence crumpled or corrugated. The main corrugations are few and simple, consisting, in fact, of two great elevations and two vast depressions, which form the two main land-masses and the two chief oceanic basins, respectively. The ridges of the main corrugations form what is called the continental axes or main lines of upheaval, while the bottoms or troughs form the regions of greatest subsidence, and, consequently, covered by the waters of the sea. Volcanoes and Earthquakes often effect great changes very suddenly, but the forces of erosion, and the unequal strains which cause what are called the secular movements of the earth's crust, act slowly, and the present land surfacenine-tenths of which has been formed from the debris of other continents-in material and structure gives ample proof that these forces must have been in incessant action during long periods of time. And although the land-forms which come under our immediate notice may seem to us to undergo no perceptible change, year after year, yet it is none the less true that, slowly but surely, they do change-in fact, no portion of the earth's crust is in a state of absolute rest-it is always rising or sinking somewhere, and while the land is being eaten away bit by bit, its disintegrated particles—the materials of future continents-are carried down by streams and rivers and deposited at the bottom of the sea. Forms of Relief: The infinite variations of form in the relief of the land may, however, be arranged in three great natural divisions, according to the area and degree of elevation, namely, 1. Elevations of large areas slightly above the level of the sea. 2. Elevation of large areas moderately above the level of the sea. 3. Elevation of comparatively small areas considerably above sea-level. 1 These divisions correspond to 1. Plains or Lowlands. 2. Plateaux or Highlands. 3 Mountains, either in chains or groups, or as isolated elevations. These three great forms of relief generally follow in natural sequence from the sea-board, and in some places merge indefinitely into each other; at other places, the transition from the low plain to the broad upland or lofty mountain is abrupt and sudden. Viewed in this three-fold aspect, the continents present some remarkable analogies and contrasts, which Guyot thus summarizes : (1) All the continents rise gradually from the coast towards the interior to the line of greatest elevation. (2) In all the continents this line of greatest elevation is not placed at the centre, but on one of the sides, at an unequal distance from the shores of the seas. From this result two slopes, unequal in length and inclination, analogous to what, in mountains, is called the slope and the counter-slope. (3) In the Old World the long slopes are turned towards the north, and the short slopes towards the south. In the New World, on the contrary, the long slopes are turned towards the east, and the short slopes towards the west. (4) In the Old World the northern slope is four or five times as large as the southern slope; while in the New World the eastern slope varies from twice (in North America) to over 25 times (in South America) the western slope. (s) But although, in the Old World, the principal slope is towards the north, the general elevation gradually decreases from east to west; and conversely, in the New World, while the main slope is from west to east, the general elevation of the land increases from north to south. In other words, the land, as a whole, rises from the Poles towards the Tropics-the highest elevation in the Old World being under the Tropic of Cancer, and in the New World under the Tropic of Capricorn.❜ Relief and Area: Viewed in the relation of relief to mass of area, we may say that the Eastern Continent is a world of great tablelands and lofty mountains, while the Western Continent is a world of vast plains. By this we do not imply that the Old World contains no plains or the New World no mountains, but that the latter predominate in the Old and the former in the New World, and this fact illustrates still more clearly the general Law of Relief: All the long and gentle slopes descend towards he 1. See further Guyot's "Earth and Man." 2. "The effect of this law is to temper the burning heat of these regions, and to give them a variety of luate which otherwise would not exist. If this order were reversed, and the elevation of the land went on increasing towards the north, the most civilized half of the globe, at the present day. would be a frozen and uninhabitable desert." B Atlantic and the Polar Seas, while all the short and rapid slopes are directed towards the Pacific and Indian Oceans.1 Absolute elevation: Some parts of the land are actually below the level of the sea; other portions rise up into the atmosphere many thousands of feet. The great depression of the Jordan and the Dead Sea, and the dyke-protected lowlands of Holland, are actually lower than the surface of the sea; while the Andes and Himalayas rise several miles above the sea-level. But, compared to the mass of the globe, the highest of these elevations is insignificant in the extreme, and would be proportionately represented by a minute grain of sand, one-twelfth of an inch in diameter, placed on a globe 30 feet in circumference! Mean Elevation: If the inequalities of the land were smoothed down to a uniform level, its surface would be about 2,000 feet above the level of the sea, which is thus the average mean elevation of the land of the globe. The average elevation of the continents is estimated at:-Europe, 958 ft.; Asia, 2,884 ft.; Africa, 1,975 ft.; North America, 1,954 ft.; South America, 1,764 ft.; and Australia, 1,189 ft.; an average of 2,120 ft. 2 Influence of Elevation: The character of a country depends largely on its position and contour; but, above all, on its degree of elevation and variations of relief. "A few hundred feet of height, which are as nothing to the mass of the globe, change entirely the aspect and the character of a country. The luxuriant vineyards which border the banks of the Swiss lakes, at 1,000 feet, or even at 500 feet, above their present level, could not be cultivated with success, hence the tillage and the occupations of the inhabitants in these more elevated situations take quite a different character. A thousand feet higher still, and the rigour of the climate no longer permits fruit trees to flourish; the pastures are the only wealth of the mountaineer, for whom all other industry ceases to be a resource. Higher still, vegetation disappears, and with it the animals, and soon, instead of the smiling pictures of the plains and the lower valleys, succeed the spectacle of the majestic but desolated regions of eternal ice and snow, where the sound and animation of life give place to a death-like stillness." Contour of the Ocean: The contour or configuration of the great oceanic basins is determined by that of the continents by which they are surrounded. The shore-line of an ocean is thus identical with the coast-line of a continent, both denoting the "line of contact" between the sea and the land. Contrasts: The oceans, like the continents, display numerous analogies and contrasts in form and dimensions; but, unlike the continents, the contrasts between the five oceans are much more striking than the similarities. 1. With regard to size, the oceans differ considerably, the Pacific having an area of 71,000,000 square miles, the Atlantic 34,000,000, and the Indian Ocean 28,000,000. That is, the Pacific embraces nearly one-half of the total water area of the globe, the Atlantic one-fourth, and the Indian Ocean one-fifth. The Atlantic and the Pacific extend equally from north and south, i.e., from the Arctic to the Antarctic Circles, a distance of 9,000 miles; but they differ in width, the Pacific stretching east and west under the equator for 12,000 miles, while the Atlantic has an average width of only 3,600 miles. The Indian Ocean has a width of about 6,300 miles. The Arctic and Antarctic Regions are, of course, 1. Guyot. 2 The highest absolute e'evations range from 7,000 f. in Australia to 29,000 ft. in Asia; but how little, even the most stupendous mountain chains increase the general elevation of a continent is apparent from Humboldt's calculation that, if the Alps were spread e plly over Europe its mean loy would only be sl by 21 feet, while the vast range of the Himalayas and connected ranges would, if similarly distributed, raise the general level of Asia only 150 feet. The diference between 21 an 150 feet and the mean elevation of Europe and Asia, 958 and 2,884 feet respectively, clearly shows the far greater importance and extent of the intermediate or central rm of lin! relief, that is, the elevations in mass, which we term plateaux or tablelands. equal in extent, but the land so encroaches upon the North Polar Sea as to reduce it to a probable area of 4,000,000 square miles, or th. part of the total sea-area. The relative land and water area of the southern circumpolar region is unknown. 2. With regard to the direction of their greatest extension: The three great oceans differ in that the Pacific extends most in an east-and-west, and the Atlantic in a north-and-south direction, while the Indian Ocean extends almost equally both ways. The great continental land-masses broaden towards the north and taper towards the south: the three great oceans,, on the contrary, open out widely towards the south and get narrower towards the north. 3. Each ocean has a form peculiar to itself, thus the Pacific is an oval, the Indian Ocean a triangle with its apex to the north, while the Atlantic is a broad double curve with parallel sides. 4. The oceans differ also in variety of contour, and this is the most important difference of all. The Atlantic sends the greatest number of indentations into the land, and has, consequently, the greatest development of coast-line, both absolutely and relatively; its shores are, in fact, so extended as to exceed those of all the other oceans taken together. Its great inland seas-the Mediterranean, Black and Baltic Seas on the east, and Hudson Bay, the Gulf of Mexico and the Caribbean Sea on the west, with their numerous gulfs and inlets, combine to make by far the most accessible, and therefore, commercially, the most important of the great oceans. The Pacific has no inland seas connected with its waters. Its eastern shores exhibit no indentations of the land of any importance, except the Gulf of California. But its western side displays a feature peculiarly characteristic of this ocean, in the range of seas and gulfs which stretch along the coasts of Asia between the mainland and the outlying groups of islands. The Indian Ocean has two comparatively small indentations, namely, the Red Sea and the Persian Gulf, but the rest of its 'limbs' are neither inland nor land-locked seas; the openings of Aden, Cutch, Cambay, and Martaban are simply gulfs, while the Ganges and Brahmaputra enter a true bay, that of Bengal. Summarizing these distinctive characteristics of the three great oceans, we may say that The Atlantic is the ocean of inland seas. The Pacific is the ocean of land-locked seas. The Indian is the ocean of great gulfs. The three oceans differ also in the number, position, and extent of their islands. The Pacific is by far the richest in islands, both continental and oceanic. The Atlantic is rich in continental islands, but has only a few oceanic islands. Oceanic Inter-communication: The oceans are connected with each other by (1) Channels and Straits: The Arctic Ocean communicates with the Atlantic by three great channels, and with the Pacific by a narrow strait. The Pacific and Indian Oceans are connected by a multitude of strits and channels between the islands of the East Indian Archipelago. Vessels enter the Pacific from the Atlantic by rounding Cape Horn or by passing through the Strait of Magellan. (2) South of 35 S. lat., the boundary between the Atlantic and the Indian Ocean is a conventional line, as is also the boundary between the Indian Ocean and the Pacife, 1. A glance at the map will show how thickly studde the Pacific is with oceanic islands and island-groups, both coral and volcanic, while the Jong chain of continental islands and archipelagoes th.. skirts its western shores has no parallel else. where. Among the conti ental islands of the At. lantic, the British Isles and the West Indies stand pre-eminent; its oceanic islands are limited to a few isolated spots, such as St. Helen, Bermuda, etc. The Indian Ocean has only two considerable continental islands-Madagascar, off Eastern Africa, and Ceylon, off Southern India; Mauritius, Réunion, Diego Garcia, and a few others, represent the oceanic group. |