Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/712

Rh G70 AMERICA. between Cape Lisburne and Melville Peninsula ; and of South America, between Pernambuco and Point Aguja. The narrowest part is 28 miles, at the isthmus of Panama. The nearest approach to the Old World is at Behring Strait, which is 48 miles across, and shallow. On the east side the nearest point to the Old World is Cape St Eoque, which is opposite the projecting part of the African coast at Sierra Leone. Greenland is separated from the archipelago of Arctic America by a deep and for the most part broad sea, and seems naturally to belong to the European rather than the American area. ysical North America, with the general f orm of a triangle, natu- of Mexico, with the strip of low country on its eastern and western shores; 2. The plateau lying between the Eocky Mountains and the Pacific Ocean, a country with a mild and humid atmosphere as far north as the 55th parallel, but inhospitable and barren beyond this boundary ; 3. The great central valley of the Mississippi, rich and well wooded on the east side ; bare but not unfertile in the middle ; dry, sandy, and almost a desert on the west; 4. The eastern declivities of the Alleghany Mountains, a region of natural forests, and of mixed but rather poor soil; 5. The great northern plain beyond the 50th parallel, four-fifths of which is a bleak and bare waste, overspread with innumerable lakes, and resembling Siberia both in the physical char acter of its surface and the rigour of its climate. South America is a peninsula likewise of triangular form. Its greatest length from north to south is 4550 miles; its greatest breadth 3200 ; and it covers an area, as already men tioned, of 6,500,000 square English miles, about three-fourths of which lie between the tropics, and the other fourth in the temperate zone. From the configuration of its surface, this peninsula also may be divided into five physical regions 1 . The low country skirting the shores of the Pacific Ocean, from 50 to 150 miles in breadth, and 4000 in length. The two extremities of this territory are fertile, the middle a sandy desert. 2. The basin of the Orinoco, a country con sisting of extensive plains or steppes, called Llanos, either destitute of wood or merely dotted with trees, but covered with a very tall herbage during a part of the year. During the dry season the heat is intense here, and the parched soil opens into long fissures, in which lizards and serpents lie in a state of torpor. 3. The basin of the Amazon, a vast plain, embracing a surface of more than two millions of square miles, possessing a rich soil and a humid climate. It is covered almost everywhere with dense forests, which harbour innumerable tribes of wild animals, and are thinly inhabited by savages, who live by hunting and fishing. 4. The great southern plain, watered by the Plata and the mimerous streams descending from the eastern summits of the Cordilleras. Open steppes, which are here called Pampas, occupy the greater proportion of this region, which is dry, and in some parts barren, but in general is covered with a strong growth of weeds and tall grass, which feeds prodigious herds of horses and cattle, and affords shelter to a few wild animals. 5. The country of Brazil, eastward of the Parana and Uruguay, presenting alternate ridges and valleys, thickly covered with wood on the side next the Atlantic, and open ing into steppes or pastures in the interior. In our more particular description of the physical con formation, the geological structure, the mountains, rivers, and forests, and the climates of America, we shall first deal with the southern peninsula, as having the more strongly marked conditions. .America: The mountain areas of South America are, as a general [contains rule, those which have received the thickest accumulations of sedimentary matter, and this thickness is nearly pro portional to their height. During the periods of the formation of such deposits, these areas were to a great extent areas of subsidence, and since those beds which once formed the sea bottoms now constitute the highest peaks, these areas must have been subjected to subsequent upheaval. Vertical movements of this kind have occurred again and again, indicating that these areas are specially liable to disturbance, either from comparative weakness or from the greater comparative power of the moving forces. The history of the mountain chains is almost co extensive with that of the continent itself. In the sea the beds were deposited horizontally, or nearly so; and at certain intervals the deposition was arrested, in consequence of the beds being uplifted above the sea. Each successive sub mergence and emergence occupied a long period of time, during which the rocks were at one time faulted, folded, and metamorphosed, and at other times denuded both by the sea and by meteoric agents. As a general rule, the strike or line of direction of the strata ran approximately parallel to the trend of the shore line on the large scale, and the dip was at right angles to their direction. During each elevation the laud was uplifted in a broad band, the axis of which ran parallel to the shore of the sea in which the beds were formed. The axes of the principal folds and faults usually run parallel to the stratigraphical axis or strike. The principal ridges formed during the same period usually coincide in direction with the stratigraphical strike of the bed forming them. In the mountains of South America, and especially in the Andes, several of these groups of ridges, formed at different periods, combine to make up a single system of mountains. The high range of moun tains which extends from the most southern parts of South America, and runs approximately on the same meridian of 72 to the isthmus of Panama, forms the Andes. These consist of a vast rampart, having an average height of some 11,000 or 12,000 feet, and a width varying from 20 to 300 or 400 miles. In most places the chain rises to heights of several thousand feet, and upon this chain rest two or three principal ridges of mountains, enclosing lofty plains or valleys, separated one from another by mountain knots, which mark the spots where ridges belonging to different systems intersect. In one sense, the lofty plains of the Desaguadero, Quito, and others, are valleys, since they are encompassed by mountains; but in a certain sense they are plateaus, since they form the broad summit of the range or platform on which the bounding ridges them selves stand. Further details respecting the Andes are given under ANDES, and in the geological remarks of this article. Three branches or transverse chains proceed from the Traiis Andes, nearly at right angles to the direction of the prin- c .iain- cipal chain, and pass eastward across the continent, about the parallels of 18 of S. and 4 and 9 of N. latitude; thus forming the three natural areas of the Orinoco, Amazon, and La Plata river basins. The most northern of these is &quot; the Cordillera of the coast,&quot; which parts from the main trunk near the south extremity of the lake Maracaybo, reaches the sea at Puerto Cabello, and then passes eastward through Caraccas to the Gulf of Paria. Its length is about 700 miles, and its medium height from 4000 to 5000 feet; but the Silla de Caraccas, one of its summits, has an elevation of about 8G32 feet; and its western part, which is at some distance from the sea, contains the Sierra of Merida, 15.000 feet in height. The second transverse chain is connected with the Andes at the parallels of 3 and 4 north, and passing eastward, terminates in French Guiana, at no great distance from the mouth of the Amazon. It consists properly of a suc cession of chains nearly parallel to the coast, and is some times called the Cordillera of Parime, but is named by Humboldt the &quot; Cordillera of the Cataracts of the Orinoco,&quot; because this river, which flows amidst its ridges in the
 * ious. rally divides itself into five physical regions : 1 . The table-land