And since the relief of the various continents determines the direction in which their rivers must flow, we find that the greatest slope of the land masses are towards the Arctic and Atlantic Oceans, which therefore receive by far the larger number of the rivers of the globe. And as the shorter slope of the New World is towards the Pacific, and of the Old World towards the Pacific and Indian Oceans, it follows that these two oceans do not receive as many rivers as the Arctic and Atlantic Oceans ; the average length of the principal streams, however, is nearly the same, but the drainage areas of the latter exceed those of the former. As the lengths, areas, and other particulars will be noticed further on in the third part of the work, we shall only give here the • names and localities of the principal rivers in each system.
The Arctic River System comprises the great Siberian rivers—Bolyma, Indigirka, Iana, Lena, Olenek, Yenesei, and Obi, draining the Asiatic Continent north of the Altai and Aldan Mountains ; the Petchora, Mezen, and Dvina, draining the northern part of European Russia ; and the Great Fish, Coppermine, and Mackenzie, draining the extreme northern part of North America.
The Atlantic River System comprises a large number of rivers that do not flow into it directly, but discharge their waters into some of the minor seas belonging to it. Thus the Baltic receives the Tornea, Dal, and other Swedish rivers, and the Neva, Dvina, Vistula, and Oder, draining western Russia and northern Germany. The Elbe, Weser, and Rhine, draining Western Germany, enter the North Sea ; the Seine, Loire, and Garonne drain France, and the former falls into the English Channel, the other two into the Bay of Biscay ; the Douro, Tagus, Gaudiana, and Gaudalquiver drain the Atlantic slope of the Spanish Peninsula. Of the principal British rivers, the Thames, Tweed, and Tay flow into the North Sea ; the Severn into the Bristol Channel ; and the Shannon into the Atlantic. The Ebro, Rhone, Po, and other rivers drain ing southern Europe, flow into the Mediterranean ; the Danube, Dneister, and Dnieper fall into the Black Sea, and the Don into the Sea of Azov. The Mediterranean also receives the largest African river, the Nile. The Senegal, Gambia, Niger or Quorra, Congo or Livingstone River, Coanza, Orange or Gariep, and other rivers draining the western slope of Africa, flow directly into the Atlantic.
We have already noticed the characteristic element of the relief of both North and South America, viz., the proximity of its main mountain chains to the Pacific coast. The Andes, in South America, lie so close to the western coast as to prevent the formation of any rivers of considerable length— nearly all flowing into the Pacific from Panama to Tierra del Fuego being mere mountain torrents. The chain of the Rocky Mountains, in North America, although preserving a general parallelism to the Pacific coast, do not lie so close to the shore, and thus allow of the formation of several considerable rivers. So that the main slope of both North and South America is towards the Atlantic, which receives the drainage of the whole continent east of the Rooky Mountains and the Andes, with the exception of a portion of British North America drained by the Mackenzie, Coppermine, and a few other rivers falling into the Arctic Ocean. Of the North American rivers, the only one of importance flowing directly into the Atlantic is the St. Lawrence ; the Saskatchewan, Churchill, Severn, and other rivers fall into Hudson Bay; and the Mississippi, Rio del Norte, Colorado, &c., enter the Gulf of Mexico.
The South American section of the Atlantic river system comprises several rivers of considerable length and area of drainage. Of these the Amazon, rising in the Andes
at a point not sixty miles from the Pacific, and draining the whole country thence to the Atlantic seaboard, is the largest river in the world. Besides the Amazon, the other principal rivers are the Magdalena, draining New Granada, and dis charging its waters into the Caribbean Sea ; the Orinocco, draining Venezuela ; the Essequibo, Surinam and Maroni, draining Guiana ; the Tocantins, Paranhyba, San Francisco, the various affluents of the Rio de la Plata, the Uruguay, Parana, Paraguay, Pilcomayo, Vermejo, Salado, the Colorado, Negro, Chupat and other smaller Patagonian streams, draining the territories east and south of the basin of the Amazon.
The Pacific River System is not so extensive as that of the Atlantic. For instance, on its eastern or American side, for the reasons already stated, it does not receive a single river approaching in size and importance to the Amazon or Mississippi. The longest is probably the Yukon, draining the Alaska Peninsula ; the only other considerable rivers are the Fraser, Columbia, Colorado (Gulf of California), and the Mexican river, Santiago. The South American section of the Pacific river system does not comprise a single river worth noticing, all being mere torrents. The principal moun tain chains of Eastern Asia do not approximate the coast so persistently as the Andes. Indeed, with the exception of the Aldan, Khinghan, and Manchooria coast range, the principal elevations traverse the slope to the Pacific in a generally west-to-east direction, thus allowing the flow of the drainage waters of the central Asiatic plateaux between them to the Pacific Ocean. The Amour or Sagalien, draining the southern and eastern slopes of the Altai and adjacent ranges, enters the Sea of Okhotsk. The Hwangho, Yang-tze-kiang, Chookiang or Canton River, drain the greater part of China; while the Indo-Chinese peninsula is drained by the Maykiang or Mekong, and the Meinam, falling into the China Sea and Gulf of Siam respectively. The Australian section of the Pacific river system presents the same limited area for develop ment as the South American,—the Australian Alps, Blue Mountains, Liverpool Range, and other northern elevations lying near and generally parallel to the coast. The Burdekin, and Mackenzie or Fitzroy, are the most considerable in length. The other numerous streams, though doubtless of great local importance, are not sufficiently large to merit special notice.
The Indian River System is naturally divided into three sections—viz., those of its limiting continents, the African on the west, the Asiatic on the north, and the Australian on the east. Of the east African rivers, the most considerable are the Zambesi and Limpopo; the Rovuma, Lufiji, Gananeh, and Shebeyli are as yet imperfectly known. The Asiatic section comprises some of the largest rivers on the globe, the principal being,—the Euphrates and Tigris, draining south western Asia, and entering the Persian Gulf; the Indus, Nerbudda, Krishna, Godavery, Mahanuddy, Ganges, and Brahmapootra, draining India ; and the Irrawady and Mar_ taban or Salween, draining Further India Of the Australian rivers flowing into the Indian Ocean, the Murray is the only one of considerable length. With its tributaries, the Darling, Lachlan, and Murrumbidgee, it drains nearly the whole of New South Wales and Victoria The Mitchell, Flinders, Roper, and other unimportant streams, fall into the Gulf of Carpentaria ; the Gascoigne, Murchison, Swan River, and other west Australian rivers, flow directly into the Indian Ocean.