Apart from this, the structural characteris tics of the northern and southern continents have striking similarities, largely nullified for human use by the difference in location already mentioned. Each is a rather slender triangle with the vertex to the south. Each is joined to the next northern portion of the globe by a northwestern peninsula, the trend of the whole as far south as Bolivia being regularly south east from Bering Strait, just as that of the Asiatic coast to the Philippines is southwest; so that the north Pacific is a semicircular gulf. Each has to the north an immense archipelago and a vast island-ringed inland sea. Each has a framework of mountain and plain correspond ent in general, though with some important differences. In each, according to the law that the largest continental mountain chain is on the side of the largest ocean, there is a western range of immense height and mass, hundreds of miles broad and split into parallel sections sometimes connected by transverse spurs, stretching its entire length; quite recent in origin, and the volcanic action which raised it still energetic in parts. The Andes in South America thus correspond to the Rockies in North America; but the current idea that they form part of one continuous system is erro neous,— the Andes end in Venezuela, and the Rockies are of different genesis. Each con tinent has on the east a much shorter chain, much older and therefore much lower, from the erosion through geologic ages, and its volcanic fires long since spent; and as the highest points are worn down earliest, each is now rather a broad plateau with some elevations than a mountain wall. The Alleghany-Appalachian system in the United States corresponds to the Brazilian chain, which has no one distinctive title. Each continent has also a lateral range beginning in the north centre, turning first south and then east till it ends somewhat north of the eastern vertical chain, and cut in its course by the chief river running northeastward; and in each it is much the oldest part of the con tinent. The Laurentian chain in North Amer ica, crossed by the Saguenay, is a trivial counterpart to the great lateral ranges of Vene zuela and the Guianas, crossed by the mightier Orinoco.
Hydrography.— In each continent the two main ranges are connected by an almost unin terrupted plain many hundreds of miles broad, sloping southward to the ocean, and drained by three immense hydrographic systems with slight and sometimes non-existent divides : one running east and emptyingjust north of the eastern vertical range, the Great Lakes and the Saint Lawrence in the north corresponding in posi tion to the oceanic Amazon in the south; the second running south and discharging a little south of the same range, which thus forms one side of a huge triangle of which the rivers form the other two — the Mississippi and Missouri in North America comparable to the Parana and Paraguay which form the La Plata in South America; .a third running northeast and discharging into the northern ocean — the Saskatchewan, with the Red River of the North and Lakes Winnipeg and Manitoba, correspond ing to the Orinoco. Besides these, each has a river following the eastern side of a spur from the main range up to the northern ocean the Mackenzie in the Arctic regions and the if ag dalena in Colombia, though the former is the drainage of a great Arctic plain while the latter is confined between two ridges. With regard
to the watersheds, those of North America lie within a few miles of each other in Minnesota the headwaters of the Illinois in the Mississippi Basin lien within a half mile of the Chicago in the Saint Lawrence system, and the two have now been connected; the Amazon and Plata sys tems are only three miles apart, and those of the Amazon and Orinoco are actually connected by the so-called *river* Cassiquiare, a deep and broad natural channel about 150 miles long, running either way according to conditions of flooding seasons.
These, however, by no means exhaust the large drainage systems of North America, though in South America the closeness of the western chain to the ocean throws the whole burden on the east. The Pacific slope of the north is drained in the semi-Arctic regions by the immense Yukon, one of the great rivers of the globe. On the eastern side the great mass of the Arctic moors sends its drainage through a network of small streams, and lakes like Great Bear, Great Slave and Athabasca lakes, by the Mackenzie to the northern ocean, the Great Fish River taking the east Arctic waters. Farther south the Pacific drainage is by the Fraser into Puget Sound, and by the Columbia into the Pacific. The smaller Sacramento drains central California. The Great Basin be tween two arms of the Rockies sends its scanty and precarious rainfall into the Gulf of Cali fornia by the Colorado. East of the range in the south the Rio Grande has a long course and forms the boundary between the United States and Mexico; hut, despite its impressive name, is not of great volume. Between this and the Mississippi system several considerable streams drain the Texas region; the Colorado, Brazos, Sabine, etc. East of the Appalachian system a number of fair-sized and beautiful rivers flow to the Atlantic—the Saint John's, Penobscot and Kennebec, the Connecticut, Hudson, Delaware and Susquehanna, the Potomac, James, Cape Fear, Savannah, etc. In South America the large rivers of the eastern slope are the Sao Francisco and the Paranahyba of northern Brazil ; but between this range and the Amazon system a great plain is drained by the huge Tocantins, which, though emptying only at the mouth of the Amazon, is really a part of its basin.
The drainage systems of America have no parallel on the globe. The Amazon discharges more water into the sea than the eight largest rivers of Asia together, and the Mississippi more than all the streams of Europe large and small. The navigable waters of the Saint Law rence, Mississippi, Amazon, Orinoco and Plata systems together amount to over 100,000 miles in length. The five Great Lakes of America alone — excluding large bodies like Winnipeg, Manitoba, Champlain, Nicaraugua, Titicaca, etc., and the polar lakes — make up an area of 89,000 square miles, or considerably more than England and Scotland together.