America, one of the four great recognized continental divisions of the globe. It is bounded X. by the Arctic ocean; E. by the Atlantic, which separates it from Europe and Africa; W. by the Pacific, which separates it from Asia; and S. by the Antarctic ocean. The longer axis of the American continent runs almost due north and south. Measured on its central line, lon. V0° W., its length from the arctic regions to Patagonia is about 10,500 ra. From east to west it presents two shorter axes, each of something more than 3.000 m.: one from Labrador to British Columbia, nearly in lat. 51° N.; the other between Capes St. Roque in Brazil and Parina in Peru, in about lat. 5° S. The American continent is separated into two not very unequal parts by the isthmus of Darien or Panama, less than 30 m. wide at its narrowest point. All north of this isthmus (taken in its more extended sense) is known as North America; all south of it as South America; the greater part of the isthmus itself being styled Central America. Estimates of the area of America vary considerably, some authorities making it a little more than 14,000,000 sq. m., others raising it, including Greenland, to more than 17,000,000 sq. m.. It may be set down at 15,000,000 sq. m., of which about 8,000,000 are in North America and 7,000,000 in South and Central America. The area is thus about four times that of Europe, nearly a third greater than that of Africa, and about six sevenths that of Asia. Geographically, America lies within the arctic, the northern and southern temperate, and the tropical zones.
About one seventh is unavailable for cultivation; the remainder is not surpassed in capacity to sustain life by any equal area of the globe. The population, including that of the islands, is about 85,000,000, not far from 1/15 that of the entire globe. - The geology of America is worthy of careful study. The oldest strata are a range of crystalline rocks which crop out from the St. Lawrence and the great lakes to the Arctic ocean; these consist chiefly of gneiss, granite, and trap. In North America this primary range is about 1,500 miles in length, with a breadth of 200, seldom reaching an elevation of 800 feet. It forms the western slope of the Andes and Rocky mountains. It extends over the eastern part of South America, hidden in the valley of the Amazon by alluvial deposits. In the central portion it dips under the Silurian strata, but is free from superincumbent deposits, showing that even in the Silurian age it formed dry land, and has suffered less disturbance than is manifested in most other formations. The Silurian rocks, consisting of sandstone, limestone, slate, shale, etc, are divided into several periods, and abound in fossil remains. The Silurian strata dip under the Devonian, which are in parts overlaid with conglomerate.
The latter forms the basis of the carboniferous strata which occupy large portions of Pennsylvania and the valley of the Mississippi. At the close of the carboniferous period the continent, nearly as large as at present, was scarcely elevated above the ocean. The great mountain ranges are of more recent origin. They were forced through the Silurian, Devonian, and carboniferous strata, dislocating and disturbing the hitherto horizontal layers. It is where the ancient rocks have been penetrated by masses of igneous rock that the precious metals are usually found. The volcanic fires have long since been extinct in the Appalachian range; but proofs of their former existence are found in the metamorphosed Silurian and carboniferous rocks of New York and Pennsylvania, which were long supposed to be primary granite. This igneous force still manifests itself in the volcanoes of the Andes and Cordilleras. Volcanoes still active, at greater or less intervals, mark the whole of the Andean range from Chili to Alaska, the most intense action within the historical period being in Ecuador, within two or three degrees of the equator. Here is the volcano of Cotopaxi, one of the two or three in constant eruption. - The animals native to America differ in many respects from those of the other hemisphere.
This is especially the case with the larger species. The elephant, hippopotamus, and rhinoceros of the eastern continent are in America represented by the much smaller tapir; the camel and dromedary by the llama and vicuna; the lion and tiger by the jaguar and panther. Of the carnivora the bear is the only species in America which exceeds its congeners in the other hemisphere, the grisly bear of California being the largest of its species. The American bison exceeds in size any others of its kindred, and the largest members of the deer family are natives of America. Among the carnivora native to America are the grisly, white, black, and brown bears; wolves and foxes of various species; the puma, jaguar, lynx, and wild cat. Of the marsupalia, there is every variety of the opossum; of the ro-dentia, the beaver, hare, marmot, mouse, porcupine, and squirrel; of the ruminantia, many varieties of deer, among which are the moose or elk and reindeer, the bison, musk ox, sheep, goat, and antelope. The quadrumana (apes) differ specifically from their congeners on the eastern continent; all of them have long tails, and many prehensile tails, which is a peculiarity of American species.
The horse and ox are introductions from Europe. Among the birds there are some species, as the wild turkey, toucan, and humming bird, peculiar to America. There are eagles, and others of the same family, vultures (among them the great condor of the Andes), ravens, crows, and an immense variety of the smaller birds, few of them being identical with those bearing the same names in Europe and Asia. Serpents are numerous. Among these are the great boa and the rattlesnake, peculiar to America. Alligators swarm in the tropical and subtropical rivers; turtles in the tropical seas. The lakes and streams are prolific in fish, among which the salmon have a wide range. The cod fisheries of the banks of Newfoundland are unequalled in productiveness. Some regions are infested with insects, especially mosquitoes. There is a native wild bee, but the common hive bee was introduced from Europe. - The vegetable productions of America are very numerous. The pine, oak, and maple are characteristic of the temperate regions; palms, of many species, of the tropical. In some parts of southern America the trees are so knotted together by twining plants as to render the forests impenetrable to wild animals, except through narrow paths which they have constructed.