AMERICA 389 pence, it rnns southwestward for 1,300 m. to northern Alabama, where it sinks to the level of the gulf slope. The Appalachian system con- sists of several parallel ridges, divided into two main lines. The eastern ridge is made up of the Green mountains of Vermont, the Highlands of New York, the South mountains of Pennsyl- vania, and the Blue Ridge of Virginia, North Carolina, and Georgia. The western ridge comprises the Adirondack, Catskill, Alleghany, and Cumberland ranges. Between these two ridges lies an almost continuous valley, with a breadth of from 15 to 60 miles, designated in various parts as the valleys of the Champlain, the Hudson, the Cumberland, the great valley of Virginia, and the valley of Tennessee. The general tendency of the Appalachian ridge is to a greater elevation as it runs southward; the White mountains of New Hampshire being merely an isolated projection from the cen- tral mass of the Green mountain range. Ex- cept in a few points this range rarely reaches an elevation of 4,000 ft. Mount Mansfield, the highest summit of the Green mountains, is 4,359 ft. ; Mount Marcy, the highest of the Adirondacks, 5,337; Mount Washington, the loftiest of the White mountains, 6,285, an ele- vation exceeded by many points near the southern extremity of the chain, the highest being Mitchell's peak, in North Carolina, 6,732 ft. The Appalachian chain is pierced at intervals by gaps which give passage for rivers, canals, and railways, linking the At- lantic slope with the valley of the Mississippi. The Appalachian ridge forms the watershed between the streams which flow into the At- lantic, with the exception of the St. Lawrence, and those which fall into the Mississippi, and thence into the gulf of Mexico. Several of these rivers are of considerable size, such as the Merrimack, Connecticut, Hudson, Dela- ware, Susquehanna, Potomac, and James. The Atlantic slope of North America, from the St. Lawrence to Florida, varies in width from 50 to 200 m., the mean elevation of its upper margin being from 150 to 1,000 ft. Through- out its whole extent it is without marked transverse ridges. The Rocky mountains and the Appalachians form two sides of a triangle, only the latter is broken off without reaching the point of junction. The third side of this triangle is formed by a broad low swell, without any defined crest, and rarely reaching the ele- vation of 1,500 ft. This swell, starting from the eastern base of the Rocky mountains in about lat. 50 N., runs eastward, separating the waters which fall into the Arctic ocean and Hudson bay from those which find their way into the gulf of Mexico. So gradual is the rise that we can define its summit only by noticing whether the general course of the streams is northward or southward. This low swell divides the continent of North Amer- ica east of the Rocky mountains into two nearly equal parts, the northern half of which is almost all incapable of cultivation. A little west of the head of Lake Superior this swell divides. One branch sweeps southeastward, the other northeastward, forming between them the basin of the lakes whose waters pass through the St. Lawrence into the Atlantic. So slight is the elevation of the southeastern watershed that a canal with no cutting of more than 100 feet would open an outlet for the waters of Lake Superior, Michigan, Huron, and Erie into the Mississippi, and thence to the gulf of Mexico, instead of into Ontario, and through the St. Lawrence into the northern Atlantic. The lake basin of North America is thus closely connected with that of the Missis- sippi. Between the eastern slope of the Rocky mountains and the western slope of the Ap- palachian range lies the basin or valley of the Mississippi. This is in some respects the most notable on the globe. Its area is about 1,250,000 sq. m., being only exceeded in extent by the val- ley of the Amazon. Latitude, elevation, and rainfall combine to render every part of it capa- ble of supporting a dense population. Next to it in this respect comes the basin of the Plata in South America. The most striking physical fea- ture of the basin of the Mississippi is its uni- form plain-like character. From the mouth of the river to its sources there is nothing like a mountain. At its junction with the Missouri it is but 381 ft. above the level of the sea; at its source in Lake Itasca it is 1,680 ft., the av- erage descent for the whole distance being less than eight inches to the mile. Its great afflu- ent, the Missouri, from Fort Benton to the junc- tion, falls only ten inches to the mile. The Ohio, from Pittsburgh to its mouth, falls less than five inches to the mile. The Red river falls a little more than a foot, the Arkansas not quite two feet to the mile. Except on its exterior rim, the basin drained by the Mississippi and its main branches falls less than six inches to the mile. The consequence is that there are no rapids to obstruct navigation, each river being navigable as far as the depth of water will permit. The entire navigable length of .these rivers is about 40,000 in. The hydrog- raphy of the remaining regions of North America is of little consequence, the Rio Grande being the only other river of any im- portance upon the eastern side. With the ex- ception of purely tropical productions, North America has nearly every species of grain, fruit, and vegetable. It has given to the eastern continent maize, which next to rice is the cereal which enters most largely into hu- man consumption, directly as an article of food, and indirectly as sustenance for animals. North America is rich in nearly every valuable mineral. Iron is so widely diffused, especially within the United States, that it may be con- sidered universal. Copper is found in many localities, the most abundant deposits being in the region of Lake Superior. Gold and silver have been found in every part of the Rocky mountain and Appalachian chains, the de- posits in Mexico, California, and the adjacent
