Page:Encyclopædia Britannica, Ninth Edition, v. 1.djvu/716

Rh 674 AMERICA [N. AND S. AMERICA. to 9000 feet in height, and from 100 to 300 miles in breadth. Across this plain, close to the 1 9th parallel, six vol- Icauoes. canoes are distributed in a line running east and west, as if a vast rent, extending from the Atlantic to the Pacific, had opened a passage for the internal fires of the globe at this spot. Two of those on the east side of the continent, with a group of four or five other cones lying between Jalapa and Cordoba, have an elevation exceeding 17,000 feet, and are the only mountains in New Spain that rise to the region of perpetual snow, which commences here at 15,000 feet above the level of the sea. Jorullo, the lowest of the six volcanoes, rose suddenly in the middle of a plain, in September 1759, after fearful concussions of the ground, which continued for fifty or sixty days. Near the tropic the Mexican Cordillera divides into three parts. One runs parallel to the eastern coast at the distance of thirty or forty leagues, and terminates in New Leon. Another proceeds in a north-western direction, and sinks gradually as it approaches the Calif ornian Gulf in Sonora. The third or central Cordillera traverses Durango and New Mexico, divides the sources of the Rio Gila from the Rio Bravo del Norte, and dies out before reaching the Rocky Mountains. In a recent scientific survey of the Rocky Mountains, conducted by Professor Hayden of Yale College, a higher peak has been discovered than was formerly known. Holy Cross mountain was computed to reach 17,000 feet above the sea, or 2000 feet higher than Big Horn (15,000), which has hitherto been supposed to be the highest of the chain. The greatest altitudes on the North American continent are now said to be the following St Elias (17,850) in Alaska, Popocatepetl (17,884) in Mexico, Orizaba (17,337) in Mexico, Holy Cross (17,000), Rocky Mountains, Big Horn (15,000), and Mount Lincoln (14,300), both in the same chain. The Great Salt Lake of Utah is in 41 N. and 112 W., and has intensely salt waters. It is nearly 300 miles in circumference, and its shores, for a breadth of several miles, are covered with an incrustation of very pure salt. It lies in a basin, which measures about 500 miles each way, and contains much fertile soil. If we run a line westward across the continent of North America at the latitude of Delaware Bay (38)&amp;gt; the geolo gical formations present themselves in the following order : 1. Tertiary and Cretaceous strata on the shores of the Atlantic ;. 2. Gneiss underlying these strata, and present ing itself &quot;on the eastern slope of the Alleghany or Appala chian mountains, but covered in parts by New Red Sand stone ; 3. Palaeozoic rocks, consisting of Silurian, Devonian, and Carboniferous strata, curiously bent into parallel fold ings, with synclinal and anticlinal axes, the crests of the latter forming the ridges of the Alleghany Mountains, which in this region rise to the height of 2500 feet. Upon these Palaeozoic rocks rest three great coal-fields the Appala chian, that of Illinois, and that of Michigan, covering a large portion of the space between the Alleghanies and the Mississippi, and embracing collectively an area equal to the surface of Great Britain. From the Mississippi west ward to Utah the Palseozoic rocks occur in great folds, be tween which are extensive areas of Triassic, Oolitic, Creta ceous, and Tertiary beds. In California the rocks are chiefly metamorphosed secondary strata on which lie patches of Tertiary sediments. In British America there is an enormous development of the Laurentian and Huronian rocks, which are the oldest yet discovered, and occupy most of the country immediately north of the large lakes. Newfoundland and the neighbouring British territories con sist of Pre-Silurian, Silurian, Devonian, Carboniferous (which includes coal-fields of considerable extent), and Triassic rocks. The area north of about 40 N. is also covered and strewed with glacial drift and boulders. The Ozark Mountains resemble the Alleghanies in their mineral structure, containing the same rocks from the granite to the carboniferous, and probably upwards to the chalk. In no single circumstance is the superiority of America N. and S over the old world so conspicuous, as in the number and America magnitude of its navigable rivers. The Amazon alone dis- Rivers - charges a greater quantity of water than the eight prin cipal rivers of Asia, the Yenesei, Indus, Ganges, Oby, Lena, Amoor, and the Hoang-ho and Yang-tse of China. The Mississippi, with its branches, affords a greater amount of inland navigation than all the streams, great and small, which irrigate Europe; and the Plata, in this respect, may probably claim a superiority over the collective water of Africa. But the American rivers not only surpass those of the Old World in length and volume of water, they are so placed as to penetrate everywhere to the heart of the continent. By the Amazon, a person living at the eastern foot of the Andes, 2000 miles of direct distance from the Atlantic, may convey himself or his property to the shores of that sea in forty-five days, almost without effort, by confiding his bark to the gliding current. If he wish to return, he has but to spread his sails to the eastern breeze, which blows perennially against the stream. The navigation is not interrupted by a single cataract or rapid, from the Atlantic to Jaen, in west longitude 78 where the surface of the stream is only 1240 feet above the level of its estuary at Para. The part of North America most remote from the sea is the great interior plain extending from the Rocky Mountains to the Alle ghanies and the lakes, between the parallels of 40 and 50; but the Mississippi, Missouri, and St Lawrence, with their branches, are wonderfully ramified over this region, and the Missouri is in some degree navigable to the centre of the continent. It is only necessary to cast the eye over a map of South America, to see that all the most sequestered parts of the interior are visited by branches of the Plata and the Amazon. These streams, having their courses in general remarkably level, and seldom interrupted by cataracts, may be con sidered without a figure of speech, as a vast system of natural canals, terminating in two main trunks, which communicate with the ocean at the equator and the 35th degree of south latitude. Since the invention of steam navigation, rivers are, in the truest sense of the term, Nature s highways, especially for infant communities, where the people are too poor, and live too widely dis persed, to bear the expense of constructing roads. There is little risk in predicting, that in two or three centuries the Mississippi, the Amazon, and the Plata, will be the scenes of an active inland commerce, far surpassing in magnitude anything at present known on the surf ace &quot; of the globe. The Mississippi is navigable for boats from the sea to the falls of its principal branch the Missouri, 1700 miles from the Mexican Gulf in a direct line, or 3900 by the stream; and the whole amount of boat navigation afforded by the system of rivers, of which the Mississippi is the main trunk, has been estimated as equal to 40,000 miles in length, spread over a surface of 1,350,000 square miles. This, however, is perhaps an exaggeration; a navigable length of 35,000 miles may be nearer the truth. The Amazon contains many islands, is broad, and in the upper part so deep, that on one occasion Condamine found no bottom with a line G20 feet long. At its mouth, two days before and after the full moon, the phenomenon called a Bore occurs in a very formidable shape. It is a high upright wave of water rushing from the sea, which no small vessel can encounter without certain destruction. The estuaries of all these great American rivers open to the eastward; and thus Providence seems to have plainly