PHYSICAL GEOGRAPHY. 



system is in Chili, where Aconcagua is 22,300 

 feet perhaps the highest volcano in the world ; 

 Chimborazo, in the equatorial Andes, is 21,424. 

 Altogether, the Andes present a most magnificent 

 spectacle to the voyager on the Pacific ; the snow 

 which permanently covers their lofty summits, 

 even under the burning sun of the equator, con- 

 trasting beautifully with the deep blue of the sky 

 beyond ; while occasionally another contrast is 

 exhibited in vast volumes of smoke and fire, 

 emitted from some of the numerous volcanoes 

 which stud the entire range. The Brazilian moun- 

 tains occupy a great breadth of country, but 

 seldom exceed an elevation of 6000 feet. 



The chief mountain-system of Central and 

 North America may be considered as a con- 

 tinuation of the Andes of the south, the whole 

 forming, as it were, the backbone of the New 

 World, and extending from Cape Horn to the 

 Arctic Ocean, a distance of nearly 10,000 miles. 

 The Cordilleras of Central America, or Mexican 

 Andes, as they are sometimes called, extend from 

 the Isthmus of Panama to the north of Mexico. 

 They spread themselves, for the most part, from 

 sea to sea. At Panama, where the range is 

 crossed by a railway, the elevation is under 300 

 feet ; but it increases towards the north. The 

 greater part of Mexico consists of magnificent 

 table-lands from 5000 to 9000 feet high, girt and 

 intersected by mountain-ranges, with peaks 

 several of them volcanic rising above 17,000 

 feet. Within the United States and British 

 America, the system is known by the general 

 name of the Rocky Mountains. It consists of 

 several parallel ranges running in the general 

 direction of the Pacific coast, and between that 

 coast and the head-waters of the streams that flow 

 into the Mississippi, and extending over a tract 

 loco miles broad from east to west. The eastern 

 range or axis, which forms the main water-shed 

 between the basin of the Mississippi and the 

 Pacific, rises in Fremont's Peak to 13,570, and 

 farther north, in Mount Brown, in British America, 

 to 16,000. The western or Maritime range attains, 

 in the Sierra Nevada of California, a height of 

 14,000; and in Mount St Elias, on the coast, in 

 lat. 61, a height of 17,800. The Alleghanies or 

 Appalachians, on the east side of the continent, 

 extend in parallel ranges, with valleys between, 

 from Alabama to Main j the highest summit of 

 the system is Mount Washington, in New Hamp- 

 shire, 6634 feet. 



In Oceania we have several minor groups and 

 ranges ; but the principal elevations are in 

 detached volcanic heights, the index-fingers, as it 

 were, to future mountain-systems. In Malaysia, 

 the highest known point is Mount Ophir, in 

 Sumatra, 13,850 feet. The east coast of Australia 

 is bordered by a range of no great elevation ; but 

 a backbone runs through the islands of New 

 Zealand, near the west coast, attaining a height ! 

 in some peaks of 10,000 to 12,000 feet. The 

 highest points in Polynesia are the active vol- 

 canoes of Mauna Kea and Mauna Loa, in Hawaii, 

 each about 14,000 feet. 



Such are the more prominent mountain-systems 

 as known to geography. Those who regard them 

 as mere ridges, rising on one side, and descending 

 as abruptly on the other, and at most intersected 

 by a few narrow passes, gorges, and ravines, form 

 a very erroneous conception of the physical con- 



tour of the globe ; for, so far from this being the 

 case, most of these systems are but the escarp- 

 ments or ramparts of elevated expanses known 

 as plateaux or table-lands, which form in some 

 instances the nucleus of continents, and the source 

 from which the rivers of such continents flow. 

 Thus, on examining the map of Asia, it will be 

 seen that all the rivers flow north, east, south, and 

 west from the central region, which in reality 

 forms a succession of remarkable plateaux. These 

 plateaux may be termed the Persian, which ranges 

 from 3000 to 6000 feet above the sea ; the Mon- 

 golian, at an elevation of from 8000 to 12,000 

 feet ; and that of Tibet, which reaches 1 7,000. 

 There are some masses of this kind in Europe, 

 but of comparatively small extent as the central 

 part of Spain, which is about 2200 feet in height ; 

 and the Swiss table-land, between 3000 and 4000 

 feet. The elevation of the great South-African 

 plateau seems to be highest towards the east side. 

 In South America, the city of Potosi, in Bolivia, 

 is situated in the elevated valley of Desaguadero, 

 at 13,600 feet above the sea-level ; and the plateau 

 on which Quito stands has an elevation of 9000 

 feet. One of the most noted table-lands is that of 

 Mexico, not less remarkable for its elevation than 

 for its extent. 



EARTHQUAKES AND VOLCANOES. 



These are rather agents than effects rather the 

 cause of geographical diversity than geographical 

 features themselves ; and in this respect belong 

 more properly to the province of geology : still, 

 as much of the superficial irregularity is the direct 

 result of their operations, and as it is often 

 impossible to separate cause from effect, it will 

 be necessary here to give them some further con- 

 sideration. 



Volcanoes affect the external features of the 

 earth chiefly by the matter they eject from its 

 interior. By the discharge of lava, loose stones, 

 scorias, fine dust or volcanic ash, and other 

 materials from these vents, multitudes of isolated 

 conical mountains have been formed ; valleys 

 have been filled up by the lava-streams, and 

 woods, villages, and cattle have been buried. 

 The immense volumes of steam generally dis- 

 charged during an eruption condense into rain, 

 and mixing with the ashes, form torrents of mud, 

 little less destructive than the rivers of lava. A 

 mud avalanche from Vesuvius overwhelmed the 

 ancient Roman cities of Pompeii and Herculaneum 

 in 79 A.D. As an example of the enormous 

 masses of material thus poured out from the 

 interior of the earth, we may cite Etna in Sicily. 

 It reaches a height of nearly 11,000 feet, with a 

 circumference of about ninety miles, and is com- 

 posed entirely of lava and ashes thrown out from 

 many different points around the central cone. 

 There are several hundreds of volcanoes now in 

 activity, and there is evidence that they once 

 existed in many places where they have long been 

 extinct. In Auvergne, in the centre of France, 

 there are lofty mountains of lava, and numerous 

 cones of loose cinders rise into conspicuous hills, 

 each with its crater, while congealed streams of 

 lava can be traced down the plateau into the 

 valleys. Yet all is cold and still, and has been so 

 for unknown ages. Sheets of lava are still con- 

 spicuous in the British Islands ; but they have 



