Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/26

16 altitude of Aconcagua in Cliili, which is generally considered to be the highest peak in America. Judging from these estimates, we may regard the bulk of the Andes as somewhere about that of a mass 4400 miles long, 100 miles wide, and 13,000 feet high, which is equivalent to 5,349,801,600,000,000 cubic feet. On this basis we find that the Mississippi would carry down an equivalent mass of matter in 785,000 years. The rate of denudation in certain river basins varies from one foot in 700 years, to one foot in 12,000 years. Assuming that similar rates would apply to the Andes, they would be denuded away in from 9 to 156 million years. In all probability, much less than 9 million years would suffice. On the other hand, the Andes would be swept away in 135,000 years, supposing the denuding powers of the globe were concentrated on them alone. From the above data, and assuming the average specific gravity of the matter forming the Andes to be 2 5, the weight of the portion above the sea may be estimated at 368,951,834,482,750 tons, giving an average of about 1000 tons on each square foot at the level of the sea. Under Aconcagua the pressure would be about 1780 tons per square foot at the same level, provided, of course, it were not, as it no doubt is, more or less modified by lateral pressure. These figures afford some, though at best a vague, conception of the mighty grandeur of this range of mountains, and of the scope there is for the exertion of enormous pressure. How vast, then, must be those forces which have counteracted such pressures, and upheaved the ocean-spread sediments of the continent, until the Andes, that— " giant of tlie "Western Star, Looks from his throne of clouds O er half the world ! But, however vast the Andes may seem to us, it should be remembered that they form but an insignificant portion of the globe itself. Aconcagua is about 3roVir tn f ^ e earth s diameter, which is relatively not more than a pimple -g^th. of an inch high on the skin of a tall man. The range may be considered as commencing on the south with Cape Horn, although for several degrees it is much broken up by arms and straits of the sea. The first portion of any extent commences between Cape Good Success and Cape San Paulo, and stretches across Tierra del Fuego, by Mount Darwin and Mount Sarmiento, and the range of hills on either side of Admiralty Sound. The mountains named are from 6600 to 6800 feet high. The Strait of Magellan also cuts through and across the range, isolating the mountainous islands of Clarence and Santa Ines. Otway Water cuts through the range, and pene trates to the plain of Patagonia. North of this are several snowy eminences, and in some places glaciers descend almost to the sea-level. At Last Hope Inlet, or a little north of 52 S., we have the commencement of the Andes as a continuous range, Disappointment Bay being the most northern place where the Pacific reaches the plains to the east of the Andes. South of this, and for several degrees to the north, the islands which fringe the coast have a mountainous character, and appear to belong essentially to the Andes range, with which there is reason to believe they were once connected. Along this space the Andes en croach upon the ocean, and have no western slope proper. Many of the sea channels are very narrow and ravine-like in character; they appear to represent a valley between two ridges of mountains, a feature which is most con spicuous farther north. The highest part or crest of the range is close to the sea, and consequently the streams which fall into the Pacific are all small. Towards the south the width is about 20 miles; and in the latitude of Mount Stokes, which is 6400 feet high, it is 40 miles. North of this the range is in places more than 40 miles across. From 46 to 42 S., the mountains become some what higher, the loftier peaks ranging from 4000 to 8000 feet. Among the more conspicuous are Mount Yanteles, 8030 feet; Mount Melimoyu, 7500 feet; Mount Corcovado, 7510 feet; and Mount Minchinmadiva, 7406 feet above the sea-level. The Eyre Sound glaciers descend to the sea- level. At about 41 30 S. lat. there is a low pass across the Andes; and to the north of this the slope is more or less distant from the sea, except, perhaps, at one part where the desert of Atacama terminates in lofty cliffs on the shore. In Chili the Andes increase in height and width, and between about 38 and 28 S. run approximately north and south; and nowhere do they recede so far from the sea as in the southern part of Chili. At this part, or in about the latitude of Antuco (36 50 S.), the lower land on the west is more than 100 miles broad, and the width of the range itself is probably more than 100 miles. Here the Andes consist of two ranges, the crests of which are from 60 to 80 miles apart, enclosing a longitudinal valley. Across these ranges there is a pass, which, with the excep tion of those near the mountains Osorno and Villarica, is the most southern in Chili. The summit of this pass is not more than 12,000 feet above the sea. The pass of Planchon lies north of Mount Dcscabezado; and to the south of Peteroa is the pass of Las Damas, which is pro bably not more than 11,000 feet at its highest point. At the head of the Maypu valley a pass traverses the two ranges of the Andes as well as the included valley of Tunuyan. That through the western range is called Peu- quenes Pass, and rises to 13,210 feet above the sea-level; while that through the eastern range is called Portillo, and rises to 14,365 feet above the sea. Near 32 38 S., Aconcagua rises to 23,290 feet, and is, so far as known, the highest peak in America, and the highest volcano in the world. A little to the south of it is the Cunibre or Uspallata Pass. In the western range it rises to 12,454 feet above the sea; and on its north flank is the pass of Los Patos. At about 30 S. the mountainous system becomes more complicated, owing to the appearance of several ranges which rise out of the plains towards the north-west corner of the Argentine Confederation, some of which run north and join the lofty highlands of the Bolivian Andes. It is doubtful whether all strictly belong to the Andes. Thus, in the latitude of Coquimbo, where both the mountains and the coast line trend somewhat to the east of north, there are three parallel mountain ranges. The western is called the Andes, the central range is known as the Sierra Famatina, and the eastern as the Sierra Velasco. The two latter ranges are quite isolated from the first-mentioned range, terminating abruptly on the north and south. North of 28 S., however, a number of sierras which rise from the Argentine plain form an extensive mass of mountains. These are continuous into the Cordilleras de los Valles, de Despoblado, and Abra de Cortaderas, which form the eastern margin of the lofty mountain plains of Bolivia. These plains slope down from the eastern side of the Andes, just as the Atacama desert seems to form part of the western slope. At about 22 S. the Andes begin to trend somewhat to the west of north. At about 20 S. the eastern and western ranges are connected by a lofty transverse chain about 60 miles broad, and similar to the mountain knots of Peru. North of this the ranges bend more to the west, and enclose the extensive valley of the Desaguadero river and Lake Titicaca, which is shut in on the north by the transverse chain of the Vilcanota Moun tains. The width of the range is in this part from 200 to 250 miles; or if the offset running eastward to Santa Cruz be included, the width is between 500 and 600 miles. One special feature about this part of the range is, that the Desaguadero valley (13,000 feet above the sea) is the