From the granitic cliffs of Diego Ramirez,--in the deeply indented and intersected Tierra del Fuego, which contains on the east silurian schists and on the west the same schists altered by the metamorphic action of subterranean fire, (Darwin’s Journal of Researches into the Geology and Natural History of the Countries visited in 1832-1836 by the Ships Adventure and Beagle, p. 266),--to the North Polar Sea, the Cordilleras extend in length more than 8000 geographical miles. They are the longest though not the loftiest chain on our planet; being raised from a cleft running in the direction of a meridian from pole to pole, and exceeding in linear distance the interval which in the Old Continent separates the Pillars of Hercules from the Icy Cape of the Tchuktches in the north-east of Asia. Where the Andes divide into several parallel chains, it is remarked that the ranges nearest the sea are usually those which exhibit most volcanic activity; but it has also been observed repeatedly, that when the phenomena of still active subterranean fire disappear in one chain, they break out in another chain running parallel to it. Generally speaking, the volcanic cones are found in a direction corresponding with that of the axis of direction of the entire chain; but in the elevated highlands of Mexico the active volcanoes are placed along a transverse cleft running from sea to sea in the east and west direction. (Humboldt, Essai Politique, T. ii. p. 173.) Where, by the elevation of mountain masses in the ancient corrugation or folding of the crust of the earth, access has been opened to the molten interior, that interior continues to act, through the medium of the cleft, upon the upheaved wall-like mass. That which we now call a mountain chain has not arrived at once at its present state: rocks, very different in the order of succession in reference to age, are found superimposed upon each other, and have penetrated to the surface by early formed channels. The various nature of the formations is due to the outpouring and elevation of eruptive rocks, as well as to the slow and complicated process of metamorphic action taking place in clefts filled with vapours and favourable to the conduction of heat. For a long time past, from 1830 to 1848, the following have been regarded as the culminating or highest points of the Cordilleras of the New Continent. The Nevado de Sorata, also called Ancohuma or Tusubaya, (S. lat. 15° 52′) a little to the south of the village of Sorata or Esquibel, in the eastern Bolivia Range: elevation 3949 toises, or 23692 Parisian, or 25250 English feet. The Nevado de Illimani, west of the Mission of Yrupana (S. lat. 16° 38′) in the same mountain range as Sorata: elevation 3753 toises, or 22518 Parisian, or 24000 English feet. The Chimborazo (S. lat. 1° 27′) in the province of Quito: elevation 3350 toises, or 20100 Parisian, or 21423 English feet.