At the boundary-line of Bolivia the chain separates into two portions, enclosing the great table-land of Desuguadero, thirteen thousand feet above the sea. At one end of this lofty region is the city of Potosi, rising above the clouds--the highest in the world, erected amid the groans and tears of the hapless natives compelled to labour at its far-famed silver-mines. At the other is found Cuzco, the ancient capital of the Incas. Between them lies the Lake of Titicaca, the centre of bygone Peruvian civilisation. Running still parallel with the coast, and looking down upon the modern city of Lima, the range passes through Peru till it again divides in three portions at the confines of the equator, where it once more forms two lines, which rise in that magnificent congregation of mountains which surround the famous Valley of Quito. Here no less than twenty-one volcanoes rear their lofty summits, many of them crowned with perpetual snow, amid which Chimborazo and Cotopaxi are pre-eminent. To the north of the equator, the Cordilleras again form one vast ridge, and passing through New Granada, spread out like the branches of a palm through Venezuela and along the northern shores of the continent washed by the Caribbean Sea. The whole of this vast range, from Cape Horn to Panama, gives evidence of the hidden fires which glow beneath its base, and by which it was originally created. Fifty-one volcanoes are found along the line. Of the twenty which surround the Valley of Quito, three are active, five dormant, and twelve are supposed to be extinct. By far the larger number rise out of the eastern range; indeed, the western contains only one active volcano, but out of it tower the peerless Chimborazo, and Pichincha with its deep crater. The whole region is subject to terrific earthquakes, which have from time to time shaken down its cities, caused huge waves to flow over the level land, and destroyed countless thousands of its inhabitants. Chimborazo was long supposed to be the most lofty mountain on the globe. It is 21,420 feet high; but Aconcagua in Chili rises to the height of 23,200 feet. Several of the summits of the Himalayan range in Asia are over 25,000 feet; and Kilima Njaro, the most lofty peak in Africa, is about the same altitude as Chimborazo. Chimborazo, for solitary grandeur--and from the excessive steepness of its sides, which has prevented the foot of man from reaching its summit--stands, however, unrivalled. From the lofty heights over which we have thus rapidly passed, numberless streams take their rise, rushing and foaming down their steep sides to feed those mighty rivers which, flowing across the continent, seek an outlet in the far-distant Atlantic. On the western side, comparatively few and insignificant rivers cross the narrow plains into the Pacific. Thus the inhabitants of the tropical portions have to depend on artificial irrigation for the cultivation of the land.