On ordinary maps this narrow Chilean half of the Andean region looks like a mere strip of coast traversed by a single range. As a consequence, it is not generally understood by those who have not visited the country that there is really here, as in Bolivia, Peru and Ecuador, a double formation, connected by transverse ridges in places, but perfectly distinct, known as the Andes proper, or main Cordillera, and the coast range, or western Cordillera. Between the two systems is a vast plateau, called the central valley, which begins in the northern Province of Atacama, and, gradually decreasing in height, extends south for seven hundred miles, with an average width of from fifty to sixty miles, through the Province of Llanquihue, about two-thirds of the way down the coast, where it disappears, with the coast range itself, in the long series of groups of islands into which the shore line is broken up. From its culminating point back of Santiago, the main Cordillera also decreases in height toward the south, but, instead of disappearing with the coast range, extends throughout the whole length of the country, from Peru to the southernmost islands of the Fuegian archipelago, forming the most magnificent background imaginable to the view from the sea. In the northern section, between the Bolivian frontier and Coquimbo, there are more than thirty extinct or dormant volcanoes of great altitude—Toroni (21,340 feet, or about four miles, high), Pular (21,325 feet high), Iquima (20,275 feet), Aucasquilucha (20,260 feet), Llulaillaco (20,253 feet), San José (20,020 feet), Socompa (19,940 feet), and many others over 17,000 feet. Imagine these in contrast with Etna (10,875 feet) and Vesuvius, which is only 3800 feet, not as high as the cones of some of them alone. South of the Province of Copaibo, the main range itself develops a plateau formation that is crossed by several relatively low passes, such as the Portezuelo de Come Caballo (14,530 feet), Los Patos (11,700 feet), and, farther south, on a line with Valparaiso, the Uspallata Cumbre (12,795 feet). Although little used even now because of its extremely rugged character, Los Patos is associated with perhaps the most memorable event in the war of independence. It was there that, in the execution of that strategic movement which South American historians say excelled that of Hannibal in the Pyrenees and Napoleon’s crossing of the Alps, the Liberator San Martín safely made his way through with his whole army in 1817—artillery, impedimenta, and all—and, within five days, joined forces with the Chilean hero, O’Higgins, surprised the Royalist army awaiting him on the plain opposite the Cumbre below, fought the great battle of Chacabuco, and entered Santiago in triumph.