Between latitudes fourteen and a half and twenty-three and a half, the mighty Andean chain is massed into a plateau five hundred miles wide, over twelve thousand feet high, and interspersed with a complex system of mountains and ridges, parallel, transverse, and interlaced. Geographers estimate that this central portion of the Andean system contains nearly five hundred thousand cubic miles of matter above sea level, and that it would, cover the entire area of South America to an average depth of four hundred feet. The great ranges which stretch north to the Caribbean and south to Cape Horn are mere arms of this massive elevation of the earth, the highest and largest in the new world. Within a few miles of the coast rises a lofty and continuous range of mountains which can be scaled only over a few passes, none of which fall far below fourteen thousand feet. From the top a vast plateau stretches to the lofty chain which forms the inland rim of the Andean massif. This plateau is Bolivia. The northern portion forms the Titicaca basin, the whole of which was formerly covered by an immense fresh-water sea, fed by the snows of the surrounding mountains, and draining south-east into the Plate Valley. Now, however, the rainfall has so decreased that the great lake is shrunk to a mere tithe of its original dimensions, and none of its waters escape out of the dry plateau. In its southern part the plateau is bifurcated by a high central range, which divides southern Bolivia into two portions, the western of which, called the Puna, is too high, cold, and dry for cultivation. To the east the plains are lower and moister, sloping very gradually toward the east until they plunge off abruptly into the great central valley of South America. The northern part of the Titicaca basin was the cradle of civilisation in South America. On the shores of the lake are ruins of great buildings erected by a race who occupied this plateau unknown centuries before the rise of the Inca power. One doorway exists in an almost perfect state of preservation, carved out of a single block of stone seven feet high and twice as long, covered with figures elaborately sculptured in high relief, while dozens of heroic statues, and walls containing hewn stones twelve yards long, remain to attest the skill of the old workmen. [Illustration: MONOLITHIC DOORWAY AT TRAHUANACO.]