Skirting the ridge on the east and draining the vast slopes of the Brazilian mountains of their tropical rainfall, is the great river Parana. In latitude 27 deg. it turns abruptly to the west, as if about to cross the pampa, but a hundred miles farther on it resumes its southward course. At this last turn the Parana flows into a river which comes straight down from the north, draining the bed of the old inland sea that used to divide South America. This junction of the Parana and the Paraguay forms the second largest river in the world--a river without obstructions to navigation, but which is so immense that it cannot be bridged. In latitude 32 deg. it turns back to the south-east, soon receives the Uruguay,--a swifter stream, that drains the southern part of the Atlantic highlands,--and then opens out into the great shallow estuary known as the River Plate. Between the Uruguay and the Parana is the Argentine Mesopotamia,--a flat region where the low-lying plains, covered with luscious grasses, intersected with streams, and interspersed with timber, gradually rise up-stream into the highlands of the Missions. [Illustration: ARGENTINA, PARAGUAY, URUGUAY, BOLIVIA AND CHILE] [Illustration: FOREST SCENE IN ARGENTINA. [From steel print.]] To the west the pampa is bounded by the foothills of the Andes and the parallel chains with which that great mountain system reinforces its flanks. At the Bolivian frontier, the great outward-jutting shoulder of the Andes looms up among a series of subordinate chains. South of them, for a thousand miles, is a belt of broken country averaging two hundred miles in width. The pampa creeps up to the very foot of the mountain ranges and where it is watered blossoms like a garden. A quarter of the population of the Republic lives in the irrigated valleys of these Andean provinces. A comparatively narrow, arid, belt stretches diagonally across the South American continent from the Pacific, in Northern Chile, to the Atlantic in Northern Patagonia. Consequently, from north to south, and from the Atlantic back toward the north-east border of this arid belt, the rainfall of Argentina decreases. On the north-eastern frontier it is about 80 inches a year; at Rosario, 40; at Cordoba, 30; at Buenos Aires, 35. In the Andean provinces it decreases from over forty, near the Bolivian frontier, to five or six at San Juan in the latitude of Santa Fe and Cordoba. In the eastern part of the great pampa the rainfall is ample for cereal crops; in the western half the rains are periodical and the region is better adapted to grazing than to agriculture, and there the grass lands are intersected with tracts of desert which grow larger towards the south. In the Andes the eastern ranges, catching the rain-laden upper currents, send down ample water to irrigate the valleys and adjacent plains.