HYDROGRAPIIY. The dry west and the rainy east of Peru naturally produce a striking con trast between the hydrographie aspects of the western and eastern slopes of the country. Only feeble streams flow to the Pacific, and most of them are lost in the desert or their waters are wholly diverted to nourish the plantations. None of them flows perennially to the Pacific excepting the Santa, which rises, lint on the western slopes of the mountains, like most of the coast rivers, but in a long valley between the maritime and central ranges. During the flood the Santa dis charges such an enormous quantity of water that it is difficult to cross. Most of the coast rivers are quite short, and their great value is derived wholly from the facilities they afford, by means of irrigation, for turning belts of the desert into the most fertile of lands. The more im portant among them, from north to south, are the Mira, the Piura, the Santa, the Rimac, which created the fertile plain on which Lima stands, and the Rio Grande.
The Amazonian affluents of the eastern slope, on the other hand, constantly increase in volume with distance from their sources. The rivulets among them carry more water than most of the Pacific• streams. The upper parts of these rivers
are interrupted by cascades and rapids, and thus the economic periphery of Eastern Peru is largely determined by the line joining the heads of navi gation on these many rivers. All the very nu merous rivers of the eastern slope of Peru are included in the Amazon basin, and belong to one or another of the three secondary basins of the ranOn, the Huallaga, and the Ucayale, which are entirely in Peruvian territory, besides a few tributaries of the Purus and Madeira. The Maranon is usually regarded as the main upper branch of the Amazon, not because it car ries so much water as the Uc•ayale, but because it prolongs farthest toward the Pacific the longi tudinal axis of the Amazon. Ocean steamers now regularly ascend the Amazon and Maranon to Iquitos, Peru. 3000 miles from the Atlantic, and light-draught steamers lu•olong navigation for 825 miles up the Ucalaye. Pachitea, and Pichis rivers. There are no important lakes excepting Titicaca (q.v.), which lies partly in Bolivia; it is 12,500 feet above sea-level, and affords navigation be tween Peruvian and Bolivian ports on its shores.