(3) The third section, also extending for 200 m., contains the valleys of Santa, Nepena, Casma, Huarmey, Fortaleza, Pativilca, Supe and Huaura.
The Nepena, Casma, Huarmey, Fortaleza and Supe rivers rise on the slope of an outer range called the Cordillera Negra, and are consequently dry during the great part of the year.
There are 9 leagues of desert between the Nepena and Casma, 16 between the Casma and Huarmey, and 18 between the Huarmey and Fortaleza.
La Viuda is off the port of Casma, in 9° 23' 30" S.; and Tortuga is 2 m.
The second-class ports are Tumbez, Talara, Pimentel, Chimbote, Samanco, Casma, Huacho, Cerro-Azul, Tambo de Mora Lomas and Chala, on the coast, Puno on Lake Titicaca, and Leticia on the Amazon near the western mouth of the Javary, Callao (qv.) is the chief port of the republic and monopolizes the greater part of its foreign trade.