Mr. Prescott on the Inca Monuments — In?uence of his Words — The Author's Aspi rations and Purposes — Threatened with Blindness. — Appointed United States Commissioner to Perm — Restoration to-sight. — Commencement of Explorations. — Extent of the Region explored — Plans, Drawings, and Photographs — Value of the Material secured — General Survey of the Inca Empire — Its Boundaries. Physical Characteristics — Lake and River Systems — Mountain Ranges — The Coast Desert. — Fertile Valleys — The Inhabitants of the Valleys — The Cordillera. The Despoblado. — Distinction between the Cordillera and the Andes — The Basin of Titicaca. — Only two other Similar Basins in America — Lake Aullagas. Lake Titicaca. — Its Sacred Islands — The Bolsones, or Valleys. — The Bolson of Cuzco. — The Montana — The Incas and the Peoples of the montafia.-probable Population of the Inca Empire — Divisions of the Ancient Inhabitants of Peru.