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x correspondents have been Don E. Larrabure y Unanue, Don Manuel Gonzalez de la Rosa, Don José Toribio Polo, and Don Ricardo Palma. I also received much kind assistance from friends in Spain, now departed, Don Pascual de Gayangos, and especially from Don Marcos Jimenez de la Espada. The literary labours of these and other Spanish and Peruvian authors attain a high standard. I have since devoted my efforts to a complete mastery of all the original authorities on Inca history and civilisation. It is not enough to dip into them, nor even to read them, in order to obtain such a mastery. The problems that present themselves in the study of Inca civilisation are often complicated, they need much weighing of evidence, and are difficult of solution. My own studies have extended over many years, during which time I have translated and annotated the principal authorities, made indexes, and