As years rolled on, the Inca began to think more and more of the land of his birth. The memory of his boyish days, of the long evening chats with his Inca relations, came back to him in his old age. He was as proud of his maternal descent from the mighty potentates of Peru as of the old Castilian connection on his father’s side. It would seem that the appearance of several books on the subject of his native land finally induced him to undertake a work in which, while recording its own reminiscences and the information he might collect, he could also comment on the statements of other authors. Hence the title of _Commentaries_ which he gave to his work. Besides the fragments of the writings of Blas Valera, which enrich the pages of Garcilasso, the Inca quotes from Acosta, from Gomara, from Zarate, and from the First Part of Cieza de Leon.[1263] He was fortunate in getting possession of the chapters of Blas Valera rescued from the sack of Cadiz. He also wrote to all his surviving schoolfellows for assistance, and received many traditions and detailed replies on other subjects from them. Thus Alcobasa forwarded an account of the ruins at Tiahuanacu, and another friend sent him the measurements of the great fortress at Cuzco. The Inca Garcilasso de la Vega is, without doubt, the first authority on the civilization of his ancestors; but it is necessary to consider his qualifications and the exact value of his evidence. He had lived in Peru until his twentieth year; Quichua was his native language, and he had constantly heard the traditions of the Incas related and discussed by his mother’s relations. But when he began to write he had been separated from these associations for upwards of thirty years. He received materials from Peru, enabling him to compose a connected historical narrative, which is not, however, very reliable. The true value of his work is derived from his own reminiscences, aroused by reading the books which are the subjects of his Commentary, and from his correspondence with friends in Peru. His memory was excellent, as is often proved when he corrects the mistakes of Acosta and others with diffidence, and is invariably right. He was not credulous, having regard to the age in which he lived; nor was he inclined to give the rein to his imagination. More than once we find him rejecting the fanciful etymologies of the authors whose works he criticises. His narratives of the battles and conquests of the early Incas often become tedious, and of this he is himself aware. He therefore intersperses them with more interesting chapters on the religious ceremonies, the domestic habits and customs, of the people, and on their advances in poetry, astronomy, music, medicine, and the arts. He often inserts an anecdote from the storehouse of his memory, or some personal reminiscence called forth by the subject on which he happens to be writing. His statements frequently receive undesigned corroboration from authors whose works he never saw.