It has now been discovered that the manuscript narrative which Mr. Prescott frequently refers to, in his _History of the Conquest of Peru_, as “_Sarmiento_”, and which he considered to be one of the most valuable of his authorities, is in reality the Second Part of the work of Cieza de Leon. Mr. Prescott quotes the title in his critical notice,[3] “_para el Illmo Señor Dn. Juan Sarmiento, Presidente del Consejo Rl. de Indias_”, and assumes that this Don Juan Sarmiento was the author, who, after having travelled in all parts of Peru and diligently collected information from the Ynca nobles, subsequently became President of the Council of the Indies. In reality, the word _para_ means “for”, and not “by”, and the manuscript is simply addressed to Dr. Sarmiento, who never crossed the Atlantic in his life, and who only held the post of President of the Council of the Indies for twenty months.[4] Mr. Prescott made much use of both parts, and considered them to be works of great merit. If what he says in praise of the author he supposed to be Sarmiento,[5] is added to what he says of Cieza de Leon,[6] it will at once be seen that the latter, really the only author, is a very important authority indeed. It is with a feeling of reverential regret that the present editor refers to any mistake, even one so slight as this, of the illustrious American historian. Some of my brightest and happiest memories are of the ten days I spent at Pepperell with Mr. Prescott, when I was on the eve of commencing my studies in the land of the Yncas. He it was who encouraged me to undertake my Peruvian investigations, and to persevere in them. To his kindly advice and assistance I owe more than I can say, and to him is due, in no small degree, the value of anything I have since been able to do in furtherance of Peruvian research. The evidence that the work attributed by Prescott to Sarmiento is in reality the Second Part of the _Chronicle_ of Cieza de Leon is quite conclusive. There are no less than ten occasions on which the author of the Second Part (Prescott’s “Sarmiento”) refers to passages in his First Part, which occur in the First Part of Cieza de Leon.[7] In one place there is a reference in the Second Part to the actual number of the chapter in the First Part.[8] In the Second Part, the author mentions having gone to Toledo to present the First Part of his _Chronicle_ to the Prince Don Felipe;[9] and this statement is equivalent to having signed his name. For only one First Part of a chronicle relating to the Indies was dedicated to the Prince, namely that of Cieza de Leon. The author of the Second Part also mentions having been to Bahaire, near Cartagena, and to the province of Arma--places visited by Cieza de Leon, and mentioned in his First Part.