On the purely historical side, the two men are in wholly different classes. Irving resembled Livy in his use of the authorities. Such sources as were ready to his hand and easy to consult, he used with conscientious care; but those that were farther afield, and for the mastery of which both time and labour were demanded, he let alone. Thus, his history of Columbus was prepared in something less than two years, in which period both his preliminary studies and the actual composition were completed. Yet this book was the one over which he took the greatest pains, and for which he made his only serious attempt at something like original investigation. His _Mahomet_ was confessedly written at second hand; while in his _Washington_ he followed in the main such records and already published works as were convenient. In the _Granada_ he only plays with history, and ascribes the main portion of the narrative to a mythical ecclesiastic, "the worthy Fray Antonio Agapida," in whose lineaments we may not infrequently detect a strong family resemblance to the no less worthy Diedrich Knickerbocker. In the letter which Irving wrote to Prescott, relinquishing to him the subject of Cortés, he lets us see quite plainly the very moderate amount of reading which he had been doing.[55] He had dipped into Solis, Bernal Diaz, and Herrera, using them, so he said, "as guide-books." Upon the basis of this reading he had sketched out the entire narrative, and had fallen to work upon the actual history with the intention of "working up" other material as he went along. When we compare these easy-going methods with the scientific thoroughness of Prescott, his ransacking, by agents, of every important library in Europe, his great collection of original documents, the many years which he gave to the study of them, and the conscientious judgment with which he weighed and balanced them, we cannot fail to see how much the world has gained by Irving's act of generous self-abnegation. It is only fair to add that he himself, at the time when Prescott wrote to him, was beginning to doubt whether he had not undertaken a task unsuited to his inclinations and beyond his powers. "Ever since I have been meddling with the theme," he said, "its grandeur and magnificence had been growing upon me, and I had felt more and more doubtful whether I should be able to treat it _conscientiously_,--that is to say, with the extensive research and thorough investigation which it merited."