A similar collection of Tupi stories was made by the late Prof. Charles F. Hartt, whose early death was a loss to more than one branch of science. It was his intention to edit them with the necessary notes and vocabularies; but, so far as I know, the only specimens which appeared in print were those he laid before the American Philological Association, in 1872.[47] The inquiries I have instituted about his MSS. have not been successful. Numerous texts of this description have been obtained from the Klamath Indians by Mr. A.S. Gatschet, and from the Omaha by the Rev. J. Owen Dorsey, both of which collections are in process of publication by the Bureau of Ethnology at Washington. Scattered specimens of stories of this kind have also been obtained by a number of travelers, and they are always a welcome aid to the study both of the psychology and language of a tribe. Section 4. _Didactic Literature_. The more civilized American tribes had made considerable advances in some of the natural sciences, and in none more than in practical astronomy. By close observation of the heavenly bodies they had elaborated a complicated and remarkably exact system of chronology. They had determined the length of the year with greater accuracy than the white invaders; and the different cycles by which they computed time allowed them to assign dates to occurrences many hundreds of years anterior. Although there are local differences, the calendars in use in Central and Southern Mexico and in Central America were evidently derived from one and the same original. A great deal has been written upon them, but for all that many questions about them remain unanswered. We do not know the Maya method of intercalation; we do not understand the uses of the shorter Mexican year, of 260 days; we are at a loss to explain the purpose of doubling the length of certain months, as prevailed among the Cakchiquels; we are in the dark about the significance of the names of many days and months; we cannot see why the nations chose to begin the count of the year at different seasons; and there are ever so many more knotty problems about this remarkable system and its variations.