"Chilan Balam" was the designation of a class of priests. "Chilan," says Bishop Landa, "was the name of their priests, whose duty it was to teach the sciences, to appoint holy days, to treat the sick, to offer sacrifices, and especially to utter the oracles of the gods. They were so highly honored by the people that usually they were carried on litters on the shoulders of the devotees."[69-1] Strictly speaking, in Maya, _chilan_ means "interpreter," "mouth-piece," from "_chij_," "the mouth," and in this ordinary sense frequently occurs in other writings. The word _balam_--literally, "tiger,"--was also applied to a class of priests, and is still in use among the natives of Yucatan as the designation of the protective spirits of fields and towns, as I have shown at length in a study of the word as it occurs in the native myths of Guatemala.[70-1] "_Chilan Balam_," therefore, is not a proper name, but a title, and in ancient times designated the priest who announced the will of the gods and explained the sacred oracles. This accounts for the universality of the name and the sacredness of its associations. The dates of the books which have come down to us are various. One of them, "The Book of Chilan Balam of Mani," was undoubtedly composed not later than 1595, as is proved by internal evidence. Various passages in the works of Landa, Lizana, Sanchez Aguilar and Cogolludo--all early historians of Yucatan--prove that many of these native manuscripts existed in the sixteenth century. Several rescripts date from the seventeenth century--most from the latter half of the eighteenth. The names of the writers are generally not given, probably because the books, as we have them, are all copies of older manuscripts, with merely the occasional addition of current items of note by the copyist; as, for instance, a malignant epidemic which prevailed in the peninsula in 1673 is mentioned as a present occurrence by the copyist of "The Book of Chilan Balam of Nabula." These "Books of Chilan Balam" are the principal sources from which Señor Pio Perez derived his knowledge of the ancient Maya system of computing time, and also drew what he published concerning the history of the Mayas before the Conquest, and from them also are taken the various chronicles which I present in the present volume. That I am enabled to do so is due to the untiring researches of Dr. Carl Hermann Berendt, who visited Yucatan four times, in order to study the native language, to examine the antiquities of the peninsula, and to take accurate copies, often in fac-simile, of as many ancient manuscripts as he could discover. After his death, his collection came into my hands.