I now approach what I consider the peculiar value of these records, apart from the linguistic mould in which they are cast; and that is the light they throw upon the chronological system and ancient history of the Mayas. To a limited extent, this has already been brought before the public. The late Don Pio Perez gave to Mr. Stephens, when in Yucatan, an essay on the method of computing time among the ancient Mayas, and also a brief synopsis of Maya history, apparently going back to the third or fourth century of the Christian era. Both were published by Mr. Stephens in the appendix to his "Travels in Yucatan," and have appeared repeatedly since in English, Spanish and French.[10-*] They have, up to the present, constituted almost our sole sources of information on these interesting points. Don Pio Perez was rather vague as to whence he derived his knowledge. He refers to "ancient manuscripts," "old authorities," and the like; but, as the Abbe Brasseur de Bourbourg justly complains, he rarely quotes their words, and gives no descriptions as to what they were or how he gained access to them.[11-*] In fact, the whole of Senor Perez's information was derived from these "Books of Chilan Balam;" and, without wishing at all to detract from his reputation as an antiquary and a Maya scholar, I am obliged to say that he has dealt with them as scholars so often do with their authorities; that is, having framed his theories, he quoted what he found in their favor and neglected to refer to what he observed was against them. Thus, it is a cardinal question in Yucatecan archaeology as to whether the epoch or age by which the great cycle (the _ahau katun_,) was reckoned, embraced twenty or twenty-four years. Contrary to all the Spanish authorities, Perez declared for twenty-four years, supporting himself by "the manuscripts." It is true there are three of the "Books of Chilan Balam"--those of Mani, Kaua and Oxkutzcab,--which are distinctly in favor of twenty-four years; but, on the other hand, there are four or five others which are clearly for the period of twenty years, and of these Don Perez said nothing, although copies of more than one of them were in his library. So of the epochs, or _katuns_, of Maya history; there are three or more copies in these books which he does not seem to have compared with the one he furnished Stephens. His labor will have to be repeated according to the methods of modern criticism, and with the additional material obtained since he wrote. Another valuable feature in these records is the hints they furnish of the hieroglyphic system of the Mayas. Almost our only authority heretofore has been the essay of Landa. It has suffered somewhat in credit because we had no means of verifying his statements and comparing the characters he gives. Dr. Valentini has even gone so far as to attack some of his assertions as "fabrications." This is an amount of skepticism which exceeds both justice and probability.