The essay of Don Pio contains calculations and details which would not be interesting to the general reader; to some, however, even these cannot fail to be so, and the whole is published in the Appendix.[1] I shall refer in this place only to the result. From the examination and analysis made by the distinguished gentleman before referred to, I am enabled to state the interesting fact, that the calendar of Yucatan, though differing in some particulars, was substantially the same with that of the Mexicans. It had a similar solar year of three hundred and sixty-five days, divided in the same manner, first, into eighteen months of twenty days each, with five supplementary days; and, secondly, into twenty-eight weeks of thirteen days each, with an additional day. It had the same method of distinguishing the days of the year by a combination of those two series, and the same cycle of fifty-two years, in which the years, as in Mexico, are distinguished by a combination of the same series of thirteen, with another of four names or hieroglyphics; but Don Pio acknowledges that in Yucatan there is no certain evidence of the intercalation (similar to our leap year, or to the Mexican secular addition of thirteen days) necessary to correct the error resulting from counting the year as equal to three hundred and sixty-five days only. It will be seen, by reference to the essay, that, besides the cycle of fifty-two years common to the Yucatecans and Mexicans, and, as Don Pio Perez asserts (on the authority of Veytia), to the Indians of Chiapas, Oaxaca, and Soconusco, those of Yucatan had another age of two hundred and sixty, or of three hundred and twelve years, equal to five or six cycles of fifty-two years, each of which ages consisted of thirteen periods (called Ajau or Ajau Katun) of twenty years each, according to many authorities, but, in Don Pio's opinion, of twenty-four years. The fact that though the inhabitants of Yucatan and Mexico speak different languages, their calendar is substantially the same, I regard as extremely interesting and important, for this is not like a similarity of habits, which may grow out of natural instincts or identity of position. A calendar is a work of science, founded upon calculations, arbitrary signs, and symbols, and the similarity shows that both nations acknowledged the same starting points, attached the same meaning to the same phenomena and objects, which meaning was sometimes arbitrary, and not such as would suggest itself to the untutored. It shows common sources of knowledge and processes of reasoning, similarity of worship and religious institutions, and, in short, it is a link in a chain of evidence tending to show a common origin in the aboriginal inhabitants of Yucatan and Mexico. For this discovery we are indebted to Don Pio Perez. CHAPTER VII.