The consideration of these indisputable facts tends to establish the historical rather than the astronomical character of the monuments. For had the erection of the monuments depended on the successive recurrences of some astronomical phenomenon, there would be corresponding intervals between the dates of such monuments[26] the length of which would indicate the identity of the determining phenomenon; and they would hardly have presented the same logical increase due to the natural growth of a nation, which the accompanying diagram clearly sets forth. _Fourth._ Although no historical codices[27] are known to have survived, history was undoubtedly recorded in these ancient Maya books. The statements of the early Spanish writers are very explicit on this point, as the following quotations from their works will show. Bishop Landa (here, as always, one of the most reliable authorities) says: "And the sciences which they [the priests] taught were the count of the years, months and days, the feasts and ceremonies, the administration of their sacraments, days, and fatal times, their methods of divination and prophecy, and foretelling events, and the remedies for the sick, and _their antiquities_" [p. 44]. And again, "they [the priests] attended the service of the temples and to the teaching of their sciences and _how to write them in their books_." And again, [p. 316], "This people also used certain characters or letters with which _they wrote in their books their ancient matters_ and sciences." Father Lizana says (see Landa, 1864: p. 352): "The _history and authorities we can cite_ are certain ancient characters, scarcely understood by many and explained by some old Indians, sons of the priests {36} of their gods, who alone knew how to read and expound them and who were believed in and revered as much as the gods themselves." Father Ponce (tome LVIII, p. 392) who visited Yucatan as early as 1588, is equally clear: "The natives of Yucatan are among all the inhabitants of New Spain especially deserving of praise for three things. First that before the Spaniards came they made use of characters and letters with which _they wrote out their histories_, their ceremonies, the order of sacrifices to their idols and their calendars in books made of the bark of a certain tree." Doctor Aguilar, who wrote but little later (1596), gives more details as to the kind of events which were recorded. "On these [the fiber books] they painted in color the reckoning of their years, wars, pestilences, hurricanes, inundations, famines and other events."