There are, however, other facts to be taken into consideration. It has been assumed that there was a condition of comparative civilisation amongst the ruling tribes, which seemed to be in such a progressive state as to lead to the conclusion that there were elements of knowledge which might have been so far developed in the course of time as to have brought these Indians into the ranks of civilised nations. With regard to this subject it should be observed that when the Spaniards conquered Central America, the progress that may have been partially made had already ceased. The monasteries at Palenque and in Yucatan had been abandoned. Even when they were flourishing, the knowledge that was taught did not extend to the people. It was confined to the priesthood, the caciques, and the few scholars who were trained for the purpose of interpreting the signs and characters by which information was spread abroad. It was by one of these interpreters that Cortes was made acquainted with the conspiracy that was being organized against him by Guatimozin during the march to Honduras. How or in what manner this comparative intelligence arose suddenly in the land is a problem of the greatest difficulty. The possibility of a previous condition of civilisation having existed amongst the aboriginal tribes cannot be considered as being within the limits of reasonable conjecture, for there are no vestiges of any stone buildings, sculptures, or of hieroglyphic inscribed characters, used as a means of recording events, except in those regions which are known to have been occupied by the Toltecs or Aztecs. With especial regard to the temples on the mounds at Palenque, it is evident that these and their sculptures and hieroglyphs were the results of a certain degree of architectural knowledge obtained by the Quiché-Toltecs after they had migrated into Mexico. But admitting that this may have been the case, it becomes extremely difficult to understand how their mechanical skill could have sprung into existence within such a limited period of time. It was found that the Indian progress in their peculiar civilisation was very local. Bishop Landa, writing exclusively about Yucatan, states that all education was under the management of the priests attached to the monasteries. Similar systems appeared to have been followed in other regions which had been under the rule of the Toltecs.[108] The results of the investigations into the subject of the extent and methods which were adopted for the purpose of maintaining knowledge amongst the Indians, confirm the opinion that the literature and civilisation found to have existed in Mexico and Yucatan was exclusively caused by the teaching of the priests. Explanations of the circumstances under which the priests became acquainted with their sciences were given to the Spaniards by the chief priests attached to the temple of Quetzalcoatl at Cholula and also by certain caciques in Yucatan. [Illustration: MEXICAN CALENDAR STONE.]