All that need be said is that the Toltec were ruled by priest-kings, representatives of their god Quetzalcoatl, who, according to one legend, was their first ruler, and that the downfall of their power was heralded by the separation of the temporal and religious authority. The cause of that downfall seems to have been the gradual incursion of later Nahua immigrants; signs of degeneration are not wanting in the legends connected with the later reigns, in particular the introduction of human sacrifice. At the fall of the kingdom, a great emigration took place in the direction of the east, to Tabasco and beyond, and, so the story tells, _via_ Tehuacan and Teotitlan to Soconusco. Many of the Toltec however remained behind, especially in Colhuacan, Cholula and Uexotzinco. The arrival of the Tlaxcalans, which probably occurred about this time, drove the Olmec further east in the path of the Toltec, with whom they claimed to be one and the same people. No doubt however the Tlaxcalans absorbed a large percentage of Toltec blood, a fact which intensified their friendship for the people of Uexotzinco and their ineradicable hostility to the Aztec. From a careful consideration of many points of evidence, I am inclined to think that the date given by the “Annals of Quauhtitlan” for the destruction of Tulan, viz. 1064, is not far wrong; how long the state had lasted is more difficult to say, but that it must have flourished for an extended period is obvious from the fact that the remains characteristic of the Toltec culture at Azcapotzalco form a stratum over three metres thick. [Illustration: FIG. 1.--Map of the Valley of Mexico. The black line shows the traditional route of the Aztec.]