This Maya race, having adopted the agricultural and sedentary life, multiplied so greatly as to send out many swarms of colonists towards the North, where the _Nahuas_, that is to say, "the skilled ones" or "experts" (for so the emigrants from the Maya land were called), found men of the same race as themselves, to whom they imparted their superior knowledge. They kept on pushing northwards, established themselves on the great plateau of Anahuac, or "lake country," where the city of Mexico is situated, and advanced up to the somewhat indefinite limit opposed to their progress by the Red-skins. This migratory movement towards the North was evidently not the affair of a day. It must have continued for centuries; and during its process the Maya civilization may have experienced great developments and undergone numerous modifications; so that, without venturing to pronounce categorically upon a problem yet unsolved, I should myself be inclined to ascribe to a population, which either consisted of bands of emigrant Mayas or was affected by this Nahua movement, those "Mounds" which still throw their galling defiance at the modern methods of research, powerless to explain their origin in regions which have since been under the reign of the most absolute savagery. However this may be, the movement by which in a remote antiquity the peoples of Central America ascended towards the North, carrying with them their relative civilization to Mexico and even beyond, was reversed at the epoch of our Middle Ages by a migration in the opposite direction. In this case it was the peoples of the northern regions that tended to beat back upon the South. They invaded, conquered and brought into subjection the peoples who had established themselves along the path followed by the previous migrations; and it is probably to invasions of this description that we must ascribe the fall of the ancient Maya society of the isthmic region. But the civilization of which it had sown the germs was not dead. Nay, the peoples who descended upon the South had in great measure themselves adopted it; and in the invaded districts there remained groups and nuclei of Nahua populations who maintained its principles, its arts and its spirit, to which their conquerors readily conformed. The last conquerors had been established as masters in the Mexican district for more than a century when the Spaniards arrived there. They were the _Aztecs_. They had conquered or shattered what was called the _Chichimec_ empire, which in its turn had destroyed, some centuries earlier, the _Toltec_ empire. But it would be a mistake to think of three successive empires, Toltec, Chichimec and Aztec, one supplanting the other in the same way as the Frankish empire, for example, took the place of that of Rome, which in its turn had replaced divers others more ancient yet. What really took place was what follows.