The civilization of the Aztecs who built the old city of Mexico will be made a separate topic; but it may be said here that when they came into the Valley of Mexico they were much less advanced in civilization than their predecessors. There is no reason whatever to doubt that they had always resided in the country as an obscure branch of the aboriginal people. Some have assumed, without much warrant, that they came to Mexico from the North. Mr. Squier shows, with much probability, that they came from the southern part of the country, where communities are still found speaking the Aztec language. When they rose to supremacy they adopted, so far as their condition allowed, the superior knowledge of their predecessors, and continued, in a certain way, and with a lower standard, the civilization of the Toltecs. It has been said, not without reason, that the civilization found in Mexico by the Spanish conquerors consisted, to a large extent, of “fragments from the wreck that befell the American civilization of antiquity.” THE GREAT RUINS AT THE SOUTH. To find the chief seats and most abundant remains of the most remarkable civilization of this old American race, we must go still farther south into Central America and some of the more southern states of Mexico. Here ruins of many ancient cities have been discovered, cities which must have been deserted and left to decay in ages previous to the beginning of the Aztec supremacy. Most of these ruins were found buried in dense forests, where, at the time of the Spanish Conquest, they had been long hidden from observation.