Ruins and other vestiges revealing an ancient civilization are found throughout the whole southern section of North America, extending as far north as New Mexico and Arizona. But here the antiquities do not all belong to the same period in the past, nor exhibit unvarying likeness and unity of civilized life. They are somewhat less homogeneous, and do not constantly represent the same degree of civilization. In this region, the monuments suggest successive and varying periods in the civilized condition of the old inhabitants, some of the oldest and most mysterious monuments seeming to indicate the highest development. In the northern part of this region we find ruins of great buildings similar in plan and arrangement to those still used by the Pueblos, but far superior as monuments of architecture, science, and skill, and much more unlike those farther south than is apparent in the principal structures of the Mound-Builders. They show that the old settlers in the Mississippi Valley did not belong to the Pueblo branch of the Mexican race. Farther south, in the central part of the region specified, development was more advanced. Here, in the last ages of American ancient history, was the seat of the Mexican or Aztec civilization, but the monuments in this part of the country are mostly older than the Aztec period. The most astonishing remains are found still farther south, in Chiapa, Tabasco, Oxaca, Yucatan, Honduras, Tehuantepec, Guatemala, and other parts of Central America. In this southern region, mostly buried in heavy forests, are wonderful ruins of great cities and temples. Only a small part of modern Mexico is included in the region where these ruins are situated, and most of them, probably, were not much better understood by the ancient Mexicans than they are by us. Many of those explored in later times were unknown to that people, just as others, more in number, doubtless, than those already described, still remain unvisited and unknown in the great and almost impenetrable forests of the country. THE NORTHERN REMAINS.