Fig. 11. Diagram of Culture Strata at Atzcapotzalco.
Temple mounds of Toltecan period. Surface finds of Aztecan period. Remains of Toltecan period. Deep stratum of water-bearing gravels containing remains of archaic period. Bed rock of hard clay.
At other sites, such as Colhuacan, the Toltecan layer is of greater thickness and the archaic layer of lesser thickness. The remains extend below the present level of the water and may indicate that considerable changes have taken place in the level of the lake. But we must remember that many of the ancient settlements were built over the water and that land was made in ancient times, as it is today in the gardens of Xochimilco, by deepening canals. Archaic remains are also common on the denuded tops of hills which may once have been covered by soil.
A stratification of archæological remains has recently been determined in Salvador.
The Cemetery under the Lava.
An ancient cemetery lying under lava has recently been explored in Copilco, a suburb of Mexico City. The lava swept down from Mount Ajusco in some cataclysm perhaps 3000 years ago, covering many square miles of territory to the depth of thirty or forty feet, and burying such villages as chanced to lie in its path. (See [Pl. VI]b). The discovery of human remains was made several hundred feet back from the original front of the lava flow in a quarry where lava rock was being removed to build roads. Tales of clay figurines found under the lava in this quarry had been current for years, but no serious investigation was made until human burials were met with in the earth under the great lava cap. Then a series of tunnels was dug and a considerable number of ancient burials were uncovered, but not moved from their original position. One now enters an electric-lighted graveyard and sees human bodies lying exactly as they have lain for untold centuries, with the funeral offerings beside them. This enormously important find gives us an historical level in mid-Archaic.
Another site, at Cuicuilco, on the opposite side of the lava flow, has received attention from archæologists. Here a great round mound rises in terraces faced with cobblestones. It is surrounded by the lava flow and some persons have assumed that the mound was already abandoned and in decay when the lava flow took place. Perhaps, however, the mound was built on a piece of land that the lava flow had spared. There are no contacts between the lava and the mound except at the ends of two projecting aprons or causeways. The pottery at this site is sufficiently different from that found at Copilco.
[Plate VI.]
(a) Cuicuilco. A view showing cobblestone facing of mound and lava in contact with apron or causeway.