Their sway seems to have been confined for a long time to Anahuac. They grew to supremacy in part probably by the arrival of new immigrants, but chiefly by conquest of the small states into which the country was divided. They could learn from their more cultivated neighbors to reform their calendar, compute time with greater accuracy, and make important improvements in other respects. They must also have modified their religious system to some extent, for it does not appear that they had adopted the worship of Kukulcan (whose name they transformed into Quetzalcohuatl) before they came to Mexico. But they brought with them an effective political organization, and very likely they were better fitted than most of their new neighbors for the rude work of war. Before the city of Mexico was built, the seat of their government was at Tezcuco. The character of their civilization after they rose to pre-eminence was shown in their organization, in their skill as builders, in the varied forms of their industry, and in the development of their religious ceremonies. It is manifest that they adopted all the astronomical knowledge and appliances found in the neighboring states which they subjugated. Their measure of the solar year and their numbering of the months were precisely like what had long existed in this part of the country; and they had the same astronomical implements or contrivances. One of these contrivances, found at Chapultepec, is described as follows: “On the horizontal plane of a large, carefully-worked stone, three arrows were cut in relief, so that the shaft ends came together and made equal angles in the centre. The points were directed eastward, the two outside showing the two solstitial points, and that in the centre the equinoctial. A line on the carved band holding them together was in range with holes in two stones which stood exactly north and south. A cord drawn tightly through the holes in these two stones would, at the moment of noon, cast its shadow on the line drawn across the band. It was a perfect instrument for ascertaining east and west with precision, and for determining the exact time by the rising and setting of the sun at the equinoxes and solstices. This stone has now been broken up and used to construct a furnace.”