Page:History of the War between the United States and Mexico.djvu/388

338 some of them are now girded by barren strips of land, covered with white sand, or incrusted salts. Standing close beside them, they appear much less beautiful than in former days, but seen in the distance, with the Sunlight streaming over them, they appear like a cluster of rich jewels in a framework of silver.

The principal lakes in the valley are five in number. The salt lake, Tezcuco, occupies the lowest ground, near the centre of the basin; separated from it by a narrow isthmus on the north, is San Christóbal, and further to the north-west is Lake Zumpango; between five. and six miles south of Tezcuco, is Xochimilco, and near the eastern extremity of the latter is Lake Chalco. At the period of the conquest by the Spaniards, the city of Mexico was entirely surrounded by the waters of Lake Tezcuco, and connected with the mainland by three massive causeways or dikes, which, at this day, form important avenues to the capital. For along time it was liable to frequent inundations, when the great central reservoir, which received the surplus waters of the other lakes, was swollen beyond its ordinary height. The elevation of the site by the ruins of the ancient dwellings of the Aztecs, thrown down by Cortés during the siege, — the subsidence of the waters — the building of embankments and sluices, — and the construction of the great drain of Huehuetoca. in the seventeenth century, — have entirely obviated the danger. The plaza mayor, or great square, is now four feet higher than the average level of Tezcuco; but the