Tezcoco, and supplies the rivers Pachuca and Quautitlan. The little village of Zumpango lies on its northern shore.
2d. The lake of San Cristoval is immediately south of the preceding, and is likewise divided by a dam into two basins, the northern called the Laguna de Xaltocan and the southern San Cristoval. In the first of these divisions are the villages of Xaltocan and Tomantla, built upon islands. This lake is twelve feet eight inches higher than that of Tezcoco, and its superficial area nearly 4 square leagues. On its shore lies the village of San Cristoval.
3d. The lake of Chalco spreads out at the southern extremity of the valley, and contains the village of Jico built on an island in its bosom. It is divided from the lake of Xochimilco by a dam, or calzada, across which the road passes from Tuliagualco to San Francisco Tlaltenango.
4th. The lake of Xochimilco is separated, as we have described, from that of Chalco; both of these basins cover a superficial area of 6½ square leagues; and their level, according to Baron Humboldt, is 3 feet 9½ inches above the great square of Mexico.
5th. The lake of Tezcoco is that in which the ancient city of Tenochtitlan was built upon the spot at present occupied by the modern city of Mexico, whose walls, however, are now reached by a canal of nearly a mile in length from the western borders of this inland sea. The rivers Teotihuacan, Guadalupe or Tepeyacac, Papalotla and Tezcoco are voided into it. The difference between its water-mark and the level of Mexico, which in Humboldt's time was four feet and one inch has been found by recent measurements to be 18 inches more. Its superficial extent is about 10 square leagues, and its waters are plentifully impregnated with salt, supplying the material for numerous works which are rudely conducted. A thick crust or deposit of carbonate of soda constantly whitens the edges of this lake, which are left bare by the receding of the waters after they have been swept over the leeward shores by the strong winds that occasionally prevail in the valley. The deepest parts of the lake of Tezcoco never contain more than from 6 to 8 feet of water, while some portions are not covered by more than two or three feet. There are two springs of mineral waters in the neighborhood of the capital;—one at Guadalupe, three miles from Mexico, and another at El Peñon, a volcanic pustule which rises abruptly from the plain on the margin of the lake of Tezcoco. The temperature of the latter is quite high.
The mode in which the valley is relieved from the danger of inundations in consequence of the rising of the waters of the lakes
