236 CHALCO, XOCHIMILCO, TEZCOCO SALT-WORKS. 



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 pre- 

 ceding, and is likewise divided by a dam into two basins, the 

 northern called the Laguna de Xaltocan and the southern San Cris- 

 toval. 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 cal- 

 zada, across which the road passes from Tuliagualco to San Fran- 

 cisco 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 

 6% square leagues ; and their level, according to Baron Humboldt, 

 is 3 feet 9|- 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 mate- 

 rial 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 Penon, a volcanic pustule which rises abruptly from the plain 

 on the margin of the lake of Tezcoco. The temperature of the lat- 

 ter is quite high. 



The mode in which the valley is relieved from the danger of in- 

 undations in consequence of the rising of the waters of the lakes 



