1st. The road to Acapulco on the west coast, which passes out of the valley over its southern rim of mountains at the point known as the Cruz del Marquez, about 2,284 feet above the city of Mexico, or 9,784 above the level of the sea. 2d. The road to Toluca, by Tianguillo and Lerma. 3d. The road to Queretaro, Durango, &c. called _El Camino de tierra adentro_, which leads across the eminences at the north of the valley, by an elevation of about 100 feet only above the level of the lakes. This road is the highway for the internal trade of Mexico with the northern provinces. 4th. The road to Pachuca and Real del Monte in the mining district, across the Cerro Ventoso. 5th. The road to Puebla, across Bonaventura and the plains of Apam. 6th. The _new_ road to Puebla and Vera Cruz, by Rio Frio and San Martin, across the northern shoulder of the volcano of Popocatepetl. It greatest elevation is at the barranca or ravine of Juanes, 10,486 feet above the level of the sea. Besides the two last mentioned roads there is a third, between the volcanoes of Popocatepetl and Iztaccihuatl, by Tlamanalco, Ameca, La Cumbre, and Cruz del Correo, passing out of the valley of Mexico into those of Cholula and Puebla. Five lakes are embosomed in the valley in the immediate neighborhood of Mexico:-- 1st. The lake of Zumpango, is the northernmost, and has an area of about 1-1/4 square leagues. A dam, called _La Calzada de la Cruz del Rey_, divides it into two basins, the westernmost of which is known as the Laguna de Zilaltepec, and the easternmost, the Laguna de Coyotepec. It is 26 feet higher than the mean level of the lake of 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 6-1/2 square leagues; and their level, according to Baron Humboldt, is 3 feet 9-1/2 inches above the great square of Mexico.