lupe. But at the period of Scott's invasion of the valley, General Valencia, with the troops that were afterwards convened at Contreras, was stationed at Tezcoco, either for the purpose of observation, or to induce an attack in that quarter, and thus to draw our forces into a snare on the northern route, or to fall on the rear of the American commander if he attacked El Peñon, or advanced by the way of Mexicalzingo. At Santiago Zacualco, west of the lake and on the route, formidable works were thrown up to defend the entire space between the western shore of lake Tezcoco and the mountains; while on the road to Queretaro, at the mountain pass north of Tenepantla, other defences were erected, so as to screen the country on all sides of the group of hills which lies west of the lakes of Tezcoco and San Cristoval and north of the town of Guadalupe Hidalgo.
The fourth and last advance to the city was that which turned to the south from the Hacienda of Buena Vista, and passing by the town of Chalco, led along the narrow land intervening between the shores of lake Chalco and the first steeps of the mountains forming the southern rim of the valley, until it fell at right angles, at Tlalpam or San Agustin de las Cuevas, into the main road from the city of Mexico towards the southern States of the Republic.
All these routes were boldly reconnoitred by the brave engineers accompanying the American army, and, where they could not extend their personal observations, the officers obtained from the people of the country, information upon which subsequent events proved that they were justified in relying. From the knowledge thus gained as to the route south of the lake of Chalco, they were induced to believe, although it was rough, untravelled, difficult, and narrowly hemmed in between the lake and the mountains, yet that the long and narrow defile, which was open to resistance at many points, was not sufficiently obstructed or fortified to prevent our passage. All the routes on the lower lands, it should also be remembered, were liable to increased difficulties from the deluging rains prevailing at this season on the highlands of Mexico, and which sometimes convert the highways and their borders, for many leagues, into almost impassable lagunes.
Santa Anna and his engineers had probably supposed that this southern route would not be adopted, but a reasonable explanation of his conduct is given by one of the most competent commentators upon the valley of Mexico and the march of the American ar-
