Reinforcements arrived but slowly, and each detachment, as it moved from Vera Cruz to the mountains, had to sustain a running fight with the guerrillas whom Santa Anna had let loose on the road. All arrived, however, in safety, and by the beginning of August General Scott was ready to move on the valley of Mexico with ten thousand seven hundred and thirty-eight men, leaving Colonel Childs with fourteen hundred to garrison Puebla. On the third day they stood upon the summit of the ridge which looks down upon the valley of Mexico, with the city itself glittering in the centre, and bright lakes, grim forts, and busy causeways dotting the dark expanse of marsh and lava. That night the troops encamped at the foot of the mountains and within the valley on the border of Lake Chalco. With the energy which characterized Santa Anna throughout the war, he had prepared for a desperate defence. Civil strife had been silenced, funds raised, an army of twenty-five thousand men mustered, and every precaution taken which genius could suggest or science indicate. Nature had done much for him. Directly in front of the invading army lay the large lakes of Xochimilco and Chalco. These turned, vast marshes, intersected by ditches and for the most part impassable, surrounded the city on the east and south--on which side Scott was advancing--for several miles. The only approaches were by causeways, and these Santa Anna had taken prodigious pains to guard. The national road to Vera Cruz--which Scott must have taken had he marched on the north side of the lakes--was commanded by a fort mounting fifty-one guns on an impregnable hill called El Peñon. Did he turn the southern side of the lakes, a field of lava, deemed almost impassable for troops, interposed a primary obstacle, and fortified positions at San Antonio, San Angel, and Churubusco, with an intrenched camp at Contreras, were likewise to be surmounted before the southern causeways could be reached. Beyond these there yet remained the formidable castle of Chapultepec and the strong enclosure of Molino del Rey to be stormed before the city gates could be reached. Powerful batteries had been mounted at all these points, and ample garrisons detailed to serve them. The bone and muscle of Mexico were there. Goaded by defeat, Santa Anna never showed so much vigor; ambition fired Valencia; patriotism stirred the soul of Alvarez; Canalejo, maddened by the odium into which he had fallen, was boiling to regain his sobriquet of “The Lion of Mexico.” With a constancy equal to anything recorded of the Roman Senate, the Mexican Congress, on learning the defeat at Cerro Gordo, had voted unanimously that any one opening negotiations with the enemy should be deemed a traitor, and the citizens with one accord had ratified the vote. Within six months Mexico had lost two splendid armies in two pitched battles against the troops now advancing against the capital; but she never lost heart. CONTRERAS