The cavalry was commanded by that redoubtable soldier, the Murat of the Army, Brt. Brig. Genl. Wm. S. Harney, and consisted of detachments of the 1st, 2nd, and 3rd Dragoons, to the number of about seven hundred and fifty. After a toilsome march of about seventy miles, across mountain spurs and along a very rugged road, the army, on the afternoon of August 17th, 1847, looked down for the first time on the valley of Mexico, and saw from afar its magnificent capital, with the golden crosses of its churches glittering in the red light of the setting sun. There lay before us the same broad lake, mirroring the same snow-crowned mountains in its glassy bosom, on which Cortez with his steel-clad warriors had gazed, in the same month, three hundred and twenty six years before. On reaching a point about nine miles from the city, General Scott ascertained by a _reconnaissance_ that the Mexicans had fortified El Peñón, a mountain that commanded the approach to the capital by the National road. He therefore ordered a counter march with the view to turn the lake (Chalco) on the south. This required a march of twenty five miles, which was rapidly made, and on the 18th, the army was concentrated at a point about ten miles from the city at Contreras, a strong position held by General Valencia, with field-works mounting twenty-four guns. These, General Scott determined to take in reverse, and we therefore made a night march of eight miles over the pedregal or lava fields, a route deemed by the Mexicans impracticable for any army. The assault was made on the rear and flanks of the surprised enemy soon after daylight on August 20th, by Riley’s Cadivalders and Shield’s Brigades, all under the command of General P. F. Smith, whom General Shields, although ranking above him, magnanimously allowed to retain the command that he might carry out dispositions made prior to the arrival of Shields on the ground. The whole line of works was stormed, and the battle won in eighteen minutes. The enemy broke at the first assault, and fled in the direction of the city, and nearly five hundred of them were captured by the New York Volunteers and the Palmetto regiment, that were posted to cut off their retreat. At this battle two guns of the 4th Artillery, that were lost without dishonor at Buena Vista, were recaptured from the enemy. The army, after resting a few hours at St. Augustine, a town about four miles from Contreras, marched against the main body of the enemy, distant six miles from the former point. We were soon in the presence of the Mexican Army, thirty thousand strong, commanded by Santa Anna, and composed of the best troops of Mexico, including several thousand volunteers. It occupied a vast intrenched camp near the village and convent of Churubusco, about seven miles from the capital.