On the 12th a reconnoissance of the Peñon was made by Captains Lee and Mason and Lieutenant Stevens, the escort consisting of a squadron of the dragoons, Captain Thornton, a section of Taylor’s battery, and the 4th artillery,—the whole under the command of Major Gardner. The Peñon was found to be an extensive and commanding position, entirely surrounded by water,—Lake Tezcuco stretching miles to the north. The base of the hill, four hundred feet high, was surrounded by a continuous parallel armed with batteries, and the defenses rose in amphitheatre to the top, which was crowned by a small work. The only causeway of approach was swept by two lines of works, and the defenses of the whole position were formidable. A road branching off from the main road, two miles from the Peñon, and leading to Mexicalcingo, was pursued some two miles, and found to be exceedingly good. The Indians in the neighborhood reported that the road was equally good throughout its whole extent, but that the bridge at Mexicalcingo was broken down.
An amusing incident occurred in the progress of this reconnoissance. Three officers—Major Gaines, of the Kentucky volunteers, Captain Mason and Lieutenant Stevens, of the engineers—approached the causeway some three quarters of a mile in advance of the escort, and advanced towards a group of Mexican officers, some eight or ten in number, who were flourishing their lances and curveting their horses as if to frighten the American officers away. The latter, well mounted, continued their course in a deliberate walk; and when they arrived within about three hundred yards, the valiant Mexicans discharged their pistols, and, finding no effect had been produced upon the American officers, who still continued to advance, they immediately took to flight along the causeway.
In the afternoon Captain Lee and Lieutenant Beauregard reconnoitred the road on the northern shore of Lake Chalco, as far as the causeway between Lakes Chalco and Xochimilco. The causeway was knee-deep in water. The object of the reconnoissance (to get boats) was not effected. During the progress of the reconnoissance of the Peñon the Mexican troops, in expectation of an attack, were brought out from the city in large numbers. Major Smith and Lieutenant Tower, from a hill one thousand feet high, in advance of Ayotla, observed the passage of troops from the city to the Peñon during the progress of this reconnoissance.
On the 3d a minute reconnoissance of the ground between the lakes was made by the engineers, supported by Shields’s brigade, who at nine o’clock left camp to block up the Peñon.
Captain Mason, supported by Sibley’s dragoons and the rifles, and accompanied by Lieutenants Beauregard and McClellan, examined the position of Mexicalcingo, seven miles from the Peñon, pursuing the road that was partially examined yesterday. This bold movement, almost under the guns of the Peñon, and extremely hazardous in presence of an enterprising enemy, was accomplished in the most successful manner. After arriving at Mexicalcingo the party was joined by Captain Lee and Lieutenant Tower, who, with a squadron of dragoons, had taken the route of the lakes to examine the roads.
Mexicalcingo was found to be a strong position, defended by seven batteries, and entirely surrounded by water and marshy ground.
The Peñon was minutely examined by Lieutenant Stevens, who entered the inundation at several points, and succeeded in examining the whole position, excepting a very inconsiderable portion on the western slope. He entered the lake, and for a whole mile the water did not rise above the fetlocks of his horse. South of the causeway the water was carefully examined to determine the best crossing-place. Two were found where water was not over two feet in depth, and the bottom very hard. The positions of the several batteries and the paths of approach were discovered. The position was even more formidable than it seemed yesterday. Over thirty guns were in position. New batteries were being erected, and stockades on the hill. The whole inundation was swept by powerful batteries. Lieutenant Stevens was engaged seven hours in this reconnoissance, most of the time within twelve hundred yards of the enemy’s guns.
We all returned late, much fatigued with our day’s work. The general expressed much gratification at the information furnished by the several reconnoissances.
The general has not yet entirely decided upon his course. He listens to everything, weighs everything, and, when he sees his way clear, will act with promptitude. Pillow arrived to-day, and immediately proceeded to Chalco.
August 14. Little was done to-day in the way of reconnoissances. Captain Mason and Lieutenant Beauregard were assigned to duty with the division of General Worth, and joined him at Chalco. Lieutenant Tower commenced a reconnoissance of the lakes, to determine the practicability of transport by water to Mexicalcingo, but did not succeed in getting into the canal of Chalco. In the afternoon Colonel Duncan arrived at general headquarters with the information that the road south of the lakes was practicable. (He had explored ten miles of the road with a column.) Accordingly, the plan of the general to attack Mexicalcingo in front, sending Worth’s division around to attack in rear, was abandoned, and it was determined to move the whole army around the lakes.