At 4 P. M., I reported to General Worth, who was then with his forces, in the suburbs of the city, on the San Cosme causeway, at the point where it changes direction, at an angle of nearly ninety degrees, and is then nearly straight for about six hundred yards to the fortified Garita in our front. He informed me that Lieutenant Stevens had just been severely wounded and this made me the senior engineer with Worth's division. He directed me to go forward in person, closely examine the condition of affairs at the front, endeavor to determine the best method of operating against the fortified Garita, and report to him the result of my observations as soon as possible. He directed me, particularly, to have in view the question whether it would be advisable to bring the siege guns forward against the embrasured battery at the Garita. Just as I was leaving him, he said: "If you find there are two different methods by which the Garita can be carried, one in a shorter time at a sacrifice of men, the other in longer time, but a saving of men, choose the latter". And he added: "There have been too many valuable lives, of officers and men, lost recently in my division, for nothing". Though he did not specify the action referred to, he meant the battle of Molino Del Rey. Under these instructions, I proceeded to the extreme front, made the requisite examination of our position and that of the enemy, and soon came back. I reported that the houses on the left of the causeway were built up continuously to the battery at the Garita, we could easily break through the walls from house to house; and, under perfect cover, reach the top of a three-story building, with flat roof and stone parapet, within 40 yards of the battery. A fire of musketry from that roof would make the works untenable; and we could thus in a short time drive the enemy from the fortified Garita, and secure a good lodgement within the city, without material loss and without using the siege guns. General Worth directed me to bring forward the engineer company, which was with the siege train a short distance to the rear, and commence operations on the proposed plan; and at the same time ordered that Clarke's brigade should render any assistance I might call for. An hour or more before sunset we reached the top of the house above referred to. From that position the inside of the enemy's works could be plainly seen almost to the foot of the interior slope of the parapet. Our first fire upon the Mexicans, who were unconscious of the impending peril, was very deadly. Those who were not killed or disabled by that fire seemed dazed for an instant; but in a few moments, they precipitately retreated, leaving the San Cosme Garita without a single defender in the works. One of their pieces of artillery was withdrawn a few hundred yards, but was then abandoned.