[4] Colonel Joseph G. Totten. Chief Engineer, had left Vera Cruz and returned to his duties in Washington City. Major John L. Smith then became Senior Engineer with General Scott's forces. CHAPTER IV. FROM PUEBLA TO CHURUBUSCO. On the 7th of August, 1847, the advance of General Scott's army, Twiggs' division, the engineer company leading, left Puebla and commenced the forward movement into the valley of Mexico. The company served with that division, until Worth's division was placed in the lead during the turning movement made by the army around Lake Chalco. In that movement the engineer company was at the head of Worth's division. The road ran between the western border of the lake and a high range of hills which, in some places, rose from the water's edge. The road was narrow and rough; and had been obstructed by rolling immense masses of stone upon it from the almost overhanging cliffs. These obstructions were of considerable height; they completely blocked our way; and at several points ditches had been cut across the road. General Worth directed the Light Battalion, under Colonel C. F. Smith, to advance and drive off the Mexicans who were firing upon us--ordered me to make the road passable for artillery and wagons as soon as possible--and notified me that the leading brigade would assist in that work when called upon. I immediately asked for a detail of 500 men; put them to work, at once, under the direction of the officers and men of the engineer company, and everything was progressing rapidly, when, to my surprise, Lieutenant J. C. Pemberton, aide to General Worth, came up to me and insisted that the whole character of the operations should be changed. Whilst he was elaborating his views I cut him short by asking if he had any orders for me from General Worth. In the meanwhile the latter had reached the front, without either Pemberton or I being aware of his presence. Before the aide had time to reply to my question, General Worth, in a very peremptory tone called out "Come away from there Mr. Pemberton, and let Mr. Smith alone. This is his business--not yours". In a few hours, the road was put in such condition that, by the use of drag-ropes and men at the wheels, we were enabled to pass artillery and wagons over the obstructions; and the column moved on without further material delay. After reaching San Augustine, and passing beyond, the forward movement, now on the main road, or causeway, leading from Acapulco to the city of Mexico, was checked by fortifications about six hundred yards in our front. These fortifications crossed the road at San Antonio, and were occupied by the enemy in large force. The afternoon of the 18th of August, was spent in reconnoitring that position.