In the course of the day two companies, and later four companies of the Thirty-first and two of the Sixteenth were, by Colonel Miles' order, thrown forward to feel the enemy's strength to the front and left in the direction of Bull Run. They found the enemy posted in the woods, and were recalled. They reported having killed several of the rebel scouts.
The afternoon, till about 4 o'clock, was passed in great inactivity, except the firing by the rifled cannon at moving columns of the enemy at great distances. I had seen unmistakable evidences in the afternoon by clouds of dust, &c., of the concentration of the enemy's troops on our left, but received peremptory orders from Colonel Miles to hold the position and remain there all night. He then left me in command for the night, and I immediately began to prepare for an attack. I threw out two companies of skirmishers in the woods to our rear, and ordered the Thirty-second forward to support them.
About 4 o'clock we saw the enemy approaching down a gorge leading into a valley which lay directly to our left, about five hundred yards distant. The field in which I was ordered to remain was was inclosed on two dies by dense woods, and covered by light bushes on the side toward the said valley on the left. After the enemy was discovered filling into the valley, no movement was made for some time. When it was supposed from the appearance of things that the last of the column was entering the valley, I ordered all the artillery (six pieces) to change front to the left, but not to fire till the rear of the column showed itself. I placed the artillery with a company of infantry between each piece, and changed the battle front of the two regiments (the Sixteenth and Thirty-first) supporting the artillery to the left, and on a line with the artillery, and ordered every man to lie down and reserve his fire. During the whole time that this order was being carried out the enemy's troops were still advancing down the hill, four abreast and at right shoulder shift. I gave orders to Lieutenant Edwards, when I saw the rear of the column, to give it a solid 20-pounder shot, which he did, knocking a horse and his ride into the air, and starting on a double-quick the rear of the column into the valley. I then ordered the whole in to the valley. I then ordered the whole artillery to pour grape and canister into the valley, and at every fire there went up a tremendous howl from the enemy. During all this time the enemy poured volleys of musketry over the heads of our prostrate men. This firing continued from twenty-fire to thirty minutes. A portion of the enemy rushed not a barn, and well-directed shots brought out what was left in great haste. The whole force of the enemy, consisting, as nearly as I could estimate from the time of their passage at one point and from what I can find out, of 3,000 infantry and 2,000 cavalry, was utterly dispersed. A small number of the dispersed troops came up into the edge of the field in the bush (from the number of shots fired, amounting probably to about fifty), and fired five volleys at our prostrate men, but did not succeeded in drawing a shot from them in return.
It having been ascertained that the enemy had left the field, from their having ceased firing, and from seeing them run through the bushes in every direction, and hearing at the same time that our troops were falling back on Centreville, I received orders by an aide from Colonel Miles, who was in Centreville, to fall back on Centreville and encamp. I immediately went over to give the same order to Richardson's brigade on the Centreville road, and also to Greene's battery, but found they had left some time before by Colonel Miles' order through an aide. The Thirty-first Regiment, under Colonel Pratt, filed out of the field in rear of the artillery, and the Sixteenth followed, under Lieutenant-Colonel