I insert my official report, as a condensed statement of my share in the battle: 

HEADQUARTERS THIRD BRIGADE, FIRST DIVISION FORT CORCORAN, July 25, 1861

To Captain A. BAIRD, Assistant Adjutant-General, First Division (General Tyler’s).

Sir:  I have the honor to submit this my report of the operations of my brigade during the action of the 21st instant.  The brigade is composed of the Thirteenth New York Volunteers, Colonel Quinby’s Sixty-ninth New York, Colonel Corcoran; Seventy-ninth New York, Colonel Cameron; Second Wisconsin, Lieutenant-Colonel Peck; and Company E, Third Artillery, under command of Captain R. B. Ayres, Fifth Artillery.

We left our camp near Centreville, pursuant to orders, at half-past 2 A. M., taking place in your column, next to the brigade of General Schenck, and proceeded as far as the halt, before the enemy’s position, near the stone bridge across Bull Run.  Here the brigade was deployed in line along the skirt of timber to the right of the Warrenton road, and remained quietly in position till after 10 a.m.  The enemy remained very quiet, but about that time we saw a rebel regiment leave its cover in our front, and proceed in double-quick time on the road toward Sudley Springs, by which we knew the columns of Colonels Hunter and Heintzelman were approaching.  About the same time we observed in motion a large mass of the enemy, below and on the other side of the stone bridge.  I directed Captain Ayres to take position with his battery near our right, and to open fire on this mass; but you had previously detached the two rifle-guns belonging to this battery, and, finding that the smooth-bore guns did not reach the enemy’s position, we ceased firing, and I sent a request that you would send to me the thirty-pounder rifle-gun attached to Captain Carlisle’s battery.  At the same time I shifted the New York Sixty-ninth to the extreme right of the brigade.  Thus we remained till we heard the musketry-fire across Bull Run, showing that the head of Colonel Hunter’s column was engaged.  This firing was brisk, and showed that Hunter was driving before him the enemy, till about noon, when it became certain the enemy had come to a stand, and that our forces on the other side of Bull Run were all engaged, artillery and infantry.

Here you sent me the order to cross over with the whole brigade, to the assistance of Colonel Hunter.  Early in the day, when reconnoitring the ground, I had seen a horseman descend from a bluff in our front, cross the stream, and show himself in the open field on this aide; and, inferring that we could cross over at the same point, I sent forward a company as skirmishers, and followed with the whole brigade, the New York Sixty-ninth leading.