[Indorsement.]

HDQRS. FIRST DIV., THIRD CORPS, ARMY OF THE POTOMAC,
Fort Lyon, September 4, 1862.

Respectfully forwarded as the official report drawn up by the late Major General Philip Kearny, and intended to have been signed by him the day of his death.

D. B. BIRNEY,

Brigadier-General, Commanding Division.

Numbers 54. Report of Brigadier General David B. Birney, U. S. Army, commanding First Division, of the battle of Chantilly.

HEADQUARTERS FIRST DIVISION, THIRD CORPS,
Camp Fort Lyon, Va., September 4, 1862.

SIR: I have the honor to report the part taken by this division in the battle at Chantilly, between Centreville and Fairfax Court-House, on Monday, September 1.

The division reached Chantilly at about 5 o'clock p.m., under orders from Major-General Heintzelman to support General Reno, and found him actively engaged with the enemy.

Under orders from Major-General Kearny I reported my brigade to General Reno, and was ordered by him to the front. On reaching that point I found the division of General Stevens retiring in some disorder before the enemy, the officers in command of regiments stating that their ammunition had been exhausted. I immediately ordered forward the Fourth Maine Regiment, and it gallantly advanced, and was soon in active conflict. I successively took forward the One hundred and first New York, Third Maine, Fortieth and First New York. These regiments held the enemy, and sustained unflinchingly the most murderous fire from s superior force.

At this juncture General Kearny reached the field with Randolph's battery, and, placing it in position, aided my brigade by a well-directed fire. I pointed out to the general a gap on my right, caused by the retiring of Stevens' division, and asked for Berry's brigade to fill it. He rode from me to examine the ground, and dashing past our lines into those of the enemy, fell a victim to his gallant daring. I sent forward the Thirty-eighth New York and Fifth-seventh Pennsylvania to complete our victory. They advanced gallantly, and night closed in, leaving my brigade in full possession of that portion of the battle-field in which we were engaged.

General Kearny not returning, and supposing that he had been taken prisoner, I assumed command of the division, and ordering forward Robinson's and Berry's brigades, relieved my tired regiments, and held until 3 o'clock a.m. September 2 the battle-ground, at which time I followed with the division the corps of General Reno to Fairfax Court-House.

During the night we removed our wounded. Our loss has been heavy, a detailed statement of which, with reports of regimental and brigade commanders, will be shortly forthcoming.

I was ably supported by the commanding officers of my regiments, all of whom sustained the high character accorded to them by our late lamented commander in his report of Friday's engagement.