Numbers 35. Report of Brigadier General Truman Seymour, U. S. Army, commanding First Brigade, of the battle of South Mountain.

HDQRS. FIRST Brigadier, PENNSYLVANIA RES. VOL. CORPS,
Near Sharpsburg, Md., September 24, 1862

CAPTAIN: Of the movements and conduct of this command during the recent battles at South Mountain and near this place, I have the honor to report as follows:

The brigade is composed of the First Pennsylvania Rifles, better known as Bucktails, Colonel McNeil; First Regiment, Colonel R. Biddle Roberts; Second, Captain Byrnes; Fifth, Colonel Fisher, and Sixth, Colonel Sinclair, all of which regiments are much reduced in numbers and strength by the battles and exposures of the Peninsula.

On the 14th instant, Hooker's corps being ordered to engage the left of the rebel position on South Mountain, this brigade was placed on the extreme right, and after being massed at the base of the slope, was advanced through open woods and over cultivated ground, on the right of a road leading up a ravine, and intersecting the turnpike in rear of the mountain. The Bucktails were thrown forward as skirmishers, supported by the Second and two companies of the First; the remainder of the brigade followed closely.

On a prominent hill on his extreme left, and on our right of the road alluded to above, the rebels had posted a regiment, the Sixth Alabama. A brisk fire was opened upon our skirmishers by this regiment, and by a battery on the mountain to our left. The exposure was great, and numbers fell under the accurate fire of the shell from these guns, but the enemy was rapidly driven, the hill won, and many prisoners taken. Looking to the left, an extended field of corn led directly to the main position on the mountain itself. The First, Second, and Fifth changed direction, and, supported by the Sixth in column of companies, continued the attack. A few volleys were fired, bayonets were leveled, three hearty cheers given, and the whole line moved quickly up the hillside with an impetus that drove the enemy from cover and gave us the crest in time to anticipate a fresh brigade which was advancing to support their line, but which then turned in retreat. Later other brigades came up on our left, and night coming on, the pursuit, from the rough nature of the ground, had to be abandoned.

Rodes' brigade of five Alabama regiments was understood to have been in our front on this occasion. The brigade lost many good officers and men, but the advance was superb in its steadiness and resolution, and was thoroughly successful in its results.

To Colonel Fisher, Colonel Sinclair, Colonel R. Biddle Roberts, Colonel McNeil, of the Rifles, and Captain Byrnes, great praise is due for the energy and courage with which their regiments were led into action, and their promptness in carrying out my orders.

I am, captain, very respectfully, your obedient servant,

T. SEYMOUR,

Brigadier-General U. S. Vols., Commanding First Brigade.

Captain E. C. BAIRD,

Asst. Adjt General, Headquarters Meade's Division,