HEADQUARTERS FIRST CAVALRY DIVISION,
August 4, 1863.

SIR: This afternoon the enemy made an advance, with a strong force of cavalry (say, 2,000) and six guns, for the purpose of seeing what we were about. He drove my picket line back about 1,500 yards, when the division came up, and in turn drove him nearly 2 miles. My picket line to-night is 800 yards in advance of where it was yesterday. The enemy's reconnaissance was an utter failure. My casualties are trifling, say 5 to 10. The First and Reserve Brigades behaved like heroes. I send a report from Devin.

I am, very respectfully, your obedient servant,

JNO. BUFORD,

Brigadier-General of Volunteers, Commanding.

Colonel ALEXANDER,

Chief of Staff, Hdqrs. Cav. Corps, Army of the Potomac.

[Inclosure.]

HDQRS. SECOND BRIGADE, FIRST CAVALRY DIVISION,
Camp near Kelly's Ford, August 4, 1863.

Captain T. C. BACON,

Asst. Adjt. General, First Cavalry Division:

CAPTAIN: This morning I sent out two parties to observe the roads leading toward Stevensburg. The party on the main road (leading from Kelly's Ford toward Stevensburg), on arriving at Mountain Run, found the ford strongly picketed, with at least a squadron drawn up in line, besides the pickets and reserve. As they have not been instructed to go farther, they are now watching that approach.

The party on the river road found no picket at the run, but captured 1 furloughed soldier, Fourth Virginia Cavalry, who states that he was in Culpeper on Saturday, while we wee fighting. A. P. Hill's corps was there; Longstreet's corps was behind Pony Mountain; Ewell was near Madison Court-House; Robertson's brigade was in Stevensburg; Fitzhugh Lee's brigade left Brandy Station on Friday. Did not hear where General Lee's headquarters were. It was reported at the quartermaster's department in Culpeper that Lee's army was to have fallen back on Sunday morning.

I purpose feeling across Barnett's Ford to discover the enemy's line in that vicinity. As near as I can ascertain now, their outposts extend from Brandy Station across Mountain Run and the Culpeper road to Germanna Ford, and perhaps to Ely's.

Very respectfully, your obedient servant,

THOS. C. DEVIN,

Colonel, Commanding Brigade.