You will please excuse the irregularity of the report, but the general left at a very early hour this morning to visit the railroad from Fairfax to Sangster's, and has not yet returned.

Yours, very respectfully,

WM. A. LA MOTTE,

Assistant Adjutant-General.

HEADQUARTERS DIVISION

Fairfax Courthouse, Va., December 18, 1863 - 5:30 a.m.

COLONEL: Lieutenant-Colonel De Lacy, One hundred and sixty-fourth New York Volunteers, who commanded the detachment of cavalry and infantry sent out in search of the enemy on the Centreville road, has returned to camp, and reports that about two miles from Centreville the enemy fired on his advance guard, composed of cavalry. The cavalry broke and ran to the rear, causing great confusion. After rallying the whole force, and throwing out skirmishers of infantry and flankers of cavalry, he pushed on about half a mile from where the enemy attacked, but not knowing their force, and fearing they might attack his rear, he retired to the Sangster's Station road, hoping that they might follow; but after waiting there an hour and not seeing any of them, he returned to camp. The enemy retired in the direction of Aldie. I am about to visit Sangster's and Fairfax Stations, and will report more fully on my return.

MICHAEL CORCORAN,
Brigadier-General Commanding.

Lieutenant Colonel J. H. Taylor,

Chief of Staff, and Assistant Adjutant-General.

[P. S.] - I request that the cavalry squadron now under my command be relieved by a more efficient detachment; and that one troop be added to the cavalry force at this post, as in this case, as well as many others, the cavalry force has proved insufficient to intercept the enemy.

FAIRFAX COURTHOUSE, December 18, 1863.

(Received 12 p.m.)

SIR: I have just returned from Sangster's Station, and ascertained beyond a doubt that the enemy were commanded by General Rosser, and left Fredericksburg on Wednesday night. The company at Sangster's Station, officers and men, deserve much credit for their gallantry. They repulsed the enemy four times, and only retreated when the enemy had got so far on their flank and rear as to have set all their tents on fire. Four of the enemy's horses have been killed and 3 ambulances were sent back with killed and wounded. The wounded man of the enemy, reported this morning, has since died on our hands. He was named Van Meter, of the Eleventh Virginia Cavalry, and had a pass in his possession giving him permission to visit Fredericksburg on the 16th instant. They went by Centreville. The party sent by me from Fairfax Courthouse came up with their rear, as reported this morning. Damage done to bridge was slight, as the fire was extinguished by our men. Trains are running now.

MICHAEL CORCORAN,

Brigadier-General.

Lieutenant Colonel J. H. Taylor,

Chief of Staff, and Assistant Adjutant-General.