immediately driven off and pursued by the reserve. Nothing else occurred during the day. The commanding officers of the pickets od the Cavalry Reserve Brigade report the enemy's vedettes near Mitchell's Station, and heard, during the night, trains moving; also the whole of the cars, and cheering and beating of drums. One pale blue rocket was sent up by the enemy to the right of Thoroughfare Mountain.

THOS. C. DEVIN,

Colonel, commanding First Cavalry Division.

Colonel C. Ross Smith,

Chief of Staff.

_________________________

DECEMBER 18-20, 1863. - Scout from Vienna to Middleburg, Va.

Report of Colonel Charles R. Lowell, jr., Second Massachusetts Cavalry.

Vienna, Va.,

December 20, 1863.

COLONEL: I have the honor to report that on Thursday night [17th instant] about 10 o'clock General Corcoran sent a communication that his picket at Sangster's Station had been attacked by a large party of guerrillas, and that he had sent a party of Cavalry and infantry out toward Centreville to intercept them. Not suspecting that it amounted to anything more than some operations of Kincheloes guerrillas, I simply assured myself that the pickets and outposts were on the alert. During Friday forenoon, hearing from Alexandria that the bridge had been destroyed, I made preparations to go out, and was just starting when your telegram reached me.

An officer whom I sent to Fairfax Courthouse failed to obtain any definite information, and inferring that the party had gone toward Aldie, I went up Little River pike and came upon their trail 2 miles beyond Chantilly. As far as I learned, the forces, consisting of Jones' old brigade (now Rosser's) of three regiments, amounting to 1,100 cavalry and 200 dismounted men, and White's battalion of from 300 to 400, left Falmouth Thursday forenoon without any wagons, starting with 1 ambulance, which they soon sent back. They traveled rapidly, and at daylight Friday morning were in Middleburg. They passed through Upperville and Paris about 9 o'clock toward Benig's Ford. Stragglers told the citizens that they were going to winter on the Shenandoah, as they did last year; that they lost a captain and two men in the attack on the picket at Sangster's and three men were drowned crossing the Occoquan. I arrived at Middleburg at daybreak Saturday morning. Going up we saw nothing but 5 of Mosby's men, whom we pursued, and captured 4 of their horses and accouterments, 3 men and 1 horse escaping in the woods. I turned around and sent a party into Leesburg to find out about White's movements. A few of his men had been there Friday afternoon, and it appears to be White's intention to winter in Loudoun County. Mosby evidently expected this movement, and his command aided as guides and scouts.

I divided my command into four parties coming home. A party returning through Dranesville, surrounded a house where they