SEPTEMBER 12-16, 1863.-Scout from Harper's Ferry, W. Va., into Loundon County, and Skirmish (14th) near Leesburg, Va.

Report of Major Henry A. Cole, Battalion Maryland Cavalry (Potomac Home Brigade).

HARPER'S FERRY, W. VA., September 17, 1863.

SIR: I have the honor to report that, in pursuance of Special Orders, No. 221, from division headquarters, dated Harper's Ferry, W. Va., September 11, 1863, I proceeded, on the morning of September 12, to Loudoun County, Va., via Vestal Gap. Passed through Hillsborough and encamped for the night, and subsequently spent Sunday at Waterford.

At daylight on the morning of the 14th of September, 1863, I proceeded in the direction of Leesburg by the Mountain road. About 2 miles from Leesburg, on the Catoctin Mountain, near the Point of Rocks and Leesburg Grade, my advance guard, consisting of one company, encountered one company of White's guerrillas, concealed in the thicket. They immediately opened fire upon my advance guard, whom I ordered to charge, which they did in gallant style, dashing into the enemy's camp, capturing 2 commissioned officers, 9 men, and finally wounding 1, whom I left in the hands of the citizens, capturing their horses, arms, and equipments, which I turned over to the provost marshal at Point of Rocks, Md., without experiencing any casualties on my part.

From thence I proceeded to Leesburg, but the skirmish upon the mountains gave warning of our advance and the enemy was non est upon my arrival there. I then proceeded about 6 miles from Leesburg and encamped for the night. The 15th instant, I scouted the mountain and the valley between the Catoctin and Short Hill, and encamped again for the night at Waterford.

On the 16th instant, I proceeded in the direction of Snickersville, and while on this road I found a wagon load of flour destined for White's camp, which I seized and sent to Berlin, Md. Eliciting nothing further of the enemy's whereabouts, I moved the command to camp, by way of Lovettsville, detaching one company, and directing it to take the mountain road in quest of Mosby and his gang. They divided into small squads and scouted the mountain thoroughly. About 4 miles from this place one of these squads came in sight of Mosby and 4 of his gang, leading two stolen horses; they immediately giving chase, he soon abandoned the stolen property and his men separated from him. But my squad, having received an accurate description of him from the citizens, followed immediately behind him, and, after chasing him a distance of 6 miles through the mountains, he abandoned his horse and clambered up among the rocks. The men immediately dismounted and followed, but night coming on he effected his escape. The stolen horses were returned to their owners, they being loyal persons.

I notified two of the most prominent citizens in the vicinity of Waterford, of disloyal proclivities, that I would hold them as hostages if Mr. Williams and Mr. Hollingsworth were incarcerated by White, he having threatened to hold them as hostages for two rebel soldiers now in prison.

I seized the two horses you directed me, and will send them to Mr. Nicewaner to-day.