HDQRS. CAVALRY CORPS, November 19, 1863.

Respectfully forwarded.

General Custer committed an error in taking a detail from a regiment of outpost duty. I have so notified him.

A. PLEASONTON,
Major-General.

NOVEMBER 18-23, 1863.- Reconnaissance from Vienna toward the Blue Ridge Mountains, Va.

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

HDQRS. CAVALRY CAMP, Vienna, November 26, 1863.

COLONEL: I have the honor to report that, in accordance with your instructions, Captain Rumery, with 25 mounted and 75 dismounted men, Second Massachusetts Cavalry, was on the 18th instant sent out toward the Blue Ridge to endeavor to capture guerrillas. He had orders to march chiefly by night, to show only his mounted party by day, and to keep the presence of the dismounted party an entire secret. He took as guides Yankee Davis and the deserter Binns.

The party passed near Frying Pan and Gum Springs, across Negro Mountain and Goose Creek to Mountsville; thence up north side of Goose Creek to Rector's Cross-roads. On Sunday morning at daybreak, I joined them by agreement at a point between Middleburg and Rector's Cross-Roads with 100 mounted men, Second Massachusetts Cavalry, and 50 of the Sixteenth New York Cavalry. Having learned exactly what information Captain Rumery had obtained, Lieutenant Sim, Second Massachusetts Cavalry, with 40 mounted men, was sent northward through Philomont; Captain Rumery, with another 40, southward through White Plains, across Manassas Gap Railroad, and back across Bull Run Mountain by Hopewell Gap; Lieutenant Manning, Second Massachusetts, with 50 dismounted men, across the mountain a few miles south of Aldie, where Mosby was said to have a rendezvous; the remainder of the force to move down the pike and wait for these parties at Mount Zion Church, near Aldie. The last party reached the church about midnight, and all returned to camp on Monday night without loss of a man.

There were captured (chiefly by Captain Rumery's dismounted party) 18 uniformed soldiers, who claimed to be Mosby's men, and were provided with his passes, though in some cases belonging to were provided with his passes, though in some cases belonging to regular regiments, 7 notorious smugglers and horse-thieves, besides 1 of Mosby's men killed and 1 prisoner who escaped, and 35 horses, 13 sets horse equipments, 25 revolvers of various patterns, and 30 army blankets.

Captain Rumery managed his part of the expedition with great judgment. The deserter Binns, proved of great assistance. As I wish to employ him again on similar work, and as he shows no unwillingness to expose himself, I recommend that he be allowed the same pay as other government scouts while in my employ.

Respectfully, your obedient servant,
C. R. LOWELL, JR.,

Colonel Second Mass. Cavalry, Commanding Cavalry Camp.

Lieutenant Colonel J. H. TAYLOR,

Assistant Adjutant-General, and Chief of Staff.