Captain Crowninshield, in his dispatch to me, does not state how much of a reserve he left at Welford's Ford as a supporting force. I am, captain, very respectfully,

J. B. McINTOSH,

Colonel, Commanding First Brigade.

Captain H. C. WEIR,

Asst. Adjt. General, Second Cavalry Division.

AUGUST 11, 1863.- Capture of Union Wagon Train near Annandale, Va.

REPORTS.

Numbers 1.- Colonel Charles R. Lowell, jr., Second Massachusetts Cavalry.

Numbers 2.- Major S. Mosby, C. S. Army.

Numbers 1. Report of Colonel Charles R. Lowell, jr., Second Massachusetts Cavalry.

HEADQUARTERS CAVALRY CAMP,
August 12, 1863.

COLONEL: I have the honor to report information on Mosby's last raid as far as collected.

Mosby's and White's men - together about 140 strong - came down Little River turnpike the day before yesterday, and passed that night near Gum Springs. Moved down yesterday forenoon through Ox road junction toward Flint Hill. Hearing that our pickets were there, turned to the north again, and, passing through Vienna by Mills Cross-Roads, to Little River pike, near Gooding's Tavern, captured one sutler's train there between 3 and 4 p. m. and another about a mile farther east. An hour later half plundered some of the wagons, took all the horses and mules, and started back in a hurry through Vienna, toward Hunter's Mill.

About 1 mile south of the mill they divided, one-half going toward Dranesville, the other by Hunter's Mill, nearly down to Chantilly, then turned to the right, and, I presume, passed through Gum Springs early this as. m.

On receiving your dispatch about camp of 40 men 5 miles from Falls Church, on Monday, I placed pickets on Ox road, at Fairfax court-House, at Flint Hill, and at all cross-roads between there and Vienna. these pickets had orders to return to Fairfax Court-House at 12 a. m. on Tuesday. Put 30 men at Vienna and 75 men at Freedom Hill and in that neighborhood. These last with orders to move toward Falls Church by all the roads from the west early Tuesday morning, carefully examining all cross-roads. These instructions were obeyed, and nothing suspicious found.

From Falls Church I sent 70 men to relieve Captain Reed at Fort Ethan Allen, and started with the remaining 30 to beat up the country round Chichester Mills. This I did thoroughly, and reached Fairfax Court-House, by back roads, about 11 a. m., and passed on to Germantown and Centreville.

The pickets at Flint Hill, &c., came in at the time ordered, and Captain McKendry, the officer in charge, was examining into the liquor traffic, said to be carried on at Fairfax Court-House, when news was brought of the capture of the sutler's train. He started down at once with 40 men, and arrived about dark, Mosby having already left.