BACK CREEK, July 20, 1863-9 p. m.

(Received, July 21, 1. 55 a. m.)

Brigadier-General CULLUM,

Chief of Staff:

Hill's corps moved from Bunker Hill to Martinsburg to-day, and at dark was pressing back my pickets. I fall back to-night to Cherry Run, and recross the river. Where is the Army of the Potomac?

B. F. KELLEY,

Brigadier-General.

HAGERSTOWN, MD., July 20, 1863. (Received 9. 15 p. m.)

Major General GEORGE G. MEADE,

Headquarters Army of the Potomac:

I have just received the following information from Major Bryson, of Averell's cavalry: General Lee is at Bunker Hill; Jeff. Davis there on the 18th; General Ewell at Darkesville; General Hood, with five brigades, at Gerardstown; six regiments of rebel cavalry at Martinsburg, operating toward General Kelley; Kelley's forces at Hedgesville. Rebels supposed to be picketing from Hedgesville toward Harper's Ferry. Kelley's force about 2, 400 cavalry and mounted infantry, and twenty-four pieces of artillery. General Averell skirmished on the 19th all day in front of Hedgesville, toward Martinsburg.

W. BRISBANE, Colonel,

Comdg. Fourth Brig., First Div., and Mil. Gov.

ANNANDALE, July 20, 1863.

(Received 9. 45 a. m.)

Colonel J. H. TYLOR:

Our cavalry returned to Centreville last evening, after visiting Wolf Run, Brentsville, and Manassas Junction. They captured 8 prisoners; among them a lieutenant-colonel who ordered the draft at Bretnsville. Colonel Lowell reports all quiet in front. The railroad is in running order beyond Bull Run. A train leaves for Manassas this morning. We are on the move toward Fairfax and Centreville.

RUFUS KING,

Brigadier-General.

FORT MONROE, VA., July 20, 1863-9 a. m. (Received 10. 10 a. m.)

Honorable E. M. STANTON,

Secretary of War:

After an inspection of Yorktown and Goucester Point, I find that the number of troops there is too small to defend the works, which are too extensive, against a determined attack. I believe the same facts to exist as regards Williamsburg. I propose to modify the defenses at Yorktown and Gloucester Point, so as to make them defensible by even a smaller force than is there now; also to do the same thing on the new line outside of Portsmouth, thus obtaining a small movable column of infantry to support cavalry raids. But to do