CUMBERLAND, July 5, 1864.

I have just returned from Patterson's Creek. I am happy to inform you that the damage to the railroad and bridges is but trifling. The Patterson's Creek bridge is tolerably badly burned, but as it was only a temporary one on tressels it could not be all burned. The tressels are mostly good, and the bridge will be repaired in forty-eight hours. At South Branch the damage is much less. I have a force on both repairing. I think the road is all safe east of South Branch to Back Creek, twelve miles west of Martinsburg. I have an engine with three iron-clad cars patrolling the road between South Branch and Sir John's Run. It was these cars that drove off the rebels from South Branch bridge by attacking them in the rear. Unless the road is attacked by a large force I have no doubt but what your troops can moved east from here to within fifteen or eighteen miles of Martinsburg within three days, if you should so desire. I am repairing telegraph line; it will be in working order to Sir John's Run to-morrow. Imboden's force may, after passing through Bloomery Gap, turn to the left, and move to Big Cacapon bridge or Sir John's Run, but I hope to be able to drive him off if he does. I have sent 200 infantry with one gun by canal-boats to-day to re-enforce those points and supply them rations. I feel that I am now safe here and at New Creek, and the road and public property west of this point. Trains are running regularly west of this. I hope to extend the route as far east as Hancock in two or three days.

B. F. KELLEY,

Brigadier-General.

Major-General HUNTER,

Parkersburg.

(Copy sent to Major-General Sigel, Maryland Heights.)

CUMBERLAND, July 6, 1864.

The enemy attacked Sir John's Run this p. m., but were driven off, not, however, until they had fired the station-house, which was consumed. The iron-clad cars and guard also drove him from Big Cacapon bridge and prevented its destruction. The bridges at Patterson's Creek and South Branch will be repaired by to-morrow morning so as to admit the passage of trains. I have nothing definite from Martinsburg or neighborhood. General Sigel, I understated, occupies Maryland Heights; the enemy are in force opposite. All my scouts and all refugees report the enemy's force about 20,000, in command of Generals Early, Ransom, and others. This estimate was made when they left Staunton. Refugees say that it was the intention of General Early's forces to entirely destroy the Baltimore and Ohio Railroad and the Chesapeake and Ohio Canal. General Sullivan arrived this evening with a portion of his division, which will proceed to Patterson's Creek and debark. The cars will be ordered back at once to Parkersburg.

B. F. KELLEY,

Brigadier-General.

Major-General HUNTER,

Parkersburg, W. Va.