BALTIMORE, MD., December 27, 1862.

Major-General HALLECK,

General-in-Chief;

Received the following telegram from General Kelley, at Cumberland, last night:

A dispatch, just received from General Cluseret, says he is safe. He thinks the force in his front is General Jones' cavalry and Maryland Line. I will keep the road open to Martinsburg, and keep him supplied. The general's telegrams were received. The telegraph line, by Baltimore and Ohio Railroad, will be completed to-morrow.

ROBT. C. SCHENCK,

Major-General, Commanding.

HEADQUARTERS ARMY OF THE POTOMAC,
December 28, 1862. (Received 10.30 p.m.)

General G. W. CULLUM,

Chief of Staff;

Dumfries, Wolf Run Shoals, Fairfax Station, and Fairfax Court-House all secured by strong guards. Lee's cavalry crossed the Occoquan, between Wolf Run Shoals, and are supposed to be making for Pohick Church, and will try to cross the railroad, no doubt, between Burke's Station and Alexandria, passing around Fairfax Court-House. Cannot some of Heintzelman's cavalry co-operate with us at once?

The enemy's cavalry are said to be under Fitzhugh Lee, and consist of two brigades and four pieces of artillery. He was repulsed at Dumfries by the guards there, and by Slocum's advance between Dumfries and Wolf Run Shoals.

Troops can be sent at once from Alexandria to Annandale, and a portion of the force at the Court-House can be ordered to the crossing of the Telegraph road. I will attend to the latter. Please have General Heintzelman move out a force from Alexandria to Annandale and to the railroad bridge over the Accotink at once with his spare cavalry.

A. E. BURNSIDE,

Major-General.

HEADQUARTERS CAVALRY DIVISION, December 28, 1862.

Lieutenant Colonel J. H. TAYLOR,
Chief of Staff, Right Grand Division:

COLONEL: My pickets, near King George Court-House, report 6 of the enemy's cavalry near Hempstead yesterday, and made a dash at 3 of our men, who were reconnoitering. The latter fell back on a company, which went in pursuit, but without result.

The enemy are busily at work on the opposite side of the river, fortifying near Port Royal, with a strong force of artillery and infantry. The enemy's cavalry seen on this side cross in boats, and are mounted below.

A heavy smuggling business is now going on at Leeds of medicines, groceries, and clothing for the rebel army opposite; also corn and wheat, 6,000 bushels alone having been sent over by one person.

The Eighth Pennsylvania Cavalry captured a herd of 150 cattle belonging to the rebel army, which they distributed to the different commissaries of the command.

Very respectfully, your obedient servant,

A. PLEASONTON,

Brigadier-General, Commanding.