WASHINGTON, December 27, 1862-5.55 p.m.

Major-General SLOCUM:

I have received your dispatch of to-day. The news is very indefinite. It is not said by what force and numbers the attack is made. I can give you no order, as you have to report to Major-General Burnside during my absence, but I advise you to do the following: Send all the cavalry you have toward Dumfries, to assist, if possible, the troops there, and to gain more reliable knowledge about the enemy. Advance at least a brigade of infantry and one battery from Wolf Run Shoals toward Dumfries. They must advance rapidly, but with the necessary precaution, and either advance fully to Dumfries, or halt on the road and wait for further orders from you, according to the strength and movements of the enemy. Ask General Heintzelman to send a cavalry force to Brentsville and toward Dumfries, to threaten the enemy in the rear ford Court-House to send also his cavalry and some artillery immediately toward Dumfries, if he has not received other orders. Please send me further information.

F. SIGEL,

Major-General.

FAIRFAX COURT-HOUSE, December 27, 1862.

Major-General SIGEL:

I shall send one division to Wolf Run Shoals to-night. If I send it beyond, I shall [?] the entire corps.

Candy at Dumfries still holds his position.

H. W. SLOCUM,

Major-General Volunteers.

WASHINGTON, December 27, 1862-6 p.m.

Major-General SLOCUM:

Your dispatch is received. I think what you propose to do is right. Please give me all the information you may receive during the night.

F. SIGEL,

Major-General.

SPECIAL ORDERS,
HEADQUARTERS ARMY OF THE POTOMAC,

No. 364. Camp near Falmouth, Va., December 27, 1862.

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III. Brigadier General H. Prince and staff will report to Major General John G. Foster, Department of North Carolina, stopping in Washington for definite orders from the General-in-Chief.

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By command of Major-General Burnside:

EDWARD M. NEILL,

Captain and Assistant Adjutant-General.