WASHINGTON, D. C., August 25, 1862.

Major-General POPE,

Warrenton Station, Va.:

Ascertain, if possible, if the enemy is not moving into the Shenandoah Valley.

H. W. HALLECK,

General-in-Chief.

WARRENTON, August 25, 1862-12.30 p.m. (Received 9.40 p.m.)

Major-General HALLECK,

General-in-Chief:

A considerable column of infantry and cavalry and artillery has just left Culpeper on road to Amissville and Luray or Front Royal. They can be plainly seen by our lookouts, who estimate them at 20,000. I have General McDowell's corps ready to march, and as soon as I ascertain certainly that they are going into Shenandoah I will push McDowell in their rear. I shall know certainly in a few hours.

JNO. POPE,

Major-General.

HEADQUARTERS ARMY OF VIRGINIA, August 25, 1862-9 p.m. (Received 11.10 p.m.)

Major-General HALLECK,
Commander-in-Chief:

The column of the enemy alluded to in my dispatch of 12.30 p.m. to-day passed Gaines' Cross-Roads, and when last seen, near sunset, was passing to the northeast, under the east base of Buck Mountain, in the direction of Salem and Rectortown. I am induced to believe that this column is only covering the flank of the main body, which is moving toward Front Royal and Thornton's Gap, though of this I am not certain.

I will push a strong reconnaissance across the river at Waterloo Bridge and Sulphur Springs early in the morning to ascertain whether the main body of the enemy has really left, and, if so, to push forward in their rear. There is certainly no force opposite Rappahannock Station.

McDowell's is the only corps that is at all reliable that I have. Sigel, as you know, is perfectly unreliable, and I suggest that some officer of superior rank be sent to command his army corps. His conduct to-day has occasioned me great dissatisfaction. Banks' corps is very weak, not amounting to more than 5,000 men, and is much demoralized. Kearny's division is the only one that has yet reached me from Alexandria. I shall at all events push McDowell's corps and Kearny's division upon the enemy's rear if I find my suspicions confirmed in the morning. I shall also put Reno across the river at Rappahannock Station and direct him to move forward cautiously upon Culpeper. Banks' corps must be left somewhere in the rear to be set up again. Sigel's corps, although composed of some of the best fighting material we have, will never do much service under that officer.

I will communicate further with you in the morning.

JNO. POPE,

Major-General.