This expedition, if fully successful, will be one of the most important of the whole campaign. It will require all your activity, energy, tact, and perseverance, and very likely will test the fighting qualities of your command.

Very respectfully, your obedient servant,

H. W. HALLECK,

Major-General.

SIKESTON, March 1, 1862.

Major-General HALLECK:

A portion of our advance guard, consisting of six companies Seventh Illinois Cavalry, encountered reconnoitering force of the enemy 3 miles south of this place this afternoon. After a short skirmish the enemy fled precipitately towards New Madrid, leaving in our possession three pieces of rifled artillery. One captain, one lieutenant, and several privates were taken prisoners. From the prisoners I learn that New Madrid is occupied by four brigades of infantry, numbering about 10,000, 900 cavalry, and four batteries of field artillery. Another brigade is expected to-night. The prisoners also state that the enemy is rapidly evacuating Columbus and occupying Island Numbers 10. My command is all well to this point and well in hand. I shall push forward to-morrow, and unless the enemy is more re-enforced than is now expected I think we are more than a match for him. If consistent with your arrangements, I think we are more than a match for him. If consistent with your arrangements, I would be glad if a considerable force could be advanced from Bird's Point as far as Oak Grove, so as to assure my communications.

JNO. POPE,

Brigadier-General, Commanding.

HEADQUARTERS ARMY IN THE FIELD, Sikeston, March 1, 1862.

General G. W. CULLUM:

I reached here to-night with my command. This afternoon, about 2 o'clock, a portion of my advanced guard, consisting of six companies of Seventh Illinois Cavalry, encountered reconnoitering party of the enemy about 3 miles south of this place. This party had been drawn up to engage a company of the First Illinois Cavalry and a portion of the Tenth Illinois Infantry. These troops, being so much exhausted by long pursuit of the enemy in the direction of Benton, gave place to the six companies of the Seventh Illinois Cavalry, which charged the enemy and completely routed him. The enemy had occupied a narrow causeway, pursued by the road, with three pieces of rifled artillery of small caliber. This battery was carried handsomely by the charge of the Seventh Illinois, and has fallen into our possession. The enemy fled precipitately towards New Madrid, and was pursued to within 4 miles of that town. One captain, one lieutenant, and several privates were captured. The pieces of artillery are of small caliber, breech-loading, beautifully rifled, and handsomely mounted on four wheels, drawn by two horses each. They have an ingenious repeating apparatus at the breech, and were undoubtedly made for service in this swampy, low region. From the prisoners I learn that New Madrid is occupied by four brigades of infantry, numbering about 10,000,900