HDQRS. DEPARTMENT OF THE RAPPAHANNOCK, Catlett's Station, April 16, 1862.

Honorable E. M. STANTON,
Secretary of War:

Brigadier-General Abercrombie, commanding at Warrenton Junction, telegraphs to me to-day, first, that an unauthorized foraging party of 5 cavalry, under a captain, was fired upon by a party of rebel cavalry to-day 3 miles southeast of the Junction; that contrabands report the enemy are to cross to-night-a report the general is not inclined to believe. He has just telegraphed that the reconnoitering party he sent out has just returned. Was fired upon by rebel pickets from the other side of the river; one horse shot. Previous reports of their throwing up entrenchments confirmed, but no bridge, as reported, found. The general reports that from the best information he has a force of 5,000 or 6,000 men is there, under General Smith. All of General King's division and Bayard's cavalry are here at Catlett's Station. One brigade of Bayard's cavalry are to leave to-morrow on the expedition I spoke to you of. One of McCall's brigades in ordered to Bristoe. The remainder of the division is still at Manassas.

IRVIN McDOWELL,

Major-General.

HDQRS. DEPARTMENT OF THE RAPPAHANNOCK, Catlett's Station, Va., April 16, 1862.

Brigadier General C. C. AUGUR,
Commanding First Brigade, King's Division:

GENERAL: The major-general commanding directs you to proceed with your brigade, Gibbon's battery, a section of Gerrish's battery, eight companies of Davies', and eight companies of Bayard's cavalry to Fredericksburg.

It is represented that there is a regiment of cavalry on this side, and another, perhaps two, on the other side, of the Rappahannock.

There are three bridges, one of them the railroad bridge, at or near Fredericksburg, which it is understood the enemy is prepared to burn at an approach.

It is desirable with reference to ulterior operations that these bridges be saved. You will organize your force into an advance, to consist of one regiment of infantry, one section of light artillery, and a squadron or battalion of cavalry; a main body of two regiments of infantry, Gibbon's battery, and the remainder of Davies' cavalry, and a reserve of two regiments of infantry and Bayard's cavalry. All your baggage with your reserve.

Have the advance go as light as possible, and move with the greatest celerity. The success will mainly depend on this.

If you come up with any of the enemy attack at once; they are demoralized, and must not be suffered to take heart by delay or hesitating.

It is reported the enemy are in force on the right bank of the North Fork of the Rappahannock. Look out well for your right flank.

Take two days' subsistence in the haversacks, four days' in wagons, and beef on hoof. A supply of subsistence and forage will be sent under a guard to Aquia Creek. So soon, therefore, as you reach Fredericksburg send your empty wagons under convoy by the road to the