SEPTEMBER 25-28, 1862.- Expedition from Centreville to Bristoe Station and Warrenton Junction, Va.

Report of Colonel N. C. McLean, Seventy-fifty Ohio Infantry, commanding Second Brigade, First Division, Eleventh Army Corps.

HEADQUARTERS SECOND BRIGADE, FIRST DIVISION,
Camp at Centreville, Va., September 29, 1862.

GENERAL: I have the honor to report the result of my expedition to Warrenton Junction, as follows:

Immediately upon the receipt of your order, on the afternoon of the 25th instant. I called in my pickets and marched, as ordered, with the whole of my brigade and such portion of the Sixth Ohio Cavalry as were present, under Colonel Lloyd, amounting, I believe, to about 120 men. I encamped the first night at Weir's house, 1 mile from Manassas Junction. The next morning, at daylight, I marched and halted at at Bristoe Station for re-enforcements of cavalry, which I understood, were to come to me. About 30 men of the Sixth Ohio Cavalry joined me about 11 o'clock. I found that the cavalry of the enemy were hovering around me, and sent a small party of the Sixth Ohio Cavalry to ascertain their strength. Upon the approach of our ment they fled, and, in the pursuit, dropped some pistols, haversacks, &c., but escaped without further loss. I met with no further interruption until within 2 1/2 miles of Catlett's Station, when my advance guard of cavalry came upon a force of the enemy, consisting of both infantry and cavalry, posted in the woods, from which they fired upon our men, driving them back upon the main body. The cavalry reported a heavy force of infantry, and I immediately ordered two pieces of artillery to the front, and shelled the woods three or four times without receiving any reply. I then ceased firing, and ordered two companies of the Seventy-fifth Ohio forward into the woods, as skirmishers, supported by the balance of the regiment as a reserve. This force I followed with the Seventy-third and Fifty-fifth Ohio, in line of battle, leaving the artillery in position, supported by the Twenty-fifth and Sixth Ohio Cavalry. The enemy, however, had retreated, and I then moved forward, cautiously and in such order as to be ready for any emergency, with my whole force. My advance guard reached Catlett's Station in time to see the locomotive and cars, in the distance, going rapidly away, but did not get near enough to engage the enemy again. I ascertained that the force which opposed my march, besides the cavalry engaged, consisted of about 300 infantry, and that they filled some seven or eight box-cars and three or four gondola cars in their retreat on the railroad. In their retreat they fired the railroad bridge over Cedar Run, but we arrived in time to extinguish the fire before much damage had been done. Very little labor will repair the bridge, and, even, now, I believe it will be sage for the cars to pass. This bridge was saved by the personal efforts of my staff. I halted on the other side of the bridge for the night, going forward, however, my self, with the cavalry, two regiments of infantry, and one section of artillery to Warrenton Junction, which was 1 mile distant. Nothing more was found of the enemy, and the bridge beyond and about 1 1/2 miles distant from the junction was all in order, so that the cars had continued on at least as far as the Rappahannock, some 10 miles distant. I could not ascertain whether the bridge at that point had been finished or not; but am under the impression that, on the 26th instant, it was still incomplete, or otherwise there was no reason for the burning of the bridge over Cedar Run. There was no alarm during the night. At about 3 o'clock next morning, about 40 of the First Maryland Cavalry reported