During the day we have heard very heavy cannonading in the direction of White Plains. It appears that General Meade, misled by the information brought by some of his scouts, expected to engage the Rebel army in Manassas Gap, or west of that, where General Buford found the enemy in force. Our army was accordingly concentrated upon this point. The Third Corps, under General French, which occupied Ashby's Gap, was sent forward rapidly to Buford's support, where its First Division, commanded by General Hobart Ward, pushed through the Gap, driving the enemy before it, but with mutual loss. Here the New York Excelsior Brigade, General F. B. Spinola commanding, greatly distinguished itself, by making three heroic charges up the frowning steeps, where the Rebels were strongly posted. Their general was twice wounded. But the effort was a success. On the morning of the twenty-fourth our soldiers pushed forward as far as Front Royal, but found no enemy. They then learned that they had been fighting only a portion of Lee's rearguard, which in the night had slipped away in the trail of their main army southward. By this move General Meade's army lost about two days' march; and when again we reached the bank of the Rappahannock, the old foe was facing us in threatening attitude from the opposite shore. This afternoon the Harris Light was sent on a scout to Thoroughfare Gap. From the heights beyond the Gap we saw the wagon-train of the Eleventh Corps moving toward Warrenton. This was a portion of the force which had expected a fight at Manassas Gap. _July 25._--Our cavalry force reached the vicinity of Warrenton Junction, when we went into bivouac. The second squadron of our regiment, under Captain O. J. Downing, moved to Thoroughfare Gap and returned to Gainesville, where it joined the regiment, and then marched with us to the Junction _via_ Bristoe and Catlett's. Before night we were sent out on picket in the vicinity of Catlett's Station, where we relieved the First Virginia Cavalry. We continued on picket through the twenty-sixth, but all was quiet along the lines. An inspection of horses was made this morning, when a large number were condemned as utterly unserviceable; and they were started off toward Washington, to be exchanged for better ones. _July 27._--I have the responsibility and honor of being in command of a company. This afternoon a detachment of our forces was sent out on a sort of bushwhacking expedition. A portion of Company F was captured by the Fourth Virginia Cavalry, while patrolling the road near Bristersburg. We are not doing much these days, except picketing, scouting, recruiting, resting. On the twenty-ninth our entire brigade was marched to within three miles of Warrenton, and then countermarched to the old camp; and on the last day of the month we advanced to Warrenton in heavy force, where General Meade has had his headquarters for several days.