On the morning of the 21st, McDowell’s forces were encamped in and around Centreville. The divisions were under orders to march at half-past two o’clock, that they might reach the ground early and avoid the heat. Before this time the encampments were in motion; but the troops were not yet sufficiently disciplined for the exigencies of a prompt march, and some delay arose with the first division in getting out of camp. Thus the road was obstructed, and other divisions thrown two hours out of time. But there was no lack of energy or zeal; the very want of discipline which caused delay rendered the scenes in the various encampments more grand and imposing. It was indeed a beautiful spectacle. A lovely moonlight flooded the whole country. Soft mists lay in the valleys—the hill-tops were studded for miles around by the camp-fires which thirty regiments had left, kindling the landscape with their star-like gleams. In the hollows, along the level grounds, and among the trees, thousands on thousands of armed men moved athwart the fires, harnessing horses to artillery, getting out army wagons, preparing ambulances and filling haversacks with the three days’ rations ordered for their subsistence. No man of all that vast host was idle—want of order there might have been, but no lack of energy. Now, thirty thousand men, horses, ordnance and wagons, were all in place, ready for a march through the beautiful night, and under that serene moon, which many of them would never look upon again. McDowell and his staff moved with the first—Tyler’s—central column, and the advance commenced. The picturesque encampments were soon left behind; the fires grew paler and twinkled out in a glow of mist; the tents dwindled into littleness, till they seemed more like great flocks of white-plumaged birds, nestled in the foliage, than the paraphernalia of war. Nothing could be more quiet and peaceful than the country the troops had left—nothing more solemnly grand than the advance. It was an army of Americans, marching through the still night to meet Americans for the first time in a great pitched battle. Nothing but holy patriotism and a stern sense of duty could have led these men into the field. They marched on, with thousands of bayonets gleaming in the moonlight, and casting long-pointed shadows over the path; staff officers formed imposing groups as they moved forward in the moonlight, casting pictures upon the earth that were like broken battle scenes. In the ranks there was something more than stern courage; generous enthusiasm and honest emulation were eloquent there. Comrade greeted comrade, for the coming danger made friends brothers; and common acquaintances fell into affectionate intimacy. Many a touching message was exchanged between men who had never met out of the ranks, for while they panted for victory, each man prepared to earn it with his life.