Having with some particularity traced the main bodies composing Lee's army, as to time and routes, to the vicinity of Gettysburg, it remains to briefly follow the Army of the Potomac to the same place. While some of its corps moved earlier, the headquarters of that army did not leave Falmouth until the 14th of June, when it was established at Dumfries; on the next day at Fairfax Station, on the 18th at Fairfax Court-House, on the 26th at Poolesville, Maryland, and the next day at Frederick, Maryland, where Meade succeeded Hooker. Before the Army of the Potomac left Falmouth a division of the Sixth Corps had been thrown across the river to observe the enemy, but it did not attack him, and was withdrawn on the 13th. Meade found his army, mainly, in the vicinity of Frederick, though some of his corps had passed northward and others were moving up by converging lines, the Sixth Corps having just arrived at Poolesville from Virginia. June 29th, Meade moved his headquarters from Frederick to Middleburg, the next day to Taneytown, Maryland, about fifteen miles south of Gettysburg. The movements of the Army of the Potomac were such as to cover Washington and Baltimore, and at the same time bring, as soon as possible, the invading army to battle. The First, Eleventh, and Third Corps, under Major-General John F. Reynolds, were in the advance on Gettysburg on July 1st, the First Corps leading, and preceded only by General John Buford's division of cavalry. Lee was then rapidly concentrating his army at Gettysburg. Reynolds found Buford fiercely engaging infantry of Hill's corps as they were debouching through the mountains on the Cashtown road. He promptly moved the First Corps to Buford's support, and it soon became hotly engaged. The Eleventh Corps, commanded by General Oliver O. Howard, was ordered to hasten to join in the battle. Howard arrived about 11.30 A.M., just as Reynolds fell mortally wounded, and the command of the field devolved on Howard. He pushed forward two divisions of the Eleventh to the support of the First Corps, then engaged on Seminary Hill, northeast of Gettysburg, and posted a third division on Cemetery Ridge, south of the town. The battle continued with great fierceness on the Cashtown road. For a time the Union success was considerable, and the Confederates were forced back, and numerous prisoners, including General Archer, were captured; but reinforcements from Cashtown and the unexpected arrival, at 1.30 P.M., over the York and Harrisburg roads, of Ewell's corps on Howard's right left him outnumbered and outflanked. He maintained the unequal contest until about 4 P.M., then ordered a withdrawal to Cemetery Ridge, which was accomplished with considerable loss, chiefly in prisoners taken in the streets of Gettysburg. Meade, learning of Reynolds' death, dispatched General W. S. Hancock to represent him on the field. Hancock arrived in time to aid Howard in posting the troops advantageously