The embarkation of this corps commenced as soon as transports were ready, and on the 20th it had all sailed for Aquia Creek. I made the following report from Barrett's Ferry:

HEADQUARTERS ARMY OF THE POTOMAC,
Barrett's Ferry, Chickahominy, August 17, 1862-11 a.m.

Everything is removed from our camp at Harrison's Bar. No property or men left behind. The Fifth Corps is at Williamsburg, with all its wagons and the reserve artillery. The Third Corps is on the march from Jones' Bridge to Williamsburg via Diascund Bridge, and has probably passed the latter before this hour. Averell's cavalry watches everything in that direction. The mass of the wagons have passed the pontoon bridge here and are parked on the other side. Peck's wagons are now crossing; his division will soon be over. Headquarters wagons follow Peck's. I hope to have everything over to-night and the bridge removed by daylight. May be delayed beyond that time. Came here to see Burnside, otherwise should have remained with the rear guard. Thus far all is quiet, and not a shot that I know of since we began the march. I shall not feel entirely secure until I have the whole army beyond the Chickahominy. I will then begin to forward troops by water as fast as transportation permits.

GEO. B. McCLELLAN,

Major-General, Commanding.

Major General H. W. HALLECK, Commanding U. S. Army, Washington, D. C.

On the 18th and 19th our march was continued to Williamsburg and Yorktown, and ont he 20th the remainder of the army was ready to embark at Yorktown, Fort Monroe, and Newport News. The movement of the main body of the army on this march was covered by General Pleasonton with his cavalry and horse artillery. That officer remained at Haxall's until the army had passed Charles City Court-House, when he gradually fell back, picking up the stragglers as he proceeded, and crossed the bridge over the Chickahominy after the main body had marched toward Williamsburg. His troops were the last to cross the bridge, and he deserves great credit for the manner in which he performed this duty. General Averell did a similar service, in the same satisfactory way, in covering the march of the Third Corps.

As the campaign on the Peninsula terminated here, I cannot close this part of my report without giving an expression of my sincere thanks and gratitude to the officers and men whom I had the honor to command.

From the commencement to the termination of this most arduous campaign the Army of the Potomac always evinced the most perfect subordination, zeal, and alacrity in the performance of all the duties required of it. The amount of severe labor accomplished by this army in the construction of intrenchments, roads, bridges, &c., was enormous; yet all the work was performed with the most gratifying cheerfulness and devotion to the interests of the service. During the campaign ten severely-contested and sanguinary battles had been fought, besides numerous smaller engagements, in which the troops exhibited the most determined enthusiasm and bravery. They submitted to exposure, sickness, and even death without a murmur. Indeed, they had become veterans in their country's cause, and richly deserved the warm commendation of the Government.

It was in view of these facts that this seemed to me an appropriate occasion for the General-in-Chief to give in general orders some appreciative expression of the services of the army while upon the Peninsula. Accordingly on the 18th I sent him the following dispatch:

HEADQUARTERS ARMY OF THE POTOMAC,
August 18, 1862-11 p.m.

Please say a kind word to my army, that I can repeat to them in general orders, in regard to their conduct at Yorktown, Williamsburg, West Point, Hanover Court-