I have abstained from giving the number of guns, colors, small-arms, prisoners, &c., captured until I could do so with some accuracy. I hope by to-morrow evening to be able to give at least an approximate statement.

GEO. B. MCCLELLAN,

Major-General, Commanding.

On the same day I telegraphed as follows:

HEADQUARTERS ARMY OF THE POTOMAC,
September 20, 1862

Major General H. W. HALLECK,

Commanding U. S. Army:

As the rebel army, now on the Virginia side of the Potomac, must in a great measure, be dependent for supplies of ammunition and provisions upon Richmond, I would respectfully suggest that General Banks be directed to send out a cavalry force to cut their supply communication opposite Washington. This would seriously embarrass their operations, and will aid this army materially.

GEO. B. MCCLELLAN,

Major-General, Commanding.

Maryland Heights were occupied by General Williams' corps on this day, and on the 22nd General Sumner took possession of Harper's Ferry.

It will be remembered that at the time I was assigned to the command of the forces for the defense of the National Capital, on the 2nd day of September, 1862, the greater part of all the available troops were suffering under the disheartening influences of the serious defeat they had encountered during the brief and unfortunate campaign of General Pope. Their numbers were greatly reduced by casualties, their confidence was much shaken, and they had lost something of that esprit de corps which is indispensable to the efficiency of an army. Moreover, they had left behind, lost, or worn out the greater part of their clothing and camp equipage, which required renewal before they could be in proper condition to take the field again.

The intelligence that the enemy was crossing the Potomac into Maryland was received in Washington on the 4th of September, and the Army of the Potomac was again put in motion, under my direction, on the following day, so that but a very brief interval of time was allowed to reorganize or procure supplies.

The sanguinary battles of South Mountain and Antietam, fought by this army a new days afterwards, with the reconnaissances immediately following, resulted in a loss to us of 10 general officers, many regimental and company officers, and a large number of enlisted men, amounting in the aggregate to 15,220. Two army corps had been sadly cut up, scattered, and somewhat demoralized in the action on the 17th.

In General Sumner's corps alone 41 commissioned officers and 819 enlisted men had been killed; 4 general officers, 89 other commissioned officers, and 3,708 enlisted men had been wounded, besides 548 missing; making the aggregate loss in this splendid veteran corps, in this one battle 5,209.

In General Hooker's corps the casualties of the same engagement amounted to 2,619.

The entire army had been greatly exhausted by unavoidable overwork, fatiguing marches, hunger, and want of sleep and rest previous to the last battle.

When the enemy recrossed the Potomac into Virginia, the means of transportation at my disposal were inadequate to furnish a single day's supply of subsistence in advance.

Many of the troops were new levies, some of whom had fought like