HEADQUARTERS ARMY OF THE POTOMAC,
September 19, 1862.

General D. N. COUCH,

Commanding Division:

As it has been reported that Stuart, with 4,000 cavalry and six pieces of artillery, is marching on Williamsport, and that infantry have come down from Winchester to the same place, the commanding general directs that you march at once, with the remainder of your division, via Jones' Cross-Roads, to Williamsport, and co-operate with General Pleasonton, who is ordered with a large force to the same place and to await your arrival at Jones' Cross-Roads. General Reynolds, with 8,000 militia, is now between Hagerstown and Williamsport, and will co-operate with you in this movement if necessary. Please report the time of your departure, and also report as often as anything of importance occurs on your march. You will return to this army after you have driven the rebels back into Virginia.

Very respectfully,

R. B. MARCY,

Chief of Staff.

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HEADQUARTERS ARMY OF THE POTOMAC,
September 19, 1862--9.30 p. m.

Brigadier General J. F. REYNOLDS:

GENERAL: The great mass of the enemy marched from Shepherdstown to-day, on the Winchester and Charlestown roads. A detachment of our cavalry was fired upon to-day by infantry at Williamsport. The captain in command reports them about 1,000 strong, with one field piece. This report is corroborated by a citizen who left Williamsport about 12 o'clock to-day. Two thousand infantry, a battery of artillery, and four squadrons of cavalry are ordered to march to-night, so as to reach Williamsport as soon after daylight as practicable, and to endeavor to capture the rebel force there. It would be well for you to co-operate with this command by marching down from Hagerstown.

I am, general, &c.,

R. B. MARCY,

Chief of Staff.

[19.]

HEADQUARTERS ARMY OF THE POTOMAC,
Keedysville, September 19, 1862--4 a. m.

Brigadier-General PLEASONTON:

GENERAL: General Sumner reports that the enemy's artillery is moving to the west, and that he (the enemy) is felling trees behind him. The commanding general directs you to ascertain if the enemy appears to be retiring, and, if so, to mass your troops and to hold them ready to move in any direction. He also desires you to send out small cavalry detachments on the various roads leading from our position in the direction of the enemy's retreat, to ascertain the nature and degree of the obstructions therein.

I am, general, very respectfully, your obedient servant,

R. B. MARCY,

Chief of Staff.

[19.]