Potomac at Harper's Ferry; also a wagon bridge over Shenandoah at the same place, on the piers now standing. The Potomac bridge must probably be build on crib-piers, filled with stone, and will be about 900 feet in length; the Shenandoah bridge about 400 feet long. I have to request that Colonel D. C. McCallum may be placed in charge of this work, and instructed to report to me at Harper's Ferry without delay. He should take steps before leaving Washington to organize the gangs of workmen, and to procure all the material possible. I cannot too strongly urge the importance of expedition in this matter. Until this or the railroad bridge is finished, it is scarcely possible to advance from Harper's Ferry, in force, and as that is clearly our true line of operations, I need not urge upon you the necessity of completing our communications there.

GEO. B. McCLELLAN,

Major-General.

HEADQUARTERS ARMY OF THE POTOMAC, September 24, 1862.

General N. P. BANKS,
Commanding Defenses of Washington, D. C.:

In reply to your dispatch of the 22d, I should not think it advisable to withdraw Stoneman from his present position until we are able to learn something more of the designs and movements of the enemy now in our front. I will keep you advised.

GEO. B. McCLELLAN,

Major-General.

HEADQUARTERS CAVALRY DIVISION, September 24, 1862-11 a.m.

Major General FITZ JOHN PORTER,
Commanding Fifth Corps:

GENERAL: By direction of General McClellan, I am about to throw a squadron of cavalry across the river at the ford near Shepherdstown. I am instructed to notify you of the same. The party will be at the ford within an hour, and a small detachment will first cross over to feel the way.

I am, general, very respectfully,

A. PLEASONTON,

Brigadier-General, Commanding Cavalry Division.

WASHINGTON, September 24, 1862.

Major-General BANKS,

Commanding:

GENERAL: Some troops must be sent to Western Virginia, and if General Milroy's brigade is available for that duty, you will have it in readiness to move by railroad. If you suggest any other, please name it.

Yours, truly,

H. W. HALLECK,

General-in-Chief.