HEADQUARTERS OF THE ARMY, October 17, 1861.

General ROSECRANS,
Big Sewell, W. Va.:

The troops heretofore promised you from Western Pennsylvania have been just ordered to Kentucky instead.

E. D. TOWNSEND,

Assistant Adjutant-General.

HEADQUARTERS ARMY OF THE POTOMAC,
Washington, October 18, 1861.

Brigadier General J. G. BARNARD,

Chief Engineer, Army of the Potomac:

GENERAL: Major-General McClellan directs that yourself and General Barry proceed as soon as practicable to determine the minimum strength of garrisons-artillery and infantry-required for the various works in and about Washington to satisfy the conditions of a good defense. A report is desired as soon as you shall have concluded your deliberations.*

Very respectfully, your obedient servant,

S. WILLIAMS,

Assistant Adjutant-General.

Sketch of a plan to cut the communications of the rebel army now at Manassas Junction.

DIVISION HEADQUARTERS,.

Fort Lyon, October 18, 1861.

Advance from Lewinsville, Falls Church, Little River turnpike, and on the left towards Elzey's and Occoquan, when the enemy will fall back beyond Bull Run, if he has not already done so.

The force on the left would by this movement reach the Occoquan and be in position to co-operate with another force to be landed between Occoquan and Dumfries. This force would advance and take possession of the railroad in front of Brentsville or at Bristoe.

To prevent the large force said to be at Aquia Creek from interrupting this movement, have some of the larger men-of-war and transports, with some troops, to ascend the Potomac, attack the batteries, and threaten to land troops to attack them in the rear, thus preventing any force from being detached towards Dumfries.

The smaller vessels and gunboats and transports could ascend the Potomac to cover the crossing between Occoquan and Dumfries. A portion or all the troops preparing for the expedition at Annapolis can be brought here, as well as a portion of those above on the Potomac. This would only delay this secret expedition a few days.

As the transports could not carry a sufficient force at one time, a portion can march down on the Maryland side.

S. P. HEINTZELMAN,

Brigadier-General.

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*See joint reports of Barry and Barnard, October 22 and 24, pp..

624, 626.

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