SPECIAL ORDERS,
HDQRS. ARMY OF THE POTOMAC,

No. 115. Washington, October 23, 1861.

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10. Brigadier General Ambrose E. Burnside, volunteer service, will establish his headquarters for the present, at Annapolis, Md., and will assemble at that point the troops under his command.

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By command of Major-General McClellan:

S. WILLIAMS,

Assistant Adjutant-General.

ARLINGTON, October 24, 1861.

General McDOWELL,

Eighteenth and Q Streets:

The following just received from General McClellan:

The affair in front of Leesburg, on Monday last, resulted in serious loss to us, but was a most gallant fight on the part of our men, who displayed the utmost coolness and courage. It has given the utmost confidence in them. The disaster was caused by errors committed by the immediate commander, not General Stone.

I have withdrawn all the troops from the other side, since they went without my orders and nothing was to be gained by retaining them there.

JAMES B. FRY,

Assistant Adjutant-General.

WASHINGTON, D. C., October 24, 1861.

General S. WILLIAMS,

Assistant Adjutant-General:

GENERAL: In our report of the 22nd instant we stated the number of men we deemed necessary for garrisons and reserves "for the various works in and about Washington to satisfy the conditions of a good defense." It seems proper to exhibit more clearly the grounds on which our estimate is founded. We have adopted the rule, which experience showed to be satisfactory for the lines of Torres Vedras, in computing the garrison of the various works, viz: Two men per running yard of front covering line and one man per running yard of rear line, deducting spaces occupied by guns. Computed in this manner, the total of the full garrisons of all the works would amount to 19,789 men, of which 6,581 should be gunners, in order to furnish three relief to each gun. Of these works, however, the following on the south side of the Potomac are on interior lines, and do not require full garrisons, while the exterior line is intact, viz: Forts Ellsworth, Scott, Runyon, Jackson, Corcoran, Bennett, and Haggerty.

Fort Albany might, perhaps, have been included in the above list in our estimate of the 22nd. However, we have considered it as fully garrisoned.

As Fort Ellsworth and Fort Scott have commanding views of the valleys of Hunting Creek and Four-mile Run, we have considered it necessary to provide for the efficient service of all their guns by three reliefs of gunners; to the others we have assigned but one relief. With regard to the assignment of garrisons to works of the exterior lines, we remark that if Washington, were thrown upon its own defenses, without external