aid, and the enemy were so far in the ascendant in the field as to be able to act on either shore, it is evident that all the works should be fully garrisoned.

We do not consider this extreme supposition the proper basis for garrisoning the works, and it is evidently desirable to shut up in them as few men as possible. The more probable supposition is that the army moves from here in force, fully occupying the bulk of the enemy's forces by its own movement, leaving the capital so strengthened by its defensive lines as to prevent danger of sudden seizure by a strategical movement of the enemy, and enable it to be held a reasonable time in case of serious reverses to our own arms in the field.

On this basis we have estimated for full garrisons of all the works of the exterior line south of the Potomac, for three reliefs of gunners for Forts Ellsworth and Scott, and for one relief for the other interior works, and for three reliefs of gunners only for all the works north of the Potomac, giving a total, as stated in our report of October 22, of 11,045 men. As without reserves a line of detached field works possesses little or no strength, we have considered as included in our instructions to provide for these. We are of opinion that two brigades should be distributed along the lines from Hunting Creek to Four Mile Run and two between Four Mile Run and Fort Corcoran, making, say, 12,000 men; one regiment in reserve at Chain Bridge of 750 men, and stationed in the city a reserve of 10,000 men; making a total of reserves of 22,750 men. As the total of full garrisons of all the works north of the Potomac is 7,343 men, it will be seen that in case of necessity part of these works or all might be full garrisoned from the reserves, still leaving over 15,000 men.

We herewith inclose two tabular statements, giving the names of works, perimeters, full garrisons, number of gunners, of works north and south of the Potomac. We would add that the system is not entirely completed, and that three or four more works than are mentioned in these statements may yet be found necessary.

RECAPITULATION.

For full garrisons of all works of exterior line south of.

the Potomac, except the Chain Bridge...................... 5,952

Full garrisons of Forts Ethan Allen and Marcy.............. 1,500

Three reliefs of gunners at Forts Ellsworth and Scott...... 363

One relief of gunners for other interior work.............. 230

For three reliefs of gunners for all works north of

Potomac................................................... 3,000

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Total...................................................... 11,045

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Total garrisons............................................ 11,045

Reserves................................................... 22,750

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Total...................................................... 33,795

We have the honor to be, general, very respectfully, your obedient servants,

WILLIAM F. BARRY,

Brigadier-General, Chief of Artillery.

J. G. BARNARD,

Brigadier-General, and Chief Engineer.