The accompanying sheets, Nos. 1 and 2, will exhibit the general location and bearings of the works.* The tabular statement herewith will show the perimeters, number of guns, amount of garrison, &c.+

It should be observed that most of the works south of the Potomac, having been thrown up almost in the face of the enemy, have very light profiles, the object having been to get cover and a defensive work as speedily as possible. The counterscaps of all the works, with few exceptions, are surrounded by abatis..

It is impossible, at present, to indicate the exact extent of forest cut down. (The drawings herewith represent the forest as it existed before the works were commenced.)++ The woods in advance of Forts Worth, Ward, and Blenker have been felled; all surrounding and between the next work on the right and Fort Richardson; all the wood on the ridge of which is Fort Scott-a square mile probably-in advance of and surrounding Forts Craig, Tillinghast, and Woodbury, besides large areas north of the Potomac, &c. This fallen timber (most of which still lies on the ground rendered an enemy's approach to the lines difficult. The sites of Forts Totten, Slocum, Bunker Hill, Meigs, Stanton, and others were entirely wooded, which, in conjunction with the broken character of the ground, has made the selection of sites frequently very embarrassing and the labor of preparing them very great..

The only case in which forts are connected by earthworks is that of Forts Woodbury and De Kalb, between which an infantry parapet is thrown up, with emplacements for field guns. The construction here was suggested by the fact that this was on one of the most practicable and probable routes of approach for the enemy. Infantry trenches have, however, been constructed around or in advance of other works, either to cover the construction (as at Fort Lyon), or to see ground not seen by the work (as at Forts Totten, Lincoln, Mahan, &c.)

The works I have now described do not constitute a complete defensive system..

We have been obliged to neglect much and even to throw out of consideration important matters. We have been too much hurried to devise a perfect system, and even now are unable to say precisely what and how many additional points should be occupied and what auxiliary arrangements should be made..

It is safe to say that at least two additional works are required to connect Fort Ethan Allen with Fort De Kalb..

The necessity of protecting the Chain Bridge compelled us to throw the left of our northern line several miles in advance of its natural position, as indicated by the topography to the sites of Forts Ripley, Alexander, and Franklin. Between these and Forts Gaines or Pennsylvania one or two intervening works are necessary. Between Forts Pennsylvania and De Russy at least one additional work is necessary..

Fort Massachusetts is entirely too small for its important position. Auxiliary works are necessary in connection with it..

Small states de-pont are required around the heads of Benning's and the Navy-Yard Bridges..

Between Forts Mahan and Meigs one or more intervening works and between Forts Du Pont and Davis another work of some magnitude are required, the ground along this line not being yet sufficiently known. A.

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*To appear in Atlas..

+No tabular statement found as an inclosure to this report, but see Barnard and Barry to Williams, October 24, pp. 626-628.

++Omitted..

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