The weakest feature in this line of works, and it obtains more or less throughout the whole line of the defenses, is their liability to be surprised. The garrisons of the works, with the exception of small guards, are quartered outside the works. No infantry force has been kept between and near the line of the works. The outpost guards have been very weak. The character of the topography of the country for miles outside of the works, with the numerous roads, all favor and invite a sudden and covered dash upon the works.

With a view to strengthen the works in this particular, I recommend that regiments of the [Veteran] Reserve Corps be stationed at the following points: One regiment between Forts Richardson and Craig; one regiment between Forts Craig and Tillinghast; one regiment between Forts Tillinghast and Woodbury and in advance of Fort Whipple; one regiment between Forts Woodbury and Strong and in advance of Fort Corcoran; one regiment between Forts Worth and Ward; one regiment between Forts Garesche and Berry, and one regiment between Forts Ethan Allen and Marcy.

From the troops of the Reserve Corps thus posted I recommend that the officers commanding the defenses south of the Potomac be instructed to establish outposts as follows: A picket reserve of three companies at Ball's Cross-Roads; a picket reserve of three companies at Bailey's Cross-Roads; a picket reserve of two companies on the Little River pike, between Clover Hill and Hunting Creek; a picket reserve of two companies on the Leesburg and Georgetown pike at the cross-roads, between Langley and Fort Marcy. I recommend that the best instructed and most efficient artillery in the line of defenses be kept in the works of the first class. Forts Ethan Allen and Marcy, in the second class, over the approaches to the city by the Chain Bridge; they are in close artillery support of each other, but beyond the range of artillery support from the nearest work (Fort Smith) on their left. If the cover of these works and their connections are properly manned it is believed they cannot be carried by assault. From the position of these works they do not offer advantages sufficient to an enemy, if possessed, to make them worth the operations of a siege; they do not immediately command the bridge, and the right bank of the river at the head of the bridge is commanded by Batteries Vermont, Cameron, Kemble, and Parrott on the left bank, and the bridge is swept by Battery Martin Scott on the left bank. The strength of artillerymen at Battery Martin Scott I do not consider sufficient. I found but 1 non-commissioned officer and 3 men in charge of four guns. I recommend that 1 officer, 4 non-commissioned officers, and 24 men be allowed this battery.

The works of the third class, extending to the left from Fort Berry to the Potomac, do not immediately command approaches to the city, and are beyond artillery range from it. They, however, command important ground, and cover the depot at Alexandria, and are in good supporting distance; and they are sufficiently strong, if properly manned, to resist an assault. The possession of them would offer no objective point to an enemy that would render them liable to a siege.

Battery Rodgers, below Alexandria, and Fort Foote, on the left bank of the river, are important works for river defense. Battery Rodgers received ammunition for its two guns on the 9th instant, and Fort Foote ammunition for its 15-inch guns on the 13th instant. From the length of time that is necessarily occupied in serving guns of the caliber in these two works, and the unfavorable height of