also be turned and used against Bolivar Heights, if required. a line of stone breastworks or rifle-pits(made by filling a crib -work of logs with stone)has been built along the northern edge of this plateau, which, in connection with the rifle -pits extending down from the summit, renders the west slope of the mountain safe against almost every attack . That portion of the north rifle-pits near the stone fort, which is on the summit of the mountain (a distance of about 100 yards), is being raised and strengthened, so as to form a strong parapet 9 or 10 feet in height, and the guns mounted here. Temporary banquettes have been placed in the stone fort, so as to use it as a citadel, from which to drive out the enemy even should he get possession of the battery. The eastern face of Maryland Heights is very steep and difficult of ascent at every point of the crest from the stone for the 30 pounder battery that affords the least facility for the approach of an enemy . Stone breastworks or rifle -pits have been constructed, and seven light field guns have been distributed along the crest, at points from which they have a raking fire on the mountain side . About 600 yards to the south of the stone fort, on a narrow point in the crest, a platform has been erected, and a 100 pounder Dahlgren gun from the naval battery mounted. This gun has a field of fire of 360 degrees. It can be used with effect against an enemy ascending either slope of the mountain in Pleasant Valley, on Loudoun or Bolivar Heights, or in Fort Duncan, and a single shot from it would render the stone fort, the almost inaccessible slopes of Maryland Heights on the east and the guns distributed along the crests, and the rifle-pits which have been built to prevent an enemy ascending them. Fort Duncan is on the left of line of defense. This work has been strengthened and the guns from the battery south of it placed in it. There should be nine additional guns in this work to give it a full armament to resists an attack from all sides. The embrasures and the platforms have been erected, so that the guns now in the work can be used as occasion may require. The guns from Fort Duncan in connection with the 50 - pounder on the spur and the batteries already mentioned, give a double cross-fire in front of our line of defense. On a spur to the north of Fort Duncan a light work has been thrown up for two guns to enfilade the canal and tow-path to the north, and to prevent an enemy turning the left flank of our rifle-pits, and it is velieved that if the works are completed, fully armed and manned, and the men do their duty, they will be able to resists almost any assault that may be made against them. Although a great deal of timber had been cut down on Maryland Heights, yet a much larger amount remained that gave cover for an enemy. All the axes that could be procured, some 600, were set to work cutting down all timber within 1, 500 yards of our line of defense, or on the eastern slope of Maryland Heights. In order to supply the place of the guns taken from the naval battery, I proposed to throw up a battery on the river bluff just west of the Sharpsburg road. This work was being laid out on June 27. If completed and armed, it will perfectly command the railroad bridge across the Potomac, the pontoon bridge above, the dam, the whole