Blockhouses.This blockhouse was near Hunting Creek, close to the Orange & Alexandria Railroad, and covering the bridge over the creek on the Telegraph Road. The walls were built of large logs from sixteen to eighteen inches in diameter. Loop-holes for musketry were cut through the walls, just above the earthern bank, and were “splayed,” or widened, toward the inside to permit a greater field of fire. Embrasures for 12-pound howitzers were cut on every face. Two such guns were placed in each blockhouse of this type. Each was provided with a magazine below the floors, arranged for a garrison of sixty men. The second picture shows a square blockhouse near the Virginia end of Aqueduct Bridge. This structure had two stories, with the upper projecting over the lower, and loop-holes in the floor of the upper story to permit the defenders to fire down on the heads of assailants near the walls. The entrance was through the door in the upper story, to which access was gained over the drawbridge from the top of the trestle. These blockhouses had not much strength, and were useful chiefly for moral effect, although, in case of necessity, a stubborn resistance could have been put up by defenders.