The Tenaille.
Draw lines parallel to the lines of defence, at the distance of 16 yards, for the faces of the work; its flanks, and curtain are constructed parallel to the flanks of the bastions, and curtain, at the distance of 11 yards.
The Ravelin.
From the re-entering angle of the counterscarp, make the capital of the ravelin 80 yards in length, and from its summit draw lines to points, on the faces of the bastions, 11 yards from the angle of the shoulder; the junction of these lines, and the counterscarp of the main ditch will determine the length of the faces of the ravelin. The gorge is formed by drawing lines 24 yards from the re-entering angle of the counterscarp to the intersection of the perpendicular, and the exterior side. From the salient angle of the ravelin, with a radius of 24 yards, describe an arc, to which draw tangents parallel to the faces, for the breadth of the ditch.
From the outline of the works draw the following parallels inwards:—
Rampart.
1. At the distance of 6 yards, for the thickness of the parapet.
2. From which 12 yards, for the breadth of the terreplein.
3. From which 6 yards, for the breadth of the interior slope.
Tenaille.
Draw lines parallel to the faces, at the distance of 6 yards, for the parapet.