Fortification....Permanent.
A parapet, to resist cannon should never be less than 18 feet thick in earth, and 8 or 9 in masonry. A wall need only be two feet thick in masonry to resist musquetry. The parapet should always be 4¹⁄₂ feet above the banquette, and 7¹⁄₂ or 8 feet above the rampart, or terre-plein.
The Rampart should always be sufficiently wide to allow for the platform, and for two carriages passing each other; about 9 fathoms at top. A parapet of earth, though it takes more room, is always preferable to one of masonry, when it can be raised; though the only objection to the masonry, is the number of splinters it produces.
Entire Revetements of masonry are not advantageous for the same reason. The masonry of revetments should not be so high as to be seen or battered from a distance; earth parapets are battered in vain, as the earth forms a natural slope.
The best Scarp is made of masonry, either in wet or dry ditches, be the earthen one ever so well fraized or palisaded. The earthen one may be stormed without making a breach. The scarp should be 30 or 35 feet high.
The Counterscarp should also be of masonry, and not less than 12 feet high. The inconveniences of an earth or low counterscarp, are the impossibility of defending to the last the covert way; as the enemy may descend into the ditch, and again mount the covert way, and so get in the rear of the traverses. The enemy may find his way along the natural slope of an earth counterscarp, and is not delayed by a tedious operation of getting into the ditch. Besides the natural slope of the end of an earth traverse prevents its effectually covering the covert way.
Ditches are generally 15 or 18 toises wide. Dry ditches are always preferable to wet ones, on account of the shelter they afford the troops, and the ready communication with the outworks, without the constant trouble and danger of bridges.
The Covert way should be 5 toises wide; less would croud the troops, and more would allow room for the enemy to erect batteries in it.
The whole of the glacis should be seen, not only from the crest of the parapet, but from the embrasures in the parapet.
The Tenaille, must not be so high as to prevent the flank guns in one bastion seeing the breach that may be made in the collateral one.