3. When you cannot procure wood for the fascines, the parapet must be covered or clothed with pieces of turf, 4 inches thick, and a foot and a half square; these are fastened to the parapet with 4 small pickets 8 inches long.
4. The fraises, or pointed stakes, must be 8 feet long, 5 inches thick, and be sharp at the top. The beams upon which they are laid, must be 12 feet long and 6 inches thick. These beams are spread horizontally along the parapet, and fraises are fixed to them, with nails 7 inches long; after which the beams are covered with earth. Two men will make 12 fraises in an hour.
5. The palisades, by which the ditch or fossé of a work is fortified, must be 9 or 10 feet long, and 6 inches thick; they must, likewise, be sharpened at the end. If you cannot procure them of these dimensions, you must use smaller ones; in which case you will have the precaution to mix a few large stakes.
6. The pickets, which are fixed in trous-de-loup or wolf-holes, must be 6 feet long, 4 inches thick, and sharp at the top.
7. The beams belonging to a cheval-de-frize must be 12 feet long, and 6 inches broad. The spokes which are laid across, must be 7 feet long, 4 inches thick, and placed at the distance of 6 inches from each other. These chevaux-de-frizes are made use of to block up the entrances into redoubts, to close passages or gates, and sometimes they serve to obstruct the fossé.
8. Gabions are constructed of various sizes. Those which are intended for field works, must be 3 or 4 feet high, and contain 2 or 3 feet in diameter. These gabions are made by means of long stakes, 3 or 4 feet long, which are placed so as to form a circle, which is 2 or 3 feet in diameter. The pickets must be covered and bound in the same manner as hurdles are. Gabions are chiefly of use in embrasures. They are fixed close to each other, and are afterwards filled with earth. There are also gabions of one foot, with 12 inches diameter at the top, and 9 at the bottom. The bank of the parapet is lined with gabions of this construction, behind which troops may be stationed, so as to fire under cover through the intervals. A quantity of large wooden mallets, rammers, hatchets, axes, and grappling irons, is required for this work.
Names of all works used in field Fortification.
Bridge heads, or têtes de pont, are made of various figures and sizes, sometimes like a redan or ravelin, with or without flanks, sometimes like a horn or crown work, according to the situation of the ground, or to the importance of its defence. Their construction depends on various circumstances; for, should the river be so narrow, that the work may be flanked from the other side, a single redan is sufficient; but when the river is so broad, that the saliant angle cannot be well defended across the river, flanks must be added to the redan; but should a river be 100 toises, or more across, half a square may be made, whose diagonal is the river side; and where the river is from 3 to 500 toises broad, a horn, or crown-work should be made. All the different sorts of heads of bridges, are to be esteemed as good works against a sudden onset only, and their use is almost momentary, as they sometimes serve but for a few days only, and at most during a campaign.
Dams are generally made of earth, but sometimes of other materials, as occasion may require: their use is to confine water.
Flêche a work consisting of two faces, terminating in a saliant angle of 90°, the faces are generally 75, or 80 feet long, the parapet 6 feet thick, and the ditch 7 feet broad.