Lines are formed for the entrenchment of armies, and are composed of a succession of redans, &c., joined by curtains, which should not be more than 120 yards distant from each other, to afford mutual protection, and defence.[37]
An Epaulment is an elevation of earth thrown up to cover troops from a flanking fire.
Loop-holes are oblong holes, from 15 to 18 inches long, 6 inches wide within, and 2 or 3 without. They are cut through timber, or masonry, for the services of small arms.
Palisades are stakes of strong wood, 8 or 9 feet long, and 6 inches thick, fixed about 3 feet in the ground, and 3 or 4 inches asunder.
Fraises are a kind of palisades, placed horizontally, or obliquely in the exterior slope of ramparts.
Chevaux de frise consist of a piece of timber from 9 to 12 feet long, and about six inches in diameter, into which staves are inserted cross-ways, about 9 inches asunder, about 2 inches thick, 6 feet long, and pointed at the end, if not shod with iron. Their use is to stop up a breach, defend a passage, or form an entrenchment against cavalry. Chevaux de frise are sometimes made entirely of iron.
Abattis consist of trees with their branches shortened, and sharpened at the ends; they are used instead of chevaux de frise on an emergency.
Hurdles are about 3 feet high, and 2 broad, and are used in sieges to stop up breaches, &c.
Trous de loup are holes dug in the ground in the form of an inverted cone, about 6 feet deep, and 4½ in diameter at the top, having a picket fixed in the centre of the bottom, 6 feet long, and 4 or 6 inches square, the point being on a level with the upper surface of the ground. These pits are used to prevent the approach of bodies of cavalry.
PERMANENT FORTIFICATION.