le
intrenchments, viz.: the polygon, redan, lunette, mitre, star-fort, and
bastion.

_Square_ or _polygonal redoubts_ are the most common forms given to
field-works, on account of the ease of their construction. But they have
many defects. There is a sector without fire in front of each salient,
and the ditches are without protection. The latter objection also holds
good against all circular works.

The _redan_ (Fig. 45) is frequently used to cover a point in rear, as a
bridge, a ford, or a defile. When used alone, its gorge should be closed
by palisades. Its ditches are unprotected.

The _lunette_ (Fig. 46) has nearly the same defects as the redan.

The _mitre_, or _priest-cap,_ (Fig. 47,) may be employed with advantage
when a cross-fire is required on the capital of the work. The
_star-fort_ has all the defects, without the merit of simplicity, which
belong to the polygonal redoubt.

The _bastion-fort_ (Fig. 48) more fully satisfies the conditions of a
good defence than any other plan; but it is less simple and easy of
execution. It is usually composed of four or five fronts, but it may be
applied to a polygon of any number of sides.

For the details of the construction of these several works, we must
refer to the special treatises on field-fortification.

Lines of intrenchments may be made either continuous or with intervals.
In adopting either plan, the engineer should avail himself of all the
natural obstacles presented by the position, so as to diminish the labor
of erecting artificial means of defence.

The simplest arrangement for a continuous intrenchment is the
_cremailliere_ or indented line. When applied to an irregular site, or
used to connect together distant and detached works, the indented line
may be regarded as a good disposition. Mitres and redans, connected by
straight curtains, are sometimes employed, as also a combination of
large and small redans, forming alternate salient and re-entering
angles. A continuous line of bastions is preferable to any other
arrangement, when there is plenty of time for their construction.

Lines with intervals are frequently formed of alternate lunettes and
square redoubts. Other detached works may be employed in the same way.
This manner of intrenching a position has several advantages, with
disciplined troops. The first shock of the assailant is sustained by the
detached works, and when he attempts to penetrate in the intervals, his
flanks become exposed t