d not
within supporting distance of the fortress, they are called _detached
works_.

In a bastioned front the principal outwork is the _demi-lune_, which is
placed in front of the curtain; it serves to cover the main entrance to
the work, and to place the adjacent bastions in strong re-enterings.

The _tenaille_ is a small low work placed in the ditch, to cover the
scarp wall of the curtain and flanks from the fire of the besieger's
batteries erected along the crest of the glacis.

The _places of arms_, are points where troops are assembled in order to
act on the exterior of the work. The _re-entering places of arms_, are
small redans arranged at the points of junction of the covered ways of
the bastion and demi-lune. The _salient places of arms_ are the parts of
the covered way in front of the salients of the bastion and demi-lune.

Small permanent works, termed _redoubts_, are placed within the
demi-lune and re-entering places of arms for strengthening those works.
Works of this character constructed within the bastion are termed
_interior retrenchments;_ when sufficiently elevated to command the
exterior ground, they are called _cavaliers._

_Caponniers_ are works constructed to cover the passage of the ditch
from the tenaille to the gorge of the demi-lune, and also from the
demi-lune to the covered way, by which communication may be maintained
between the enceinte and outworks.

_Posterns_ are underground communications made through the body of the
place or some of the outworks.

_Sortie-passages_ are narrow openings made through the crest of the
glacis, which usually rise in the form of a ramp from the covered way,
by means of which communication may be kept up with the exterior. These
passages are so arranged that they cannot be swept by the fire of the
enemy. The other communications above ground are called _ramps, stairs,_
&c.

_Traverses_ are small works erected on the covered way to intercept the
fire of the besieger's batteries.

_Scarp_ and _counterscarp_ galleries are sometimes constructed for the
defence of the ditch. They are arranged with loop-holes, through which
the troops of the garrison fire on the besiegers when they have entered
the ditch, without being themselves exposed to the batteries of the
enemy.

In sea-coast defences, and sometimes in a land front for the defence of
the ditch, embrasures are made in the scarp wall for the fire of
artillery; the whole being protected from shells