tack. Garrison pieces of long range and large howitzers are brought
forward on the salients of the bastions and demi-lunes of attack, so as
to fire in ricochet along the capitals on which the boyaux must be
pushed: light and fire-balls are thrown out as soon as it becomes dark,
to light up the ground occupied by the besiegers, thus exposing them to
the fire of the work and to the attacks of the sortie parties. These
parties are composed of light troops who charge the guards and compel
the workmen to abandon their sapping tools and stand upon the defence.
They are most effective when the besiegers commence the second parallel,
as the guards in the first parallel are not so immediately at hand to
protect the workmen. When the sortie detachment has driven these workmen
from the trenches, instead of pursuing them into the first parallel, it
will display itself in battle order to cover the engineer troops, (who
should always accompany the detachment in this enterprise,) while they
fill up the trenches and destroy the implements of the besiegers. When
the guards of the trenches appear in force, the detachment will retire
in such a way, if possible, as to draw the enemy within range of the
grape and musketry of the collateral works. These sorties, if
successful, may be frequently repeated, for they tend very much to
prolong the siege. The best time for making them is an hour or two
before day, when the workmen and guards are fatigued with the labors of
the night. While the besiegers are establishing their enfilading
batteries, a strong fire of solid shot and shells will be concentrated
on the points selected for their construction. The garrison will also
labor during this period to put the work into a complete state of
defence: constructing all necessary palisadings, traverses, blindages,
barriers; and strengthening, if necessary, the covering of the
magazines.

_Third period._--After the completion of the third parallel, the
crowning of the covered way may be effected by storm, by regular
approaches, or (if the work is secured by defensive mines) by a
subterranean warfare.

In the first case stone mortar-batteries are established in front of the
third parallel, which, on a given signal, will open their fire in
concert with all the enfilading and mortar batteries. When this fire has
produced its effect in clearing the outworks, picked troops will sally
forth and carry the covered way with the bayonet, sheltering themselves
b