The second parallel (B) is made some three hundred or three hundred and fifty yards from the place, and being much exposed to grape, the flying-sap is employed in its construction.  Batteries (H) are established between the first and second parallels to silence the fire of the demi-lunes of the collateral bastions, and others (I) near the second parallel, to enfilade the faces of the front of attack.  These are armed in part with mortars and in part with heavy siege-pieces.

The works are now gradually pushed forward to the third parallel, (C), which is constructed about sixty yards from the salients of the place.  As the operations of the besiegers are here greatly exposed to musketry fire, the trenches are constructed by the full-sap.  The third parallel, having to contain the guards of the trenches, and being of less development than the two preceding, is made much wider.  The second parallel now contains the reserve, and the first parallel becomes the depot of materials. Demi-parallels (G) are frequently established between the second and third, to be occupied by detachments of guards.

The operations of defence during this period are so directed as to harass the workmen in the trenches and retard the advance of the works of attack.  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.