The day succeeding the night on which the trenches are opened, and the side to be attacked determined, a new arrangement of the artillery must take place. All the 24 and 18 Prs. must be removed to the front attacked, and the other bastions, if required, supplied with 12 Prs. The barbettes of the bastions on this front may have each 5 guns, and the 12 18 prs. may be ranged behind the curtain. The six mortars in reserve must be placed, two in each of the salient angles of the covert way of this front, and with those already there, mounted as howitzers,[5] to fire down the prolongations of the capitals. Three 4 pounders in each of the salient places of arms of the ravelins on the attacked fronts, to fire over the palisading, and five 9 Prs. in the ravelin of this front. This arrangement will bring 47 guns, and 18 mortars to fire on the approaches after the first night; and with a few variations will be the disposition of the artillery for the second period of the siege. As soon as the enemy’s batteries are fairly established, it will be no longer safe to continue the guns _en barbette_, but embrazures[6] must be opened for them; which, embrazures must be occasionally masked, and the guns assume new directions, as the enemy’s fire grows destructive; but may again be taken advantage of, as circumstances offer. As the enemy gets near the third parallel, the artillery must be withdrawn from the covert way to the ravelins, or to the ditch, if dry, or other favorable situations; and, by degrees, as the enemy advances, to the body of the place. During this period of the siege, the embrazures must be prepared in the flanks, in the curtain which joins them, and in the faces of the bastions which flank the ditch of the front ravelins. These embrazures must be all ready to open, and the heavy artillery mounted in them, the moment the enemy attempts a lodgement on the glacis. [5] Our iron mortars, on iron beds, all admit of being fired at low angles. [6] A German author proposes that the mounds of earth which enable the guns to fire _en barbette_, should be so arranged, that the embrasures may be opened between them; and when the guns descend to the embrazures, the barbettes will serve as traversers. Every effort should be made to take advantage of this favorable moment, when the enemy, by their own works, must mask their former batteries, and before they are able to open their new ones. The expenditure of ammunition will be nearly as follows: _First period_ of the siege—5 rounds per gun, per day, with only half the full charge, or ⅙ the weight of the shot, and for only such guns as can act. _Second period_—20 rounds per gun, per day, with ⅙ the weight of the shot. _Third period_—60 rounds per gun, per day, with the full charge, or ⅓ the weight of the shot. _Mortars_—At 20 shells per day, from the first opening of the trenches to the capitulation.