The strength and reputation of the Garrison were the reason for the decision to establish it at the usual distance, and to fortify it by redoubts against sorties. The advanced works on the enemy’s left made it necessary even to increase the distance of the right of the attacks from the body of the place. The lay of the ground determined its outline; the right resting on the steep bank of the river, on the left of the great ravine.
In the night of the 6th to 7th, the first parallel was opened, and the construction of the redoubts necessary for safety began. This work was only interrupted by the batteries, the fire of which was turned upon the new redoubts from the beginning of their construction.
The same night an end of a parallel with a flying sap was opened to support a battery which served the double purpose of disturbing the advanced redoubt on the right of the besieged and of driving off the ships of war which might have taken the left of the great attack in reverse.
This work, information of which was given by a deserter, was greatly troubled by the batteries of the besieged, and the attention which they paid to it diverted their attention from the opening of the great attack.
October 7th.—At daybreak the guard batteries entered the parallel. From the 7th to 8th the perfectionment of the first parallel and the redoubts was continued, and the construction of the batteries begun. The nature of the ground on the left decided their establishment behind the parallel, and one was placed on its left flank beyond the ravine.
October 8th.—At noon the parallel and the battery at the left attack were completed.
From the 8th to the 9th the perfectionment of the parallel, and of the redoubts and batteries was continued, and communications opened in their rear.
October 9th.—The construction of a battery of mortars was begun in part of the parallel.
In the afternoon the batteries began their fire, and subdued that of the enemy.
The fire of that on the left compelled the frigate and the other vessels of war to withdraw.