When day dawned on the 15th, the breaching batteries on the Great Teson opened again with excellent effect. Their fire was concentrated on the rebuilt wall of the _enceinte_, where the French breach of 1810 had been mended. It was necessary to batter both the town wall proper and the _fausse-braye_ below it, so as to make, as it were, an upper and a lower breach, corresponding to each other, in the two stages of the _enceinte_. It will be remembered that, as was explained in our narrative of the French siege[185], the mediaeval ramparts of the old wall showed well above the eighteenth-century _fausse-braye_ which ran around and below them, while the latter was equally visible above the glacis, which, owing to the downward slope from the Little Teson, gave much less protection than was desirable to the work behind it. The French breach had been carefully built up; but, lime being scarce in the neighbourhood, the mortar used in its repairs had been of inferior quality, little better than clay in many places. The stones, therefore, had never set into a solid mass, even eighteen months after they had been laid, and began to fly freely under the continuous battering. [185] See vol. iii. p. 239. The illustration of Rodrigo on the morning after the storm, inserted to face page 186 of this volume, shows the facts excellently. The breaching being so successful from the first, Wellington resolved to hurry on his operations, though there were still no signs that Marmont or Dorsenne was about to attempt any relief of the garrison. Yet it was certain that they must be on the move, and every day saved would render the prospect of their interference less imminent. Accordingly it was settled that the second parallel should be completed, and that, if possible, more batteries should be placed in it, but that it was to be looked upon rather as the base from which an assault should be delivered than as the ground from which the main part of the breaching work was to be done. That was to be accomplished from the original parallel on the Great Teson, and one more battery was marked out on this hill, close to the Redout Renaud, but a little lower down the slope, and slightly in advance of the three original batteries. From this new structure, whose erection would have been impossible so long as San Francisco was still held by the French, Wellington proposed to batter a second weak point in the _enceinte_, a mediaeval tower three hundred yards to the right of the original breach. All the attention of the French being concentrated on the work in the second parallel, this new battery (No. 4) was easily completed and armed in three days, and was ready to open on its objective on January 18th.