On the 21st the besiegers sent a summons, the governor refused to receive the letter, the firing was renewed, and though the main wall resisted the parapets crumbled; the batteries on Monte Olia also plunged into the horn-work at sixteen hundred yards’ distance, with such effect that the besieged, having no bomb-proofs, were forced to dig trenches to protect themselves. The French fire, directed solely against the breaching batteries, was feeble, but at midnight a shell thrown from the castle into the bay gave the signal for a sally, during which French vessels with supplies entered the harbour. The besieged now isolated the breach by cuts in the rampart and other defences, yet the besiegers’ parallel across the isthmus was completed, and in its progress laid bare the mouth of a drain four feet high and three feet wide, containing the pipe of the aqueduct cut off by the Spaniards. Through that dangerous opening Lieutenant Reid,[30] a young and zealous engineer, crept even to the counterscarp of the horn-work, where he found the passage closed and returned. Thirty barrels of powder were placed in this drain, and eight feet was stopped with sand-bags, forming a globe of compression to blow, as through a tube, so much rubbish over the counterscarp as might fill the narrow ditch of the horn-work. On the 22nd the fire from the batteries, unexampled from its rapidity and accuracy, opened what appeared a practicable breach in the eastern flank wall, between two towers called Los Hornos and Las Mesquitas; but the descent into the town behind this breach was more than twelve feet perpendicular, and the garrison were seen from Monte Olia diligently working at the interior defences to receive the assault: they added also another gun to the battery of St. Elmo, just under the Mirador battery, to flank the front attack. On the other hand the besiegers had placed four sixty-eight pound carronades in battery to play on the defences of the breach, yet the fire was slack because the guns were now greatly enlarged at the vents. On the 23rd, the sea blockade being null, the French vessels carried off the badly-wounded men. This day also the besiegers, judging the breach between the towers practicable, turned the guns, at the suggestion of General Oswald, to break the wall on the right of the main breach. Smith opposed this, urging, that no advantage would be gained by making a second opening, to get at which the troops must first pass the great breach; time would be thus lost, and there was a manifest objection on account of the tide and depth of water at the new point attacked. His counsel was overruled, and in the course of the day, the wall being thin, the stroke heavy and quick, a second breach thirty feet wide was rendered practicable.