At eleven o’clock on the morning of the 29th the two French batteries opened[116], with twelve heavy guns. The weakness of the old town wall at once became evident: the first shot fired went completely through it, and lodged in a house to its rear. Before evening there was a definite breach produced, just south of the Retiro ravine, and it was clear that the enemy would be able to increase it to any extent that he pleased--the masonry fell to pieces the moment that it was well pounded. The two small field-guns on the tower of Jesus were silenced by 3 o’clock, and the heavy gun on Guzman’s tower also ceased firing--of which more anon. By night only the distant guns on the island, and the ships in the south-western bay, were making an effective reply to the French. [116] The breaching battery on the lower slope with four 16- and two 12-pounders: the upper battery with four howitzers for high-trajectory fire against the more distant guns of the besieged and the island, and two 12-pounders. This, from the psychological point of view, was the critical day of the siege, for on the clear demonstration of the weakness of the walls, Colonel Skerrett, who had never much confidence in his defences, proposed to evacuate the city of Tarifa. At a council of officers he argued in favour of withdrawing the garrison into the island, and making no attempt to hold the weak mediaeval walls which the French were so effectively battering. This would have been equivalent, in the end, to abandoning the entire foothold of the British on this point of the coast. For there was on the island no cover for troops, save two or three recently erected buildings, and the recesses of the ‘Cueva de los Moros.’ Some of the inhabitants had already taken refuge there, and were suffering great privations, from being exposed to the weather in tents and hastily contrived huts. It is clear that if 3,000 men, British and Spanish, had been lodged on the wind-swept rocks of the island, it would soon have been necessary to withdraw them; however inaccessible the water-girt rock, with its low cliffs, might be, no large body of troops could have lived long upon it, exposed as they would have been not only to wind and wet, but to constant molestation by heavy guns placed in and about the city and the hills that dominate it. Meanwhile the French would have possessed the excellent cover of the houses of Tarifa, and would have effectively blocked the island by leaving a garrison to watch the causeway, the only possible exit from it. It is certain that the abandonment of the island would have followed that of the town within a few days: indeed Skerrett had already obtained leave from General Cooke, then commanding at Cadiz, to bring his brigade round to that port as soon as he should feel it necessary. He regarded the evacuation of the place as so certain, that he ordered the 18-pounder gun on Guzman’s tower to be spiked this day,