"Because, after we have fired one, the French will come on in greater strength again, thinking we have done our worst, and the explosion of the second will have a shattering effect on them in every way." "An excellent idea, Señor!" said Don Cristobal, "but our men are not too strong, and it would cost immense labour to drive two galleries. It is forty feet across the plaza between this and the houses opposite; you must allow for several feet of tunnel in each house if you want to spare the walls facing us—" "Eight feet at least," interrupted Jack. "I don’t want to destroy the houses entirely." "Well, that makes ninety-six feet of tunnelling for each house, and all the earth to be carried back as it is dug out. You will work your men to death, Señor." Jack considered. For the moment he envied some friends of his who had commissions in the Engineers. "They would have mugged up all this sort of thing in their books," he said to himself. How could he achieve his purpose without running the risk Don Cristobal had pointed out? He stood for a time unconsciously tapping the stone floor with his foot as he thought over the problem. "I have it!" he exclaimed suddenly. "It’s a case of letter Y—you see? Drive one gallery half-way; then two branching out from it like the arms of a capital Y. It won’t save time, but it will save labour, and we can’t afford to knock the men up." "That is it, Señor," said Pulgar, rubbing his hands. "Then I will get you to arrange with the men so that they take turn and turn about. And by the way, two short tunnels must be cut between the Casa Vallejo and the house next it on this side—the Casa Hontanon, is it not? Those houses are not so capable of defence as this is, but we must do what we can to beat the enemy there also." Pulgar at once set off to arrange with the workmen, while Jack proceeded to organize the garrisoning of the houses. Except for a few shells thrown over the ramparts nothing had been done by the French since the explosion of the previous evening. The barricades in the streets and lane were held by men of the Valencia regiment; Jack selected other men from the same regiment, and some of the best of the guerrilleros, and thus formed three companies of twenty men each to garrison the three casas, Vega, Tobar, and Vallejo. Fifty men were held in reserve in the Casa Alvarez.