When he left the Casa Alvarez, two hours before, he had given instructions for the commencement of operations by which he hoped to beat the French at their own game. From what he had learnt from Don Cristobal he saw that the mistake up to the present had been the waiting for the explosion of the French mines, the result being that the enemy gained positions from which it usually proved impossible to dislodge them. The only means of keeping them effectually in check was to practise countermining, not in the hand-to-mouth manner in which it had hitherto been attempted, but systematically, with a longer outlook, with a regard to ultimate developments rather than to the immediate repelling of attack. During his interview with the foreman that morning he had explained his ideas, and learnt that, so far as the man's limited experience went, there was no practical obstacle to their accomplishment.
The French, as he had seen, had been for some days past working steadily through the three parallel blocks of buildings that ran from the Santa Engracia direction towards the Plaza Alvarez. They had made equal progress in all three blocks. The limit of destruction was marked by the Casas Vega, Tobar, and Vallejo, the first two being at the end of their blocks immediately facing the Casa Alvarez, separated from each other by a narrow lane, while the last was separated from the Casa Tobar by the street running into the plaza. These three houses were still standing, but it was obvious that they would form the next points of attack, and it was highly probable that even now the enemy had begun to cut galleries towards them.
Jack had made up his mind to anticipate the attack. Before leaving in the morning he had learnt from the foreman, whose name was Pulgar, that the work of mining underground could usually be heard from a distance of about forty feet. From this he calculated that, if the French began to work from their side immediately after their last attack, there would be time for his own men to drive a short gallery beneath the wall of each of the three houses before there was any risk of their operations being heard by the enemy. He had therefore left instructions for a hole to be cut beneath the farther party-wall of each house, where it adjoined the house last demolished. He told Pulgar to see that the digging was done as quietly as possible, and to be on the alert to catch the slightest sound of the approach of the French miners in the opposite direction.
"Well, how are things getting on?" he asked of Don Cristobal, on arriving at his post after his interview with Juanita.
"Excellently," was the reply. "Pulgar has kept the men at work without relaxation."
"In shifts, I suppose?"
"Only one man can work at each tunnel, so he gave each man half an hour; then his place was taken by another. Here is Pulgar himself."
"You are doing capitally, I hear, hombre," said Jack. "How far have the men got?"
"The tunnels are nearly three feet long by this time, Señor. It takes about an hour to cut away a foot."
"Any sound of the French?"