Bertie looked surprised. "Why, I should have thought the thicker they were the more difficult to break up."
"Beyond a certain point that would be so. But suppose they are six inches thick, you may take it for granted that underneath there will be rubble, loose stuff, except where any chambers may be built. If we were to bore a hole through this top layer the powder, instead of splitting the stones up, would expend its force among the loose stuff beneath it; and besides, instead of remaining in its place, it might get scattered, and we would then get no explosion at all."
"Then we should only have to make the hole four inches deep, Harry?"
"As a result of which there would only be two inches of tamping over the powder, and this would blow right out, as if from a little mortar, and would have no effect whatever upon the stone. I have no doubt that we shall find some way to get over these difficulties, but it is evident that the work will not be all clear sailing."
"Of course we shall manage it somehow, Harry, even if we have to smash up all the stones with the sledge-hammers Dias will bring us."
"Is breakfast nearly ready, señora? That swim in the sea has given us a prodigious appetite. Did you enjoy it?"
Maria nodded.
"It is very nice, señor; but I should have liked it better if the water had not been so blue. It seems so strange bathing in blue water."
"You will soon get accustomed to it," Bertie laughed. "There are no pools except that one two miles up the valley. Besides, it is much nicer to have a great bathing chamber all to yourself. Here comes José!"
"Well, José, are the mules all right?" he shouted.