"The acids rot the cement," he went on. "That's the principle. They disintegrate it. You see? Then the saw sets to work. It goes through the cement as if it's Bath brick. We shall get down two lots of azulejos in two places. That'll give us elbow-room for cutting through the cement backs of the lot between with a mason's saw. You understand--a long saw with two handles? D'ye see? The acid and the round saw here and there; and the long saw in between. That's the principle." The baronet stared at Antonio, waiting for his opinion. "Well?" he demanded impatiently. "I am quite unable," said the monk coolly, "to suggest the smallest improvement in your Excellency's invention. But the daylight is failing. If your Excellency works by candle-light or lamp-light, some azulejos will probably be broken. Let the acids work all night; and let us all meet here at eight o'clock to-morrow morning." "Nonsense," cried Sir Percy. "We've time to get down the first lot." "And what about dinner?" asked Crowberry _père_, in great alarm. "Yes. Dinner?" echoed Crowberry _fils_. "Dinner be hanged!" cried Sir Percy angrily. "Your Excellency must give the acids all night to work," said Antonio. "Yes, your Excellency really must," added young Crowberry. "Perhaps your Excellency has forgotten that the great Carthaginian Hannibal likewise employed an acid--namely vinegar--to make rocks friable, during his famous crossing of the Alps, as is narrated by the historian Livy in his twenty-first book. I know the passage well, having had to copy it out twenty times at school for putting pepper in the usher's pipe." "Shut up!" snapped his indignant father. But the youth was not abashed. "If Hannibal left his puddles of vinegar out all night," he said, "I, for one, cannot be a party to your Excellency's doing differently. I'm off." He moved away. Antonio followed. Mr. Crowberry senior, glad of any excuse to get back punctually for dinner, hurried in their train. Sir Percy gaped after them in deep disgust. Then he flung down his chisel upon the pavement and strode out after the others. "At eleven o'clock to-night," whispered young Crowberry in Antonio's ear. "At eight o'clock to-morrow morning," said Antonio in a loud voice. He went his way and they went theirs. VIII Had the black monk's ghost attended his vigil in the abbey chapel young Crowberry could hardly have seen it. His labors among the azulejos preoccupied him for over four hours, and it was within an hour of dawn when he stole back on tip-toe to his room in the guest-house.