After dinner the doctor was busy, but Frank went out alone into the soft moonlight to enjoy the cool evening breeze. He soon made the acquaintance of the ordnance sergeant, and together they climbed the solid stone stairs in one of the bastions up to the upper casemates. "Why, this is like fairy-land, if there is such a place!" Frank exclaimed. "Just see the moonshine through the long rows of brick arches! What a tre_men_dous big place! And the water looks like silver outside, and in the enclosure everything is dark green." "This is only one section of the fort that you see," the sergeant said, smiling at Frank's enthusiasm. "There are six sections just like this. To-morrow I will take you up on the parapets. You can almost see Cuba from there, but not quite." "And to think that three thousand people once lived on this little island!" Frank exclaimed. "They must have been packed pretty thickly in these casemates." For days Frank spent all his spare time in wandering about the great fort, sometimes alone, and sometimes with the doctor or sergeant. There were so many queer things to see! And everything was so solid and warlike! And every evening while the moon lasted he climbed to the upper casemates to enjoy the silvery water and the cool breeze. But after a while the moon disappeared and the nights became dark. Then he moved about with caution, for the bushes in the enclosure tripped him, and the vastness and silence of the great place awed him. Late one evening, after he had said good-night to the ordnance sergeant and was thinking of going to bed, the notion occurred to him: "How terrible it must have been to be shut up for months in one of those lower casemates, with only a big columbiad and a pile of shells for company! It makes a fellow shiver just to think of it!" "Pshaw!" he exclaimed, a moment later. "I don't like this being scared at a shadow. I'm going over to some of those cells this minute, just to punish myself. I know every inch of the way now, and can easily find them in the dark."