Late in the afternoon he caught a fairly large fish. After pressing water from its meat, he drank a little. “Not impossible,” was his verdict. He ate some of the meat, then offered a bite to his gony, who, to his surprise, swallowed it. “You must be a young fellow,” he said. “Friendly and green, like myself.” He laughed, and felt better. Just as the sun was sinking in the west he saw a dark smudge that soon obscured the sun. “A ship!” He became greatly excited. Another smudge, and yet another. “The task force!” he exclaimed, standing up and nearly overturning his raft. “If only it would come this way!” CHAPTER XV THE SECRET BOOK On the island of mysteries Jack watched with increasing astonishment as the jet plane soared away. It climbed up until it looked to be the size of a star, let out a scream, then faded with the speed of sound into the blue sky. “Some plane!” he exclaimed, straining his eyes for one last glimpse of it. A plane like that could change the whole science of aviation. Yes, it’s a military secret, but whose secret? That’s the question. He was about to begin his homeward journey when a book, lying on the rocks, caught his attention. _Murder at Midnight_, he read on the cover. “So that’s what they read!” Picking up the book, he flipped it open, then a whistle escaped his lips. Two thirds of the pages of the original book had been replaced by pages on which clippings had been pasted. “A scrapbook! How strange!” He stood staring at it. A moment later he nearly dropped it in his excitement. “It’s all about that mysterious plane! What a find!” he whispered. Sitting down upon a flat rock, he began to read. There were articles in English, French, German, and Italian. Many he could not read at all, but the articles in English were more than enough to satisfy his curiosity. Much that he read about equalizers, reflecting blades, direpeller blades, slip streams, and burbles he understood only in part. At last he came to an article which gave him the desired information. This article read in part: “Rocket propulsion, of course, is not a new thing; the basic idea is centuries old. As applied to aerial warfare it was employed on a crude basis even in World War I. The Italians made public an experimental flight of a propellerless jet-type plane several years ago. Long before that, automobiles were driven by rocket engines, and special rockets for making meteorological soundings in the substratosphere were in use.... “Nevertheless, the Anglo-American jet-propelled airplane represents the broadest application of the principle yet achieved.