"By bringing my knowledge of Morse into play. I think that when the flag is run up slowly it means a dash and a quick run is a dot. Let's try it anyway." Luckily the spot where the two boys were was grown with high, coarse grass, and the sand dunes rose high in places, affording protection for them. As the flag rose and fell they spelled out a word according to the Morse code. "That's 'Ready'," proclaimed Rob exultingly; "we have hit on their code, all right." "They're still at it," exclaimed Merritt, as the flag continued its eccentric rises and falls; "what's next, I wonder?" Dash--dash--dash--dash, spelled out the flag. "That means 'to'," declared Rob. "Yes, and there comes 'night'," exclaimed Merritt a moment later. "And now they've stopped. Let's see what message we've caught." "Short and sweet," laughed Rob. "I guess we came in at the tail end of their confab. All we've got is 'Ready to-night'." "Well, isn't that something?" demanded Merritt. "At all events it's a complete sentence and tells us that somebody will be ready for something to-night." "Right you are, and that 'somebody' is to be Barton, I'll bet a doughnut." "But ready for what?" "That remains to be seen. I've always thought Barton would bear watching. I'm certain of it now, and if the submarine isn't mixed up in this tangle somewhere, call me a Chinaman." "Are you going to tell the ensign about this?" "Not till we have something more tangible to go upon. After all, we have proved nothing, but to-night we'll keep a close watch on Barton and in that way find out if our suspicions are correct or not." And so it was arranged. The boys hunted a bit more, but somehow the strange signals and the peculiar behavior of Barton had got on their minds, and they gave up their sport earlier than they had expected and trudged back to camp to complete their arrangements for the night's work. CHAPTER XVI. SCOUTING FOR UNCLE SAM. "Rob! Rob! Rob!" Merritt nudged his dozing companion as they lay near to the submarine shed, where they had taken up their position earlier in the night. Immediately after supper the lads had, apparently, slipped off to their tents; but as soon as they were sure that they were free from observation they had, in pursuance of their plans, taken up a position close to the sheltering place of the _Peacemaker_. Rob had dozed off shortly before midnight, and the words at the beginning of this chapter formed Merritt's notification to him that it was time to bestir himself. The boy, aroused at once from his nap, sat up at his comrade's summons. "What is it?" he asked in a whisper. "Look! Look yonder! Don't you see Barton sneaking toward the shed?" There was no moon, but in the starlight Rob, thus admonished, could distinctly discern a shadowy figure gliding across the sand dunes to the submarine shed. "It _is_ Barton, sure enough!" he exclaimed in a low, tense voice. "I guess we were right, Merritt, when we read that 'Ready to-night' message."