"Sleep!" ejaculated Jack. "I couldn't sleep now." "No, I suppose you couldn't," replied the lieutenant thoughtfully. He was silent for some moments. "I'll tell you what I'll do," he said finally, "we have come to the surface again I'll ask Captain Von Cromp to allow you to go upon the bridge, if you wish. He realizes your feelings as well as I do, in spite of his apparent gruffness. The cool air will do you good." "If you will be so kind, I am sure we shall appreciate it," said Frank. The lieutenant left the cabin. Frank, espying something at one end of the room, walked over to investigate. He came back to Jack, holding something gingerly in his hand. "By Jove!" he exclaimed. "What is it?" asked Jack. Frank held the object up before his friend's eyes. "Look at it!" he exclaimed. "Do you know what it is?" Jack took a long look and then stepped suddenly back, exclaiming: "Put it down, quick! Do you want to blow us all up?" "What do you suppose it's doing here?" asked Frank, still holding the object out at arm's length. "How should I know? But I suppose all submarines carry them. I have heard that many have been planted by submarines." For the object that Frank held in his hand was a small melinite floating mine! "I suppose this would blow any ship to kingdom come, wouldn't it?" asked the lad. "I should say it would; so you had better put it down unless you want to send us all there." Frank leaned close to his chum, and whispered rapidly: "See if you can't find a gun around before the lieutenant comes back. Quick! A revolver, rifle, or anything!" "What for?" demanded Jack, in surprise. "Never mind what, for. Look quick, while I hide this thing under my coat." Without knowing what Frank had on his mind, Jack did as requested. After rummaging through the lieutenant's desk, he at last straightened up with a heavy revolver in his hand. "Will this do?" he asked. "All right," replied Frank, "but a rifle would be safer." "Safer? What do you mean?" "Sh-h-h," whispered Frank. Footsteps were heard on the outside. Jack hastily shoved the revolver into his pocket. Frank by this time had concealed his explosive under his coat. It bulged out a bit, but the lad folded his arms in front of him, and the bulge was not noticeable. Lieutenant Stein entered the room. "It's all right," he said. "Captain Von Cromp has given his consent. If you wish, I will conduct you up." "Thanks," said Jack, and the two lads followed the officer. Captain Von Cromp was on the bridge when the two boys emerged from below, and he walked over to them. "I regret," he said, "that you should have had to witness what you have; but it is the fortune of war, you know." "I have heard that before," said Frank dryly. "Tell me, would you have blamed us had we put up a more stubborn fight below a while ago?"' "No," was the reply. "I could blame you for nothing you did to an enemy in time of war and especially under such a stress of excitement."