He moved across the narrow triangular room to its apex, where a great disc of magnifying glass, like a porthole, came in direct contact with the water outside. He stood for a moment peering out through it. The water beyond was lit with a ruddy glow that left it extraordinarily translucent. It was powerful, and seemingly the power of the rays extended a considerable distance. But though the water was thus lit it was not rendered transparent. For some silent moments he gazed out, then a shadow moved across the field of light--and he understood. He turned to the silent inventor. "That was a fish which crossed our bows," he said, in suppressed tones which indicated something of his feelings. "I think--yes, I understand. This light will reveal any solid body ahead, any obstruction--mines, rocks, any danger to progress." The Prince beamed his satisfaction. "The submersible need no longer be a blind lumbering monster," he said. "The mine-field we are shortly going to pass through is not the danger you may have anticipated. The moment we have passed the patrol boat we shall rise till our periscope is above water. Then we shall move slowly. The helmsman will remain in the conning-tower, but he will be controlled from here by---- Ah, here is Captain Ludovic." The steel door was thrust open and the chief officer entered the room. "The mines begin about sixty fathoms on, Excellency," he said, with a brevity and utter lack of anything approaching the servility one might have anticipated in his relation to so powerful a master as the Prince. But Ruxton understood. The Prince's simple nature demanded nothing of that from those intimately associated with him. Hence, perhaps, the devotion of those who served him. "If you will forgive, Excellency, I will take _sole_ charge here." The Prince turned to his guest with a laugh of genial humor. "Come, my friend, we will leave the excellent Ludovic to his work. We are dismissed." Then he turned to the captain, who had taken his place at the forward porthole, and had adjusted the telephone receivers over his ears. He raised his voice so that the man could hear. "Once clear of the last batteries, Ludovic, we travel on the surface," he said. "Yes, Excellency." The man made no attempt to turn from his watch upon the ruddy field ahead. CHAPTER X THE FUTURE On the way back to the saloon a further truth began to dawn upon Ruxton. Nor did he lose a moment in challenging his host when they reached the luxurious apartment. "You have brought those cylinders away. May I ask why?" he enquired. The Prince had seated himself, and was in the act of lighting a cigar. He desisted, and held his case out towards his guest. Ruxton helped himself and waited.