As Jack clamped the receivers to his ears a hail of dots and dashes beat against his organs of hearing. Somebody was transmitting a message at a furious rate. Expert as the lad was, it was all he could do to make head or tail of it. His pencil fairly flew over the recording pad, and when he got through he had nothing for his pains but a sheet covered with figures, and again that annoyingly mysterious signature X. Y. Z. Tom had returned to the cabin while Jack’s pencil was scurrying across the paper. He leaned over, the other lad’s shoulder and watched intently. When Jack stopped and affixed the signature X. Y. Z., he looked up at his cousin wonderingly. “It’s X. Y. Z. again. He was sending like blue blazes, too. What do you make of it?” “Blessed if I know. Using his cipher again, too, isn’t he? Say, Jack! See here,—X. Y. Z.,—whoever he is,—is within our radius right now—at this instant. Call him, and see if you can find out who or what he is and where his station is. If the _Sea King_ is badly off he may be of great assistance to us.” Jack switched his current over for sending out a call. With a puzzled frown on his face he adopted Tom’s suggestion. “X-Y-Z! X-Y-Z! X-Y-Z!” he flashed out, and then added the signature “L-I.” “Now to see if we get any result,” he said, adjusting the receivers to his ears and throwing the switch for the detection of a reply. He had not long to wait. “L-I! L-I! L-I!—X-Y-Z!” came billowing through the ether, “what do you want?” “We are proceeding to rescue of disabled yacht _Sea King_,” flashed back Jack. “Where are you? Can we rely on you for help?” A long silence followed. Then the Continental code began to throb and beat in the receivers, once more. But it was another question that came. “Where is yacht _Sea King_?” Jack flashed the bearings as he had received them earlier in the day, and then repeated his former question. But no reply came. For an instant the lad thought he had got out of tune with the wireless mystery, but although he ran the gamut of the tuning coil, nothing more came. For all that was further heard of him, X. Y. Z. might have been as intangible as the atmosphere out of which he had projected his questions. For half an hour or more Jack persisted in his endeavors to reach X. Y. Z. again, but finally gave it up as a bad job. Grounding his current, he laid down his head band and swung in his chair. “Lost him?” inquired Tom. “I’d rather say that he lost us,” responded Jack, “it must have been a deliberate cut-out. One second he was coming strong and then—silence. How do you figure it, Tom?” “I don’t attempt to. I give it up, unless X. Y. Z. is some sort of a wireless lunatic.” Jack gave a rather mirthless laugh. “Hardly. Or, if so, I begin to fear there is some method in his madness. You notice that he only seemed to want to find out the exact position of the _Sea King_?”