“You mean S. O. S.,” rejoined Jack. “C. Q. D. isn’t used as an urgent call any more. Too many would-be jokers used to send it out and cause endless confusion.” He threw the switch again into a sending position, and began to flash out another message. “o o o —— —— —— o o o” “S. O. S.” It was the most urgent call known to seamen. The despairing cry of the wrecked the lost. Again and again Jack volleyed it out, and the far-flung appeal went skyrocketing off on the electric waves, spreading like the ripples on a pond from the tightly stretched aerials. It was signed “The Chadwick Party.” Then the lad tried listening again. Suddenly a look of joy flashed over his face. “He’s getting an answer!” yelled Tom in huge excitement. Ned Banks, hardly less enthusiastic, capered about. Jack’s pencil traced the message from space on a pad of paper placed on an empty box before him. “What is it? What’s the matter?” Once more he began sending furiously. “We have been driven on a desert island off the Mexican coast.” “Where is it?” came the reply. “Give latitude and longitude.” Jack swiftly flashed back the required information. Then he asked a question. “Who is this?” “The _Sea King_,” was the astonishing reply. “We are coming to your aid. Have you got the gems?” “Yes. They are safe, and we are all well, but in need of help,” the lad sent back with a joyous heart. He listened for a reply, but none came. In fact, there was no need for more communication. The castaways knew what they wanted to know most of all, namely, that they would be taken off the island as soon as possible. In the meantime. Professor Chadwick ordered Jupe to prepare a royal spread in celebration of the event. “We look like a lot of pirates,” commented Jack, as, after a hearty meal, they lay stretched about the fire. “I suppose that, like most boys, you have a sort of admiration for those gentry?” inquired Captain Andrews. “Well, he’s stuffed his head with enough books about them,” chuckled Tom. “Guess that applies to you, too,” parried Jack, with a grin. “I don’t suppose, though, that either of you ever saw a real pirate,” commented the captain quietly. “I can tell you they are mighty different beings from the red-sashed, romantic sort of chaps you read about.” “Why, have you ever seen any?” asked Jack, sitting up eagerly. “Yes, and fought with ’em, too. Care to hear the yarn?” responded the seaman. The boys’ prompt affirmative removed all doubts on this score and Captain Andrews, without further preliminaries, struck into his tale.