Then he broke off, horrified, as he saw another figure follow the professor from the cabin. "Joan!" he gasped. "Present!" she replied. "But, my daughter!" the professor's voice broke in. "My dear child!" A sob shook him. "Why, why, this is--" "Please don't let's talk about it!" she begged, giving his arm a little pat. "I'm here and it can't be helped now. I was only afraid you'd find me before it was too late and take me back." Then, edging over to Jim and slipping her arm in his, she murmured: "Oh, my dear! Don't you see I couldn't stay behind? I had to be with you at the end, Jimmy, if--" "It won't be!" he cried, pressing her cold hand. "It can't be!" Then he turned to give his attention to her father, who had already mounted to the cockpit and was working absorbedly over his mechanism in the pale light of the coming day. Any moment, Jim knew, those flaming termites might discover them, and come swooping down. With keen eyes he scanned the horizon. No sign of them yet. "How are you up there?" he called. "About ready," was the reply. "But I shall want more light than this for my mirrors." Tensely, counting the seconds, they waited for the sunrise.... * * * * * And now, as they waited, suddenly a sinister tinge of orange suffused the rosy hues of the east. "The Fire Ants!" cried Joan, shrinking. "They've seen us! They're coming!" It was true, Jim saw with a heavy heart. Turning to Professor Wentworth, he gasped out: "Quick! We've got to do something! You've no idea how fast they move!" "Very well." The professor's voice was strangely calm. "You may start your motor. I shall do what I can. Though if we only had the sun--" Jim leaped for the cabin. A touch of the starter and the powerful engine came in. Braking his wheels hard, to hold the plane on the ground, he advanced the throttle as much as he dared, and sent a high-tension current surging through the wires the professor had connected with his tube above. Soon came that high, whining hum they had heard in the laboratory--a thousand times magnified now--and the nib of the big tube glowed a livid, eery green in the lemon dawn. "Joan!" called her father sharply. "Get in the cabin with Jim!" She did so, her eyes still fixed in horrified fascination on the eastern horizon; and in that tense instant, she saw two things. First, a great orange arc of fiery termites, bearing down on them; and second, another arc, far greater--the vast saffron rim of the rising sun. Those two things Joan saw--and so did Jim--as their eardrums almost burst with the stupendous vibration that came from the gun in the cockpit. Then they saw a third, something that left them mute with awe. As Professor Wentworth swung his cannon ray upon that advancing horde, it melted, vanished, leaving only the clear yellow of the morning sunlight before their bewildered eyes. * * * * *