The _Winged Arrow_ swerved unexpectedly to one side, and her right wing scraped along the ice cliff. The plane was jarred from stem to stern and several cables snapped. The collision dislodged a huge mass of the ice that came tumbling down, barely missing the tail of the boat and falling with a thunderous crash into the bottom of the gorge. “You’d better get out of this, Tom!” yelled Ned. “Shoot her up!” The passage between the ice cliffs was too narrow and crooked, however, for Tom to risk any abrupt ascent. Still rocking from the force of that slam against the ice, the seaplane staggered on, but at reduced speed. The valley was several miles long. Again and yet again the end of one wing or the other touched the ice. These slight collisions did no particular harm, but they emphasized the fact that Tom could not govern the mechanism as perfectly as he had before. The balance of the plane was overset. She was likewise sinking. When Tom signaled for a “lift,” Brannigan could not work his levers properly. Like a huge wounded air fowl, the _Winged Arrow_ fluttered lower and lower. “My goodness, Tom! are we done for?” gasped his chum. Tom’s face was pale, but he did not lose his self-control. He dared not raise the nose of the flying boat sharply, for if he did and she then took a tail spin she would land upon her propeller and put that out of commission. The craft continued to descend. Tom waved a disengaged hand toward the right hand window. Ned and the others saw what he wished to call their attention to. The airtight pontoon at that end of the great wing had been smashed in the collision with the wall of ice and now hung partly disengaged from its proper fastenings. This had so disarranged the balance of the boat that her management was most difficult, especially in this narrow chasm. Another sharp turn in the valley of ice loomed before them. Below, Tom saw that the bottom of the gorge was comparatively smooth for some distance. If they could make a fair landing, they might be able to repair the pontoon and then rise on even keel again. He quickly signaled Brannigan, who shut down the motors. The roar of them ceased almost at once. The great flying boat sank to rest in the heart of the giant iceberg. CHAPTER XX IMPRISONED IN THE ICE When the throbbing of the motors ceased and the flying boat had stopped rebounding on its wheels and tail, the party in the pilot room stared at each other in a silence that was pregnant with anxiety. Even Koku, who stood on guard, felt that the situation of the _Winged Arrow_ was serious; yet Koku believed that the “magic” of his Master Tom was equal to almost any emergency. Tom as a usual thing had plenty of confidence in himself, and especially in his ability to get out of scrapes. But this was one event over which he seemed to have little control. “What shall we do?” asked Ned.