And then, ere any of his friends could reach him (for the professor had gone back to the cabin), the boy, fighting for his sight--indeed, for his very life--by some unfortunate movement depressed the planes. Like an arrow from the bow the _Snowbird_ shot downward into the yawning crevasse which split the glacier from wall to wall. With a yell of terror Mark Sampson sprang forward to the operator's bench. But he was too late--if he could have done any good at all. The _Snowbird_ swung to one side. Her right forward plane crashed against the wall of ice, shattering some of the hard crystal. But on the rebound the fluttering flying machine sank lower. Jack tried to make her rise. She refused to obey the lever. And then, with a suddenness that made them all catch their breath, the _Snowbird_ plunged down into the ice-gulf and ended her dive with a terrific crash on a narrow shelf at least two hundred feet below the surface of the glacier. CHAPTER XVI PROFESSOR HENDERSON REVEALS THE TRUTH The force with which the flying machine had plunged into the chasm in the ice was sufficient to smash her keel-fin to bits. There was other damage done, too--how great this damage was the boys and the professor could not immediately discover. They were all alive--that was one thing to be thankful for. And Washington White's Shanghai, aroused from sleep by the disturbance, began to crow vociferously. The _Snowbird_ was wedged into a very small space upon the ledge of ice. At first view it was quite certain that she could not be launched again from this position by any ordinary means. And the steering gear was practically a wreck, so that she positively must be repaired before attempting another flight. Jack's wounds were dressed by Andy first of all. Mark and the professor made some attempt to look over the wreckage. The disaster was so great that Mark gave up hope. "We're done for now!" he cried. "The poor _Snowbird_ is a wreck. And how are we ever going to get out of this hole?" "Hush, my boy!" admonished the professor. "Don't lose your grip. This is truly a serious predicament; but we have been in tight places before." "Nothing worse than this," grumbled Mark. "Nor half so bad. How are we going to get out of this chasm? Why, just as Washington says, we've been swallowed up like a duck gobbling a June bug." "This is certainly a bad situation," Phineas Roebach remarked. "But, as the professor says, it isn't the worst that might happen." "What worse could happen?" demanded Mark. "Hold on! Don't you step too near the edge of this shelf," warned the oil man. "If you step off and fall clear to the bottom of this crevasse you'll probably find _that_ a good deal worse than our present position. B-r-r! Isn't it cold?"