“Going she is!” came from Ned.
There was a hissing as the automatic pumps began compressing the lifting-gas, and a few seconds later Jerry yanked on the lever that would tilt the big rudder to such a position that the ship would dive downward. At the same time the propellers, which had been revolving slowly, to keep the Comet from drifting, were whirled with great rapidity as more power was turned into the motor. While navigating as a dirigible balloon the propellers were not needed to keep the ship afloat, but once the lifting-gas was not used they were vitally necessary, for only by keeping in motion can a “heavier than air” machine be prevented from falling.
Bob, who was looking through the glass floor in the main cabin, tracing the course of the object that had so excited the boys, suddenly looked up at Jerry.
“Something’s wrong!” cried the fat lad, and by his tones it could easily be told that he referred to the motorship, and not to the object below him in the water.
“I should say there was!” gasped Jerry, for the Comet had plunged downward with such abruptness that the boys were fairly dizzy.
“What’s the matter?” yelled Ned, making his way from the motor room by fairly pulling himself along. He had to do this as the ship was tilted at such a sharp angle. “What happened?” Ned went on.
“It’s that deflecting rudder again!” answered Jerry. “I thought we had it adjusted too fine. Now it’s jammed again.”
“Shut off the motors! Stop the propellers!” cried Bob.
“I’m doing it as fast as I can!” returned tall Jerry. He had reached over and snapped off a switch that controlled the electric current which fired the gasoline motor.