The Celt had been in the pilot-house and chanced accidentally to press the motive valve. Instantly the Dolphin darted forward like an arrow.
Barney gripped the valve and tried to shut off the current and check the awful speed of the boat.
But he was unable to do this. For some reason or other the valve stuck and would not move.
No harm would have been done had the boat been a fathom higher in the water, as there was no obstacle which she could not easily have passed.
But a moment later there was a terrific rending shock. Every one was thrown from his feet.
The Dolphin came to a dead stop, and for an instant all was darkness.
CHAPTER IV.
THE SUNKEN WRECK—THE SHARK.
The crash had for an instant broken the current, but the light quickly flashed up again.
The electric engines were whirring like a top, and seemed likely to go to smash. But Frank Reade, Jr., was almost instantly upon his feet.
He rushed into the engine-room and checked them. The screw ceased its mad and useless revolutions.