Patter, patter—smash!
"Great spark plugs!" cried Matt. "What was that? Something broke."
"The periscope ball!" gasped Speake. "They've put the periscope out of commission. Empty the tanks!" he yelled into the tank-room tube.
The periscope table reflected nothing of the treacherous channel along which the current and the propeller were carrying the Grampus at a terrific pace.
It was necessary to come to the surface as quickly as possible and use the conning-tower lunettes.
"Reverse your engine, Dick!" cried Matt to the motor room. "Full speed astern!"
The engine was instantly reversed, but not until the submarine had run into some obstruction, halting her with a jar that threw all her passengers off their feet.
For a moment the silence was broken only by the hum of the fiercely working cylinders, and the splash and bubble of the current as it met the obstruction of the huge steel shell.
"Cut out the turbines!" yelled Matt; "empty the tanks by compressed air. Full speed astern, Dick! Every ounce of power now!"
"What's happened, do you think, Matt?"