Forward in the engine room the gas motors were soon moving merrily. By the time that Eph had cast loose from moorings Jack signaled for slow speed ahead, and the grim-looking little Benson moved on out of the harbor.
Once out of the harbor Captain Jack rang, successively, for two higher speeds. The "Benson" answered both like a charm.
"The gasoline part of the craft is working all right," declared the youthful skipper to Eph, who had come up into the tower.
Fifteen minutes later Hal shouted up:
"All electric connections appear safe, Captain. And all the air compressors are working."
"Are you ready to shut off the gasoline motors?"
"Yes, sir."
"Go ahead, then, and we'll take a dive." Down they shot below the surface, the boat going on a diving keel. Then, for some minutes, Captain Jack ran his submarine pride along at a depth of fifty feet below surface.
"Might as well rise, Captain," called up Mr. Farnum, coming from his stateroom.
So Eph, at the young commander's orders, stood by to let the compressed air gradually into the water tanks. As gracefully as ever the "Benson" rose to the surface. Gasoline power was turned on again.