Hal," he called back over his shoulder. "And,
as soon as we get way, test all the electric connections, before we
attempt to do any diving. Be sure of everything old fellow."

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.

"Everything is all safe, Captain," nodded Mr. Farnum. "Run back and get
your naval party."

As they were to run, now, on the surface, Jack stepped out to stand
by the deck wheel Eph and Hal came out with him, David Pollard standing
further aft.

As the submarine rounded in under the gunboat's stern the voice of
Kimball called:

"As well done as ever, Mr. Benson! When shall we come on board?"

"As soon as we're moored, sir," Jack shouted

As the "Benson" ran to her moorings the youthful captain espied a shore
boat that bore, as sole passenger, one of the uniformed, colored bell
boys from the hotel.

When Eph made the mooring cable fast, this shore boat ranged alongside.

"Box for Captain Benson, sah," called the negro.

"Right here," acknowledged Jack, going over to the rail. The box
proved to be of pasteboard.

"Are you going to open it?" whispered Farnum.

"Why, yes, sir; of course," Jack answered.

"Better do it on deck, then," came the dry answer. "It might contain
something explosive, you know."

Though he laughed, young Benson carefully untied the string that held