boat's emerging performance.

Now, other sections of cadets were transferred from the gunboat to
the two submarines, and the trips below surface proceeded.

The last section of all to go aboard the "Farnum" had just finished
their first experience under water, when the gunboat signaled:

"'Farnum,' take a half-hour's run below the surface, then come back
above surface."

"That will be a longer experience than I have yet had for one time,"
remarked Mr. Trahern, with a smile, as he interpreted the signal to
Captain Jack.

"We have run for hours below, with safety, sir," Benson answered.

Two minutes later the section of middies that had just come up from a
brief trip under water were below again.

"I think you'll find, gentlemen, that it will seem like the longest half
hour you can remember," announced young Captain Benson. "My friends
and I have spent many long hours under the surface, though we have
never yet gotten over the terrible monotony of such a trip.
Twenty-four hours under, I think, would make a lunatic of the bravest
or the most stolid man."

As they ran along, in the silence and the darkness, the young midshipmen
began to look curiously at one another.

"Did you misunderstand the time, Mr. Benson?" asked one of the
midshipmen, at last. "It's surely more than a half hour since we made
the last dive."

"Almost twelve minutes," Jack corrected, quietly.

"Whew-ew-ew!" whistled several of the naval cadets. Not one of them
was a coward, yet, in their experience, the thought that they had put
in barely more than a third of the ordered time under water made some
of them fidget.

"Say, this gives us some idea how long a whole hour would be," remarked
one of the midshipmen.

"Stop that man from talking," jibed another severely.

Jack had most of the time clear for instruction, after that, as few of
the young men cared to talk. But at last another ventured to inquire:

"How much of the time is gone?"

"Nineteen minutes," Benson answered, after a look at his watch.

"O-o-o-oh!" The response came in a chorus that sounded like a protest.

Then passed what seemed like an eternity of seconds. All the time the
electric motors ran, almost noiselessly. The slight tremor imparted
to the craft by the propeller shafts seemed like an ominous rumbling.
Jack's voice had ceased. No one felt like talking. From time to time
Skipper Jack glanced at his watch; his face, expressionless, gave no
clue to the ea