his hands Jack carried a small wooden box. Hal and Eph looked
delightfully mysterious.

"Time to look at something?" repeated the inventor, with a laugh. "I
seem to have plenty of time for almost anything these days."

There being none of the office employees about at the moment, Benson led
the way to one of the desks, opened the box and took out a
complicated-looking little model.

"You know, Mr. Pollard," murmured Jack, while the other two boys drew
close, "although we have hit upon the way for some of a submarine's crew
to escape when the boat is at the bottom, or in deep water, it always
needs at least one of the crew to remain behind to close the rear port
of the torpedo tube and to operate the compressed air a little. So,
valuable though our trick may be, it really means that, in case of
serious accident, one member of the crew would have to remain behind in
order to help the next to last to get away. So, in case of accident,
there would always be one member of the crew who would have to be left
behind to die. That's the thing we fellows have been working on, and
here's the result. At least, it's the best we can do with it."

"What's the idea?" inquired the inventor, examining the small model
curiously.

"Why," laughed Jack Benson, good-humoredly, "it's an automatic device,
set to a time principle, for closing the after port of the torpedo tube
and letting off some compressed air. By means of this automatic device
the last fellow could let himself out safely. That's the theory, you
see; but we're new inventors, and so there's some flaw in the device.