He was trembling with the fever of the intense inventor.

Out in the little harbor the "Pollard" lay on the bottom. In the cabin,
besides the three submarine boys, were only Jacob Farnum and David
Pollard.

The eyes of all five were fixed on a small but ingenious bit of mechanism
that had been carefully adjusted near the rear port of the boat's
torpedo tube. This was the automatic device, first planned by Jack
Benson, with the aid of his mates, and carried forward to working order
by Mr. Pollard. By the aid of this automatic mechanism it was believed
that the last man aboard a torpedo boat could let himself into the tube,
relying upon the automatic device first to close the rear port, then
opening the forward port and at the same time letting just the right
amount of compressed air into the tube. By this means the last man
aboard a submarine below the surface could provide for his own escape,
without the aid of a comrade.

Eph Somers had been chosen to make the effort. He now stood, in his
bathing suit, awaiting the word.

"Go ahead, Eph," ordered Mr. Farnum. "Be very careful to set the device
just right. Not one of us is going to touch it."

Eph carefully set the time hand on the dial, next crawled into the
torpedo tube, the rear port of which stood open. Sixty seconds later
the automatic device closed the rear port with a sharp click.

David Pollard counted up to fifteen.