tion of the passing vessel, then
the microphones would reveal the approach of the returning ship.

But, as Smith listened intently, the sound of the revolving propeller
blades gradually diminished and the commander and crew of the _Dewey_
knew only too well that either Jack had lost his life in the venture
or had been unnoticed as he floated in the sea.

"There don't appear to be anything doing up above," ventured Mike
Mowrey as he glided up alongside the two boys.

"Guess not," faltered Ted. "We seem to be right up against it."

All hope of rescue was abandoned. For nearly thirty-six hours now
the _Dewey_ had remained under water. Her crew of men, breathing over
and over again the same supply of air, were rapidly exhausting the
life-sustaining reserves of oxygen. Little by little the precious
stores had been liberated until now very little remained. Many of
the men were coughing asthmatically; several were languishing in a
dumb stupor from the fetid air.

Ted could not help turning his attention to the huge ventilator shaft
that fed fresh air into the _Dewey_ when she was cruising on the
surface. He remembered well that first undersea dive back home in
an American port when he and Jack had discussed the possibilities
of ever being lost on the bottom of the sea with the ship's air
supply cut off. Now he was face to face with that very situation.
The thought chilled his blood and he found it very hard to be brave
under the circumstances.

Jean Cartier, his face blanched and his hair ruffled, appeared in the
torpedo compartment, the picture of dismay.

"It ees ze veery hard thing to breathe back there," he gasped, pointing
over his shoulder toward the engine room aft.

Almost immediately the boys forward could hear Commander Mcclure
giving orders to open the reserve oxygen tanks. Under the emergency
measures adopted living conditions were for the time greatly relieved;
but every man aboard knew this relief was but temporary and realized
that in twenty-four hours more at the most the supply of oxygen
would be entirely exhausted.

The morning wore on to noon and mess was served to a crew of men who
cared little to eat. Grim disaster stared them in the face.

The meal over, Commander McClure called a council of his aides in the
control chamber. It lasted ten minutes, at the end of which time
"Little Mack" sent word to Chief Engineer Blaine to assemble all his
men with the remainder of the crew in the to