floor; the bad air rises,
being lighter with carbonic acid. Lie down!"

All obeyed, Tom following the advice he himself gave. It was a little
easier to breathe, lying on the tilted cabin floor, but how long could
this be kept up? That was a question each one asked himself.

"Is every bit of our reserve air used?" asked Tom, speaking to Earle.

"As far as I can learn, yes, sir. If I had known that the auxiliary
tank was empty I wouldn't have ordered the compressed air motor used.
But I didn't know."

"No one is to blame," said Tom in a low voice. "It is one of the
accidents that could not be foreseen. If there is any blame it attaches
to me for not installing the gyroscope rudder. If we had had that when
we were caught in the cross current, or the whirlpool swirl, our
equilibrium would have been automatically maintained. As it is--"

He did not finish, but they all knew what he meant.

"Bless my soda fountain, Tom!" murmured Mr. Damon, "but isn't there any
way of getting fresh air?"

"None without rising to the top," Tom answered. "We'll have to try
that. Come with me to the engine room, Mr. Earle. It may be possible we
can pull her loose."

They started to crawl on their hands and knees, to take advantage of
the purer air at the floor level. The situation of the M. N. 1 was
exactly the same as it had been when she ran into the mud bank in the
river, with the exception that now she was in graver danger, for the
supply of air for breathing was almost exhausted.

Reaching the engine room, where he found the crew lying down to take
advantage of the better air near the floor, Tom made a hasty
examination of the apparatus. There was still plenty of power left in
the storage batteries, but, so far, the motors they operated had not
been able to pull the craft loose from where her nose was stuck fast.

"Are the tanks completely emptied?" asked Tom.

"As nearly so as we could manage with the pumps not acting to their
full capacity," answered Earle. "If we could turn the craft on a more
level keel we might empty them further, and then her natural buoyancy
would send her up."

"Then that's the thing to try to do!" exclaimed Tom, his head beginning
to feel the heaviness due to the impure air. "We'll move every
stationary object over to the port side, and we'll all stand there, or
lie there, ourselves. That may heel her over, and help loosen the grip
of the sand."

"It's worth trying," said Earle. "Get ready, men!" h