send me up first if it becomes necessary to use the tube."

Tom did not answer. But as he looked out of the observation windows to
see if possible the conformation of the mud bank, the young inventor
whispered to Ned one word. And that word was:

"Yellow!"

"You said it!" was Ned's whispered rejoinder.

Tom Swift arrived at a sudden determination. Once again the motors were
stopped, and the boat gradually assumed an even keel.

"What are you going to try, Tom?" asked Ned.

"I'm going to shove her farther into the mud bank," announced the young
inventor. "I think that's the only way to get her loose."

"Bless my apple pie, Tom!" cried Mr. Damon, "doesn't that seem a
foolish thing to do?"

"It's the only thing to do, I believe," was the answer. "This mud is of
a peculiar sticky and holding kind. The sub's nose is in it like a peg
in a hole. What I propose to do now is to enlarge the hole, and then
our nose will come loose--I hope."

"But you haven't any right to shove our nose further in!" cried Mr.
Hardley. "I won't allow it! I demand to be put on the surface! I won't
be drowned down here before I get the gold that's coming to me--the
gold and--"

"Now look here!" suddenly cried Tom. "I'm in command of this boat, and
you'll do as I say. I'll gladly set you on the surface if I can, and
this is the only way it can be brought about--it's the only way to save
all of us. I'm going to enlarge the mud hole so we can pull out. Please
keep still!"

Mr. Hardley stared at the young inventor a moment, seemed about to say
something, and then changed his mind.

"Hold fast, everybody!" suddenly called Tom. The next moment the M. N.
1 began behaving in a most peculiar manner.

She appeared to be acting like a corkscrew. While her bow was
comparatively steady, her stern described a circle in the water which
was churned to mud by the two propellers, each being revolved in a
different direction.

"I'm trying to make the hole bigger just as an amateur carpenter makes
a nail hole bigger, so he can pull out the nail, by twisting it
around," explained Tom. "The motion may be a bit unpleasant, but it is
needful."

And indeed the motion was unpleasant. Tom, veteran airman and sailor
that he was, began to feel a trifle seasick, and Mr. Hardley was in
very evident distress.

Suddenly, however, something happened. The M. N. 1 gave a lurch to one
side and then shot upward so quickly that Ned and Mr. Damon lost their
balance an