my," suggested Washington, rolling his eyes until
only the whites were visible.

"I presume you mean that a giant squid or cuttle fish has attacked us,"
spoke the professor.

"Yas, sir," replied Washington.

"That's nonsense," went on the inventor. "However, we must make an
investigation."

"How are you going to do it?" asked Mark. "You can't see the end of the
tube from inside the ship, and, even if we went to the surface it would
still be under water."

"We are going to look at it while here, under the ocean," said the
inventor.

"Well, maybe you're a good swimmer," put in Jack, "but I don't believe
you can stay under, in this depth of water, long enough to see what the
trouble is."

"I think I can," answered Mr. Henderson.

"How?"

"I'll show you. Washington, bring out the diving suits."

The colored man, his eyes growing bigger every minute, went to a locker
and brought out what seemed quite a complicated bit of apparatus.

"With the aid of these," said the professor, "I will be able to go out,
walk along the ocean bed, and investigate the mystery. Do you boys want
to come along?"

"Is it safe?" asked Mark, who was inclined to be cautious.

"As safe as any part of this under-sea voyage," replied the professor.
"These diving suits are something I have not told you about," he went
on. "They are my own invention. Besides the regular rubber suits there
is an interlining of steel,--something like the ancient suits of chain
mail--to withstand the great pressure of water. Then, instead of being
dependent on a supply of air, pumped into the helmet from an apparatus
in a boat on the surface, each person carries his own air supply with
him."

"How is that?" asked Jack, and Mark also asked the question.

"Simply by attaching a little tank of the compressed gas to the shoulder
piece of the suit," said the inventor. "There is enough air in the tank
to last for nearly a day. It is admitted to the helmet as needed by
means of automatic valves. In other respects the diving suit is the same
as the ordinary kind, except that there is a small searchlight, fed by a
storage battery, on top of the helmet."

In spite of their fears at venturing out under the great ocean, the two
boys were anxious to try the suits. So, after some hesitation, they
donned them.

"Here, take these with you," said the professor, before their helmets
were screwed on. He held out what looked like long sticks.

"What are they?" asked Jack