He rushed up to shake hands with the travelers when they came out of the ship, though to greet him it was only possible for the adventurers to grasp one of his immense fingers.

As soon as the greetings were over Hankos began to speak rapidly to the professor, at the same time going through many strange motions.

“It is as I feared!” suddenly exclaimed the scientist.

“What is the matter?” asked Mark.

“The worst has happened!” went on Mr. Henderson.  “The great hole by which we came into this place has been closed by an earthquake shock!”

“The hole closed?” repeated Jack.

“An earthquake shock!” murmured Mark.

“Then how are we going to get back to earth?” asked old Andy.

A terrible fear entered the hearts of the travelers.  The closing of the opening by which they had come to the strange world meant, in all probability that they would have to spend the rest of their lives in this underground place.

“What good did it do us to get all those diamonds and that gold?” asked Mark in a sorrowful tone.

Hankos began to speak again, using his gestures which were almost as eloquent as words.  The professor watched and listened intently.  Then there seemed to come a more hopeful look to his face.  He nodded vigorously as Hankos went on with what seemed to be an explanation.

“It’s worth trying, at all events!” the scientist exclaimed.  “It is our only hope!”

“What is?” asked Jack.

“Friends,” began the professor in solemn tones.  “I must admit our plight is desperate.  At the same time there is a bare chance of our getting back to our own earth.  As you remember, Hankos went from this place to the upper regions through the upward spouting column of water.”

“If we had our submarine we might also,” interrupted Jack.  “But the Mermaid isn’t built to sail in that fashion.”

“Nor would the Porpoise have served us in this emergency,” said the professor.  “It would prove too heavy.  But, nevertheless, I think I have a plan.  Now, Mark, you are about to learn the secret of the storeroom.  The real one, not the hiding of Hankos in there, which you imagined to be the cause of my desire to keep something hidden.  When we planned a trip to this underground world I had a dim idea that we might meet with trouble.  So I planned and made a cylinder lifeboat.”

“A cylinder lifeboat?” repeated Mark.

“Yes,” replied Mr. Henderson.  “I have it in the storeroom.  I did not want any of you to see it for fear you would have faint hearts.  I thought there might be no necessity of using it.  But, since there is, we must do our best.  I will admit it may be a fearful ordeal, but we will have to risk something in order to escape.

“I have in the storeroom a large cylinder, capable of holding us all.  It will also contain food and drink for a month, but we will all have to go, packed almost like sardines in a box.  My plan is to take the Mermaid to the place where the column of water shoots up.  There we will get into the cylinder, close it, and trust ourselves to the terrible force that may bring us back to the upper world.  What do you say?  Shall we attempt it?”