“Quick!” cried the professor.  “We must start the ship and get away!”

“I can’t close the door!” yelled Washington, who had been the last to enter.

“Never mind that!  Go up with it open!  Drag them along if they won’t let go!” answered Mr. Henderson, as he ran toward the engine room.

There was a sudden rush among the giants, and a sound as if something was being thrown over the top and ends of the ship.  Mark turned the gas machine on, while Jack worked the negative gravity apparatus.  They waited for the ship to rise.

“Why don’t we go up?” asked the professor.

“’Cause they’ve caught us!” called out Washington.

“Caught us?  How?”

“They’ve thrown ropes over the top and ends of the ship, and fastened them to their big houses!”

Running to a side window the professor saw that the Mermaid was fastened down by a score of cables, each one six inches thick.  They were held captives by the enemy.

CHAPTER XXVI

 A friend indeed

Though the giants, man for man, were no match for the travelers, collectively the horde proved too much.  They had swarmed about the ship, and, by passing the big cables over her, effectively held her down.

“Let me get out and I’ll cut ’em!” cried Andy.  “We must get away from these savages!”

“No, no, don’t go out!” exclaimed the professor.  “They would eventually kill you, though you might fight them off for a time.  We must wait and see what develops.  They can have no object in harming us, as we have not injured them.”

“I’d rather fight ’em,” insisted the old hunter.

But the professor had his way and Andy was forced to obey.  The giants had withdrawn their big feet from the side door and Washington had closed it.  But nothing else had been accomplished, and the ship could not rise.  The gas and negative gravity machines were stopped, as they were only under a useless strain.

Suddenly, the colored lights which had been growing dimmer and dimmer, with the approach of night, went out altogether.  Almost as suddenly, Mark, who was watching the giants from the conning tower, as they made fast the loose ends of the cables, saw them make a dash for the mound houses.

“They’re afraid of the dark!” he cried.  “Come on!  We can go out now and loosen the ropes!”

He hurried to tell the professor what he had noticed.

“Good!” exclaimed Mr. Henderson.  “Perhaps we can escape now!”

They waited a few minutes, listening to the sound of many big feet running away from the ship, and then, Bill cautiously opened the side door.  The others were behind him, waiting, with knives and hatchets in their hands, to rush out and cut the restraining cables.

“All ready!” called Bill.  “There doesn’t seem to be a one in sight!”

He stepped out but no sooner had he set foot on the ground than there came a thud, and Bill went down as if some one had knocked his feet from under him.