“They needn't have told us that,” observed Tom, as he and the others were talking over their situation in low voices. “I don't believe any one could loosen these ropes.”

“They certainly are pretty tight,” agreed Mr. Damon. “I've been tugging and straining at mine for the last half hour, and all I've succeeded in doing is to make the cords cut into my flesh.”

“Better give it up,” advised Mr. Jenks.

“We'll just have to wait.”

“For what?” the scientist wanted to know.

“To see what they'll do with us. They can't keep us here forever. They'll have to let us go some time.” Following their capture, Folwell and Munson, the latter the stowaway of the airship, had been in earnest conversation regarding our friends, but what conclusion they had reached the adventurers could only guess.

“And we didn't have time to examine the diamond-making machinery close enough so that we could duplicate it if necessary,” complained Tom, a little later.

“No,” agreed Mr. Jenks. “There are certain things about it that are not clear to me. Well, I don't believe I'll have another chance to inspect it. They'll take good care of that, though they seem to be getting ready to make more diamonds.”

“Perhaps they're going to manufacture a big batch, and then leave this place,” suggested Mr. Damon. “They will probably go to some other secret cave, and leave us here.”

“I hope they untie us before they leave, and give us something to eat,” remarked the young inventor.