“That’s so.  Well, we have the diamonds, anyway,” spoke Mark.  “They ought to make us rich.”

And the jewels did, for the stones proved to be of great value, even though the adventurers had saved only a few of the many they found in the ruined temple.

But there was money enough so that they all could live in comfort; the rest of their lives.  As the professor was getting quite old, and incapable of making any more wonderful inventions, he closed up his workshop and settled down to a quiet life.  As for Washington, Andy, and Bill and Tom, they invested their money received from the sale of the diamonds in different business ventures, and each one did well.

“I am going in for a good education,” said Jack to Mark.

“Just what I am going to do,” answered his chum.  “And after we’ve got that——­” He paused suggestively.

“We’ll go in for inventing airships, or something like that, eh?”

“Yes.  We’ve learned a great deal from Mr. Henderson, and in the course of time we ought to be able to turn out something even more wonderful than the Electric Monarch, the Porpoise, or the Flying Mermaid.”

“Yes, and when we’ve invented something better——­”

“We’ll take another trip.”

“Right you are!”

And then the two chums shook hands warmly; and here we will say good-bye.

 The end.

*** End of the project gutenberg EBOOK, five thousand miles underground ***

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