“Do you care to state where these diamonds came from?” asked Mr. Roberts, looking critically at Tom.

“I had rather not,” answered the lad.  “It is enough for me to know that they are diamonds.  How much is your charge?”

“Nothing,” was the unexpected answer.  “We are very glad to have had the opportunity of seeing such stones.  Is there any chance of getting any more?”

“Perhaps,” answered Tom, as he accepted the gems which the expert held out to him.

“Then might we speak for a supply?” went on Mr. Roberts, eagerly.  “We will pay you the full market price.”

“What is the value of these stones?” asked Tom.

Mr. Roberts looked at his gem expert.

“It is difficult to say,” was the answer of the man who had handed Tom the gems.  “They are so far superior to the usual run of diamonds, that I feel justified in saying that the cut one would bring fifteen hundred dollars, anywhere.  In fact, I would offer that for it.  The other is larger, though what it would lose in cutting would be hard to say.  I should say it was worth two thousand dollars as it is now.”

“Thirty-five hundred dollars for these two stones!” exclaimed Tom.

“They are worth every cent of it,” declared Mr. Roberts.  “Do you want to sell?”

Tom shook his head.  He could scarcely believe the good news.  Mr. Jenks had told the truth.  Now the young inventor could go with him to seek the diamond makers.

“Can you get any more of these?” went on Mr. Roberts.

“I think so—­that is I don’t know—­I am going to try,” answered the lad.

“Then if you succeed I wish you would sell us some,” fairly begged the proprietor of the store.

“I will,” promised Tom, but he little knew what lay before him, or perhaps he would not have made that promise.  He thanked the diamond merchant for his kindness, and arranged to have the cut stone set in a pin for Miss Nestor.  The uncut gem Tom took away with him.

Thinking of many things, and wondering how best to start in his airship Red Cloud for the mysterious Phantom Mountain, Tom hurried back to where he had left the monoplane, wheeled it out, and was soon soaring through the air toward Shopton.

“I think I’ll go with Mr. Jenks,” he decided, as he prepared for a landing in the open space near his aeroplane shed.  “It will be a risky trip, perhaps, but I’ve taken risks before.  When Mr. Jenks comes to-night I’ll tell him I’ll help him to get his rights, and discover the secret of the diamond makers.”

As Tom was wheeling the Butterfly into the shed, Eradicate came out to help him.

“Dere’s a gen’man here to see yo’, Massa Tom,” said the colored man.

“Who is it?”

“I dunno.  He keep askin’ ef yo’ de lad what done bust up Earthquake Island, an’ send lightnin’ flashes up to de sky, an’ all sech questions laik dat.”

“It isn’t Mr. Damon; is it, Rad?  He hasn’t been around in some time.”