“Do you know, I would like to know the history of this box,” observed Dick, as he looked it over.  “As it belonged to one of those smugglers it ought to have quite a story to tell.”

“It will make a nice jewel casket,” put in Tom.  “When you settle down with Dora, you can give if to her for her dia——­”

“Oh, stow that, Tom!  If Dora ever does take me for a husband, it won’t be for some years to come, you must know that.”

“Let me take a look at the box,” put in Sam.  “I never got the chance to look it over carefully.”

“It’s odd that they should engrave it inside,” went on Dick.  “Especially since the outside silver corners are plain.”

“Perhaps there is a secret spring hidden by the engraving,” suggested Tom.  “Hunt around.  It may fly apart and let out a hundred thousand in diamonds.”

“Don’t be foolish, Tom,” said Dick.  “It isn’t likely there is a spring.”

“But there just is a spring!” exclaimed Sam, who was handling the box.  “Hark!”

He ran his finger nail over a spot on one side of the box, and there followed a tiny click.  Then he ran his finger nail back, and there was another click.

“Hurrah!  Sam has solved the mystery of the sphinx!” cried Tom.  “Can you open it?  I claim a third share of the diamonds!”

“Give me the box,” said Dick, also a bit excited.  When he got it in his hands he, too, ran his finger nail over the engraved brass.  Several tiny clicks followed.

“There must be some opening beneath the brass lining,” he said.

“Take it to the window, and perhaps you’ll be able to see something more,” suggested Sam.

Dick did as advised, and, with his brothers gathered close beside him, worked over the money casket for fully quarter of an hour.

“It seems to click, and that’s all,” he said disappointedly.  “If I could only——­Oh!”

Dick stopped short.  His finger had run across the lining in a certain way.  There were three clicks in rapid succession, and on the instant one of the brass plates of the box flew back, revealing a tiny compartment behind it, not over a quarter of an inch in depth.

“No diamonds there,” said Tom, his face falling.  “Full of emptiness.”

“No, here is a sheet of parchment,” returned Dick, pulling it forth.  “A map!” he added, as he unfolded it.  “Well, I never!”

“Never what?” came from Tom and Sam.

“Unless I am mistaken, this is like the map that was on that table in the cave, only this is much smaller.”

“That’s interesting, too,” said Tom.

“The back of the map is full of writing,” said Sam.  He looked closer.  “It’s in French.”

“This box must have belonged to one of those French-Canadian smugglers,” said Dick.  “We’ll have to get Uncle Randolph to read the writing and tell us what it says.”

The three boys had been up to Dick’s room.  Now they lost no time in going below.  In all eagerness they burst into the library, where Anderson Rover sat reading a magazine and Randolph Rover one of his favorite works on scientific farming.