side," 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.

"Dick has got the money casket open!" cried Sam.

"And he has found a map," added Tom. "We wa