formed in limestone rocks, and the stalactite hangings
on the ceilings and walls, and the stalagmites on the floors made the
scene a weird one.

John glanced upwardly to view the ceiling, above the mound, and said:
"That does not seem to be a natural formation. Let us examine it first."

With the small pick which John always carried, and by means of which he
was always careful to examine rocks and geological formations, while on
these tours, the top parts of the stalagmites were chipped off. This was
an exceedingly simple matter, since they are generally soft.

After the top layer was removed, the part beneath readily yielded, but
before they had an opportunity to dig into it very deeply the pick
struck something which gave forth a metallic sound. John stopped as
though paralyzed.

The pick was again driven in. Again the plain contact with some hard
substance. The digging was now feverish, and when the broken parts were
cleared away, a small metallic box, about twelve inches square across
the top, and about ten inches deep, was exposed to view.

The dent made by the pick was clearly visible, and the fresh mark showed
that the metal was red.

"It is copper!" said John.

Every part of the material around the box was removed, and this enabled
them to remove it from its resting place. John grasped it and securing a
good hold, finally raised it.

"No, it is not any heavier than I thought it would he," he remarked as
he lay it down.

"Did you expect to find this?" asked George in amazement.

"No; this is a surprise to me as it is to you."

"Then why did you make that remark?"

"Because I believe that this box contains treasure of untold value. I
should have been surprised if it weighed very much."

"Could it not have contained treasure if it had been heavy?" asked
Harry.

John laughed, a peculiar exultant chuckle, as he responded: "Not the
kind of treasure I have had in contemplation."

The box was turned over and over. There was not the sign of any lid, or
crack which showed the cover or means of opening it. "We must take this
out and open it at our leisure," remarked John, "but before doing so it
would be well to examine the other outlets to this chamber, if it has
any."

The chamber was found, on measurement, to be thirty feet in diameter,
and the vaulted ceiling fully thirty feet high, singularly uniform in
the domed formation, and not rough or jagged like the ceiling of the
other chamber which they