isappointment in his
voice.

"No."

"It is just a homely, twisted ring, with an old scratched black stone
set in it."

"That's right."

"Perhaps the man in black is crazy."

"It is possible."

"In which case the mystery amounts to nothing."

For a few seconds the two lads sat staring at each other. Then Frank
removed a pin from some hidden place, and held it toward Bart.

"Here," he said, "take this and see how easily you can scratch that
stone."

Hodge took it, and attempted to scratch the black stone that was set in
the ring.

"Why, the thing is hard as flint--yes, harder!" he exclaimed. "The pin
will not leave a mark upon it, and it has already turned the point of
the pin over."

"Still, as you said, the stone is scratched."

"What do you make of that?"

"It strikes me it was not scratched by accident."

Hodge started and whistled.

"Do you imagine these marks were made here intentionally and
deliberately?"

"Doesn't it seem that way?"

"Well, it is not impossible."

"If they were made there deliberately and intentionally, cut by some
instrument that could mark that hard stone, doesn't it stand to reason
that the one who made them did not do all that work for nothing?"

"Of course."

"Then those marks may mean something."

"By jingoes! you are right!"

"This may be known to the man in black, which makes him so fierce to
obtain the ring."

"Sure!"

Again the boys stared silently at each other, but there were traces of
eager excitement on the faces of both.

"How are you going to find out what those marks mean, Frank?"

"That is a question easier asked than answered."

"Did you ever examine this stone under a microscope?"

"No."

"Then I advise you to do so without delay. These scratches are not
very plain to the naked eye, but a microscope may reveal a great secret
to you."

As Bart passed the ring back, Frank said:

"You are right. My curiosity is thoroughly aroused, and I will examine
it under a magnifying glass at the earliest opportunity."

"Get leave to look at it under the big glass in the experimenting room."

"I will try it to-morrow."

Until very near taps the boys talked of the mystery of the ring, and
that night both of them dreamed over and over of the ring and the
sinister man in black.

CHAPTER XXIX.

BART MAKES A PLEDGE.

The following day Frank obtained permission to look at the ring through
the powerful microscope belonging to the academ