"And that is just enough to make the thing a decided mystery. I have heard of magic rings used by East Indian fakirs and magicians. Perhaps this is one of those rings."
Frank smiled a bit, and shook his head.
"Hardly that, I think," he said. "From its appearance, I should say this ring was made by some crude workman in the West."
"In, that case, what can there be about it that is mysterious or valuable?"
"You have asked me something I cannot answer."
"Let's look at the thing."
Bart held out his hand, and Frank removed the ring from his finger, handing it over.
"It slips off altogether too easily," said Hodge. "I should think you would fear losing it."
"It does come off easy, and, for that reason, I have not worn it much till of late."
"Yes; I never noticed it on your hand till a short time ago."
"I have kept it among my valuables."
Hodge looked the ring all over, examining it slowly and carefully.
"There doesn't seem to be anything about it to make a fellow think it so very mysterious," he said, with a shade of disappointment 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 academy. Bart accompanied him to the experimenting room, and they were soon taking turns in looking at the marked stone.
"What do you make of it, old man?" asked Bart.
"It looks like a map," said Frank.
"Right!" exclaimed the other lad. "It looks like a map, and I believe that is what it is."
There is a river, or road, and mountains, something that looks like a lake, and then a tiny cross. The cross must be a landmark.
"Yes; and you will note that it is at the end of what looks like a river."
"But that must be a road."
"It is, if this is a map, for it runs over that range of hills, or mountains."
"That is plain enough."
"And you will see there is a tiny, snake-like thread that winds away from that spot, which looks as if it was intended for a lake."
"I see it."
"That must be a river, or stream."
The boys were now very excited. All doubts were fading from their minds; the lines on the black stone had surely been intended to represent a map.
But what portion of the face of the earth did it portray? That was a question the ring did not answer.
"Supposing it is a map," said Frank, helplessly; "what good will it do me? I do not know what it is a map of."
"But you may bet your last dollar the man in black knows."
"I don't see how that is going to do me any good.
"It will do him some good, if he gets hold of this ring."
"Well, I shall take care that he does not get hold of it."
The map—if it were a map—on the stone served to more fully arouse the curiosity of the boys, without in any way satisfying them concerning the mystery of the ring.
Frank became so absorbed in trying to discover the true meaning of the map and in getting some light on the mystery that he began to neglect his studies. This, however, was quickly noted by Hodge, who said:
"Be careful, old man; don't let that ring get into your head so that you will lose your chance of standing well up in your class. You are all right in drill work, and you should be appointed a corporal next month."
"Hang the old ring!" exclaimed Frank, petulantly. "I never had anything cause me so much bother before. Whenever I try to study I fall to thinking of it, and I dream of it every night."
Two days passed, and nothing more was seen of the man in black during that time, which led Bart to believe that the mysterious individual had left the vicinity.
"He must have fancied that you would have him arrested for attacking you on the road," said Hodge. "You are not likely to see him again very soon."
"Don't get that impression into your head," returned Frank. "He is not far away. I seem to feel that he is lurking near,