posed. The drawing (Fig. 31) shows how this is arranged.
Now iron shows these colors differently arranged, aluminum in another
way, and so on with all different substances, and the light projected
from each is called its spectrum, its particular analysis."

John's recital during the day had produced a powerful impression on
all, as well it might. It shows what wonderful trials men can endure.
Ralph and Tom were frequently affected by it, and at times could not
prevent tears from coming. They recalled their own sufferings.

The Professor thanked John that evening for his story, and said: "We
must not tax the patient with any more talk to-night. We have learned a
lesson of perseverance and trials. The history of man is always
profitable, and we are thankful for the news it gives us of the people
here but you must be patient and wait a more opportune time to hear our
story, and then we can advise with each other as to our future course."

The boys were early in conference with each other after they left John,
because there were some interesting things to them in John's story,
which needed clearing up.

"Did you hear what he said about that cave?" was Ralph's first question.

"Yes; and I think I know where that cave is?" answered Harry.

"Where?" asked Tom and George in a breath.

"Right at the camp where we found you."

"Oh, you mean that cave we found at the hillside after we started for
the river?"

"Don't you recall that John took me around to the mouth of the cave, and
when we said that we might use that to hide in, he shook his head, and
moved away?"

"I thought the Professor acted queerly about it, too, because he urged
us away from the place."

All remembered the circumstance, and they also recalled that the
Professor gave a vague reply when they asked him the reason why.

George cast a scrutinizing glance at Harry, who waited for him to speak.
"Harry, do you think he found any treasure in that cave?"

Ralph and Tom now opened their eyes in wonder. Was that what he meant
when he said there was something wonderful there? Harry looked at the
boys for a moment, in the intensity of the situation, and said: "And we
have also found a cave." But the eyes of George caught Harry, who
suddenly stopped, because he recalled their agreement not to divulge it
to the boys until the matter was mentioned to him.

"Where is it?" exclaimed Tom, eagerly.

"Not far from here."

"Will it be much trouble to visit it?"