“Well,” exclaimed the man with the gun, impatiently, “I ask you folks a question.  What do you want?”

Fortunately, neither Mr. Damon nor Mr. Parker replied.  The former because he deferred to Tom and Mr. Jenks, and the scientist because he was busy inspecting some curious rocks he picked up.  As it turned out this was the luckiest thing he could have done.  It lent color to what Mr. Jenks said a moment later.

“What are you doing up here?” demanded the man again.  “Don’t you know this is private property?”

“We—­we were just looking around,” answered Mr. Jenks, which was true enough; as far as it went.

“Prospecting,” added Tom.

“After gold?” demanded the second man, suspiciously.

“We’d be glad to find some,” retorted the lad.  At that moment Mr. Parker began breaking off bits of rock with a small geologist’s hammer which he carried.  The men with the guns looked at him.

“So you think you’ll find gold up here?” asked the one who had first spoken.

“Is there any?” inquired Tom, trying to make his voice sound eager.

“Nary a bit, strangers,” was the answer, and the two men laughed heartily.  “Now, we don’t want to seem harsh,” went on the man who seemed to be the spokesman, “but you’d better get away from here.  This is private ground, and dangerous too—­how’d you ever get up the trail—­we heard it was destroyed.”

“There is still a narrow path,” said Mr. Jenks.  “We came up that—­the lightning and landslide haven’t left much of it, though.”

Mr. Parker looked quickly up from the rocks at which he was tapping with his small hammer.  “You have terrific lightning up here,” he said.  “I am much interested in it, from a scientific standpoint.  I predict that some day the entire mountain will be destroyed by a blast from the sky.”

“I hope it won’t be right away,” spoke one of the men.  “Now I guess you folks had better be leaving while there’s a path left to go down by.”

“Might I ask,” broke in Mr. Parker, as calmly as though he was lecturing to a class of students, “might I ask if you have noticed any peculiar effect of the lightning up here on the summit of the mountain?  Does it fuse and melt rocks, so to speak?”

“What’s that?” cried the spokesman, with a sudden flash of anger.  The two men looked at each other.

“I wanted to know, merely for scientific reasons, whether the lightning up here ever melted rocks?” repeated Mr. Jenks.

“Well, whether it’s for scientific reasons or for any other, I’m not going to answer you!” snapped the man.  “It’s none of your affair what the lightning does up here.  Now you’d all better ’vamoose’—­clear out!”

“All right—­we’ll go,” said Tom, quickly, at the same time motioning to Mr. Jenks to agree with him.  The eyes of the young inventor were roving about.  He saw what looked like a second trail, leading down the mountain, from the far side of the cave.  He was convinced now that there was another way to get to it.  Possibly they might find it.  At any rate nothing more could be done now.  They must go back, for the cavern was too well guarded to attempt to enter it by force—­at least just yet.