“A landslide!” cried Mr. Parker.  “That is the landslide which I predicted!  The lightning bolt has split Phantom Mountain!”

CHAPTER XVI—­THE VAST CAVERN

For a time the roiling, slipping, sliding and tumbling of the mass of earth and stones, down the side of the mountain, effectually drowned all other sounds.  Even the thunder was stilled, and though Tom and his companions called to one another in terror, their voices could not rise above that terrific tumult.

Finally, when they found that the direction of the slide was away from their tent, and that they were not likely to be engulfed, they grew more calm.

Gradually the noise subsided.  The great boulders had rolled to the bottom of the valley, and now only a mass of earth and stones was sliding down.  Even this stopped in about five minutes, and, as though satisfied with what it had done, the electrical storm passed.  Not a drop of rain had fallen.

“Bless my shirt studs!” exclaimed Mr. Damon, who was the first to speak after the din had quieted.  “Bless my soul!  But that was awful!”

“It was just what I expected,” said Mr. Parker, calmly.  “I knew, from my observations, that we were in a region where landslides and terrific electrical storms may be expected at any time.  I fully looked for this.”

“Well,” remarked Mr. Jenks, rather sarcastically, “I hope it came up to your expectations, Mr. Parker.”

“Oh, fully,” was the answer, “though I wish it could have happened in daylight, so that I could better have observed certain phenomena regarding the landslide.  They are very interesting.”

“At a distance,” admitted Tom, with a laugh of relief.  “Well, I’m glad it’s over, though we’ll have to wait until morning to see what damage has been done.  Lucky we weren’t struck by lightning.  I never saw such bolts!”

“Me, either!” declared Mr. Damon.  “This mountain seems to attract them.”

“It is like a magnet,” said Mr. Parker.  “I think I shall be able to make some fine observations here.”

“If we live through it,” murmured Mr. Jenks.

They watched the play of lightning about a distant bank of clouds, but the storm was now far away, only a faint rumbling of thunder being heard.

“I’m wondering what happened to the phantom,” said Tom, after a pause.  “Seems to me he was right in that track of the storm.”

“Do you think it was a ’he’?” asked Mr. Jenks.

“I think we’ll find that it’s some sort of a man,” answered the young inventor.  “We may find out very soon, now.  I’ve changed my theory about the ghost being reflections of light.”

“How’s that?” Mr. Damon wanted to know.

“Well, I think we are on the side of Phantom Mountain where the diamond cave is,” went on the lad.  “The fact that the phantom appeared here, soon after we arrived, shows that the men kept close track of our movements.  It also shows, I think, that the phantom did not have to travel far to be on the spot, whereas we had to make quite a trip to get around the base of the mountain.  I think the cave is up there,” and Tom pointed toward the spot where the weird figure had been last seen, before the storm drove it back.