Tom's cries awakened the sleepers in the tent. Mr. Damon was the first to rush out.

"Bless my nightcap, Tom!" he cried. "What is it? What has happened? Are we attacked by a mountain lion?"

For answer the young inventor pointed up the mountain, to where, in the dim light from a crescent moon, there stood boldly revealed, the figure in white.

"Bless--bless my very existence!" cried the odd man. "What is it, Tom?"

"The phantom," was the quiet answer. "Watch it, and see what it does."

By this time Mr. Jenks and Mr. Parker had joined Tom and Mr. Damon. The four diamond seekers stood gazing at the apparition. And, as they looked, the thing in white, seemingly too tall for any human being, slid slowly forward, with a gliding motion. Then it raised its long, white arms, and waved them threateningly at the adventurers.

"It's motioning us to go back," said Mr. Parker in an awed whisper. "It doesn't want us to go any farther."

"Very likely," agreed Tom, coolly. "But we're not going to be frightened by anything like that; are we?"

"Not much!" exclaimed Mr. Jenks. "I expected this. A ghost can't drive me back from getting my rights from those scoundrels!"

"Suppose it uses a revolver to back up its demand?" asked the scientist.

"Wait until it does," answered Mr. Jenks. But the figure in white evidently had no such intentions. It came on a little distance farther, still waving the long arms threateningly, and then it suddenly disappeared, seeming to dissolve in the misty shadows of the night.

"Bless my suspenders!" cried Mr. Damon." "That's a very strange proceeding! Very strange! What do you make of it, Tom?"

"It is evidently some man dressed up in a sheet," declared Mr. Jenks. "I expected as much."

"The work of those diamond makers; do you think?" continued Mr. Damon.

"I believe so," answered Tom, slowly, for he was trying to think it out. "I believe they are the cause of the phantom, though I don't know that it's a man dressed in a sheet."

"Why isn't it?" demanded Mr. Jenks.

"Because it was too tall for a man, unless he's a giant."

"He may have been on stilts," suggested Mr. Parker.

"No man on stilts could walk along that way," declared Tom, confidently. "He glided along too easily. I am inclined to think it may be some sort of a light."

"A light?" queried Mr. Damon.

"Yes, the diamond makers may be hidden in some small cave near here, and they may have some sort of a magic lantern or a similar arrangement, for throwing a shadow picture. They could arrange it to move as they liked, and could cause it to disappear at will. That, I think, is the ghost we have just seen."

"But the diamond makers have only been in this mountain recently," objected Mr. Jenks, "and the phantom was here before them. In fact, that was what gave the place its name."

"That may be," admitted the lad. "There are many places that have the name of being haunted, but no one ever sees the ghost. It is always some one else, who has heard of some one who has seen it. That may have been the case here. I grant that this place may have been called 'Phantom Mountain' for a number of years, due to the superstitious tales of miners. The diamond makers came along, found the conditions just right for their work, and adopted the ghost, so to speak. As there wasn't any real spirit they made one, and they use it to scare people away. I think that's what we've just seen, though I may be wrong in my theory as to what the phantom is."

"Well, it's gone now, at any rate," said Mr. Jenks, "and I think we'd better get back inside the tent. It's cold out here."

"Aren't some of us going to stand guard?" demanded Mr. Damon.

"What for?" asked Mr. Jenks.

"Why--er--bless my key-ring! Suppose that ghost takes a notion to come down here, and use his gun, as he did on the miners?"

"I don't believe that will happen," remarked Tom. "The diamond makers, if the white thing had anything to do with them, have given us a warning, and I think they'll at least wait until morning to see how we heed it."

"We aren't going to heed it!" burst out Mr. Jenks. "I'm going to go right ahead and find that cave where they make diamonds!"

"And we're with you!" exclaimed Tom. "We'll have a good fire going the rest of the night, and that may keep intruders away. In the morning we'll begin our search, and we'll go up the trail where we saw the white figure."

A big pile of wood had been collected for the fire, and Tom now piled some logs and branches on the blaze. It would last for some time now, and the adventurers, still talking of the "ghost" went back into the tent. It was over an hour before they all got to sleep again, and Mr. Jenks and Mr. Damon took turns in getting up once or twice during the remainder of the night to replenish the fire.

Morning dawned without anything further having occurred to disturb them, and, after a hearty breakfast, to which Tom added some fish he caught in a nearby mountain stream, they set off up the trail on Phantom Mountain.

They had left their tent standing, as they proposed making that spot their headquarters until they located the cave they were seeking. What their course would be after that would depend on the circumstances.

If they had expected to have an easy task locating the cavern in which Mr. Jenks had seen diamonds made, the adventurers were disappointed. All that day they tramped up and down the mountain, looking for some secret entrance, but none was disclosed. The higher they went up the great peak, the fainter became the trail, until, at length it vanished completely.

But this was not to be wondered at, since it was on solid rock, in which no footsteps would leave an impression.

"They never brought you up here in a wagon, Mr. Jenks," decided Tom, when he saw how steep the place was.

"I'm inclined to think so myself," admitted the diamond man. "They must have reached the cave from some other way. As a matter of fact, I walked some distance after getting out of the vehicle, before we got to the cavern. But, even at that, I don't believe we came this way."

"Yet the phantom was here," persisted Tom, "and I'm convinced that the cave is in this neighborhood. It's up to us to find it!"

But they searched the remainder of that day in vain, and as night was coming on, they made their way back to the camp. As Tom, who was in the lead, approached the tent, he saw something black fastened to the entrance.

"Hello!" he cried. "Some one's been here. That wasn't on the tent when he left this morning."

"What is it?" asked Mr. Damon.

"A black piece of paper, written on with white ink," replied the lad. He was reading it, and, as he perused it a look of surprise came over his face.

"Listen to this!" called Tom. "It's evidently from the diamond makers."

Holding up the black paper, on which the white writing stood out in bold relief Tom read aloud:

"Be warned in time! Go back before it is too late! You are near to death! Go back!"

"Bless my shoelaces!" cried Mr. Damon. "This is getting serious."