The three stood gazing up toward the summit of the great mountain.  Suddenly, as the sun rose higher in the heavens, it sent a shaft of rosy light on the face of the berg that had been scarred by the landslide.  Tom Swift uttered an exclamation, and pointed at something.

“See!” he cried.  “Look where the trail is—­the trail down which the phantom must have come.  It is on the edge of a cliff now!”

They looked, and saw that this was so.  The increasing light had just revealed it to them.  When the lightning bolt had torn away a great portion of the mountain it had cut sheer down for a great depth and when the earth and stones fell away they left a narrow pathway, winding around the mountain, but so near the edge of a great chasm, that there was room but for one person at a time to walk on that footway.  The uncertain trail up Phantom Mountain had all but been destroyed.

“The way up to the peak is by that path, now,” spoke Tom, in a low voice.

“Bless my soul!” cried Mr. Damon.  “It’s as much as a man’s life is worth to attempt it.  If he got dizzy, he’d topple over, and fall a thousand feet.  Dare we risk it?”

“It’s the only way to get up,” went on Tom.  “It’s either that way, or not at all.  We’ve tried the other side without success.  We must go up this way—­or turn back.”

“Then we’ll go up!” cried Mr. Jenks.  “It may not be as dangerous as it looks from here.”

But it was even more dangerous than it appeared, when they went part way up it after a hasty breakfast.  The trail was a mere ledge of rock now, and in some places, to get around a projecting edge of the mountain, they had to stand with their backs to the dizzy depths at their feet, and with both arms outstretched work their way around to where the trail was wider.

“Shall we risk it?” asked Tom, when they had tried the way, and found it so dangerous.  “We can’t take anything with us—­even our guns, for we couldn’t carry them, and if we reach the month of the cave, and find those men there—­”

He paused significantly.  The adventurers looked at one another.  The search for the diamond makers was becoming more and more dangerous.

“I say let’s go on!” decided Mr. Damon, suddenly.  “We want to locate that cave, first of all.  Perhaps, when we do find it, we may see some easier way of getting to it than this.  And if those diamond makers do attack us—­well, I don’t believe they’ll shoot defenseless men, and they may listen to reason, and give Mr. Jenks his rights—­tell him how to make diamonds in return for the money he gave them.”

“I don’t believe those scoundrels will listen to reason,” replied the diamond man, “but I agree with Mr. Damon that we ought to go on.  We may find some other means of reaching the cave—­if we can discover it, and we’ll take a chance with the men.”

“Forward it is, then!” cried Tom.  “I have a revolver, and I can supply one of you gentlemen with another.  They may come in useful in an emergency.  Let’s go back to camp, take a little lunch in our pockets, and try to scale the mountain.”