The airship once more rose in the air, and, following the directions the miner had given him, Tom pointed his craft for the depression in the mountains which had been given the name Black Gulch.  It was reached in a short time, and then, making a turn up a long valley the airship proceeded at reduced speed.

“We ought to see that stone head soon now,” spoke Tom, as he peered from the windows of the pilot house.

“It’s queer we didn’t notice it when we were up in the air,” remarked Mr. Jenks.  “We’ve been over this place before, I’m sure of it.”

The next moment Mr. Damon uttered a cry.  “Bless my watch-chain!” he exclaimed.  “Look at that!”

He pointed off to the left.  There, jutting out from the side of a steep mountain peak was a mass of stone—­black stone—­which, as the airship slowly approached, took the form and shape of a giant’s head.

“That’s it!  That’s it!” cried Tom.  “The great stone head!”

“And now for Phantom Mountain and the diamonds!” shouted Mr. Jenks, as Tom let the airship slowly settle to the bottom of the valley.

CHAPTER XIII—­ON PHANTOM MOUNTAIN

Out from the Red Cloud piled Tom and the others.  They made a rush for the irregular mass of rock which bore so strong a resemblance to the head of some gigantic man.

“That’s the one!  That’s the thing I saw when they were taking me along here blindfolded!” exclaimed Mr. Jenks.  “I’m sure we’re on the right trail, now!”

“But what gets me, though,” remarked Mr. Damon, “is why we couldn’t see that landmark when we were up in the air.  We had a fine view, and ought to have been able to pick it out with the telescopes.”

The adventurers saw the reason a few seconds later.  The image was visible only from one place, and that was directly looking up the valley.  If one went too far to the right or left the head disappeared from view behind jutting crags, and it was impossible to see it from overhead, because the head was almost under a great spur of a mighty mountain.

“We might have hunted for it a week in the airship, and been directly over it,” said Tom, “and yet we would never have seen it.”

“Yes, but we never would have gotten here in such good shape if it hadn’t been for your wonderful craft,” declared Mr. Jenks.  “It brought us here safely and quickly, and enabled us to elude the men who tried to keep us back.  We’re here in spite of them.  If we had traveled by train they might have interfered with us in a dozen ways.”

“That’s so,” agreed Mr. Damon.  “Well, now we’re here, what’s to be done?  Which way do we start to reach the cave where the diamonds are manufactured, Mr. Jenks?”

“That I can’t say.  As you know, I only had a momentary glimpse of this stone head as they wore taking me along the trail.  Then one the men noticed that the bandage had slipped and he pulled it into place.  So I really can’t say which direction to take now, in order to discover the secret.”