“Oh, don’t worry,” said Mr. Jenks, quickly, “we’re not going to toss you overboard.  We’re not as desperate as your crowd.  But we’re going to get rid of you, and then go on before you can send any word to your confederates.  We’ll put you off in the most lonesome spot we can find, and I guess you’ll be some time getting back to civilization.  By that time we’ll have the secret of the diamonds.”

“You never will!” declared the man, firmly.  And he would say nothing more, though by threats and promises Mr. Jenks tried to get from him something about the men in with him, and where the cave of the diamonds was located.

Heavily bound with ropes the man was locked in a small closet, to be kept there until a favorable spot was reached for letting him go.  Mr. Jenks’ plan, of dropping him down in some place where he would have difficulty in sending on word to his confederates was considered a good one.

Three days later, in crossing over a lonely region, near the Nebraska National Forest, Farley Munson, which was one of the names the spy went by, was dropped off the airship, when it was sent down to within a few feet of the earth.

“It will take you some time to get to a telegraph office,” said Mr. Jenks, as a package of food, and a flask of water was tossed down to the stowaway.  He shook his fist at those in the airship, and shouted after them: 

“You’ll never discover the secret of Phantom Mountain!”

“Yes, we will,” declared Tom, as he sent the Red Cloud high into the air again.

CHAPTER XI—­A WEARY SEARCH

During the three days when the stowaway had been kept a prisoner, the Red Cloud had made good time on her western trip.  She was now about two hundred and fifty miles from Leadville, Colorado, and Tom knew he could accomplish that distance in a short time.  It was necessary, therefore, since they were so close to the place where the real search would begin, to make some more definite plans.

“We will need to replenish our supply of gasoline,” said Tom, shortly after the stowaway had been dropped, and when the young inventor had made a general inspection of the airship.

“Is it all gone?” inquired Mr. Damon.

“Not all, but we will soon be in the wildest part of the Rocky Mountains, and gasoline is difficult to procure there.  So I want to fill all our reserve tanks.  But I would rather do that before we get far into Colorado.”

“Why?” inquired Mr. Parker.

“Because airships are not so common but what the appearance of one attracts attention.  Ours is sure to be talked about, and commented on.  In that case, in spite of our precaution in putting Munson off in this lonely place, word of the Red Cloud being in the vicinity of Leadville may reach the diamond makers, and put them on their guard.  We want to take them unawares if we can.”

“That’s so,” agreed Mr. Jenks.  “We had better get our gasoline at the first stopping place, then, and proceed with our search.  Our first object ought to be to look for the landmark—­the head of stone.  Then we can begin to prospect about a bit.”