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."

"My idea, exactly," declared Tom. "Well, then, I'll go down at the first place we cross, where we can get gasoline, and then we'll be in a position to hover in the air for a long time, without descending."

The airship kept on her way, traveling slowly the remainder of that day, and at dusk, when there was less chance of big crowds seeing them, the Red Cloud was sent down on the outskirts of a large village. Tom and Mr. Damon went to a supply store, and arranged to have a sufficient quantity of the gasoline taken out to the airship. It was delivered after dark, and little talk was occasioned by the few who were aware of the presence of the craft. Then, once more, they went aloft, and Tom sent several wireless messages to Shopton, including one to Miss Nestor.

"Please tell my wife that I am well, and that I have a good appetite," said Mr. Damon.

Mr. Parker also sent a message to a scientific friend of his, stating that he made some observations among the mountains, of the region in which the airship then was, and that the indications were that a great landslide would soon take place.

"That won't worry us," spoke Tom, "for we'll be far above it."

"I hope we will be near enough to enable me to observe it, and make some scientific notes," came from Mr. Parker. "I am positive that one of these mountain peaks that we saw to-day will disappear in a landslide within a few days. I have an instrument somewhat like the one that records earthquakes, and it has been acting strangely of late."

Tom wondered what enjoyment Mr. Parker got out of life, when he was always looking for some calamity to happen, but the scientist seemed to take as much pleasure in his gloomy forebodings now, as he had on Earthquake Island.

They reached the vicinity of Leadville the next day, but took care to keep high above the city, so that the airship could not be observed. With powerful glasses they examined the mountainous country, looking for the little settlement of Indian Ridge.

"There it is!" exclaimed Mr. Jenks, just as dusk was settling down. I can make out the hotel I stopped at. Now we can really begin our search. The next thing is to find the stone head, and then, I think, I will have my bearings."

"We'll begin the hunt for that landmark in the morning," said Tom.

High in the air hovered the Red Cloud. At that distance above the earth she must have looked like some great bird, and the adventurers thought it unlikely that any one in the vicinity of Leadville would observe them.

The quest for the great mountain peak, that looked like a stone head, was under way. Back and forth sailed the airship. Sometimes she was enveloped in fog, and no sight could be had of the earth below. At other times there were rain storms, which likewise prevented a view. Mr. Parker was on the lookout for his predicted mountain landslide, but it did not occur, and he was much disappointed.

"It's queer I can't pick out that landmark," said Mr. Jenks after two days of weary searching, when their eyes were strained from long peering through telescopes. "I'm sure it was around Indian Ridge, yet we've covered almost all the ground in this neighborhood, and I haven't had a glimpse of it."

"Perhaps it was destroyed in a landslide, or some cataclysm of nature," suggested Mr. Parker. "That is very possible."

"If that's the case we're going to have a hard time to locate the cave of the diamond makers," answered Mr. Jenks, "but I hope it isn't so."

They continued the search for another day, and then Tom, as they sat in the comfortable cabin of the airship that night, hovering almost motionless (for the motor had been shut down) made a proposition.

"Why not descend in some secluded place," he suggested, "and wander around on foot, making inquiries of the miners. They may know where the stone head is, or they may even know about Phantom Mountain."

"Good idea," spoke Mr. Jenks. "We'll do it."

Accordingly, the next morning, the Red Cloud was lowered in a good but lonely landing place, and securely moored. It was in a valley, well screened from observation, and the craft was not likely to be seen, but, to guard against any damage being done to it by passing hunters or miners, Mr. Parker and Mr. Damon agreed to remain on guard in it, while Tom and Mr. Jenks spent a day or two traveling around, making inquiries.

The young inventor and his companion proceeded on foot to a small settlement, where they hired horses on which to make their way about. They were to be gone two days, and in that time they hoped to get on the right trail.