He cudgeled his brains to find a reason for the presence of Masterson so far from home, but was unable to arrive at any solution till an idea suddenly struck him.

“They’re out here trailing us,” he muttered.  “Yes, I’m sure of it.  But how in the world did they ever learn our plans?  I guess I’ll get back to camp and put the rest on their guard, for we don’t want any spies hanging about, and those fellows were out on a spying expedition or I miss my guess.”

CHAPTER XXVI.

THE START FOR THE UNKNOWN.

But the days went by, and the Wondership stood once more assembled and ready to take the greatest flight of her career, and no further sign of the three worthies, whom Dick suspected of designs against them, appeared.  Zeb went to town once or twice, using a small burro for a saddle animal.  Jack heard from his father, who said that he was progressing well, but was very much worried over money matters.

“If only you can find the Z.2.X.,” he wrote, “we can all be happy again.”

“I will find it,” Jack murmured to himself, as he concluded reading the letter, and passed it over to Tom for his perusal.

Dick helped with the Wondership and spent the rest of the time fishing and hunting.  He managed to get a few rabbits, but there was no other game in the vicinity.  It was too barren for deer, although it was said there were plenty of them further down the river.  The young reporter, who had quite a mechanical genius of his own, constructed a rough sort of boat out of boards from the walls of the old shack, and used it on his fishing expeditions, “punting” it along with a long pole made from a willow sapling from a grove on the river bank some distance below where they were camped.

One afternoon the fancy took him to pole up the current and round the bend below which Masterson’s boat had appeared the evening Dick saw and recognized the son of the Moon proprietor.

He had not gone that way before and was surprised to find that, instead of the low banks that edged the river where the boys were camped, round the bend were steep, almost clifflike acclivities on both sides of the stream.  In places these were honeycombed with caves, running back, apparently, some distance into the bank.  Although Dick did not know it, these caves had once been the dwelling places of an extinct tribe of Indians.

The boy was surprised to see smoke coming from one of them, for he had supposed that they were uninhabited.

“Maybe there are Indians up there,” thought the boy.  “I guess I’ll give them a look, and maybe get a good picture,” for Dick invariably carried his camera with him on the chance of getting a good snapshot at something or other.

A rough path led up to the cave and it was well worn by feet which had, apparently, traversed it recently.  Dick reached the entrance of the cave and peered in.