“Have you got that map?” asked the professor.

“Yes, if you’ll reach my coat I’ll show it you,” said the miner.

Jack gave him the ragged garment off a hook at the back of the door.  Zeb fumbled in the pockets for a minute and then brought out a knife.

“A rip more or less won’t make no difference,” he said, and cut a slash down the lining.  There, carefully stowed inside, where it could not be suspected, was a folded, time-yellowed paper.

The miner opened it slowly and spread it out on the counterpane.  The boys, not without a sense of shock, noted a dark, rusty-looking stain upon it.  It struck them that the marks might be the life blood of the treacherous Foxy’s friend who had met a tragic end in Yuma.

Zeb, with a broad and blackened forefinger, traced the course of the Colorado.  At length his finger paused at an island marked in red.  There was some fantastic Indian lettering, or sign-drawing, about it, and underneath, in a white man’s handwriting, were the words:  “Rattlesnake Island.”

“I reckon Foxy Joe’s friend must hev written that in,” commented Zeb.

“It looks that way,” said the professor, who had poured the sample of mineral-bearing sand back into the vial and restored it to Zeb Cummings.

“Rattlesnake Island,” repeated Jack.  “Are there any rattlers down that way?”

“Yes, and gila monsters and tarantulas and centipedes,” replied Zeb cheerfully.  “But you soon get used to ’em.”

Some other islands were marked on the map, but Rattlesnake Island was the only one designated by name.

“That must be the place whar all that stuff is, then,” decided Zeb.  “I wish thar was some way of gittin’ thar.”

“If there is even only a small fraction of the mineral-bearing sand there,” said the professor, “there’s a fortune in it.”

“Wa’al if you can’t git it out what good is it?” said Zeb philosophically.  “Anyhow, I’m glad that Sanchez spoke the truth with his dying words.  Maybe thar is some way, except by water, in spite of what he said.”

“Maybe there is,” said Jack.  “It seems a shame to think of all that rich stuff lying there neglected and unobtainable.”

“It does indeed,” agreed the professor.  “In that sample I find traces of metals from which filaments for electric lights could be made and substances invaluable in medicine for X-ray purposes as well as the Z.2.X. which your father is convinced would make the radio telephone as practical as the wireless telegraph.”

They would like to have stayed there all the morning poring over the map and asking further questions of the rugged miner, but at that moment the nurse came in and declared that the injured man must have quiet.

And so there, for the present, the matter rested.  The professor departed for his home greatly excited over the events of the morning, but his excitement was a little allayed by the fear that he would be late for his mid-day meal with dire results from Miss Melissa.