two locoed
fortune-hunters ever undertook. How it ended you know. They both got
fever, but Sanchez was the worst. He died that same evening, his
tumble in the water havin' made him worse. I buried him there as best
I could and then, as he had wished, I takes the sample and the map.

"'Some day,' he told me, just afore he closed his eyes for good,
'you'll be glad you saved me, even though it was too late.'

"Well, I beat it back and get out of the canyon more dead than alive
and finally make a small strike. I go to San Francisco with it and try
to git ther stuff analyzed, but everyone I tole about it laughed at me
and said I was crazy. So, thinks I, I'll come East. My money was about
all gone, so I shipped afore ther mast on a Cape Horn ship, and got
here.

"Now, you have me tale, old top," grinned the good-natured miner, and
added: "Well, has my toe-and-heeling been worth its salt?"

The professor nodded solemnly.

"What is it?" cried Jack, his heart beating with a strange, wild hope.

Tom and Zeb echoed Jack's eager question.

"My friends," declared the little man of science pompously, "we have
reason to believe that a wonderful discovery has been made, namely,
Z.2.X."

CHAPTER XVI.

ZEB CUMMINGS.

"Z.2.X., the most radio-active stuff in the world!" exclaimed Jack.

"I suppose that approximately describes it," said the professor, "but
what do you know about it?"

Jack explained how ardently his father had wished for the missing
element to make his system of radio telephony the most efficient in
use.

"Well, if what Sanchez said was true, and the map is right, there is
plenty of it right on that island," said the miner.

"Yes, that may all be," objected the professor, "but how are you going
to get at it?"

"Wa'al that's a poser. You can't reach it in a boat and you can't
reach it over the desert," said Zeb. "The country all round there is
dry as an oven and, anyhow, if you got to ther banks of ther Colorado
right by ther island ther's no way of gitting _down_ to ther island.
Sanchez says that the Injuns told Foxy's friend that a long time ago,
when first they found the stuff on the island, there was a way of
getting down to it. But an earthquake sunk the river bed and nobody
had been thar since the Injuns that found it. He said that they first
come to take notice of it by reason of the way it shined at night. But
only a few of the tribe would go near on account of their thinking the
place wa