“Come now,” continued the voice, “you just let up on that mule, you d——­d old Greaser.  Don’t you see she’s slipped her shoulder?”

Alarmed as Concho was at the information, he could not help feeling to a certain extent relieved.  She was lamed, but had not lost her standing as a good Catholic.

He ventured to lift his eyes.  A stranger—­an Americano from his dress and accent—­was descending the rocks toward him.  He was a slight-built man with a dark, smooth face, that would have been quite commonplace and inexpressive but for his left eye, in which all that was villainous in him apparently centered.  Shut that eye, and you had the features and expression of an ordinary man; cover up those features, and the eye shone out like Eblis’s own.  Nature had apparently observed this too, and had, by a paralysis of the nerve, ironically dropped the corner of the upper lid over it like a curtain, laughed at her handiwork, and turned him loose to prey upon a credulous world.

“What are you doing here?” said the stranger after he had assisted Concho in bringing the mule to her feet, and a helpless halt.

“Prospecting, Senor.”

The stranger turned his respectable right eye toward Concho, while his left looked unutterable scorn and wickedness over the landscape.

“Prospecting, what for?”

“Gold and silver, Senor,—­yet for silver most.”

“Alone?”

“Of us there are four.”

The stranger looked around.

“In camp,—­a league beyond,” explained the Mexican.

“Found anything?”

“Of this—­much.”  Concho took from his saddle bags a lump of greyish iron ore, studded here and there with star points of pyrites.  The stranger said nothing, but his eye looked a diabolical suggestion.

“You are lucky, friend Greaser.”

“Eh?”

“It is silver.”

“How know you this?”

“It is my business.  I’m a metallurgist.”

“And you can say what shall be silver and what is not.”

“Yes,—­see here!” The stranger took from his saddle bags a little leather case containing some half dozen phials.  One, enwrapped in dark-blue paper, he held up to Concho.

“This contains a preparation of silver.”

Concho’s eyes sparkled, but he looked doubtingly at the stranger.

“Get me some water in your pan.”

Concho emptied his water bottle in his prospecting pan and handed it to the stranger.  He dipped a dried blade of grass in the bottle and then let a drop fall from its tip in the water.  The water remained unchanged.

“Now throw a little salt in the water,” said the stranger.

Concho did so.  Instantly a white film appeared on the surface, and presently the whole mass assumed a milky hue.

Concho crossed himself hastily, “Mother of God, it is magic!”

“It is chloride of silver, you darned fool.”