“That means ‘blue mass,’” said the Doctor.  And gave it to him,—­a bolus as large as a musket ball, and as heavy.

Concho took it on the spot, and turned to go.

“I have no money, Senor Medico.”

“Never mind.  It’s only a dollar, the price of the medicine.”

Concho looked guilty at having gulped down so much cash.  Then he said timidly: 

“I have no money, but I have got here what is fine and jolly.  It is yours.”  And he handed over the contents of the precious tin can he had brought with him.

The Doctor took it, looked at the shivering volatile mass and said, “Why this is quicksilver!”

Concho laughed, “Yes, very quick silver, so!” and he snapped his fingers to show its sprightliness.

The Doctor’s face grew earnest; “Where did you get this, Concho?” he finally asked.

“It ran from the pot in the mountains beyond.”

The Doctor looked incredulous.  Then Concho related the whole story.

“Could you find that spot again?”

“Madre de Dios, yes,—­I have a mule there; may the devil fly away with her!”

“And you say your comrades saw this?”

“Why not?”

“And you say they afterwards left you,—­deserted you?”

“They did, ingrates!”

The Doctor arose and shut his office door.  “Hark ye, Concho,” he said, “that bit of medicine I gave you just now was worth a dollar, it was worth a dollar because the material of which it was composed was made from the stuff you have in that can,—­quicksilver or mercury.  It is one of the most valuable of metals, especially in a gold-mining country.  My good fellow, if you know where to find enough of it, your fortune is made.”

Concho rose to his feet.

“Tell me, was the rock you built your furnace of red?”

“Si, Senor.”

“And brown?”

“Si, Senor.”

“And crumbled under the heat?”

“As to nothing.”

“And did you see much of this red rock?”

“The mountain mother is in travail with it.”

“Are you sure that your comrades have not taken possession of the mountain mother?”

“As how?”

“By claiming its discovery under the mining laws, or by pre-emption?”

“They shall not.”

“But how will you, single-handed, fight the four; for I doubt not your scientific friend has a hand in it?”

“I will fight.”

“Yes, my Concho, but suppose I take the fight off your hands.  Now, here’s a proposition:  I will get half a dozen Americanos to go in with you.  You will have to get money to work the mine,—­you will need funds.  You shall share half with them.  They will take the risk, raise the money, and protect you.”

“I see,” said Concho, nodding his head and winking his eyes rapidly.  “Bueno!”

“I will return in ten minutes,” said the Doctor, taking his hat.