“If the ore always runs as well,” Tom rejoined, “it ought to be one of the richest gold and silver properties in the world.”

“Pouf!  The ore usually runs much better—­is worth much more than that which you saw to-day,” protested Don Luis.

“Then you are to be congratulated on possessing a treasure among mines,” Tom commented.

“I am delighted to hear you say that.”

“But when we adjourn to your office,” Reade continued, “there are a few questions that I shall want to ask you.”

“Why not ask them here, Senor Tomaso?” queried Don Luis, in his purring, half affectionate voice.

“Here at your table?” protested Reade.

“But this is not dinner.  This is a mere business luncheon,” replied Don Luis, with another smile.

“Yet I would like to discuss some of the samples with you, Don Luis,” Tom explained.  “Surely, you do not wish me to bring out dirty samples to spread on your fine linen.”

“It would matter not,” declared the Mexican.  “Still, if you have scruples about the proprieties, then we will go to the office within a few minutes.”

The two who were smoking continued to do so.  Don Luis started to describe some of his experiments in raising Spanish mules.  The finest mules that come out of Spain, class, in price, with blooded horses.  Don Luis talked with the enthusiasm of one who understood and loved mules.

Then, finally, they passed to the office.

“Now, I shall be glad to talk with you for hours,” the Mexican hidalgo assured the young engineers.

Dr. Tisco, as though to show that he took no personal interest in the talk, retired to an armchair at the further end of the room.  Nevertheless, the secretary observed carefully all that was said.  Covertly he studied the faces of the young engineers at all times.

“Ask me what you will,” begged Don Luis, as he sank into an easy chair close to the table on which Tom began to arrange his envelopes of specimens taken from the mine.

“First of all, Don Luis,” Tom began, “you spoke of some problems that you wished us to solve in the operation of your mine.”

“Yes, Senor Tomaso.”

“I would like to ask you what the problems are that we are to consider,” Tom announced.

“Did you not see some of the problems before you, while we were going through the mine?” inquired Montez.

“At the risk, Don Luis, of appearing stupid, I must confess that I did not.”

“Ah, well, then we shall come to the problems presently.  You have other questions.  Ask some of them.”

For a moment or two Reade studied what he had written on the various envelopes before him.  Then he picked out two.

“Here, Don Luis,” the young chief engineer went on, “are samples of two lots of ore.  The first is from the pile that we found pried loose when we went into the first tunnel that we visited.  It is rich ore.”