ou 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."

"It is good enough ore," Montez replied, with a polite shrug of
the shoulders.

"Now, from the second tunnel that we entered, and where we also
found a pile of loose ore, here is another sample. It is as rich
as the first sample."

"Certainly, Senor Tomaso."

"But in this second tunnel I had a drilling made and a blast fired.
Here," picking up a third envelope and emptying it, "is a sample
of the ore that we saw taken from that blast. If this sample
contains any gold or silver the quantity is so small, evidently,
as to render this kind of ore worthless."

"Yes?" murmured Don Luis, softly. "What is it that you have to say?"

"Why, sir, how does it happen that, right on top of such extra-fine
ore we run upon blank rock at the very next blasting."

"That sometimes happens in _El Sombrero_," Don Luis replied, smoothly,

"How often has it happened?" asked Tom, looking up from the table
and glancing keenly at Don Luis.

Dr. Tisco, though he appeared to be almost asleep, stirred uneasily.

"How often has it happened?" repeated Don Luis. "Oh, perhaps
a dozen times in a few months, taking all the tunnels together."

"How long have these streaks of blank rock been?" insisted Tom
Reade, while Harry wondered at what his chum was driving.

"How long?" echoed Montez, with a shrug of his shoulders. "Oh,
how should I know? Personally I am not interested in such things."

"But have you gone as much as a whole week drilling and blasting
through blank rock?" Tom pressed.

"A week? No; not for two days. Of that I am certain. But why
do you ask all this, Senor Tomaso?"

"In order that I may better understand the nature of the mine,"