hat quizzical reply, "to show your nerve."

"Unless there is some good reason other than that, there are
plenty of ways to show our nerve without lowering ourselves to
the bottom of an old mine."

"There is a good reason," was the reply.

"Then tell us. If it is good, there can be no objection."

"The object of this descent," said the stranger calmly, "is to
see if we cannot solve the mystery of the abandonment of the
mine."

"Have you ever been down?" asked Billie.

"Often."

"There is no foul gas at the bottom?"

"Not now, as you may see by the condition of Ambrosio, who has
been clear to the bottom."

"Then I am willing to be the first to descend; but first I must
know more about you than I do."

"What difference does that make? You will have three friends here
with me. They are all armed and I can see they know how to use
their weapons. I cannot possibly harm you. I will be the third to
descend. I assure you that the descent and the ascent are
comparatively easy for athletic young chaps, as the sides of the
shaft are very uneven. By the aid of this rope you can come up
almost as easily as you would climb a ladder. The adventure is
well worth your while."

"And you won't tell us who you are?"

"I have already told you. I am an American soldier of fortune. My
name, if that means anything to you, is Francis Strong, and I
have assumed this character of a mountebank solely for the
purpose of going about the country without being molested. What I
hope to do, is of no interest to any one but myself."

It was a straightforward statement and the boys saw no reason to
doubt its truthfulness.

"All right, then," exclaimed Billie. "Here goes!"

He grasped the rope and lowered himself over the side. It was as
Strong had said and in a very few minutes he found himself at the
bottom. He could see nothing except the dim light at the mouth of
the shaft.

Giving the rope a vigorous shake, as had been agreed upon, he saw
another figure begin to descend, and in a short time Pedro stood
beside him. Strong was next to descend, then came Ambrosio, and
after him Adrian and Donald in the order named--Donald having
determined to be the last, that he might be sure that everything
was safe above ground.

"I should have given you this," was Strong's first remark upon
alighting at Billie's side, and he drew from his pocket an
electric torch. "But it slipped my mind."

"We all have them in our trunk in the City of Mexic