traveled
through the tunnel at a good speed.

"We've been walking quite a while," Rick said finally. "How long do you
suppose this shaft is?"

Scotty thought it over. "It can't be any longer than the hill is wide,
because we're traveling through the hill. It must be about the same
length as the lower tunnel."

"Why two tunnels?" Rick asked. "I doubt that there were two veins of
ore."

Scotty reminded him of the good ore they had seen in the ceiling of the
lower tunnel. "There might have been just one vein, about two tunnels
high. They were limited to pick and shovel for tools in those days,
remember, maybe with a little powder for blasting. It would have been
more convenient to work within range of tools like shovel and pick. So
the ceiling is as high as a man with a pick can reach, and as wide as
the ore vein was wide. That's a little confused, but I'm sure you follow
me."

"Sounds reasonable," Rick agreed. "Only this tunnel can't go on much
farther, or we'll be in the middle of the picnic--Hey! Scotty, take a
look!"

Ahead in the tunnel was a box, and on the box was metal that reflected
the flashlight's beam. In a second the boys stood over it.

Rick's heart pounded rapidly. Here was the proof. Here was Missing Fact
Number One. Here was verification of at least part of their speculation.

An eight-millimeter motion-picture projector!

Rick motioned to the front of the machine with a trembling hand. "Look,
there's a film in place, and it's a continuous loop. Once it's threaded
it will repeat over and over unless cut off."

Scotty was probing into the box. "Batteries. Two of them, twelve volts
each. And I'll bet the motor in the projector is designed to operate on
twelve volts. There's even a hydrometer for testing the batteries."

Rick took a look. As Scotty had said, there were two automobile
batteries, their cables running up into the projector.

"Simple enough," he commented. "Let's see what's on the film."

He opened the film gate gingerly and removed the film from the
sprockets. Then, without disengaging the spindles, he put the flashlight
behind it and bent close. The eight-millimeter frames were pretty small,
but not so small that he and Scotty couldn't make out the image.

The scene had been shot against a black background, that was clear. Only
the central figure was illuminated, the figure of a Union cavalry
officer.

"Meet the Blue Ghost," Rick said happily.

"Delighted," Scotty said emph