shaft and I'll take the other. Feel along with your hands for anything
like a door or an opening. I think we've passed them."

Without another word, Astro turned around and headed back, feeling along
the tunnel wall.

It did not take the two cadets long to discover what they were looking
for. A heavy wooden door was set flush with the side of the tunnel. And
when Tom pressed his ear to it, he could hear the roaring sound
throbbing heavily inside.

"See if you can open it, Astro," said Tom. "But take it easy."

Astro felt along the side of the door until he found a wooden latch and
he lifted it gently. The door swung back, as if pushed, as a powerful
draft caught it from the other side. The roar was now deafening.

Tom stepped inside cautiously, followed by Astro. They found themselves
on a small balcony overlooking a huge subterranean room. In the room
they saw Quent Miles and Charles Brett bending over a table on which
were several delicate electronic instruments. Tom and Astro recognized
them immediately as testing machinery for radioactivity, much more
advanced and sensitive than the ordinary Geiger counter. Around the two
men was ample evidence of Astro's original assumption that they were
digging into a hot vein of uranium pitchblende. To one side of the room,
lead sheets lined a rough boxlike structure that Astro and Tom guessed
was covering for the radioactive vein. Against the wall lay the
lead-lined suits used by the miners. Further to one side, Tom saw a
huge open pipe. He nudged Astro.