wn more
than a few himself.

"Nansen bottles in the next tent, professor," Rick said. "There must be
something to this business of getting stuff out of the lake. But golly,
you don't get heavy water out of natural water, do you?"

"I don't know," Zircon said. "There is only one precedent I can think
of. Have you ever heard of Lake Baikal?"

Neither boy had.

"It's a very large lake in Siberia, just above Mongolia," the scientist
told them. "It is also very deep. A few years ago, before the Iron
Curtain closed down, word came out of Russia that some scientists had
succeeded in getting heavy water samples out of Baikal. That is the only
precedent that I know.

"It is true," he continued, "that heavy water has a tendency to sink.
Naturally enough, since it is heavier. But for enough to form on the
bottom of a body of water, there would have to be great depth and
complete calm. Any current would stir the water up and the heavy water
would merge with the normal once more."

"In other words, you need a lake like this one," Rick concluded.

"I must admit it fits the requirements," Zircon agreed. "And we've seen
no sign of an industrial plant. These caverns certainly would be no
place for one."

"We can soon tell," Scotty suggested. "Let's take a sample. When we get
out, you can test it."

"Quite right," Zircon said. "And let's be quick about it."

It didn't take long to discover the reason for the odd little derricks
on the barge. Each was equipped with a pulley and a reel of wire.
Obviously, it was from here that the Nansen bottles were lowered.

While Chahda and Scotty remained on shore, Zircon and Rick pushed the
barge out into the lake. Rick got a Nansen bottle ready.

The bottle was made of metal, each end equipped with a spring cap. The
bottle was lowered on a wire with the ends open, permitting water to
flow through it freely. When it reached the desired depth, a metal
weight called a "messenger" was attached to the wire and dropped. The
weight of the messenger released devices that closed the caps, thus
trapping the water sample inside. A brass spigot on the side permitted
the sample to be taken out easily when the bottle was hauled up again.

They had brought four bottles from Long Shadow's stores. The first one
was lowered to the very bottom, and it took a long time getting there.
The reel of wire with which the barge was equipped ran out and out until
a full seven hundred feet of it had disappeared i