I'm not afraid of their falling down on the
job. But it's a big one. I'll tell Zircon this when he comes, but you
can be thinking it over in the meantime. You're to find out who is
bringing heavy water to the Asia coast and what they're doing with it.
You're to find out where it comes from, and why it is being made. You're
to get samples and send them back here. And most important of all,
you're to locate and pinpoint for us any industrial plants you find."

Scotty scratched his head. "Fine. Only let's get back to the beginning.
What is heavy water? And why are you so excited about it?"

"I don't know, either," Barby added.

Hartson Brant looked at his son. "You do, don't you, Rick?"

"I know what it is, but I don't know why it's so important to Steve,"
Rick said. He had read a great deal about heavy water in studying
elementary physics. It had many uses in physics experiments.

"Let's see how much you know," Steve directed. "Sound off."

Rick searched his memory, trying to marshal all the facts he knew.
"Well," he began, "ordinary water is composed of oxygen and hydrogen. In
every water molecule there are two atoms of hydrogen and one of oxygen.
The important part, for what we're talking about, are the hydrogen
atoms. Hydrogen is the lightest element, and it has the simplest atom.
There's just one proton and one electron."

He looked at his father, waiting for a nod to tell him he was on the
right track. When the scientist nodded approval, he went on.

"That kind of hydrogen atom has a mass of one, as the scientists say.
But there are other kinds of hydrogen atoms, and they are pretty rare,
called isotopes. An isotope is just a different variety of the ordinary
kind of atom in each element. The thing that makes it different is a
change in the nucleus. Well, hydrogen has two isotopes. One kind, which
has a mass of two, is found in nature. It is called deuterium. Its
nucleus is called a deuteron. Another kind, which can be made in a
nuclear reactor, is called tritium. A little of it is found naturally
but not enough to count for much."

He took a deep breath. "I hope I know what I'm talking about."

"You're doing fine," Hartson Brant said. "Go on."

"All right. Well, heavy water is made of one atom of oxygen plus two
atoms of deuterium, which is the first isotope of hydrogen. In
chemistry, there's no difference in the way heavy water acts. You can
even drink it. In fact, people do drink it every day, because