popping out like marbles. He was looking at the ceiling."

I thought for a moment.

"Then it is not a gem?"

He shrugged his shoulders. "Not if I'm a jeweller. Whoever heard
of a stone without weight? It has no gravity, that is, apparently.
I doubt whether it is a substance. I don't know what it is."

It was puzzling. I would have given a good deal just then for a
few words with Dr. Holcomb. The man, Kennedy, had kept it in his
pocket. How had he held it a prisoner? The professor had use for
it in some scientific work! No wonder! Certainly it was not a
jewel. What could it be? It was solid. It was lighter than air.
Could it be a substance? If not; what is it?

"What would you advise?"

In answer the jeweller reached for the telephone. He gave a
number.

"Hello. Say, is Ed there? This is Phil. Tell him to step to the
phone. Hello! Say, Ed, I want you to come over on the jump.
Something to show you. Too busy! No, you're not. Not for this. I'm
going to teach you some chemistry. No; this is serious. What is
it? I don't know. What's lighter than air? Lots of things? Oh, I
know. But what solid? That's why I'm asking. Come over. All right.
At once."