out where the rest stand," said Ken. "How about it, you guys?"

"I'll go for it," said Ted, "as long as we aren't out to prove a medieval superstition."

One by one, the others nodded agreement. Joe Walton said intensely, "We'll find out whether it's superstition or not! There's no other possible cause, and we'll prove it before we're through."

Ken smiled and waved him down. "We're working on a hypothesis only. Anyway, here's what I have to suggest by way of procedure: Since the tail of the comet is so rarefied, there aren't many molecules of it in the atmosphere of this entire valley. I don't know just what the mathematical chances of getting a measurable sample are. Maybe you can work out some figures on it, Dave. We'll have to handle an enormous volume of air, so let's get a blower as large as we can get our hands on and funnel the air through some electrically charged filters. We can wash down these filters with a solvent of some kind periodically and distill whatever has collected on them."

"You won't get enough to fill the left eye of a virus suffering from arrested development," said Ted.

"We'll find out when we get set up," said Ken. "My father has agreed to give us access to the electron microscope at the college. Maybe we can use their new mass spectrograph to help analyze whatever we collect."

"If we knew how to use a mass spectrograph," said Ted.

"He's offered to let one of the teaching fellows help us."

"What will all this prove, even if we do find something?" Dave asked. "You'll get all kinds of lines from a spectrogram of atmospheric dust. So what?"

"If we should get some lines that we can't identify, and if we should get those same lines from metallic specimens taken from the disabled engines, we would have evidence of the presence of a new factor. Then we could proceed with a determination of what effect, if any, this factor has on the engines."

Ken looked around the group once more. "Any comments, suggestions, arguments? There being none, we'll consider the project approved, and get to work this afternoon."

As they left to go to their first classes, Ted shook his head gloomily. "Man, you don't know what you're biting off! All we've done so far is build a few ham radios, a telescope, and some Geiger counters. You're 

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