he electron microscope?"

"I wouldn't have time to run any such tests for several days. If you are
intent on pursuing this thing, however, I'll tell you what I'll do. You
and your science club friends can come up and use the equipment
yourselves."

"We don't know how!"

"I'll arrange for one of the teaching fellows to show you how to prepare
metallic samples and operate the electron microscope."

Ken's eyes lighted. "Gee, that would be great if you would do that, Dad!
Will you, really?"

"Come around after school today. I'll see that someone is there to help
you."

Art Matthews was disappointed when Ken called and said none of the
science club members would be around that afternoon. He couldn't keep
from showing in his voice that he felt they were letting him down.

"It's not any use trying to get those engines running," Ken said. "The
pistons would never come out of most of them without being drilled out.
We're not equipped for that. Even if we got things loosened up and
running again, what would keep the same thing from happening again?
That's what we've got to find out."

Art was unable to accept this point of view. He held a bewildered but
insistent belief that something ought to be done about the mounting pile
of disabled cars outside his garage. "We can get some of them going,
Ken. You fellows have got to lend a hand. I can't tackle it without
help."

"I'm sorry," Ken said. "We're convinced there's got to be another way to
get at the problem."

"All right. You guys do whatever you figure you've got to do. I can
probably round up some other help."

Ken hung up, wishing he had been able to make Art understand, but the
mechanic would probably be the last person in Mayfield to accept that
the comet could have any possible connection with the frozen engines.

As Ken walked to school that morning he estimated that at least 25
percent of the cars in Mayfield must be out of commission. Some of the
men in his neighborhood were in their driveways futilely punching their
starters while their engines moaned protestingly or refused to turn over
at all. Others were peering under the hoods, shaking their heads, and
calling across the yards to their neighbors.

In the street, some cars were lugging with great difficulty, but others
moved swiftly along without any evidence of trouble. Ken wondered how
there could be such a difference, and if some might prove immune, so to
speak, to the effect.

He had called a m