es, but, in the meantime, no one really seems to have a good
answer.

"In connection with the comet, however, from widely scattered areas
comes the report that people are even blaming these engine failures on
our poor, old comet. In the Middle Ages they blamed comets for
everything from soured cream to fallen kingdoms. Maybe this modern age
isn't so different, after all. At any rate, this comet will no doubt be
happy to get back into open space, where there are no Earthmen to blame
it for all their accidents and shortcomings!"

Ken switched off the radio and lay back on the pillow. That was a real
choice one--blaming the comet for car breakdowns! Page Granny Wicks!

The breakdowns were curious, however. There was no good reason why there
should be a sudden rash of them. He wondered if they had actually
occurred, or if the story was just the work of some reporter trying to
make something out of his own inability to get into a couple of garages
that were swamped by the usual weekend rush. This was most likely the
case.

However it didn't explain why his own car had suddenly conked out, Ken
thought irritably. He'd have to get it over to Art Matthews' garage as
soon as school was out.

At school that morning there was little talk of anything but the comet.
After physics class, Ken was met by Joe Walton and three other members
of the science club, of which Ken was president.

"We want a special meeting," said Joe. "We've just had the most
brilliant brainstorm of our brief careers."

"It had better be more brilliant than the last one," said Ken. "That
drained the club treasury of its last peso."

"I was watching the comet last night, and I began to smell the dust of
its tail as the Earth moved into it...."

"You must have been smelling something a lot more powerful than comet
dust."

"I said to myself--why don't we collect some of that stuff and bottle it
and see what it's made of? What do you think?" Joe asked eagerly.

Ken scowled. "Just how many molecules of material from the comet's tail
do you think there are in the atmosphere over Mayfield right now?"

"How do I know? Six--maybe eight."

Ken laughed. "You're crazy, anyway. What have you got in mind?"

"I'm not sure," Joe answered seriously. "We know the comet's tail is so
rarefied that it resembles a pretty fair vacuum, but it _is_ composed of
something. As it mixes with the atmosphere we ought to be able to
determine the changing makeup of the air and