ire Movie Theater, and the Rainbow
Skating Rink.

Ken wished their efforts at the college laboratory were going half as
well. As the days passed, it seemed they were getting nowhere. The first
effort to identify any foreign substance in the atmospheric dust was a
failure. Calculations showed they had probably not allowed sufficient
time to sample a large enough volume of air.

It was getting increasingly difficult to keep the blower system going.
All of their original supply of small engines had broken down. The town
had been scoured for replacements. These, too, were failing.

In the metallurgical department hundreds of tests had been run on
samples taken from frozen engines. The photomicrographs all showed a
uniform peculiarity, which the scientists could not explain. Embedded in
the crystalline structure of the metal were what appeared to be some
kind of foreign, amorphous particles which were concentrated near the
line of union of the two parts.

Berkeley and Pasadena confirmed these results with their own tests.
There was almost unanimous belief that it was in no way connected with
the comet. Ken stood almost alone in his dogged conviction that the
Earth's presence in the tail of the comet could be responsible for the
catastrophe.

Another theory that was gaining increasing acceptance was that this
foreign substance was an unexpected by-product of the hydrogen and
atomic bomb testing that had been going on for so many years. Ken was
forced to admit the possibility of this, inasmuch as radiation products
were scattered heavily now throughout the Earth's atmosphere. Both
Russia and Britain had conducted extensive tests just before the
breakdowns began occurring.

The members of the science club had been allowed to retain complete
control of the air-sampling program. They washed the filters carefully
at intervals and distilled the solvent to recover the precious residue
of dust.

As the small quantity of this grew after another week of collecting, it
was treated to remove the ordinary carbon particles and accumulated
pollens. When this was done there was very little remaining, but that
little something might be ordinary dust carried into the atmosphere from
the surface of the Earth. Or it might be out of the tail of the comet.
Dust from the stars.

By now, Ken and his companions had learned the use of the electron
microscope and how to prepare specimens for it. When their samples of
dust had become sufficie