pecial towers where they grow
crops by artificial light only. Some of the plants he sketched look
amazingly like wheat, by the way. The name of the town is"--he looked
at his notes--"Yugna. There are some other towns, ten or twelve of
them. Rahn is the nearest, and it's worse off than this one."

"Of course," said Evelyn, smiling. "They use _cuyal_ openly, there!"

"How'd you learn all that?" demanded Tommy.

"Ahnya told me. We made gestures and smiled at each other. We
understood perfectly. She's crazy about her husband, and I--well she
knows I'm going to marry you, so...."

Tommy grunted.

"I suppose she explained with a smile and gestures just how much of a
strain it is, simply keeping the city going?"

"Of course," said Evelyn calmly. "The city's fighting against the
jungle, which grows worse all the time. They used to grow their
foodstuffs in the open fields. Then within the city. Now they use
empty towers and artificial light. I don't know why."

* * * * *

Tommy grunted again.

"This planet's just had, or is having, a change of geologic period,"
he explained, frowning. "The plants people need to live on aren't
adapted to the new climate and new plants fit for food are scarce.
They have to grow food under shelter, now, and their machines take an
abnormal amount of supervision--I don't know why. The air-conditions
for the food plants; the machines that fight back the jungle creepers
which thrive in the new climate and try to crawl into the city to
smother it; the power machines; the clothing machines--a million
machines have to be kept going to keep back the jungle and fight off
starvation and just hold on doggedly to the bare fact of civilization.
And they're short-handed. The law of diminishing returns seems to
operate. They're trying to maintain a civilization higher than their
environment will support. They work until they're ready to drop, just
to stay in the same place. And the monotony and the strain makes some
of them take to _cuyal_ for relief."

He surveyed the city from the oval window, frowning in thought.

"It's a drug which grows wild," he added slowly. "It peps them up. It
makes the monotony and the weariness bearable. And then, suddenly,
they break. They hate the machines and the city and everything they
ever knew or did. It's a sort of delayed-action psychosis which goes
off with a bang. Some of them go amuck in the city, using their
belt-weapons until t