How does Pat Frank use imagery in Alas, Babylon?

Imagery:

"'Peewee may be a mouse aboard ship, but he's a tiger in a Tiger. If I sent him up with orders to shoot down the moon, he'd try.'"

"The end of the corn and exhaustion of the citrus crop had been inevitable. Armadillos in the yams was bad luck, but bearable. But without fish and salt their survival was in doubt."