"We received some last shipment. There's hardly any left. Space knows when we'll get more—if ever."
A civilization falling. Nuclear power forgotten. Science fading into mythology—until the Foundation had stepped in. (III.1.10)
"I started that way at first because the barbarians looked upon our science as a sort of magical sorcery, and it was easiest to get them to accept it on that basis." (III.1.68)