“OKAY, THEN,” SAID LOU Graham. “Now we build a Le Clanche cell. Ask Harla does he recognize carbon. A black or light-absorbing element. Carbon is extremely common, it is the basis of life chemistry. It is element number six in the periodic chart. Does Harla know carbon?”
“Harla knows carbon.”
“Now we add zinc. Zinc is a light metal easily extracted from the ore. It is fairly abundant, and it is used by early civilizations for making brass or bronze long before the culture has advanced enough to recognize zinc as an element. Does Harla know zinc?”
“He may,” said Teresa very haltingly. “What happens if Harla gets the wrong metal?”
“Not very much,” said Lou. “Any of the light, fairly plentiful metals that are easily extracted from the ore will suffice. Say tin, magnesium, sodium, cadmium,
