“Optical density! The whole subject is a network of riddles⁠—a network with solutions glimmering elusively through. And being but two-and-twenty and full of enthusiasm, I said, ‘I will devote my life to this. This is worthwhile.’ You know what fools we are at two-and-twenty?”

“Fools then or fools now,” said Kemp.

“As though knowing could be any satisfaction to a man!