His misfortune was that he loved youth — he was weak to it, it kindled him. If there was one eager eye, one doubting, critical mind, one lively curiosity in a whole lecture-room full of commonplace boys and girls, he was its servant. That ardour could command him. It hadn't worn out with years, this responsiveness, any more than the magnetic currents wear out; it had nothing to do with Time.

Book I, Ch. 1 - The Professor's House (1925)