The Protector of the People celebrating the union of the People and the lawful society, a union thought "lost."
Though "the night of ages" seems merely the narrator's figure of speech, we have a good idea of what night is actually meant. Nostromo was "lost" to society on the same night that Giorgio's grief began -- the long night of Separation that lasted from Chapter 2-6 to Chapter 3-3. It was a night of "ages" in that it marked the turn from Separatism to Unionism (the cyclical political poles), and more profoundly because of the People's allegorical breach with society.