Night-time and dusk were popular subjects among these artists. They portrayed darkness as a kind of frontier zone which turned the day-to-day world into something mysterious and even frightening. The softness of dusk wraps the world in a soft blanket and generates a sense of mystery.
This is expressed equally in a piano Nocturne by Romantic composer Frédéric Chopin, a poem by Finnish poet Eino Leino, and many late 19th century landscapes. The Midnight Sun of the far north was felt to be particularly magical.