The "red and green will-o'-the-wisps" in the first sentence
of Circe seem to be electric traffic lights telling
tram cars whether to stop or go, but Joyce's language makes
them heralds to a place of witchery. Will-o'-the-wisps are
ghostly lights that hover over swamps at night, constantly
receding, drawing travelers into unseen dangers. In Goethe's Faust,
one leads to a Witches' Sabbath.
In Hades, Bloom thinks of them in practical terms,
as perhaps caused by off-gassing: "Will o' the wisp.
Gas of graves." But Gifford observes that 'In
folklore, the will-o'-the-wisp is considered ominous, often
thought to be a soul rejected by hell and condemned to carry
its own hellcoal on its wanderings." In the 21st scene of Part
1 of Faust, he notes, a will-o'-the-wisp "lights the
way up the 'magic-mad' mountain as Faust and Mephistopheles
make their way toward the Walpurgisnacht (Witches' Sabbath)
assembly."
Walpurga's Night, celebrated in Germanic countries on the
night beginning May 1, is named after an early Christian
saint. But German literature, in the centuries leading up to
Goethe, depicted it as a night when witches and sorcerers
convened, often on the boulders of a mountain called the
Brocken, to commune with devils, practice orgiastic rites, and
celebrate the coming of spring. People in Germany,
Scandinavia, the Netherlands, and lands that were once part of
Prussia still observe the holiday with eating, drinking, huge
bonfires, and (sometimes) witch paraphernalia, in a spirit of
carnival celebration.
It is probably significant that, in that 21st scene of the
first part of Faust, Mephistopheles seeks to divert
Faust's thoughts from the tragic fate of his lover Gretchen by
introducing him to a beautiful and quite naked young witch,
but Faust is pulled away from this sexual temptation by a
vision of Gretchen. In Circe Bloom follows Stephen
through the streets of Monto into a house of ill repute, and
all the available female flesh on display turns Bloom's
thoughts to Molly and the sexual preoccupations that
complicate his relation with her.