Page 535. " Soon they through dim, bewildering mediums saw her sidelong fading phantom, as in the gaseous Fata Morgana "

A Fata Morgana is an unusual and complex form of mirage, a form of superior mirage which is seen in a narrow band right above the horizon. It is an Italian phrase derived from the vulgar Latin for "fairy" and the Arthurian sorceress Morgan le Fay.

Page 536. " at the axis of that slowly wheeling circle, like another Ixion I did revolve. "

In Greek mythology, Zeus punished King Ixion by binding him to a spinning, fiery wheel for eternity.