William A. Ulmer claims the "plumes of fire" (218)
are Apollo's contribution to an inherently visionary love. Since they allow the poet his flight toward the stars, but cannot grant him his "one desire," he soon becomes a "dizzy moth," his language temporalizing the lodestar of desire as "Hesper's setting sphere," love's star in its subjection to earthly cycles of day and night. (139)
And Ulmer suggests that the leaf smile--"as a dead leaf's in the owlet light" (221)--
connotates an uncertain fluttering motion, yet unescapably suggests descent as well, the dead leaf's autumn fall to the earth. If Shelley's metaphor of ascent contains a downward spiral, if it turns on antithesis, unable to go up without going down, that is because the object is seeks is a coincidence of difference. (139)
Ulmer, William A. The Rhetoric of Romantic Love. Princeton: Princeton UP, 1990.