a feverish joy
This oxymoronic construction calls attention to itself in ominous ways.
It at once reminds the literate reader of the "fearful joy" that the
youths momentarily "snatch" on their school playing field in Thomas Gray's
"Ode on a Distant Prospect of Eton College" (line 40) and recalls the anxiety-ridden
states of fever that have furnished a recurrent counterpoint to Victor's
experiences with the Creature (see 1.3.8, 1.4.7).