Is Mr. Rossetti acquainted with the proleptic use of adjectives and participles?
"Hopeless is here used in a proleptic or anticipatory way" (Hales).
The adjective is redundant and "proleptic," as the bird must be "enthralled" before it can be called "captive."
The italics are ours, but the proleptic idea is a happy invention of the author himself.
proleptic: 'The flame-tips would become bright and furnish a good omen for your prayer'.
1570s, "the taking of something anticipated as already done or existing," from Latin prolepsis, from Greek prolepsis "an anticipating," literally "a taking beforehand," from prolambanein "to take before," from pro- "before" (see pro-) + lambanein "to take" (see analemma). Related: Proleptic; proleptical; proleptically.
prolepsis pro·lep·sis (prō-lěp'sĭs)
n. pro·lep·ses (-sēz)
The return of paroxysms of a recurrent disease at intervals that progressively become shorter.