Figure of speech. Ned Lambert's reading of Dan's
Dawson's fulsome praises of Irish streams, seas, riverbanks,
sunlight, trees, mountains, plains, pasturelands, and twilight
draws an exasperated protest: "— The moon, professor
MacHugh said. He forgot Hamlet." But Lambert reads on:
"— That mantles the vista far and wide and wait till
the glowing orb of the moon shines forth to
irradiate her silver effulgence..." Rhetorical theory
has a name for this kind of anticipatory mention of something
not yet discussed: prolepsis.
Greek for "preconception" or "anticipation" (pro =
before + lambanein = to take), prolepsis refers to an
orator's 1) raising and answering potential objections to his
argument before opponents have the opportunity to voice them,
2) introducing a descriptive word before mentioning the
circumstance in which it will prove applicable, or 3)
referring to a future event as if it has already occurred.
Some rhetoricians used a similar term, procatalepsis, for the
Both Gilbert and Seidman identify Professor MacHugh's reference to "the moon" as prolepsis, because it anticipates the sentence of Dawson's speech that comes after. I see no reason to disagree with them. Although Joyce is not doing exactly what an orator would––instead of a single speaker introducing a word with the intention of using it soon after, he has one character introduce a word that he does not know another character will soon use––the second of the three kinds of prolepsis is pretty clearly at work here. And the device allows Joyce to produce a wonderfully comic effect:
MacHugh: Jaysus, and what about the moon, then? Couldn't he mention that, while he was at it?
Lambert: Wait till the glowing orb of the moon shines forth....
Dedalus: O Christ! Shite and onions! That'll do, Ned. Life is too short.