"Upon Julia's Clothes" is full of subtle repetitions of sounds. You might not notice them at first, but the more you read it aloud, the more those repetitions will make themselves known. Let's take a look:
Short A sounds:
"Whenas" (1), "liquefaction" (3), "cast" (4)
Note that the repeated short A sound in "cast" in line 4 helps create a bridge between the two stanzas. We get used to hearing the short A in the first stanza, so we're looking for it in the second. But it soon gives way to…
Long A sounds:
"brave vibration" (5), "way" (5), "taketh" (6)
Those long A's really slow us down as we read the second stanza. Like the speaker, we get to revel in the beautiful imagery of Julia's stunning outfit.
Of course we can't forget the E's, either.
Short E sounds:
"Whenas" (1), "Then, then" (2), "Next" (4)
Long E sounds:
"methinks" (2), "sweetly" (2), "see" (4), "free" (5), "me" (6)
With these E sounds, we get a similar pattern to the A sounds. The shorter E's give way to the long E end rhymes of the second stanza, drawing out the reading, and the impact of Julia's getup.
The second stanza slows down our reading in other ways, too. In line 4, the repetition of the long I sounds "I," "mine," and "eyes" makes us take a beat as we plow through the plunky sounds. But then, the poem speeds up again, in its final line: "O how that glittering taketh me!" There are no similar vowel sounds or internal rhymes in that last line. Each syllable is its own sound, and we bounce from syllable to syllable, enjoying the glittering image of Julia's flowing gown. You can't help but feel just as lightheaded and swooning as the speaker does when you prance your way down that line.