How does Dickinson use devices such as sound, rhythm, meter, and rhyme to further the meaning of the poem?
Dickinson’s basic metrical structure in this poem, and one she uses often, is the song-form of the ballad, in which the lines are made up of alternating “threes” and “fours” in terms of rhythm. For example: “I felt | a Fune | ral in | my Brain” followed by “And mourn | ers to | and fro.” Notice, however, that from the very first line Dickinson complicates/disrupts this pattern with the comma placed in the middle of that line, thus introducing a caesura that causes us to, instead, read the line more like “I felt | a Funeral, | in my Brain.” Thus the “rhythm” of the line—the pattern of beats we follow in actually voicing it—cuts against its “meter.” In this case, the effect is that we linger over the word “Funeral,” reading it as three fully enunciated syllables, as opposed to compressing it to two in response to the meter like many readers would if the comma were not there. “Funeral” thus takes on an especially solemn, sonorously formal tone, which clashes harshly with the hard consonants and nasal “a” sound of “Brain.” Thus we feel, sharply, the dissonance, the psychic turmoil this “Funeral” (however we understand it) is inflicting on the speaker. This is just one example, but in it you can see how Dickinson uses the dynamic relationship between sound, meter, rhythm, to carefully control the tone, and thus the sense, of her lines.
What does it mean when the speaker says she “finished knowing - then -”?
The first thing to notice about this line is the strangeness of the use of “knowing” here. Though the grammar isn’t at all irregular, “knowing” is not, typically, something we think of as able to be “finished.” You can “finish learning,” you can “forget” something you knew, or suddenly find yourself without knowledge you generally have (“suddenly I stopped knowing how to speak”). This tells us something significant about what Dickinson is saying about the concept of “knowledge” in the poem as a whole. "Knowing" is, here, best described as a way of relating to the world, and the use of “then” signals that the lyric voice is speaking from this place of being finished knowing (as in “I’m finished with [i.e., done with] praying”). This might be Dickinson’s way of suggesting that the intensity of some experiences pushes us outside the boundaries of knowledge, that at some point “knowing,” or trying to know, becomes a constraint. Perhaps poetry, or at least this poem, begins where “knowing” ends.