Summary
The speaker references dusk and morning. Then she compares summer to a valued guest who carries herself with grace. She notes the various types of mechanical assistance summer does not have to aid in her departure, including a "wing" or "keel." Finally, she describes summer's "light escape" towards "the beautiful."
Analysis
The latter portion of the poem marks an interesting shift. Dickinson's language becomes at once more abstract and more personal. The speaker personifies summer and describes "her" various admirable qualities. However, at the poem's end, she depicts summer's exit in a way that is almost impossible to actually visualize. This ending is also a surprising reversal from the opening. Whereas before, the speaker seemed to focus on her own negative response to summer's absence, here she seems drawn in by the aesthetic beauty of its departure.
The middle of the poem starts with two more depictions of transitional times of the day: sunset ("The Dusk drew earlier in —") and sunrise ("The Morning foreign shone —"). The dashes in these lines serve to isolate these images. They are sectioned off as individual moments before the speaker transitions into a different subject matter. These two scenes seem to complete the pair of preceding afternoon and twilight moments. They show more instances of natural time passing unobserved. The speaker shifts gears and offers a humanizing portrait of summer as a guest about to depart an event ("A courteous, yet harrowing Grace, / As Guest, that would be gone —), showing her as someone who will be missed as soon as she leaves. This brief depiction imagines summer as a beloved figure, whose absence will not be taken lightly. It is also plain, given the use of the words "courteous" and "grace," that while summer is making "her" exit, she will do so politely and quietly. This complements all of the preceding thematic material in the poem. Summer is shown as someone who leaves softly and whose departure is cause for sadness. This fulfills the theme with which the poem opens: summer's "imperceptible" end.
Structurally, the poem's lack of stanzas makes a great deal of sense. Unlike some of Dickinson's other work, this poem does not divide quite so neatly into sections. While the first half roughly follows a four-line schematic, this latter half works very differently. The first two images stand on their own. Then there is a two-line description of summer as a gracious and courteous guest. From there, as indicated by the dashes, the final four lines are relatively unbroken: they follow one thought in the context of a single scene, namely, the end of summer.
The final four lines show summer's end. The speaker describes how "without a Wing / Or service of a Keel" summer makes "her" exit. These references are meant to be in opposition to each other. A keel is a structural element at the bottom of a boat that helps it stay upright and stable in the water. This stands in clear contrast to a wing, which would allow her to fly. The speaker mentions these very different tools to highlight the unfussy quality of summer's departure. The final two lines ("Our Summer made her light escape / Into the Beautiful.") are almost sublime in what they attempt to depict. The phrase "light escape" lines up perfectly with the earlier descriptions of the various times of day and their relative amounts of light. The use of the possessive "our" shows a level of familiarity and warmth on the part of the speaker. In enjoying summertime's presence, the speaker has taken on a feeling of kinship, bordering on possessiveness. This usage connects with her earlier complementary portrait of summer as her guest. To the end, she considers summer to be a desired companion. Dickinson uses the abstract phrase "into the beautiful" to imagine summer's unseen exit. As emphasized repeatedly in the poem, this moment of transition is never observed. As such she reaches for another sort of language, beyond the concrete details she has been using in the other scenes, to try and capture this moment. This phrase also works to show the transition as "beautiful." While the speaker may be disappointed about summer coming to a close, she cannot help but admire the grace of the moment.
The poem as a whole is wrestling with ideas about nature, time, and loss. Dickinson is interested in using natural cycles to highlight how these transitional moments are invisible, and yet the absences they leave are intense and permanent. The speaker's attempts to hold onto summer demonstrate a kind of universal to stop or slow time. In this poem, Dickinson seems to be expanding on the adage that people only appreciate what they have when it is gone. While Dickinson is discussing the close of a beautiful summer, she is also talking about the various sorts of change and loss that time creates.
