Shelley begins his evening scene with a list of what has stopped and what has started. The sun is down and the swallows are asleep, but the bats are "flitting fast" and the toads creep out of "damp corners". The first stanza gives us dusk as a handover between day creatures and night creatures. The toads are an unusual choice for a poet often thought of as lofty and idealistic. "Slow soft toads" is humble, almost tender, and the sibilance makes the line itself move slowly. Right after this comes the first surprise: the evening breath passes "over the quivering surface of the stream" yet "wakes not one ripple from its summer dream". The water is personified as a sleeper, and the wind is too gentle to disturb it.
The second stanza turns away from that calm. Here the poem becomes a study of dryness and unease: "no dew on the dry grass", no damp under the trees. The wind is "intermitting, dry, and light" and "inconstant", words that stumble through the line as the breeze itself does. It pushes "dust and straws" up and down and whirls them about the pavement of the town. Where the first stanza gave an image of sleep, this one gives small, aimless movement. The poem keeps setting a hushed, dreamy world beside a restless, fidgeting one, and it never explains which is the truer picture of evening.
The third stanza is where the poem seems to be reaching for an idea. The river holds a reflection of the city, "wrinkled" by the water, "Immovably unquiet". That phrase is an oxymoron, and it is the poem's best summary of itself. The image never leaves, yet it never stops shaking. The word "forever" sits at the end of a line, so the sense of permanence hangs there before the next line adds that the image "trembles, but it never fades away". Then the text we have breaks off. The sentence beginning "Go to the…" is left incomplete, so we cannot say what Shelley told the reader to go and look at. The line that follows still gives the point: "You, being changed, will find it then as now." The scene stays constant while the person looking at it changes. That is a quiet, rather moving thought, and the poem leaves it unforced.
The last stanza lifts our eyes from the water to the sky. The sun has sunk into a "chasm", and that chasm is "shut / By darkest barriers of cinereous cloud", with "cinereous" meaning ash-grey. The clouds are "like mountain over mountain huddled", "growing and moving upwards in a crowd". Here the restlessness of the second stanza returns on a huge scale, and the clouds seem alive and crowding. Above them is "a space of watery blue", an image that quietly echoes the stream, and through it "the keen evening star" is shining. Ending on the star gives a small, sharp point of light after all the heaviness below it.
The form is steady. The lines are mostly iambic pentameter, and each stanza rhymes ABABCC: "asleep / creep" and "air / there", then a closing couplet such as "stream / dream". That final couplet gives each stanza a settled, closing click, which suits the theme of calm. Within that order Shelley lets his language wobble. Words like "flitting", "quivering" and "whirled" bring movement into lines that are metrically tidy, so the form holds still while the subject trembles.
What makes the poem worth reading is its restraint. Shelley is often remembered for grand, visionary writing, but here he looks closely at a single evening and trusts small details: toads, straws, a shaky reflection. The central idea, that something can be both unchanging and unquiet, and that we are the ones who change, comes from those details and is never announced as a moral. Even in the incomplete version we have, the poem makes you slow down and look at the world the way the speaker does.