The Wild Swans at Coole
How we cite our quotes:
The trees are in their autumn beauty,
The woodland paths are dry,
Under the October twilight the water
Mirrors a still sky; (1-4)
The language of the first four lines anticipates or foreshadows the sad tone that becomes more prominent as the poem proceeds. "October," "twilight," and "autumn" all describe literal things (a month, a season, a time of day) that are associated with darkness and gloom. As the poem proceeds, the speaker describes a more emotional kind of gloom.
I have looked upon those brilliant creatures,
And now my heart is sore. (13-14)
The speaker offers an interesting scenario here: after he looks on something "brilliant," he feels sad. It is probably because he realizes that he's changed, and so has the world, while these magnificent animals have not. The swans are still "brilliant," but life isn't so brilliant (people kill each other, people die, bad things happen).
All's changed since I, hearing at twilight,
The first time on this shore,
The bell-beat of their wings above my head,
Trod with a lighter tread. (15-18)
We get the sense that things are changed, and not for the better. It is interesting that the speaker separates the word "I" from "trod with a lighter tread." It is as if the speaker wants to avoid talking about how things used to be different (it makes him sad).