Tennyson's The Brook is a mid-length poem written in the form of a dramatic monologue. (Mid-length by nineteenth century standards: it is around 200 lines all told). The speaker seems to be a young woman who is remembering her lover who has left to travel abroad (a common theme with Tennyson).
The poem intersperses lyric episodes in its blank verse narrative (another favourite technique with Tennyson) and has a wide range of poetic devices, including apostrophe (talking to an inanimate object as if it were a person):