* Movement and Energy: "Foamy flake" suggests the movement and energy of the brook. The brook is not still and stagnant, but constantly in motion, churning up the water and creating these "flakes" of foam.
* Lightness and Ephemerality: The word "flake" evokes a sense of lightness and ephemerality. The foam is temporary, constantly changing with the flow of the water. This relates to the fleeting nature of life and the cyclical nature of time.
* Whimsical Nature: The image of "foamy flake" adds a whimsical touch to the poem, reminding us of the brook's playful and lively nature. It contrasts with the more somber and introspective tone of the poem's later lines.
Overall, "foamy flake" is a simple but powerful image that captures the dynamic and fleeting nature of the brook, serving as a metaphor for the passage of time and the impermanence of life.