Standing before a frozen-looking lake, the speaker watches water and sky blur into one cold, silent view. The opening is almost like a painting: flat purplish-blue water, a pale sky, and a horizon that seems to curve with the earth itself. The two elements "glide" together, and the speaker treats them as a single metaphor for something timeless.
Then the poem turns inward. The speaker's unconscious "simmers," and feelings and thoughts drift outward onto the horizon, as if the landscape were a screen for the mind. Inner and outer worlds start to merge, and time and distance move together.
By the end, the speaker seems to leave the body behind, rushing through frigid air toward the edge of the world while the sky falls. The mood is hushed, vast, and a little dizzying: calm on the surface, but charged with the pull of something much larger than one person. It feels less like sadness than like surrender.