It is six lines, two tercets, and one whole image. In the first, the eagle clasps the crag with crooked hands, alone in lonely lands, close to the sun and ringed by the azure of the sky. In the second, far below, the wrinkled sea crawls, and the eagle — watching it from its «mountain walls» — lets itself fall «like a thunderbolt».
Tennyson packs the whole poem into that last line: the absolute stillness of the five lines before it exists only to make the plunge more sudden. It is a perfect miniature about height, the watching eye, and the instant when force lets go.