"Upon the brimming water among the stones..."
See in text (The Wild Swans at Coole)
Yeats employs an interesting metrical scheme. In each stanza, the first four lines follow a pattern of alternating tetrameter and trimeter—four beats and three beats—a classic song-like scheme. The fifth line, however, is in pentameter, a five-beat line. This causes a noticeable pause before the stanza ends in a line of familiar trimeter. The pause is fitting with one of the the poem’s themes: the desire to stop and appreciate the world while there is still time, before the swans fly away.