Yeats wrote “The Second Coming” in blank verse, which is unrhymed iambic pentameter. (Recall that lines of iambic pentameter consist of five iambs, which have one unstressed syllable followed by a stressed syllable, as in the word “en-joy’d.”) By the twentieth century, blank verse had long been the meter of choice for English-language poets working on serious subjects. Five-foot lines were considered ideal because they approximated the cadence of natural speech and hence avoided the sing-song quality associated with tetrameter. Christopher Marlowe had been the first to popularize the use of blank verse in English poetry in the late sixteenth century. Shakespeare then masterfully showcased the versatility of the meter in his plays. Later still, John Milton used blank verse for his great epic, Paradise Lost (1667). In choosing blank verse, Yeats therefore adopted a metrical form with a renowned historical pedigree. Yet instead of employing blank verse to write a poem in an epic mode, he uses it for a shockingly apocalyptic poem in which he reflects on the collapse of the current world order.

Yeats arguably reflects this projected collapse through his often rather loose application of iambic rhythm. The meter is loose from the opening line:

     Turn-ing / and turn- / ing in / the wid- / en-ing gyre

From the perspective of meter, two points of interest arise in this initial line. First, the line arguably has only four stressed syllables, given the lack of a strong accent in the third foot. Although the reader could force a stress on the word “in,” the result would sound slightly unnatural. However, without a proper accent this foot must be read as a pyrrhic, which consists of two unstressed syllables. Second, it’s important to note that the scansion of the final foot depends on whether we pronounce the word “widening” with two syllables or three. In order to fit into iambic rhythm, the reader would need to elide the middle syllable: “wid’ning.” Otherwise, the final foot must be read as an anapest (unstressed–unstressed–stressed).

Elsewhere in the poem, the meter becomes increasingly loose, to the point when iambic rhythm collapses almost entirely. As an example, consider lines 9–13:

     Sure-ly / some rev- / el-a- / tion is / at hand;
     Sure-ly / the Se- / cond Com- / ing is / at hand.
     The Se- / cond Com- / ing! Hard- / ly are / those words / out
     When a vast / im-age / out of Spir- / it-us / Mun-di
     Troub-les / my sight

The first two lines are almost strict iambic pentameter, except for the substitution of a trochee (stressed–unstressed) in the first foot. In subsequent lines, however, the rhythm becomes increasingly irregular. The third line features an ambiguous extra syllable at the end; we could read the last three words as an anapest (“those words out”), which would confine the line to five feet, even if not all five are iambs. Yet when we read the line aloud it seems more appropriate to stress both of the final words, which adds a sixth accented syllable to the line: “those words / out.” The fourth line brings additional complication. Of the five feet in the line, only one is an iamb. Otherwise, the line features two trochees and two anapests. In this passage, Yeats’s meter breaks down almost entirely. The apocalypse envisioned in the poem appears to be creating a cataclysm on the level of form. Thus, the historical pedigree of blank verse collapses on the verge of a new world order.