Here are the conventional terms for metrical feet in poetry.

a line with two feet is a dimeter;

a line with three feet is a trimeter;

a line with four feet is a tetrameter;

a line with five feet is a pentameter;

a line with six feet is a hexameter;

a line with seven feet is a heptameter.

However, it is worth noting that the most interesting meters are those of the primes 5 and 7.

Verse can also be dactylic (falling foot) or iambic (rising foot), but that is not the topic currently under discussion.

Because of four-line stanzas in tetrameter, heroic Augustan couplets and conventional sonnets, we tend to think of verse as always having a regular stress – “written in iambic pentameter” for instance. However, this is not the only way to write verse which scans.

A madrigal such as many of those written by William Drummond of Hawthornden will scan the prime numbers:

x

Like the Idalian queen,

Her hair about her eyne,

With neck and breast’s ripe apples to be seen,

At first glance of the morn

In Cyprus’ gardens gathering those fair flowers

Which of her blood were born,

I saw, but fainting saw, my paramours.

The Graces naked danced about the place,

The winds and trees amazed

With silence on her gazed,

The flowers did smile, like those upon her face;

And as their aspen stalks those fingers band,

That she might read my case,

A hyacinth I wished me in her hand.

x

Here Drummond scans trimeter with pentameter. But all primes scan, so the madrigal form could use pentameter juxtaposed with heptameter. Heptameter will scan with trimeter as well and with Endekameter (an eleven-foot line). I have written poems making use of such an extended madrigal structure.

But what makes the primes of particular interest is the irregularity of the caesura. A caesura is a pause that occurs within a line of poetry, and in my view, strictly speaking, it needs to be more than one foot long. Modernists may bend such a rule, fair enough. But if we stick with the rule some interesting ratios become evident.

The caesura on 5 (Pentameter)

3:2

The caesura on 7 (heptameter)

5:2

4:3

The caesura on 11 (Endekameter)

5:6

3:8

9:2

7:4

Of course the ratios can be reversed. But it is the inequality of the caesura which makes pentameter so vital to English poetry.

I am writing my epic THE RUNIAD in a meter that is loosely Heptameter, because I enjoy the possibility of using two caesurae. A great book dealing with these niceties of the metrical foot in English verse is F T Prince’s “The Italian Element In Milton’s Verse”  Pub: Oxford – 1954.