Meter for the Masses

Ever wondered why that pesky, seemingly arbitrary, hiatus appears? Ever come across the term diastole (normally defined as artificial lengthening of a short syllable) and wondered why?

Well, neither is arbitrary, and actually diastole and hiatus are products of thesame phenomenon.

Diastole is derived from the old Greek grammatical term for a comma. It came to be used later as a technical term for the comma in texts which distinguishes ὅτι ('wherefore') from ὅ,τι (that).

But I digress. The primary function of the comma is to mark a kind of pause, and that's precisely what the metrical phenomenon labeled 'diastole' does.

Now, as I alluded to before the term is used in Latin prosody of a position normally counted short but which is counted long. This is a bit misleading (it seems arbitrary but it's not), so let's take a look at Catullus 64. 20 (we'll us d for dactyl and s for spondee):

tum Thetis humanos non despexit hymenaeos

This scans d-s-s-s-d-s. The phrase despexit hymenaeos is s-d-s, with the final syllable of despexit counted long. Now, initial h is never counted as a consonant and can not force the -t to close that syllable (i.e. it can't make it 'long by position'). So why is it scanned long? Why diastole?

The culprit is a 5th caesura which I found also at Aeneid 1. 720, also preceding hymenaeos: profugus | hymenaeos.

Diastole only occurs when (1) the syllable is composed of a short vowel + consonant, and (2) it is followed by a pause. Necessarily the following letter must be a vowel or h (a consonant would force the syllable to be counted long).

This pause is most often the 4th, 2nd, or 3rd foot caesura, in that order (in
Vergil at least, based on a quick glance at occurences of diastole in the Aeneid), but there are other possibilities. Vergil has a few examples of 5th foot caesura causing diastole.

Hiatus is the term used when such a pause causes a vowel-final syllable not to
be elided (again, a cursory glance at occurrences in the Aeneid shows a preference for hiatus at the 3rd foot caesura). Check out any occurrences of diastole or hiatus that you find in Latin hexameters. I'm willing to bet you'll find that caesura explains it.

I just figured this out today, so if there's anything I've missed or some deeper significance, please pass it along.