19) Altogether this category of vowel combinations accounts for well over a third (423) of the diaereses in the poem.
Diaereses in this category are generally marked in Petrocchi's edition, but not in the following: I|arba and I|ole (2.
As with accented a, e, and o followed by another vowel, the number of diaereses produced by this combination is small (well under 100; taken all together, combinations in which the first vowel is accented thus produce only 15% or so of the diaereses in the Divine Comedy).
Table 6 (1): Exceptional diaereses (after accented i, u) 122.
I shall consider later whether there is any other way of accounting for the exceptional diaereses in this category.
15): while most of his diaereses with sinalefe conform to this rule, three occur before an unaccented initial vowel, three (in 1.
The important issue is that final accented falling diphthongs followed by an initial vowel regularly count as two syllables in the Divine Comedy, and it seems reasonable to conclude that they should all be treated in the same way, either as diaereses followed by sinalefe or as synaereses followed by dialefe; my own preference, which I have adopted throughout, is for the latter, as the simpler and more consensual solution.
But distinctions must be made between: (a) diaereses that are a normal consequence of vowel structure, in combinations beginning with unaccented a, e and o (category (1) above); (b) those that are the regular marker of a particular lexical register, as in the etymological diaereses that refer back to a word's Latin origins (mostly in category (3) above); and (c) exceptional diaereses, such as I have sought to identify in Tables 5 (2) and 6 (1), to which may be added the diaereses on io in Table 6 (2) (categories (2) and (4) above).