Messe ocus Pangur bAN cechtar nathar fria saindAN bith a menma sam fri SEILGG mu menma cein im sainchEIRDD.

As we see, the consonants in the rhyme-words were merely related:  l, r, n, ng, m, dh, gh, bh, mh, ch, th, f could rime together just as could gg, dd, bb.  Soon the poets did not limit themselves to end-rhymes, which ran the risk of becoming monotonous, but introduced also internal rhyme, which set up what we may call a continuous chain of melody: 

is aire caraim DOIRE ar a reidhe ar a ghlOINE ’s ar iomad a aingel fIND o ’n CIND go aoich arOILE.

This harmonious versification was replaced in the seventeenth century by a system in which account was no longer taken of consonantal rhyme or of the number of syllables.

The rules of Irish verse have nothing in common with classical Latin metres, which were based on the combination of short and long syllables.  In Low-Latin, indeed, we find occasionally alliteration, rhyme, and a fixed number of syllables, but these novelties are obviously of foreign origin, and date from the time when the Romans borrowed them from the nations which they called barbarous.  We cannot prove beyond yea or nay that they are of Celtic origin, but it is extremely probable that they are, for it is among the Celts both of Ireland and of Wales that the harmonizing of vowels and of consonants has been carried to the highest degree of perfection.

This learned art was not acquired without long study.  The training of a poet (file) lasted twelve years, or more.  The poets had a regular hierarchy.  The highest in rank, the ollamh, knew 350 kinds of verse and could recite 250 principal and 100 secondary stories.  The ollamhs lived at the court of the kings and the nobles, who granted them freehold lands; their persons and their property were sacred; and they had established in Ireland schools in which the people might learn history, poetry, and law.  The bards formed a numerous class, of a rank inferior to the file; they did not enjoy the same honors and privileges; some of them even were slaves; according to their standing, different kinds of verse were assigned to them as a monopoly.

The Danish invasions in the ninth century set back for some time the development of Irish poetry, but, when the Irish had driven the fierce and aggressive sea-rovers from their country, there was a literary renascence.  This was in turn checked by the Anglo-Norman invasion in the twelfth century, and thereafter the art of versification was no longer so refined as it had formerly been.  Nevertheless, the bardic schools still existed in the seventeenth century, more than four hundred years after the landing of Strongbow, and, in them, students followed the lectures of the ollamhs for six months each year, or until the coming of spring, exercising both their talents for composition and their memory.