2. There must be four lines in each quatrain of two couplets. The sense may be complete in the couplet, but must be complete in the quatrain.
3. Concord must be observed; i.e., two words (not being prepositions or particles) in each line must begin with a vowel or with the same consonant. If these alliterated words be the last two, the concord is perfect, if not, it is an improper concord. The third and last lines must have perfect concord.
4. Correspondence must be observed. The bards grouped the consonants into five classes, according to the characters of the sound. Perfect correspondence demanded that the end words in two lines should agree in possessing letters of the same class. [This may sometimes result in what we call rhyme.] If only the vowels rhyme, whilst the consonants are disregarded, then this is termed imperfect concordance.
5. Termination required the final word of each couplet to be one syllable longer than the final word in the preceding line.
6. Union is another essential. Similar to correspondence, in some respects, the same vowels need not be repeated—it suffices that they belong to the same class; the final word of one line chimes with a central word in the next.
There are other rules besides, but these are surely enough to prove that classic Irish verse was an extremely elaborate affair. It would be impossible to adapt the English language to verse so intricate. Its existence betrayed a highly refined development of the organs of speech and of hearing, which latter is what we should expect from the musical taste and skill of the race. From such rules, we can readily understand that the bardic corporation was competent to carry this refinement of technic, and to develop an intricacy of meaning to such a degree, that the outer world required an explanation. Some of the poems of Seancan Torpeist, in the seventh century, were quite as unintelligible as the most obscure of Browning’s, but, unlike Browning, he was always able to translate them to a puzzled prince. Poets seemed to have a natural tendency in the direction of over-elaboration; they had been judges until they developed technicalities and an artificial law language, so that neither suitors nor audience could understand them. Then the princes interposed, adding laymen to the court. With their poetic tongue there was no interference, until it had been unduly exercised in oppressing the chiefs.
Now, if we examine the mechanism of any of these elaborate verses, we shall perceive that it contains a lesson greater than has been hitherto noticed. Open the Book of Kells and look at one of the initial letters, with its wonderful intricacy of interwoven lines, its exquisite grace of form, and marvellous delicacy of tint. The first glance shows it to be a beautiful work of art, and at once we recognise that it must have been produced by men whose minds, eyes, and hands had been cultivated to the highest degree. It is not the product of the training and refining of an individual or of a generation, but of a series of successive individuals in many generations. Than some of these initial letters nothing of the kind seems to have ever been made so beautiful before, nor anything since. Thus human skill in particular departments may ascend progressively till it reach its zenith and then gradually decline. Mankind acquires, but loses also; its advance in one direction may mean retreat in another. And as works such as these are indices to the development of refinement, and to the co-operation of certain qualities and senses in man, these also must have their time of rise and fall.
Now the form-and-colour picture presented by one of these fine initials is, in another department, the sound-picture presented by Gaelic verse. A little examination shows that, besides possessing the sounds we recognise, and those which other Europeans nations have noticed, the ancient Irish composers noted, identified and employed other and more subtle shades of sound. Consider this question for a moment, for it has a physiological as well as a literary interest. We all know what the term rhyme now means in English: the sound-echo of vowels and consonants in two or more terminal words.[3] It has many charms, but tends to become monotonous in long poems; hence authors sometimes abandon it completely for blank verse, or, using it, endeavour to evade the danger of monotony by alternating the rhyme, carrying over the sense, or varying the length of line. Now this comes of narrowing the conditions. There is no cause, save custom and imperfect audition, why only the last vowel and consonant should be echoed. The ear recognises the echo of the initial letter, or of initial consonant and vowel, in concord or alliteration. Readers of Spanish dramas and of Irish street ballads notice also the chime of the accented vowel, the vowel-rhyme, or assonante, although the consonants differ. But the ancient Irish, in addition to these, had also other varieties, such as the correspondence between letters of the same class. This avoided the monotony produced by a reiteration of exactly the same letter, whilst it repeated the sound with a harmonious variation, and maintained a delicate airy phantom-chime which must have been delightful to the educated ear.
In connection with this question of sound-echo I have a proposition to put forward which may well seem startling. Of all the literary possessions of the human race, the wide world over, nothing now seems to us so constant, so universal, so eternal as rhyme. Now the fact is that rhyme was quite unknown to all the dialects of Europe, with one exception, for some centuries after the Christian era. The Greeks and the Romans wrote much poetry, but never rhymed it.[4] Their metrical system was elaborate, satisfactory, and pleasing, but it did not recognise the concordant chime of syllables. Again, there is no recognition of rhyme, as the term is now understood, in any of the Gothic dialects previous to the ninth century.
Now, what are we to infer from all this? Here I state my proposition, which is, that the human ear had not then acquired the power of distinguishing and taking pleasure in these sound-echoes or repetitions which we call rhymes. That these would have been adopted, could they have been discriminated, must be inferred from their quick-extending popularity when introduced, and their subsequent universal prevalence.