long narrow vowels
The long vowels è (eu, etc.), and ì (io), in certain cases in which they are retained in the south, are diphthongised in the north. The resulting diphthongs are alike from both vowels, as beul ‘bial,’ deug ‘diaog,’ dìon ‘dian,’ fìor ‘fiaor.’
eu, èa, èi, è.
‘The crucial distinction,’ says Dr. MacBain in his Gaelic Dictionary (p. xviii.) in reference to the two main dialects ‘consists in the different way in which the dialects deal with é derived from compensatory lengthening; in the south it is eu, in the north ia (e.g., feur against fiar, breug against briag, etc.).’ He has pointed out elsewhere as another characteristic of the words in which this change is found, that their original stems ended in o or a. There are exceptions drawn in perhaps by the influence of analogy. Compensatory lengthening of a vowel takes place when the first of two or more following consonants, of which one must be a liquid, is lost. Ceud hundred, for example, has lost the n seen in Welsh cant, Cornish cans, Breton kant, Latin centum, English hund-red, and to compensate for this loss the vowel, which was short originally, extended itself into the blank thus left, and so became long in the Gaelic form of the word. The process is not unknown in the modern language. Words like annrath, innleachd, innseadh show loss of nn or assimilation of the nasal to the following consonant, and consequent compensatory lengthening of the preceding vowel in the spoken forms ‘àrath,’ ‘ìlleachd,’ ‘ìseadh.’ Compare also sòise, ‘a bolide’ (MacAlpine), for soillse. In some instances it is an original ei, which appears normally in Old Irish and in Gaelic as èi in some instances and as ia in others, that has diverged in the two Scottish dialects and is heard as è in the south and as ia in the north, as in mèith, reub, sgreuch.
The vowel that changes to ia in the north is usually written eu, but it occurs also as èa, èi, and è. In southern
