short and sometimes long, but in the great majority of cases the lengthening of the vowel is firmly established.
vowels diphthongised
Diphthongisation before long liquids is confined to a and o and consists in the introduction of a u sound like that of u in the English words ‘foul,’ ‘hound,’ or of w in the English ‘howl,’ ‘town,’ between the vowel and the liquid. The sound of the whole diphthong in words like poll, bonn, com, is that of ou or ow in those English words. In words like ball, bann, cam, the diphthong has an a sound instead of the o sound before the u and so resembles au in German ‘haus.’ Such diphthongisation does not exist in the extreme south or in east Perthshire. It is found before l and n in Lorne and west Perthshire. It extends to m when we cross into Inverness-shire and the part of Argyllshire beyond Loch Linnhe, and prevails before the three liquids throughout the rest of Gaeldom northwards.
When the vowel is preceded by e, the pronunciation varies somewhat. The regular diphthong, preceded by a y sound of course, prevails in Badenoch and Strathspey, as meall, ‘myaull,’ ceann, ‘cyaunn.’ Geall, seall, steall have there as usual eo for ea, gyoull, etc. In Skye ea is retained in the words ‘gyaull’ etc., while meall (lump) and meall (deceive) have short ao in place of a in the diphthong. In Rannoch, Skye, and west Ross-shire before nn a diphthong consisting of the Gaelic sounds of e and u is heard, as beann, ‘beunn,’ ceann, ‘ceunn,’ etc. In Rannoch and Ross meall likewise is ‘meull.’ In Sutherland meall (‘myull’ with u nasal) seems to follow leann, ‘lyunn,’ and seann, ‘shunn,’ as those words are pronounced there and in Ross and Strathspey. Other Sutherland pronunciations are gyaull, shaull, cyaunn, glyaunn, greunn (for greann). Diphthongisation is heard in that county once before a short liquid, with o for a also, in the word dealt (dew) ‘djoult.’
In Glenlyon, Rannoch, and Badenoch diphthongisation is heard occasionally before rd and even rt with or without an
