 a ' preceding a non-intervocalic ' is ).Traditional spelling systems also use the acute accent on the letters ', ' and "" to denote a change in vowel quality rather than length, but the reformed spellings have replaced these with the grave.Certain 18th century sources used only an acute accent along the lines of Irish, such as in the writings of Alasdair mac Mhaighstir Alasdair (1741–51) and the earliest editions (1768–90) of Duncan Ban MacIntyre.