History of Scottish Gaelic
All surviving dialects are Highland and/or Hebridean dialects. Dialects of Lowland Gaelic have become defunct since the demise of Galwegian Gaelic, originally spoken in Galloway, which seems to have been the last Lowland dialect and which survived into the Modern Period. By the 18th century Lowland Gaelic had been largely replaced by Lowland Scots across much of Lowland Scotland. According to a reference in "The Carrick Covenanters " by James Crichton, the last place in the Lowlands where Scottish Gaelic was still spoken was the village of Barr in Carrick: only a few miles inland to the east of Girvan, but at one time very isolated. Crichton gives neither date nor details.
Seas west of Scotland
The coastline is part of the Celtic fringe. Gaelic is spoken as a minority language in many parts of the area with strongholds in the Outer Hebrides and Tyrconnel in Donegal. Scottish Gaelic is declining in Scotland although the compulsory teaching of the Irish language in Irish schools means that most Irish citizens understand it to some extent. The variant of Gaelic spoken in Donegal is distinctive, and shares traits with Scottish Gaelic. Its Gaeltacht (Irish speaking area) uses the West Ulster dialect. Inishowen, which lost its Gaeltacht areas in the early 20th century, used the East Ulster dialect.