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.
Celticisation
In the modern era, there are attempts made to reverse the effects of centuries of Anglicisation and other assimilations and re-introduce Celtic languages. Most particularly in Wales, Welsh language has seen a halt in its decline and even signs of revival, with approximately half a million fluent speakers. There have also been recent attempts to revive the Cornish language, as its last native speaker died in the 1970s, and there are now several schools in Cornwall teaching in Cornish. The Breton language remains endangered as the number of its speakers continues to decline.