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.
Sorley MacLean
Before he went to university, MacLean was writing in both English and Gaelic. After writing a Gaelic poem, "A' Chorra-ghritheach" ("The Heron"), in 1932, he decided to write only in Gaelic and burned his earlier poems. MacLean later said, "I was not one who could write poetry if it did not come to me in spite of myself, and if it came, it had to come in Gaelic". However, it is also clear from his correspondence with MacDiarmid that his choice was also motivated by his determination to preserve and develop the Gaelic language. The Gaelic language had been in decline for several centuries; the 1931 census registered 136,135 Gaelic speakers in Scotland, only 3% of the Scottish population. Despite his decision to write in the language, at times MacLean doubted that Gaelic would survive and his poetry would be appreciated.