Published in 1895, the map which charts the prevalence of Gaelic speaking in Scotland, is the first of its kind.
Produced by Edinburgh map company Bartholomew’s, the map contains information distilled from the first census, in 1881, that counted Gaelic speakers in Scotland.
The map is also one of Bartholomew’s first thematic maps, which the company pioneered to illustrate trends in a particular subject.
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In 1881, a total of 231,594 people in Scotland were recorded as speaking either Gaelic only or a mix of Gaelic and English.
This represented 6.2 per cent of a population of 3.7m - although some believe the rate is underrepresented.
The historic, deep concentration of Gaelic speakers in the Western Isles and the Highlands is shown on the map as well as the prevalence of the language to the east of the Highland Line, including areas around Crianlarich and Loch Tay.
It also illustrates a form of border where both Gaelic and English are spoken in near equal measure.
This stretches from Brora in the north to Dornoch, Inverness, Kingussie, Pitlochry and Perth.
From Perth, the line moves west into Argyll, and loops around Inverary into the west side of Arran and over to Campbeltown.
Professor of Gaelic, Wilson McLeod and Professor of English Language, Charles Jones, both of Edinburgh University, gave a detailed history of Gaelic speaking in Scotland in an essay, Standards and Differences, Languages in Scotland, 1707-1918, published by Edinburgh University Press.
Long before the map was published, the shift in use of Gaelic had begun in some parts.
“By the middle of the 18th Century, language shift was evidently underway in certain Highland areas, especially those near the Highland line.
“In such districts transactional bilingualism had developed with the language passing out of community use soon thereafter,” McLeod and Jones said.
Improved transport links and increased economic interaction with the English-speaking world led to the shift, as well as migration to other parts of Scotland, the professors added.
Lighter pockets of Gaelic speaking, where it was spoken by 5 to 25 per cent of the population, are recorded in the area around Nairn, Grantown, Tomintoul and pockets around Braemar, Lochnagar and parts of the Angus Glens.
Glasgow is marked as having between 0 and 5 per cent of a Gaelic speaking population as are parts of Lanarkshire and West Lothian.
English only is marked in Aberdeen, large parts of Aberdeenshire - Doric was not included in the Census - large parts of Fife, Edinburgh, the Borders, Dumfries and a significant portion of Ayrshire.
The 1881 Census was taken following the turbulent period of Highland depopulation, driven by famine, clearances and emigration, both overseas and to Scotland’s industrial heartlands.
In the whole of the region covering the west coast north of Ardnamurchan and the Inner and Outer Hebrides, the population decline averaged a third between 1841 and 1861.
In the mid 1700s, 25 to 30 per cent of the Scottish population of 900,000 spoke Gaelic.
By the start of the 19th Century, the proportion was around one-fifth of the population.
By 1881, it had dropped to 6.2 per cent.
By 1921, the number of Gaelic speakers had fallen to 158,779 (3.3 per cent of the national population) with just 9.829 Gaelic speakers recorded, according to McLeod and Jones.
Gaelic, by this time, had become a minority language in most Highland parishes, with the lowest rate in Black Isle and Highland Perthshire (around 10 per cent).
“On the other hand, most of the mainland to the north and west of the Great Glen, to say nothing of the islands, remained well over 75 per cent Gaelic speaking.
“Ten Parishes, mostly in Skye and the Western Isles, stood at over 90 per cent, with Applecross, at 91 per cent, being the strongest Gaelic area on the mainland,” McLeod and Jones added.
The publication of a Bible in vernacular Scottish Gaelic in 1801 and the activities of the Society in Scotland for Propagating Christian Knowledge (SSPCK), which ran 300 schools by 1795, eventually increased Gaelic literacy rates in the first half of the 19th Century, Jones and McLeod said.
While the society had originally sought to rid the “Irish tongue” its position later altered and Gaelic dictionaries were produced.
However, the Education Act of 1872, which introduced a system of state schools where Gaelic was completely excluded, was a “disaster” for the Gaelic language, the professors said.
Teaching of the language remained marginal in the state system until the 1960s, when some Gaelic-medium initiatives were introduced in Inverness-shire.
On Census Day, 27 March 2011, a total of 87,100 people aged 3 and over in Scotland (1.7 per cent of the population) had some Gaelic language skills. This included 57,600 people who could speak Gaelic.
The Education (Scotland) Act 2016 introduced Gaelic-medium education (GME) provisions, assuring a national entitlement to learning at primary-school level.
New GME schools opened in Glasgow and Fort William, with building works underway in Portree, adding to three existing Gaelic schools across Scotland.
Scotland’s first director of Gaelic education, Mona Wilson, has also been appointed.