In 1887, John Bartholomew's Gazetteer of the British Isles described Lough Swilly like this:
Swilly, Lough, sea-lough, NE. co. Donegal, entering from the Atlantic between Fanad Point and Dunaff Head (4 miles across), and extending about 25 miles inland between the peninsula of Inishowen and the main body of the co.; average width, 3 miles; has a lighthouse on Dunree Head, with fixed light seen 13 miles, and 1 on Fanad Point, with fixed light seen 14 m.
GB Historical GIS / University of Portsmouth, History of Lough Swilly, in and County Donegal | Map and description, A Vision of Ireland through Time.
URL: https://www.visionofireland.org/place/29227
Date accessed: 19th February 2025
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