36O'Sullivan, Muiris, and Liam Downey. "Summit Cairns." Archaeology Ireland 25.3 (2011): 20-23.
The authors count more than 2,000 cairns if modern triangulation specimens are included. They noted, "The degree of overlap between the positioning of prehistoric cairns/passage tombs and the sites identified by engineers as optimal for the erection of triangulation stations testified to the spatial and technical understanding applied by the societies that erected these monuments so as to ensure their distant visibility, and indeed intervisibility."
Coyne notes, "Certainly the large and immovable man-made structures such as megalithic tombs presented very clear messages of ownership, and the same is applicable to the mountaintop cairns." (Coyne, Frank. Islands in the Clouds: An Upland Archaeological Study on Mount Brandon and The Paps, County Kerry. Tralee, Co. Kerry: Kerry County Council in Association with Aegis Archaeology Limited, 2006. 24-251.)