Rathlin Island lies six miles off Ballycastle in North-east Ireland and 16 miles from the Mull of Kintyre in Scotland. It is eight miles long and less than one mile wide.
Shaped like a boot, made with layers of basalt on limestone on the higher parts. It is surrounded by limestone and basalt sea cliffs reaching 470 ft in places. Three lighthouses stand as monument to its wild coast while over 40 recorded shipwrecks lie in the depths of underwater cliffs and caves. The waters around the island are a marine botanical paradise.
An initial field survey of the island identified many clusters of houses in various states of occupation or dereliction. We also got the impression that most of these had been clachans. It would not have been possible to include all of these clachans within our study so we decided to do a general survey of all of the clusters both past and present and investigate two of them in more detail. The two clachans eventually chosen were Knockans North (1) in the townland of Knockans and Ballygill Middle (2) in the townland of Ballygill Middle.