This was the terminal for an undersea telegraph cable, according to a local resident. In that case, it must be the 1906 cable to Faroes and Iceland. See http://atlantic-cable.com/Cableships/Cambria/ for a photo of SS Cambria at Burwick.
Uploaded to Geograph by Rob Burke on 7 July 2017
Photo © Rob Burke, 7 July 2017. Licensed for reuse under this Creative Commons licence