Secret Scotland says
Greenock leading lights lie at the end of Madeira Street on Greenock Esplanade, and are part of a larger network set up to provide safe navigation within the shipping channel in the Firth of Clyde.
The lights on the esplanade are used to mark a deep water anchorage in the Clyde known as "The Hole".
The front light is located on the shore side of the Esplanade, and mounted on top of a Corinthian column on a square pedestal, which was probably relocated there c. 1860 from Steamboat Quay (c. 1810), when the esplanade was created using material excavated to form the nearby Albert Dock.
The rear light is located in Madeira Street, mounted on top of a metal pole similar to a lamppost, unusually located in the roadside gutter, rather than on the footpath.
Survey maps c. 1900 show the location marked as Leading Lights (Fixed Red). The lights do not appear to be marked on later OS mapping, c. 2000.
Photographs taken prior to 2010 show the earlier rectangular housings on top of the two columns. Later photographs show these to have been replaced by cylindrical projector units.
pics at
http://www.secretscotland.org.uk/index. ... dingLights
I hear the people sing.