Casquets lighthouses per ton of ship when vessels passed the rocks and in turn he paid Trinity House 50 pounds per year for the right to run the lighthouses. The lighthouses reverted to Trinity House in 1785. They were converted to oil lamps with metal reflectors which were first used on 25 November 1790; and upgraded again with apparatus to rotate a beam of light in 1818. This had a clockwork mechanism which was wound up every hour and a half and gave one flash every 15 seconds. The lighthouses were badly damaged and the lanterns smashed in a severe storm on
Lighthouses on the Isle of Arran rebuilt between 1821 and 1830. Pladda was one of Northern Lights' lighthouses where paraffin as a new fuel together with multiple wicks were tested successfully in 1870. This allowed substantial savings with a simultaneous increase in power between 10% and 100%. Fog signals were introduced in the 1870s as well. In 1901, the formerly fixed light was changed to a more powerful group-flashing which was Northern Light's plan for most Scottish lighthouses at the time. Pladda lighthouse operates fully automatic since 1990. Pladdas position is 55° 25.512'N, 005° 07.113'W. Its light flashes Fl.(3)30s40m23M. The Inner lighthouse on Holy Isle faces