The light was shown from a lantern at the foot of a tapering tower, 10.7m (35ft) high and 5.5m (18ft) in diameter, which may have been used previously as a day-mark. The tower has the considerable taper characteristic of the numerous Anglesey windmills and presumably a mason experienced in this work may have been employed here, assuming the tower was not originally used as a windmill. The present lantern window is some 2m (6ft 6ins) by 0.61m (2ft) and presumably is primary to the building. The optic, silver plated reflector and Fresnel lens, used into the 1970s, were dated 1861 and was originally lit by six Argand lamps with reflectors. The north-east door of the tower is flanked by small windows; the two floors above were lit by windows but a considerable space at the top of the tower shows no signs of ever having had openings. The top is covered by a conical slate roof with flag-pole. Some 200 metres to the south-east is a smaller conical stone tower with a domed top (see nprn 421443); presumably this simple structure is earlier than the taller tower although its precise date is uncertain. Both towers are shown on the manuscript edition of the 1818-23 Ordnance Survey 2in map, but not on Lewis Morris's hydrographic chart of 1800.
Event and Historical Information:
A coastal light was first exhibited on 1 January 1846. The cost of the lantern and fittings was £250 7s 6d which included the adaptation of the `earlier tower'.
Admiralty Sailing Directions dating to 1870 note the two white towers, the northernmost, called the large tower, 'with a flagstaff, exhibits from a lantern elevated 50 feet a fixed red light, which can be seen about 5 miles over the arc between NW by N and SW by W. Marryatt's code of signals are kept at the large tower, and vessels wishing to communicate will be answered therefrom. A black ball is hoisted at the pilot's house as long as there is 10 feet water on the bar'.

Sources:
Admiralty, 1870, Sailing Directions for the West Coast of England from Milford Haven to the Mull of Galloway including the Isle of Man, pg79
Hague, D, 1994, Lighthouses of Wales: Their Architecture and Archaeology, pg49-52
Historic Admiralty Chart 1412-A7, RCAHMW Digital Collections sourced from UK Hydrographic Office (published 1842)
Lloyd, L, 1989, The Port of Caernarfon, 1793-1900, chapter 9.
Royal Commission on Lights and Buoys, 1861, p.299.

RCAHMW, October 2011.