Melin Geirn is a tall tapering rubblestone tower, 5.7 metres in diameter at ground level with square window openings, built against and partly into a farm barn. It has two opposite doors at third-floor level, which formerly gave access to a wooden gallery supported on timbers radiating from the walls, their position marked by close-spaced rectangular holes. The gallery would have provided access for setting the sails, which must therefore have been very short, to clear the roof of the barn.
The windmill is not named on the 1st edition of the 25-inch O.S. map (1889), and is marked "Old Windmill" on the 2nd and 3rd editions (1900 and 1924). In 1975 there was no internal machinery, and the lack of sockets for large timbers, as seen in other Anglesey windmill towers, suggests that the purpose of this windmill was to drive machinery in the barn rather than in the tower itself.
W J Crompton, RCAHMW, 1 October 2008.