Mullaghderg Tower

Situated towards the S edge of a large flat-topped, steep-sided hill (52m OD). Located on flat ground. The surrounding area consists of heavily eroded blanket bog, enclosed with modern wire fences to define large areas of rough pasture. The signal tower has unobstructed views in all directions. It was built to be intervisible with the site of the signal tower at Bloody Foreland (DG0023-003), now demolished, located c. 14.2kms to the NNE; and the tower at Crohy Head (DG056-003----), which is located c. 13.2 kms to the SSW-S, and which is still visible from this site in clear weather. Site lies c. 1.5kms to the NE of a group of holy wells (DG040-003/003001/003002-) located in a graveyard on Cruit Island. An early nineteenth-century two-storey square-plan signal tower, built with roughly coursed rubble stone masonry (int. dims. 4.15m NW-SE x 4.15m NE-SW). The signal tower survives close to its original full height (H 11.77m), but is missing the machicolation over the first floor doorway, the bartizans on the rear corners to SE and some short sections of parapet wall. The tower is positioned with walls facing NE, SE, SW and NW. The first-floor doorway faces to the NW and would have been originally accessed via a retractable ladder. The machicolation that would have protected the doorway is now completely collapsed, and the head of the doorway has also collapsed. The NE and SW elevations feature pairs of square-headed window openings at ground floor and first floor levels; there are shallow segmental-headed windows to the NE elevation to the first floor with roughly dressed sandstone voussoirs. There are cut limestone lintels with central projecting keystones surviving to the first floor windows to the SE elevation; the surrounds and sills elsewhere now gone. The SE wall bows out slightly to house the chimney flue. Remains of roughcast lime render still survives to most exterior elevations. A rough hole has been opened through the S corner of the SE wall to provide a ground level entrance. Bartizans would have been located over the E and S corners of the signal tower, but they have now collapsed leaving ragged gaps in the main walls of the tower. The internal space consists of a semi-basement level (which is now partially infilled), a ground-floor room originally with a split-mezzanine level, a first-floor room, and a low attic level. The flat roof would have been accessible from the attic level, and a parapet wall protected the edge of the roof, and would have connected to the bartizans and the machicolations; the parapet wall has now collapsed in places. The floors and the roof of the building were wooden and were carried in the thickness of the wall. No parts of the floors or the roof have survived, but rows of joist-holes indicate their former positions. The internal walls are covered in a layer of smooth render, although this does not extend into the semi-basement level. The SE wall features central fireplaces flanked by square-headed alcoves on the ground floor and first floor. There are roughly dressed sandstone voussoirs surviving to the fireplace at first floor level. The lower part of the SW alcove on the ground floor has been removed when the later ground level entrance was knocked through the wall. A square-sectioned internal drainage channel runs down the E corner of the building. This is thought to have originally brought rainwater from the roof to storage barrels in the semi-basement. The site was re-used later in the 19th century as a Coast Guard Station. During that period a rectangular enclosure was constructed immediately W of the signal tower, which is depicted on the 3rd edition Ordnance Survey map, surveyed 1900-5. No traces of this later enclosure are now visible. A small mass concrete pillar or open-topped tank is located to the W of the signal tower. This may be a remnant from this secondary period of use. The signal tower was part of a system of over 80 signal stations constructed by the British Board of Ordnance in the first decade of the 19th century to warn of the approach of a French invasion fleet. Signalling between sites was accomplished using a naval signal post. The system formed a continuous chain from Dublin Bay running clockwise all the way around the coast to Malin Head in County Donegal. It was abandoned by the mid-1810s when the threat of a French invasion diminished (Kerrigan 1995, 157-66).