The Signal Stations

The construction, survival and historical context of the Signal Defensible Guard Houses in Connacht is a post graduate research project being undertaken at IT Sligo by Stuart Rathbone and Dr James Bonsall. This site presents some of the early results of the project, providing a page of information about each of the early 19th century Signal Station sites in the province of Connacht, linked to an interactive map. In addition to the photographs and other images presented here the project has involved creating detailed elevation drawings, plans and where possible 3D photogrammetric models of each of the sites, providing a vital record of what currently survives at each site.

The Irish Signal Stations are prominent but poorly understood features of much of the Irish Coast. The sites were constructed in the first decade of the 19th century as part of an extensive program of coastal defences commissioned in response to the repeated attempts by French forces to invade Ireland that occurred in 1796 and 1798. The system of signal towers ran from the very northern tip of Ireland, Malin Head in Donegal, all the way around the west coast and the south coast and up the east coast as far as Dublin Port where the chain terminated at Pigeon House Fort. Construction on the sites began in 1804 and was largely completed by 1806. Around 80 sites were utilised but it is thought that not all of them were completed or utilised and in some locations additional stations seem to have been added where intervisibility was found to be problematic. The sites were only in use for a few years before stretches of the system began to be abandoned, as the threat of another French Invasion diminished. Parts of the system were re-commissioned during the War of 1812 when American Privateers operated off  the west coast of Ireland. Most of the abandoned sites were stripped of timber and dressed stone and left to fall into ruin, although a small number such as the site at Malin Head, Donegal, or the site at Inishmore, Galway, were subsequently utilised for new purposes. The signal station at the Old Head of Kinsale in Cork has recently been fully restored and houses a small museum with one floor dedicated to the Irish signal stations and the other dedicated to the sinking of the RMS Lusitania 11 miles out to sea in 1915.

The restored signal station at the Old Head of Kinsale in Cork offers a unique chance to see how  the signal stations would have originally appeared.

Commonly referred to as ‘Signal Towers’ of ‘Napoleonic Signal Towers’ these sites were originally designated as ‘Signal Defensible Guardhouses’ and on this website they are termed Signal Stations, reflecting their purpose and the occasional absence of signal towers from some sites which utilised other types of building to provide accommodation, such as Martello Towers or Lighthouses. The main architectural element of the signal stations is a small but sturdy square tower, used as a defensible residence. The signal towers were often located within a rectangular stone walled enclosure. A large signal mast would have been set next to the tower on which a series of pennants and balls would have been suspended, with different patterns used to denote particular signals. Smaller rectangular buildings were often built within these enclosures or close to the unenclosed towers which are thought to have provided additional storage or accommodation areas. Finally small lime kilns are a frequent additional architectural element found at the sites, thought to have been used during the construction phase in the production of mortar and render for the walls. There are 6 signal stations in Galway, 8 signal stations in Mayo and 6 signal stations in Sligo.

This site includes descriptions of each of the Signal Stations in the province of Connacht and is linked to an interactive map that utilises the ArcGIS Online platform. Each of the sites in Connacht is given a separate entry which describes the current condition of the signal station, records the different elements that are present, discusses how the site can be accessed and notes any other interesting features in the vicinity. The site is one of the outcomes of an ongoing research project being undertaken by Stuart Rathbone and Dr James Bonsall of IT Sligo.

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Semi transparent wire frame model of a ‘standard’ signal tower,

The signal towers in Connacht have been built to quite a standardised design, although there is some variation. In Galway and Sligo the signal towers seem to follow an almost identical design, whilst the examples in Mayo are slightly different. Externally the towers generally measure around 5.85m across (19 feet and 2 inches) and the internal space is usually around 4.3m across (14 feet and 1 inch).

Each tower had a semi-basement level that is partially below ground and was used for storage. The ground floor had four small windows and a fireplace flanked by two alcoves. This floor was used to accommodate the small crew of signal men. The wall containing the fireplace is often notably bowed outwards in order to house the chimney for the fireplace.

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Rendered wire frame model showing the placement of floors within the signal towers. Note the split mezzanine level between the ground floor and the first floor.

Between the ground floor and the first floor was a split mezzanine floor, thought to provide additional storage areas or possibly even sleeping areas for the signal crew. These split mezzanines are not present at any of the sites in Mayo. The first floor again features four windows and a fireplace flanked by alcoves. Compared to the ground floor the windows on the first floor are larger and the fireplace is often a little grander. The wall opposite the fireplace featured the doorway that provided the only access to the signal tower. It was accessed via a retractable ladder. The first floor was used by the signal officer and consisted of a small office and apartment.

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The ‘back’ wall of the signal tower with its fireplaces and alcoves. Note the joists for the split mezzanine level above the ground floor alcoves, the joists for the small attic layer above the first floor and the chimney stack on top of the wall.

Above the first floor at the most of the sites in Galway and Sligo there is a low attic level. The roof was flat and was an important area for observation and for defense. It features a low parapet and there are bartizans projecting over the corners of the ‘back’ wall and a machicolation projecting over the doorway on the ‘front’ wall. In general terms the sites in Galway and Sligo feature almost square bartizans whilst the sites in Mayo have rounded bartizans. Rathlee in Sligo is an exception as the signal tower features round bartizans and lacks an attic level, suggesting it follows the Mayo design template. However unlike the other Mayo sites it features the split mezzanine level between the ground floor and first floor, although uniquely the slots slope downwards into the interior of the building. Two of the towers in Galway, Inisheer and Inishmore, have an external layer of render over which there were several layers of weather proof slates, portions of which still survive. It is not clear if the other sites in Connacht originally had similar external treatments. Rathlee in Sligo has an external layer of render but no slates survive, however it is not certain that the render is an original feature as the site has had some restoration work. No evidence of external wall treatments survive at the other sites but it is possible that the valuable slates were removed for use elsewhere and that this left the render exposed to the weather and it simply fell off the sides of the buildings over time.

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A plan view of one of the Galway/Sligo style signal towers with square bartizans.

Only seven of the signal stations in Connacht show definite evidence of enclosing walls, Inisheer and Inishmore in Galway, and Clare Island, Achill Island, Glosh, Tower Hill and Glinsk in Mayo. There is inconclusive evidence to suggest that the signal stations at Cuileen Hill and Cleggan Hill in Galway may also have featured enclosures, and it is not known if the demolished site at Creevagh in Mayo had an enclosure or not. It is noticeable that none of the sites in Sligo feature enclosures, although the site at Carrowmably is set within a large oval pre-existing enclosure that may have a prehistoric origin.

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A 3D model of Inishmore signal tower placed within an image of the Inishmore signal station from Google Earth showing its location within the large rectangular enclosure.

The enclosures are typically large and rectangular and measure around 50m by 30m. Generally the enclosures have not survived in a very good condition  but combining information from different sites it is possible to suggest that they originally featured walls that were between 0.6m and 0.9m wide (2 to 3 feet) and 1.8m to 2.6m tall (6 to 8 1/2 feet) with a single narrow entrance along one of the long sides. The signal tower was positioned between 1/3 and 1/4 of the way along the long axis of the enclosure. Small rectangular buildings were sometimes built against the corners of the enclosures but there is little consistency amongst the known examples and these are covered in detail in the individual entries.

The individual sites can be explored via an Interactive Map or by clicking on the following links.

County Galway



Golam Head

Cuileen Hill

Bunowen More

Cleggan Hill

County Mayo


Clare Island

Achill Island


Tower Hill

Benwee Head



County Sligo

Lenadoon Point



Knocklane Hill


Kilcologue Point

County Donegal

St John’s Point

Carriganl Head

Malin Beg

Glen Head

Dawros Head

Crohy Head


Bloody Foreland

Horn Head

Melmore Head

Fanad head

Malin Head

For more information on the how the signalling system worked please see here.

For details of the team undertaking the project please see here.

The Irish Signal Stations Project is carried out at the Centre for Environmental Research Innovation and Sustainability (CERIS), an innovative and expert research cluster at IT Sligo.

Outcomes of this project to date are;

The Irish Signal Stations website.

The Coastal Signal Stations in the Province of Connacht and Ulster interactive map.

A short paper called ‘Analysis of low cost methods for assessing Signal Defensible Guardhouses in challenging environments across North West Ireland‘ published in the Institute of Archaeologists of Ireland News Letter (Winter 2016).

A 45 minute podcast about the Signal Stations was presented on ‘The Archaeology Show‘ in February 2017.

A longer paper called ‘– Looking for a pointless answer? Archaeological contributions to the understanding of Signal Tower sites of known date and function’ is due to be published in 2017 in the Proceedings of the IAI 2016 Conference. The paper is based on a presentation given in Galway on the 29th of April 2016.