Signal Towers


Visitors to some of Ireland’s most remote coastal locations might find themselves drawn to the sight of a lone grey tower, perched on an exposed hill-top or headland. These are the Napoleonic-era signal towers — central players in an early nineteenth century observation and communication system implemented in response to the threat of a French invasion of Ireland.

Initial Plans
With initial plans mooted in 1803, the establishment of the signalling system began in earnest a year later when eighty-one strategic locations were initially identified as the sites for the signal stations. Between 1804 and 1806 most of the signal towers were constructed, furnished and staffed. Initial budgets were often surpassed, as building in such remote locations proved extremely difficult. The towers themselves were a defensible quarters for the signal crew, which normally comprised a naval lieutenant, a midshipman, two signalmen and a military guard (usually between eight and twelve men in total). At some stations, however, there was no tower constructed — the crew instead being housed in a nearby Martello tower, light house or other fortification.

The Towers
Although local variation exists, the towers were all of broadly similar construction — square in plan, two (sometimes three) storeys high, flat roof with parapet, main door at first floor level (accessed by a ladder), and fireplaces. They also contained defensive features like machicolation (projections from the walls to allow objects to be thrown directly down on attackers). Their exteriors were rendered or weather-slated for protection against the elements, but even the earliest reports suggest that many suffered from damp and were difficult to maintain. There may also have been smaller ancillary structures at these sites, and the remains of cultivation ridges at a number of towers suggest the crew were growing some of their own food. The whole complex was usually enclosed by a wall or sloping bank (glacis) which afforded some extra protection. Unlike their burly bigger brothers — the Martello towers — the signal towers were not designed to hold heavy artillery and provide cannon fire to protect strategic harbours and water routes. Their main role was to house their crew and help protect them from attack by a small force.

The Signalling System
The signalling system itself, referred to as an optical telegraph, was similar to that in use on the English coast at the time and required that signal stations were inter-visible with their counterparts at either side. The process of sending a message involved the raising and lowering of a large rectangular flag, a smaller blue pendant and four black balls or hoops in various combinations along a system centred on a tall wooden mast. This mast was positioned at the seaward side of the tower and the main enclosure often fanned out to encompass a semi-circular area around this. The signal stations were not only in contact with each other, but also communicated with ships at sea and would have relayed messages to and from inland locations.

A Signal's Journey
A signal could originate at any point along the line and travel in either direction. The message may also have only concerned a number stations and would not necessarily travel all the way to Dublin — perhaps instead terminating at a regional barracks like Cork or Waterford for example. Assuming that all of the original eighty-one stations proposed in the 1804-06 plans were operating simultaneously (though some accounts suggest that this was never the case), a signal could theoretically travel some 1076km (670 miles) around the coast of Ireland between Malin Head and Dublin. Its average journey between stations was some 13.5 km (8.3 miles), with its shortest trip between Brow Head and Mizen Head at 3.8km (2.4 miles) and its longest between Ballydavid and Kerry Head at 36.9km (24.6 miles). The majority of these distances would seem to have been within range of contemporary telescopes, but that is assuming conditions of fair to good visibility. Low cloud and sea fog, phenomena all too familiar to the Irish coastline, were a very real threat to the effectiveness of the signalling system. Later additions to the network, like at Kilshannig Point for example, seemingly sought to address these problems by bridging larger transmission distances or taking advantage of more strategic locations. The use of fires was also associated with these towers, as to relate a simple warning in conditions of poor visibility or over significant distances the use of flames and billowing smoke would have been a most effective means.

The Aftermath
The working lives of many of the Napoleonic-era signal towers were relatively short. Maintenance of structures in such remote and exposed locations was costly and many were abandoned not long after their construction. The threat of invasion was also significantly diminished following Napolean’s defeat at Waterloo in 1815. A number of the towers were incorporated into later buildings like coastguard stations, semaphore stations and World War watch towers. More recently again, some towers have been restored and become part of modern residences. While the tower at the Old Head of Kinsale is at the centre of exciting plans for restoration as part of a local community initiative.

Many of the original signal stations can be located on the Ordnance Survey’s first edition maps, compiled some thirty years after they were built. These maps note a large number as being ‘in ruins’, with some having completely disappeared. On the 20th of August 2006, an event organised by the Beara Archaeological and Historical Society took place to mark the two-hundred year anniversary of the building of the towers. Local communities all along the Irish coast came together and a new lease of life surged through these remote outposts – a fire lit at the Black Ball Head tower in Beara began a signal that spread westward and eastward, bound for Malin Head and Dublin.

Find out more:
See Paul M. Kerrigan’s Castles and Fortifications in Ireland 1485 – 1945 (Collins Press, 1995) to read in wonderful detail on signal towers and the defence of the Irish coast during this period.

To view photographs of the 2006 event and some of the towers, visit John Eagle’s website at:

Daphen Pouchin Mould considers in great detail the barracks of Ballinskelligs Bay in Archaeology Ireland Vol 8 No. 2 (Summer 1994)

Muiris O'Sullivan and Liam Downey continue the excellent 'Know You Monuments' series in Archaeology Ireland Vol 26 No. 2 (Summer 2012) with an article on Martello and Signal Towers, marking the 100th issue of the publication.

Tomás Ó hArgáin with the support of Comhchoiste Ghaeltacht Uíbh Ráthaigh has produced a very informative booklet on the Signal Stations of Co. Kerry to mark the 200 year celebrations. This booklet contains map extracts and photographs.


SMR: O137-008 | NIAH: 20913706
The signal tower at the Old Head of Kinsale is located at the apex of the Old Head ring route in the townland of Ballymackean. It commands extensive views in all directions, with a vast Atlantic panorama spanning the southern horizon. It is station twenty-five from the original list of eighty-one that ran from Pigeon House Fort in Dublin around the coast to Malin Head, Co. Donegal. The Old Head’s sister station (number twenty-four) at Barry’s Head – which no longer survives – is 13.7km to the north-east. The station at Seven Heads was the next in the line and is visible against the skyline 13.1km to the south-west.

The signal tower at the Old Head is of a typical construction – two storey and square in plan. Its ground floor encloses some 14.5 square metres and the tower stands at just over 9 metres (30 feet) tall with walls up to 0.80 metres in thickness. The north wall splays outward slightly at its centre to accommodate the chimney flue. The remains of the original chimney stack (over a metre tall) are visible above this. The original doorway faces seaward at first-floor level in the southern wall. Above this a feature known as machicolation projects from the wall. This defensive feature allowed projectiles be thrown directly downward at attackers and is also found in older castles and tower houses. There is also evidence of corner-machicolation (referred to as bartizans) in the north-west and north-east top corners of the tower. Remains of the original weather-slating are visible on the west, south and east walls. The north wall is of block construction and does not appear to have been originally slated.

There are three square-set windows on the ground floor, with the doorway in the west wall likely to be a later enlargement of an original fourth. There are also four slightly larger windows at first floor level. Fireplaces can be seen on the north wall on both floors, with tall recesses for storage at both sides of these. Beam holes in the walls show where floor and roof levels were originally. The flat timber roof was accessible and would have been used as the primary look-out post. Movement between levels seems to have been by ladder.

Contemporary records show that a signal crew was in place in 1804 and the tower was fully completed the following year, though severely affected by dampness. The 1842 Ordnance Survey map lists a ‘signal tower’ and depicts a rectangular enclosure around the site, with a semicircular projection extending at the seaward side. This is where the signalling mast would have been located. The 1899 Ordnance Survey map lists the site as being in ruins and notes the area of this enclosure as 0.81 acres (3280 square metres). The north and east stretches of this enclosure no longer remain, but those at the west and south survive as large banks with a significant slope on their exterior (often referred to as a ‘glacis’). This map also appears to show the footprint of additional structures in the immediate vicinity of the tower.  A concreted trigonometrical (or ‘trig’) station is found today to the north of the tower.

The signal tower at the Old Head of Kinsale looking seaward from the north-west. Note the remains of the defensive bartizan (corner-machicolation) in the top northwestern corner of tower. There are also the remains of a bartizan in the northeastern corner. A machicolation is located directly over the original door which is at first-floor level in the southern wall. The door at ground level in the west wall is likely a later enlargement of an original window. The slight thickening of the north wall at its centre would have accommodated the chimney flue.


Take a closer look at the Signal Tower on the Old Head with this Photosynth. To have a look inside, navigate your way through the door on the ground floor. The synth opens with the viewer looking eastwards at the west-facing wall.

For full-screen mode, you can visit this Synth at the Photosynth website here

(Silverlight or Photosynth Viewer is required. Available on Windows, Mac OS, iOS. Not currently availble on Android).


Of the eighty-one original signal stations, all but seven of these can be tied down to a location on the Ordnance Survey's first edition six-inch maps of the 1840's. The remaining seven have a townland name or headland name associated with them, so can be located to within kilometre or so (perhaps even closer considering that the stations would be sited on a point of some prominence). The proposed station on Hog's Island (Scariff Island) off the tip of the Iveragh Peninsula is alleged never to have been built, but the site for the purposes of the current map is given a notional location at the centre of the island.

There are five additional stations included on the map (yellow dots). These are generally considered later additions to the original network of eighty-one. The stations are located at Brandon Head and Kilshannig Point and Hog's Head in County Kerry, the island of Inishbofin off the Galway coast, and at Lenadoon in County Sligo. With the exception of Lenadoon, all of these sites are labelled on the 1840's maps. Daphne Pouchin Mould (1994) suggests that the station at Brandon Head may have been abandoned during construction due the problem of 'summer mists', which would have severely limited its visibility. Interestingly, the towers at Hog's Head, Bolus Head and Kilshannig point all share a similar construction — a more elaboratle design than the standard signal tower and employing corner flankers in their enclosing walls. They have been referred to as 'barracks' and Pouchin-Mould draws comparisons with similar strucutres in the Scottish Highlands (ibid.). Kerrigan sugests that the original Bolus Head Station may have been sited closer to the coast as there are the footings of a structure some 500m WNW atop the Ducalla cliffs simialr in size to the typical signal tower. This original site may have proven unsuitable (perhaps due to its very exposed location), and the nearby structure was subsequently constructed and took over signalling duties.


You can download the KMZ file below if you would like to take a closer look at the signal towers, or to follow the journey of a signal as a fly-thru tour from Malin Head to Dublin.

This file is for use with Google Earth (free and paid versions). To access the file, you must first unzip/extract it. Once you have Google Earth installed on your system, double-click on the extracted KMZ file and it should launch automatically. You can navigate around the coastline looking in more detail at each station location. When you click on a station symbol, a pop-up will appear containg some information about the site. This attribute information includes:

  • NAME: Site name by townland/headland/fort/etc.
  • COUNTY: County wherein site is located
  • POSITION: The station's position from the original line of 81. Stations not in the original list are noted as 'Later addition'
  • Map_1840s: How the station is depicted on the Ordnance Survey's first edition six-inch maps (Signal Station, Telegraph, Lighthouse, Tower, etc.). Where a site is not depicted, it is noted as 'not shown'.
  • LAT/LONG: Latitude and Longitude in decimal degrees (WGS84)
  • ITM E/N: Irish Transverse Mercator coordinates
  • Map_Link: A hyperlink to the OSi Public MapViewer to where the site is located on the Ordnance Survey first edition map. Once in the OSI MapViewer, you can change the backdrop layers like the twenty-five-inch map (circa. 1900), and aerial photographs from 1995, 2000 and 2005. Please note: Linking to webpages within Google Earth can be quite slow. View the links through your default web-browser to speed up the process (select the 'View in...' tab the will appear in the very top-right corner of the Google Earth window).
  • Other: This field includes some short notes relating to select sites.


To begin the tour, double click on the Signal Tower Tour (you will need to expand the KMZ file in Google Earth by clicking on the small + symbol). Each station is labelled by name and this should appear as you pass by them. At any time you can pause the tour using the small tour toolbar that appears at the bottom-left of the window. Once paused, you can call the pop-up relating the site information by clicking on the site symbol (as above).

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