Ireland's Napoleonic-era signal towers

Picture of Ireland: Ireland’s Napoleonic-era signal towers were central players in an early-19th-century communication system…

Picture of Ireland:Ireland's Napoleonic-era signal towers were central players in an early-19th-century communication system implemented in response to the threat of a French invasion. Sited in remote coastal locations, most of these lone, grey signal towers were constructed, furnished and staffed between 1804 and 1806.

The towers were a defensible quarters for the signal crew, which normally comprised a naval lieutenant, a midshipman, two signalmen and a military guard (usually eight to 12 men). They were of broadly similar construction: square, two storeys, flat roof with parapet, main door at first-floor level (accessed by a ladder) and fireplaces. Unlike their burly bigger brothers the Martellos, the signal towers were not designed to hold heavy artillery.

The signalling system, referred to as an optical telegraph, required that each signal station be visible to its counterparts on either side. Sending a message involved raising and lowering a large rectangular flag, a smaller blue pendant and four black balls in various combinations along a system centred on a tall wooden mast. The stations also communicated with ships.

If all of 81 stations proposed in the 1804-6 plans were operating simultaneously (some accounts suggest this was never the case), a signal could travel 1,076km around the coast of Ireland. Its average journey between stations was 13.5 km. The shortest trip was between Brow Head and Mizen Head, at 3.8km; the longest was between Ballydavid and Kerry Head, at 36.9km. Low cloud and sea fog, phenomena all too familiar on the Irish coast, were very real threats to the effectiveness of the system.


The threat of invasion was significantly diminished following Napoleon’s defeat at Waterloo in 1815. Maintenance of the structures was costly, and many were abandoned. Some towers have been restored and become part of modern residences.

Many of the original stations are on the Ordnance Survey’s first-edition maps, compiled about 30 years after they were built. These note a large number as being in ruins; some have completely disappeared.

Paul M Kerrigan’s Castles and Fortifications in Ireland 1485-1945 (Collins Press, 1995) is full of detail about signal towers and the defence of the Irish coast

View from the ground How one community has been restoring its tower

The signal tower at the Old Head of Kinsale, Co Cork, is being restored by the local community.

"By the end of the year, we hope to have restored the tower so people can climb to the top and have a view," says Con Hayes, a retired physics and maths teacher and civil engineer.

"We also plan to restore the signalling system. Eventually, we hope to have a 'Lusitania' museum, which would have an official opening in 2015, the 100th anniversary of the ship's sinking . . .

"This could greatly increase tourist traffic to the area, especially if it becomes part of the Wild Atlantic Way project, which starts in Donegal and finishes in Kinsale."

The tower, at the apex of the Old Head ring route, has extensive views. The station at Seven Heads is visible against the skyline 13.1km to the southwest.

The Kinsale tower is just over nine metres high, with walls up to 80cm thick. Records show a signal crew was in place in 1804 and the tower finished the following year, though severely affected by dampness. The 1899 Ordnance Survey map lists the site as being in ruins.

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Ordnance Survey Ireland licence EN 0063512 © Ordnance Survey Ireland/ Government of Ireland. Data sources: UCC, OSi. Produced by All-Island Research Observatory. Not to be reproduced without permission from Airo