Nendrum monastic site - Sun Dial
Nendrum monastic site - Sun Dial

The monks who were engineers – Nendrum monastic site


There are some wonderful Ireland-focused blogs. Perhaps we need an official directory of high-standard personal blogs pertaining to the island. This one is a charm – by archaeologist Robert M Chapple, which contains a wide variety of engaging topics. I certainly will not be trying to compete with someone who keeps a catalogue of Radiocarbon Determinations and Dendrochronological Dates….

To me, as an outsider to the world of Irish archaeology, there seems to be a scarcity of information online about prehistoric sites. The same limited information is repeated over and over. Very few Irish academics choose the Internet to publicise their ideas – which is a pity. (If anyone reading this can recommend good Irish blogs, please get in contact!). Enough meandering. I ended up with Chapple, when trying to learn more about Nendrum, a former Christian monastery on Mahee Island in Strangford Lough, County Down.

Nendrum monastic site
Nendrum monastic site

The monastery closed between 974 and 1178, but its church served as a parish until the site was abandoned in the 15th century. St Mochaoi (a disciple of St Patrick) may have founded a monastery on this western shore of Strangford Lough in the 5th century. Though there’s some evidence for occupation of the area,  there is no archaeological support for a monastery at this early date. A 7th century date is more likely.

The Annals of the Four Masters say that Setna Ua Demain, an abbot of Nendrum, was burned in his house in 976, maybe during a Viking raid. After that there is no evidence of occupation  until 1177 when John de Courcy, an Anglo-Norman knight who invaded Ulster, gave Nendrum monastery to the Benedictine house of St Bees in Cumberland. This same John de Courcy also built the castle at Carrickfergus.

Nendrum monastic site
Nendrum monastic site

By 1306 Nendrum was named in the papal taxation list as a parish church. In the 15th century the church was abandoned and a new parish church was founded on the mainland at Tulynakill. The monastery was forgotten about for centuries until 1845 when William Reeves, searching for the churches on the 1306 list, rediscovered the site at Nendrum. In 1922 the site was excavated by H.C.Lawlor.  Reeeves was shown what people believed to be a ‘lime kiln’, but he recognised it as the remains of the Round Tower.  Chapple says that the work of Lawlor was somewhat poorly thought-out and as such the archaeological record of the site has been potentially polluted by the ideas and methods of those involved in the reconstruction of the site.

Nendrum Monastic Site aerial photo
Nendrum Monastic Site aerial photo from


The site is enclosed by three concentric walls and contained a variety of buildings and functions such as houses, gardens, orchards, a cemetery, workshops, and of course religious buildings.

For me there are four major items of interest: The workshops, the base of a round tower, a sundial (reconstructed by Lawlor), tidal mills which were contained outside these circles in the shore of Strangford Lough. The work shop was interpreted by Lawlor as a workshop as there were several half-finished pieces perhaps used for learning. I find this quite interesting.

I have visited St Paul’s missionaries in Turkana in Northern Kenya. A small group of priests live in an environment difficult which is challenging with poor access to food and water  – they also have workshops where local people are thought how the necessary manual skills (carpentry, mechanical etc) in order for the settlement to survive and also to build a relationship with local-people. It is probable that the monastery in Nendrum were faced with exactly the same challenges. They had to have a good relationship with the local community in order to feel secure. Here are the St Paul’s Missionaries:

The dig discovered an array of items including knives, pottery, brooches, pins etc. But more impressively a bronze-coated iron bell discovered near the outer enclosure wall. All these artefacts are stored within the Ulster Museum. A curious connection is a novel written with the same name – The Bell of Nendrum – “Nial Ross, a fifteen-year-old, twentieth-century boy sailing alone in Northern Ireland is suddenly transported back in time to a tenth-century monastery threatened by a Viking raid”. I cannot find anything else on the internet related to this bell. Perhaps it looks like the famous bell found in Bangor:

Bell of Bangor
Bell of Bangor from

The excavation also discovered 15 cross-inscribed stones.   Chapple says that this is the largest group of monastic crosses from Northern Ireland and also represents some of the earliest carved crosses in Ireland. They may have been used as simple grave markers for deceased monks. Eight of them are described as the Nendrum Cross – this is an outline Latin cross with hollows at the intersections between the arms and the shaft (or ‘armpits’).

In an attempt to protect them from theft, Lawlor had them built into a wall of the Church. However they were later moved to the new Visitor Centre – something which Chapple mentioned that the casual visitor might easily miss it. Compared to him I am undoubtedly that sort of casual visitor floating around missing visitor centres! Chapple mentions that the Visitor Centre has some excellent interactive exhibitions focused on children. The photo below I had to find on another blog.

Model of Nendrum in Visitor's Centre
Model of Nendrum in Visitor’s Centre from

In 1999 excavations at Nendrum resulted in the re-interpretation of linear wall structures in the waters to the east of the monastic complex as mill dams, rather than fish weirs as had hitherto been believed. Dendrochronological dating confirmed that this was the site of the earliest example of a tide mill in the world. Most of what I learned about this comes from Researchers from several universities study how livelihood and community has been moulded links to the environmental processes of rivers, constructed watercourses, energy systems and infrastructure – their blog is quite inteesting:

Nendrum monastic site - Tidal Mill
Nendrum monastic site – Tidal Mill

The first mill was  constructed between AD 619 and AD 621 and comprised a large dam, 110m in length, which captured water within a triangular millpond, 6,500 square metres. The pond filled up at high tide and retained the water as the tide receded outside the embankment, thereby providing a source of power to drive a horizontal waterwheel as it was released back into the Lough. This wheel would have been located in a wheelhouse. In the late 7th or early 8th century the first mill was no longer used and was replaced by a second complex of features on the same spot. The size of the mill pond was reduced, with a new dam forming a smaller, rectangular area of water adjacent next to the shore.

In addition to the workshops, the missionaries in Turkana also build water dams to collect rainwater. So there is a long tradition of monastic settlements getting involved with engineering works.

It is possible that Nendrum, with its educative and experimental focus, was the wellspring of widespread use of tidal mills. All this happened in a different age where time was broken up into planetary changes – sunrise, the tides, and teh seasons. Even their sundial was developed for a different need. The day was not split into hours but rather canonical hours which mark the divisions of the day in terms of periods of fixed prayer at regular intervals. They are a type of sundial known as a Tide Dial (

Nendrum monastic site - Sun Dial
Nendrum monastic site – Sun Dial

The name tide dial preserves the Old English term tīd, used for hours and canonical hours prior to the Norman Conquest of England, after which the Norman French hour gradually replaced it. I had not known that the sea-related word Tide, and its adjective Tidal have the same origin. According to – “Old English tīd time; related to Old High German zīt, Old Norse tīthr time” And something like springtide is a less use denotation of springtime.

Nendrum monastic site and Strangford Lough
Nendrum monastic site and Strangford Lough


Nendrum –

Nendrum Monastry –

Nendrum Monastic Site –

Nendrum Monastry –

Saints and Sea Power in the Tidal Waters of the Irish Sea –

The Bell of Nendrum –

Christianity in Comber –

Canonical hours –

Tide dial –

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