
What can you say about a castle where only fragments remain of the original structure? Turns out – a surprising amount!

Fragmentary remains is the phrase used in the National Monuments record to describe the two castles which are the subject of this post – Dunbeacon and Castle Island. In each case only enough is still standing to confirm that it was indeed a medieval tower house. Fortunately, in the case of Dunbeacon, there is also historical evidence.

Let’s look at Castle Island first, and begin with the name. Samuel, in his thesis on The Tower Houses of West Cork, tells us that it was known locally as Castleduff, or Caisleán Dubh, the Black Castle. However, this was the name more commonly applied to Black Castle/Leamcon, so he says there might be some confusion there. There is no other name in the historical records – no mention, indeed, at all. Perhaps it was too insignificant to merit a mention – a fortified outpost rather than the high-status residence of one of the ruling O’Mahonys.

We have noted with other of the O’Mahony castles that they were built on the site of a ring fort (Ardintenant) or a promontory fort (Dunlough). The National Monuments records notes a promontory fort at this site, although it is not obvious on the ground any more. There are, in fact several promontory forts noted on Castle Island, perhaps indicating that this was the preferred type of fortified dwelling here, since there are no ringforts.

Like all the O’Mahony castles, it was strategically sited – it was beside the waters that separates the island from the mainland, and within sight of two other castles – Rossbrin and Ardintenant. The three form a triangle that overlooked and guarded the sheltered waters of Castle Island Channel. But also, from the top of the castle, there would have been a clear view south across the low land in the centre of the island, out to Roaringwater Bay.

We know that these waters would have been crowded with Spanish, French, Portuguese and British fishing boats, coming in to salt their catches in the fish palaces along the coast and to replenish their supplies. For all of these services and for permission to fish around Roaringwater Bay they paid hefty fees to the O’Mahonys, who got fabulously wealthy as a result.

The castle was much smaller than all the others. Samuel says,
Working on the assumption that Castleduff was an RE tower house [i.e Raised entry], its smallness is striking. The surviving ‘end wall’ makes possible a reasonably accurate estimate of the plan’s original length. It is assumed that like its neighbours, its plan had a length-to-breadth ratio of 3:4 to 4:5; the ratios suggest a length of 7.96-7.46m (measures above the base-batter). The surviving north wall probably represents the full length of the ground-floor chamber.
Mark Wycliffe Samuel
the tower houses of west cork
The only surviving opening is a loop in one wall, and a row of corbels that would have supported the first floor is still visible. There is no trace of anything that might suggest a vault, so it is possible that this small tower was unvaulted – Samuel thinks that the walls are noticeably thinner than the other castles, implying that this was a much simpler and shorter tower.

Samuels concludes his study of this tower by saying:
The jetty is modern, but the beach that it is laid upon was the best natural landing point on the island, well sheltered from the Atlantic swell. The landing clearly determined the siting of the tower house and was an important resource to the family that built the tower house. It is tempting to see a direct continuity between the recent settlement and a settlement around the tower house. Only excavation could determine if this was the case.
Mark Wycliffe Samuel
the tower houses of west cork

Dunbeacon (images below) is even more vestigial than Castle Island, but fortunately we do have some historical evidence for it. The name could mean Fort of Beacan – where Beacan is the name of a chieftain. However, it could also mean The Fort of the Mushrooms – since the Irish word for mushroom is beacán. I like to think of the chieftain and his lady chowing down on a plate of eggs and mushrooms for breakfast.

As with Castle Island, there are signs that the castle was built within a former promontory fort, also underscored with the name Dún, which means fortress. A fosse, or ditch, cut through the rock, is all that remains of the fortifications of that promontory fort.

The majority of the O’Mahony tower houses in Ivagha were built by or for the sons of Conchobar Cabach. Dunbeacon castle was allegedly built by his brother Dohmnall. This seems to be a traditional rather than documented attribution. If it is assumed that Dohmnall was born c. 1400, he may have built the tower house at any date during his adult life (c.1420 to c.1470).
Mark Wycliffe Samuel
the tower houses of west cork

The siting is magnificent. From it, there is a clear view of the whole of Dunmanus Bay, right to the end of the Ivaha (Mizen) and Sheep’s Head Peninsulas. This, of course, also meant that it bore the responsibility, along with Dunmanus, of defending O’Mahony territory from attack or incursion on the north side of Ivaha. The pro-English Owen O’Sullivan of Beara, for example, is known to have conducted cattle raids on the lands surrounding Dunbeacon.

Samuel tells us that the chief of Dunbeacon, Domhnall O’Mahony, forfeited his lands as a result of his participation in the Desmond Rebellion, and it became a ruin – beautifully captured in Brian Lalor’s sketch, above.
The tower house and four ploughlands were confiscated, and passed into the possession of an English settler who probably built a timber house to the east. The O’Mahonys did not attempt to reconquer the lost part of their pobol; instead they contented themselves with attacking and burning the tower house, an event recorded in a letter written by an English judge in 1588. The tower house probably remained a ruin.
Mark Wycliffe Samuel
the tower houses of west cork

The O’Mahonys regained possession of their Dunbeacon lands but lost them again when they were granted to an English settler. See my post Planning a Plantation: Jobson’s 1589 Map of Munster Part 1 and Part 2 for how the land was mapped preparatory to the Plantation of Munster. As you can see above, Dunbeacon (or Donbeken) was clearly marked out for colonisation. William Hull came to own it at one point, and even the conniving ‘lawyer’ Walter Coppinger laid claim to it – as he did with much of the O’Mahony and O’Driscoll territory.

Although so little remains, Samuel’s careful analysis indicates that Dunbeacon was probably a typical raised entry tower house, with a vault supporting the third floor which held the principle private chamber. See my posts on Ardintenant and Black Castle for what it may have looked like.

It’s hard to look at ‘fragmentary remains’ and think of them as vibrant centres of life. Yet, these two castles were once part of the mighty O’Mahony federation – a large network of connected families that ruled Ivaha and the surrounding seas. Sic Transit Gloria Mundi.
