Publication Account
Date 2007
Event ID 587503
Category Descriptive Accounts
Type Publication Account
Permalink http://canmore.org.uk/event/587503
NL58 1 SRON AN DUIN ('Dun Sron Duin', 'Barra Head')
NL/549802
This promontory semibroch stands on the edge of the high cliff on the south side of Barra Head on Berneray, the southernmost island of the Outer Hebridean archipelago (visited 2/6/1988).
Description
The structure consists of a curved, galleried wall – convex towards the front – barring the neck of the promontory which gives the site its name. The area immediately inland of the wall is now within the grounds of the lighthouse near Barra Head (built in 1833) which is now disused; the promontory fort forms one end of the lighthouse enclosure. The tip of the promontory measures about 42m long by 13m across at the centre; the surface was thought to have been hollowed out at some stage, leaving a ragged parapet of rock around the edges some 1.8 - 3.0m (6 - 10 ft) high [2]. To the author these 'parapets' seem to form a natural amphitheatre and doubt-less partly explain why the site was fortified; several huts could have stood behind the defensive wall, in a fairly sheltered position despite the gales which blow over this high cliff.
At present the wall is about 20.1m (66 ft) in length along the chord of its arc [4, fig. 191] although the south end is almost completely reduced to foundation level and certainly extended a few feet further in the past. Thomas gives the length as 29m (95 ft) but this figure is too great; Anderson's plan [3, fig. 6], made shortly before 1893, shows a length of 21.4m (70 ft) along the same chord. Both plans show how the south-east end curves backwards quite sharply along the edge of the south cliff and ends at a built face which was parallel to the line of the main wall at the opposite end.
The wall stood up to 3.97m (13 ft) high at about 1865 [2] and its outer face stood 2.71m (9 ft) high for much of its length in 1914 [4]; by 1988 however the outer face had been reduced to 2m or less at the centre. Thomas’ elevation of the front face shows several courses of masonry rising above the entrance passage – to almost double its height – but now there are only two. The wall thickness was given as 4.58m (15 ft) [2] but this is now visible only at the entrance passage (near the north-west end) which is 3.97m (13 ft) long (it is possible that the wall is thicker in the centre, as at Rudh an Dunain – NG31 1). Some of the facing stones are very large, one being 2.12m (7 ft) long by 84cm (2 ft 9 in) high. A crudely rebuilt facing has been put on top of the front of the wall to help corral sheep.
A partly lintelled entrance passage – the outer end of which is well preserved – is 3.66m (12 ft) from the north-west end of the wall; it stands 1.60m (5 ft 3 in) high, 66cm (2 ft 2 in) wide at the outer end and has a paved floor. The innermost three-fifths of the left wall has dis-appeared (presumably dismantled) but that on the right is almost complete. In this right wall is a built door-check – 1.04m (3 ft 5 in) from the exterior – with the bar-hole behind it. From this point forward the Iron Age lintels are in situ but the innermost lintel (just behind the door-frame) is not in its original position; it rests on a facing of secondary masonry which has been built against the left wall and which conceals the left door-check while narrowing the outer part of the passage. It comes to a neatly built end 2.1m (7 ft) from the exterior. As noted the later lintel rests on this end, at a slightly higher level than those further out. Thus the secondary masonry has been inserted under the original lintels in the outer part of the passage.
The face of the primary left wall of the passage emerges from behind this later masonry and immediately there is a sharp, well built corner as the face turns into the wall; this is clearly shown on the Commission’s plan. This must be the outer side of a doorway leading directly from the entrance into the basal intra-mural gallery – a feature noted, but not diagnosed as a doorway, by the Commission's investigators [4, 133]. It is also implied in the plan given to Joseph Anderson [3] and in that of Capt. Thomas. A mural gallery connecting directly with the entrance is not so far known in any other semibroch (though it may exist at Dun Grugaig 1 – NG81 1), although it occurs in a few brochs .
At the inner end of the entrance there is now only 79cm (2 ft 7 in) of inner wall-face between its right corner and the edge of the cliff; at the outer end the thickness is about 3.6m (12 ft). Thus the ground plan of this last section of the wall is distinctly wedge-shaped, and the face running along the cliff edge is clear.
In 1915 it could be seen that the promontory wall contained two super-imposed galleries, the lower being about 1.14m (3 ft 9 in) wide and having several of its roofing lintels in position; these last are also shown schematically on Anderson's plan. The outer face of the upper gallery then stood 1.07m (3 ft 6 in) above the lintels at one point. Now the wall is much more broken down and the lintels just mentioned have almost certainly disappeared; a trough along the centre of the wallhead probably marks the position of the gallery but the base of this appears to be lower than the primary entrance lintels – which should be at the same height as those of the Level I gallery. There are now no signs of the face of the upper gallery. The inner face of the main wall is buried so its thickness is not measurable except at the entrance.
Discussion
Excavation might reveal a doorway leading into the rear wallface from the interior and an intra-mural stair rising to its right; however there are no signs of these features at the moment and the fact that the gallery connects with the entrance may mean that no other door into it was needed. One would also expect there to have been a scarcement on the rear wallface (at the level of the lintels of the entrance) but this has probably disappeared. The parallels with Rudh an Dunain (NG31 1) and Dun Grugaig 2 (NG51 1) seem very close and the site is an excellent example of how, at one stage, the sophisticated high, hollow wall of the brochs was used to build simple promontory defences rather than round towers.
The secondary block of drystone masonry which has been inserted into the outer part of the entrance to narrow it suggests that the promontory fort was re-occupied at a later stage of the middle Iron Age, or even later, in the late Iron Age. One could surmise that the inner half of the galleried wall was then taken down to ground level and the outer half rebuilt to make a refurbished stronghold, but only excavation will reveal the true story.
If the hints of an early Iron Age date for the galleried wall at Clickhimin in Shetland (HU 44 1) and Rudh an Dunain in Skye (NG31 1) are applicable to this site, Sron an Duin was probably built in the 6th or even the 7th century BC.
Sources: 1. NMRS site no. NL 58 SW 4: 2. Thomas 1890, 404: 3. Anderson 1893: 4. RCAHMS 1928, 132-33, no. 450: 5. Feachem 1963, 179-80.
E W MacKie 2007
