1992:141 - BOFEENAUN, Mayo

A number of archaeological features were investigated over a 3-week period in October 1992 at Lough More, Bofeenaun. Lough More is situated in a shallow basin surrounded by pear covered hills at the south-eastern side of Nephin Mountain. Recent drainage of the lake had exposed a variety of archaeological sites including a crannóg and two fulachta fiadh. Of the 13 or so other features, most were lines of wooden stakes driven into the soft peat at the lake edge. Several of these may have been some form of deer trap, and a piece of antler was found along one line of stakes. Many of the archaeological features, however, had been badly damaged by continuous lake edge erosion. This included both the crannóg and the fulachta fiadh, which were rapidly collapsing into the lake. The crannóg had also been badly disturbed by trampling and many of the remaining features, including the posts, had been dug up or damaged.

Crannóg
A detailed investigation of the crannóg was carried out with the aim of raising the lake level and attempting to preserve the remaining archaeological features. The crannóg is located on a small knoll or flooded peninsula of peat which projects into the lake some 29m from the south-eastern pre-drainage shoreline. This knoll is currently some 0.5m to 0.7m above the water level. The edges of the knoll were defined by a palisade of wooden posts and the interior was lined with flags and large pebbles. The overall diameter of the palisade ranged between 14.6m east-north-east/west-south-west and 11.8m west-north-west/east-south-east. The construction of the palisade varied considerably with regularly placed double rings of posts in some areas whereas other areas were made up of irregular posts and stakes apparently driven in at random. The spacing between individual posts also varied considerably and ranged from immediately adjacent to over 1.5m apart. Over 90 posts were used in total and these ranged between split oaks and a variety of intact roundwood. The average diameter of the roundwood posts ranged from 0.28m to 0.35m whereas the split oaks averaged 0.35m+ by 0.14m in dimension. Many of the posts protruded some 0.4m above the peat level but all were driven in to a surprisingly shallow depth. The longest was only 1.2m with the average being no more than 0.6m. The range of species for the roundwood posts varied over the site. Oak was generally preferred, however, over 60% of the south-eastern quadrant was made up of large birch posts. This was the only area where birch was used and the size and quantity of the posts suggests that this area may have required more reinforcement than other areas. Smaller ash posts were found in a number of areas.

The surface of the crannóg was covered by a single layer of stone flags and large pebbles. This covering was missing from an oval 5m by 3m, area at the crest of the knoll. The stone layer was also missing from small pockets of the crannóg. Examination of the lake-bed revealed that a considerable amount of material had been washed off the crannóg along the western edge and that only the lowest stone levels remained anyway intact. In depth analysis of the sub-stone levels revealed that no further stratigraphy was present. Large concentrations of iron slag were recovered from the crannóg surface, particularly in the north-eastern area. In one instance, a small sandstone flag was found fused with slag, probably as a result of molten slag being placed on the stone. Two hollowed flags were also recovered. One of these measured 0.43m by 0.26m in diameter and 0.5m in depth had been pocked out in the centre. Several small pieces of furnace lining were also found scattered in the north-eastern area. These were mainly composed of clay tempered with quartz.

Several finds, including a hammer stone, an iron spade, two metal gouges and two furnace bases, had been removed from the site prior to excavation. Unfortunately, the Unit were not made aware of these items until excavations had been completed.

The overall function of the crannóg is as yet unknown. No internal structures, other than several concentrations of small stakes, were noted. It was constructed on an already existing peat island, reinforced by the palisade, and the stone layer and few finds would seem to indicate that it was primarily a metalworking site.

Fulacht fiadh
A detailed examination was also undertaken of one of the two fulachta fiadh on the eastern shore. Much of the structure had already collapsed into the lake prior to excavation and the remainder was exposed on the lake edge. Nevertheless, a large amount of the burnt stone mound and part of a wooden trough remained intact. The burnt stone mound was of the classic kidney-shape in appearance. It measured 8.3m in length by 3.2m in maximum width. The burnt stones formed two deep concentrations on either side of the trough area and were piled some 0.3m to 0.6m in depth. All of the stones showed traces of heat splitting and the sub-angular sections indicated a variety of parent rock types, probably obtained from the glacially-deposited hillocks nearby. Scattered amongst the burnt stone were concentrations of ash and birch charcoal. Given that the fulacht fiadh was constructed at the original lake edge, the discarded stone mound would have eventually formed an ideal platform on which to light the necessary fires to heat the stones. The concentrations of charcoal may represent the washed-through remains of these fires.

Removal of the collapse in the trough area revealed the remains of a wooden trough constructed in a box fashion of horizontally laid roundwood, predominantly ash. The roundwood spars, averaging 0.8m to 0.1m in diameter, were tightly packed together to prevent leakage and were fixed in place by corner posts. The intact section of the trough was 1.1m in length and was 0.6m in height. The base of the trough was made up of a layer of leaves and small twigs, covered over with a layer of moss. There was no evidence for a more substantial wooden base. Resting on the base were several large stones, averaging 0.25m in diameter. These were of a similar type to the shattered burnt examples and may represent the last heat stones used in the trough. In one case, a small heat-split fragment was found broken off from the larger stone and could be re-fitted exactly. Examination of the petrological and other details are currently being undertaken.