Iona Monastery, Torr An Aba

An small area around the corss base on Torr an Aba was excavated by Charles Thomas in 1956. A cutting was made on the middle part of the ridge where, even before the turf was removed, stones were visible in a manner suggesting that they were not part of the natural rock so evident to thenorth and south. Once the turf was removed, the central portion of the top of the ridge was seen to be artificial: 'the main feature seems to be a large square mortared plinth containing a single slab of micaceous rock, with a socket through it for a cross (-shaft)'

Information from E Fowler and PJ Fowler 1988.

A further small area was excavated by Charles Thomas in 1957 to the south of the cross base (revealed in 1956) on Torr an Aba. In 1956 it had been noted that the southern and south-eastern edge of the plinth of the crossbase overlay further masonry. It was therefore decided in 1957 to excavate a larger area across the slightly lower and more or less flat central part of the ridge-top immediately south of the plinth. The excavations revealed traces of a building, thought to be the cell of St Columba mentioned by Adamnan

Information from E Fowler and PJ Fowler 1988.

(Carved Stone No.6, 225) At the summit of Tórr an Aba a masonry pedestal about 2.7 m square incorporates an irregular slab of Moine granulite with mica partings measuring 1.01 m by 0.80m and 65mm in thickness. This appears to have been used at first as a millstone having a diameter of about 1.1 m and a central hole 0.18m in diameter, but subsequently one edge was damaged and it was adapted for use as a cross socket with a rectangular slot 0·36m by 0.13m cut through the original aperture. When the base was exposed by excavation in 1956, having been concealed below turf since the late 19th century (126), a course of granite boulders about 0·25m high and incorporating a slot was found in situ above the socket-stone (127), but these have since been removed. The construction of the existing pedestal suggests a late medieval date (128), although the socketed slab may have been first used at an earlier period.

RCAHMS 1982, visited September 1980

(126) Plan in Dryden MS 7

(127) Information from Professor A C Thomas

(128) Cf. the base of MacLean's Cross (no. 224) and the cross-base at Texa, Islay (Inventory of Argyll, 5 (forthcoming)).

The narrow rocky spine of Torr an Aba was described by Martin in 1695 as 'Dun Ni Manich, i.e. Monk's Fort, built of stone and lime, in form of a bastion' (29), and a revetment of massive boulders, apparently designed to enlarge the summit area, is still evident on the w face . The stone footing of a sub-circular structure, immediately s of and partly overlain by the medieval cross-base platform on the summit (No. 6, 225), was excavated in 1957 (30). It measured about 3m in maximum internal span, and the entrance was probably in the E wall , where any trace of a supporting revetment had disappeared. Along the tops of the walls were found traces of charcoal, thought by the excavator to represent stakes supporting the roof structure; the walls themselves were fitted into the irregular surface of the outcrop in a manner that has been compared with the construction of a hut on Dun Cui Bhuirg (No. 2) (31). This building has been identified by the excavator as Columba's cell (32), but the claim must be regarded as doubtful. It rests partly upon the conflation of Adomnan's references to the tegoriolum 'built in a higher place' and described as tabulis suffulto, interpreted by Professor Thomas as 'supported on revetments' (33), with those to the hospitiolum where Columba slept on the bare rock , whereas other scholars interpret these as two distinct buildings. It is true, however, that Torr an Aba is the only area E of Cnoc nan Carnan, apart from a knoll in Reilig Odhrain, where bedrock is exposed. When excavated, the structure was found to have been filled with pebbles, presumably after its abandonment. The line of its walls is now marked by a modern setting of mortared stones.

RCAHMS 1982, visited September 1980

(29) Martin, Western Islands, 288; (30) Coracle, no. 31 (1957), 12-13; Chadwick, N K et al., St Columba: Fourteenth Centenary 563-1963 (1963), pi. opp. p. 22; (31) DES (1958), 15; (32) Coracle, loc. cit.; (33) Adomnan, Columba (Anderson), 258. The normal meaning of this phrase is 'supported on planks, or joists'. The comparable phrase used by Adomnán to describe houses built on wooden supports near the River Nile is misquoted by the Andersons (ibid., 110). In the most recent edition it reads ‘in domibus transuersis trabibus (beams) suffultis' (Adamnan, De Locis, 104).

Scheduled as element within 'The monument known as St Mary's Abbey, Iona, monastic settlement [comprising] the remains of the large early historic monastic settlement founded by St Columba in AD 563, St Martin's Cross, and parts of medieval buildings associated with the Benedictine Abbey of St Mary founded around AD 1200.'

Information from Historic Scotland, scheduling document dated 28 October 2011.