Monument record 1910 - CNOC AN TURSA, LEWIS

NB23SW 29 213 329

A flat platform below five large natural boulders to the S of Callanish 1 (NB23SW 1) and immediately outside the Historic Scotland protected area was investigated by excavation of an 'L'-shaped 2m by 10m by 10m trial trench. Two large pits (or ditch terminals?) were partially exposed at the N end of the trial trench. Immediately to the S of these pits lay a setting of four post-sockets in a shallow arc. On the E side of the site a shallow ditch running N to S and containing worked flint was discovered. Silting or backfilling of this ditch appears to have been floowed by the erection of at least two phases of upright posts, the sockets of which cut through the ditch-fill into the underlying drift deposits. A spread of ash and charcoal was found to the E of these features. To the SW of the area bounded by the ditch and post-pit features a number of isolated post sockets were found.
Sponsors: University of Edinburgh, Historic Scotland
G M Coles 1993

Expansion of the trial trench opened in 1993 appears to confirm that the site represents a southern extension of NB23SW 1 and is probably broadly contemporaneous with it.
A 10m by 20m trench was opened and excavated to the underlying till. Features present in the subsoil and cut into the till were concentrated in the area immediately adjacent to the c 2m high rock wall of the roche moutonnee which forms the southern boundary of the site. Prehistoric activity appears to have been focused on a vertical fissure in this rock face.
The fissure contained a complex sequence of deposits. The upper part of the fissure was sealed with an evidently modern layer of organic silt containing sub-angular stones and bottle glass together with what appeared to be modern 'new age' offerings. This sealed several archaeologically sterile layers of coarse angular sands alternating with fine organic rich silts, possibly turf lines. Below these coarse sands and silts were a number of heart-like packings of flat stones set upon one another in a black charcoal-rich matrix. The dark matrix extended slightly beyond the fissure itself and overlay the edge of the fill of a c 2m diameter pit immediately in front of the fissure. This pit was haphazardly packed with possibly redeposited till.
The fill and edges of this pit feature were counter-cut by several pits and shallow scoops, previously noted in 1993, and which contained worked flint and pottery fragments of indeterminate type. The stratigraphic relationship suggests that the excavation of the large pit and its deliberate backfilling took place in antiquity. The location of the fissure and the pit on a direct alignment with the southern standing stone row of NB23SW1 may indicate that these features are contemporary.
Approximately 10m from the rock face and also on the alignment of the southern standing stone row was a large flat bottomed pit. This feature (part excavated in 1993) is thought on the basis of the presence of 'packing stones' and an irregular edge indicating removal damage to represent a previously unknown addition to this standing stone row. This stone is not indicated on any known historic plan or illustration of NB23SW 1. In 1993 a setting of four post-sockets in a shallow arc was noted immediately to the S of this pit; further possible post sockets were noted in 1994 but no convincing structure plan was evident.
The western boundary of the site appears to be marked by a shallow ditch-like feature extending 3m N from the western end of the rock face. This feature was part exposed in 1993 and closer examination during 1994 has revealed that the apparent 'ditch' is composed of multiple counter-cutting post settings, sockets (with packing stones) and shallow scoops following the same alignment. At least two and possibly more phases of post replacement are indicated.
Pottery fragments of indeterminate type and worked stone were present in many of these features and they appear to mark some form of post built'wing wall'or screen along the eastern boundary of the central focus of the site. It is not known if these features are paralleled by a similar series to the W since this area has yet to be excavated and geophysical survey has so far proved ineffectual.
Sponsors: University of Edinburgh, Historic Scotland.
G M Coles and T Rees 1994.

G M Coles, 1993a, Discovery and Excavation, Scotland, 110-1 (Bibliographic reference). SWE28579.