Monument record 14951 - Tolsta Chaolais, Uig, Lewis

Site 2
Head dyke/boundary wall
A large dyke nearby runs down to the east of the stream which runs into Loch a'Bhaile and terminates on the shore of the latter. It is not marked upon the first edition OS making its first appearance on the 2nd edition. However, evidence from the trial excavations may indicate otherwise - see discussion below in section 2.
McHardy 2007, 6

The large dyke on the north east corner of the village was investigated ahead of the pumping station which will be constructed there. The dyke was cross sectioned at a suitable looking point within the target area and excavated down to natural.
The results were unexpected, showing what looks like two distinct phases of wall/dyke, separated by a substantial layer of peat growth, and hence presumably a considerable amount of time.
It could be seen that the wall (s) had been constructred at the edge of a natural terrace of glacial clays which was probably 'made' by the nearby stream cutting through them, as evidenced by the riverine deposits directly overlying the glacial clays.
All that remains of the first 'wall' is a bank shaped heap fo yellow clay. It may well have been more substantial originally with tones later robbed out or not present at this particular section. There is also the possibility, although thought to be unlikely, it is not an earlier wall at all but some chance deposition a proposition which could only be checked through further excavation.
The layer of peat over this is up to 400mm thick at its greatest, but lenses out to 200mm thick where it separates the two possible dykes. Again, there is the possibility that this peat was dug up from nearby during or for the construction of the latest phase of dyke, which may then have not been a long time after the first. However, this is not thought likely as the peat looked like it had grown in situ and not re-deposited. Red staining at the upper surface of the peat also indicates widespread burning immediately before the upper dyke was re-built.
This would imply that a wall or some form of barrier followed this line or re-used this line after falling out of use for a quite a long period. It seems very difficult to make any estimate as to how long it would have taken for this depth of peat to grow, as a great deal depends uon the local conditions. Perhaps we could guess at least 100 years, the true length of time probablay a great deal longer.
The ordnance survey shows no wall here in 1852 (the 1st edition), it only appears on the 2nd edition in 1897. The wall under the peat would then presumably have been present but indictinguishable (at least to the surveyors) at the time of the 1st edition, and re-made by the time of the 2nd.
We could then speculate ………….
Samples of the soil from both above and below this peat as well as from the base of the peat were taken for dating and/or analysis should funding become available.
McHardy 12-13

Ian McHardy, 2007, An Archaeological Study of Tolsta Chaolais (Unpublished document). SWE41190.