Chambered Cairn, Frachdale, Islay

I had a feeling Carl had posted some time ago about the ruined village of Frachdale and his trip there and his futile search for a chambered cairn. I can't find that post now, but, always up for a challenge, I went on an adventure yesterday. It wasn't really an adventure to start with, following an easy track through Cornabus forest, until the track stopped and the fun began. Glad of the partially frozen bogs, I trod cautiously through vastly flooded areas, nearly lost my welly, fought my way through dense forestry and was 'rewarded' by coming out onto a huge expanse of boggy moorland. Undaunted, I continued my quest west, round to Frachdale. I realised I was close to the aforementioned chambered cairn, but where exactly was it on the map and why don't they mark its exact location and why hadn't I checked for co-ordinates before I set off this morning? Despite my uncertainty, I checked all possibilities and found it. I don't normally have much success with these things, so I feel quite proud of myself! I attach photos and some info from Scotland's Places website.
Becky

NR 310 469 A Clyde group chambered cairns crowns a knoll (just below 250ft OD) at the side of a small valley. Only a small amount of cairn material remains around the chamber; its edges are impossible to define with any confidence. The cairn slopes down to the east in front of the chamber and merges with the knoll. On the north side two stones about 25ft from the chamber appear to revet cairn material and might be part of a kerb. Another stone about 20ft south west of the chamber may also be a kerb stone. Behind the chamber the cairn appears to have been robbed to the old ground surface. Beyond this a stony spread extends to 60ft from the chamber, but this seems to be derived from the scattered remains of a small building. It is unlikely that the cairn was much more than 50ft in diameter, its shape is uncertain. Three stones of the chamber walls, and a septal slab remain, about 1 1/2ft above the turf; the chamber axis lies just west of north to south of east, with the entrance at the latter end, where there are three large irregular blocks of stone, probably two portals with a stone either fallen from the chamber roof, or used to block the entrance, between them.
A S Henshall 1972, visited 1962.

This chambered cairn occupies a small knoll 500m W ofruins of Frachdale on the SW side of an unnamed stream. The cairn material has been severly robbed, but four possible kerb-stones, as shown on the plan (RCAHMS 1984), suggest a cross-measurement of about 15m; the original shape, however, is unknown. The chamber is aligned almost E-W, with the entrance facing E; in front of it the two massive portal stones now lie dislodged, with a third large stone between them. The three surviving side-slabs, which are exposed to a height of about 0.5m, indicate that the chamber measures about 3.5m by 1m internally; a septal stone divides it into two unequal compartments.
RCAHMS 1984, visited May 1979.

Frachdale just visible in the centre of photo.

Looking south-east towards Cornabus Forest

Looking east

Looking north-west towards Grasdale

View of the knoll on which the chambered cairn is situated. Taken from the north.