Welsh Journals

Further Thoughts on Arthur's Stone by T. R. OWEN IN VOLUME VIII OF Gower, Dr. Bosse-Griffiths wrote on The Secret of Arthur Stone In this brief article, the writer hopes to show that this important megalithic tomb hides some more secrets. Arthur's Stone is a late Neolithic dolmen, built almost 4,000 years ago as a chambered tomb. Its main feature was the large capstone weighing at least 35 tons. This tremendous stone was later split into two portions, the smaller of which now lies on the floor. The capstone was supported by a number of smaller stones and the whole structure was covered with a round earthen mound. Two other such tombs, known as Sweyn's Houses, occur, at almost the same height above sea level, on the eastern flank of Rhosili Down. That portion of Arthur's Stone which still stands has an estimated weight of 25 tons, is nearly 14 feet long and almost 7 feet broad. It is made of an extremely hard rock which is seen to comprise large rounded pebbles of quartz embedded in a matrix of siliceous composition. The rock is what the geologist terms a quartz-conglomerate and is similar in appearance to the rocks which form Cefn Bryn, the high backbone of Gower. Beds of quartz conglomerate, adding up to a total thickness of 300 feet, form the uppermost portion of the Old Red Sandstone in Gower. On Cefn Bryn, these pebbly Devonian rocks fall into two divisions, an upper one of white conglomerate and a lower of red conglomerate. The pebbles of both are mainly of vein- quartz but occasionally of grey quartzite and of a strikingly red angular rock called jasper. A good place for seeing these rocks is Penmaen. Rutter, in Prehistoric Gower, agrees with the views of the 1907 Geological Survey Memoir concerning the very local character of the capstone of Arthur's Stone. In other words, the capstone rock is formed of Old Red Sandstone conglomerate. The sting in (or near) the tail of this article is the question But is it ? A close examination of the capstone and of the split portion reveals the abundance of large, well-rounded, quartz pebbles, some up to seven inches long. A few pebbles are of chert, sandstone and even well-indurated slate. There are signs of red staining in the large capstone, whilst the bedding is seen on the west face to be vertical. The most crucial pebbles, however, in the two large stones are (a) of brown clay-ironstone (occurring fairly frequently and