Stone Circles

by Martin J Powell

There are nine recognised stone circles in the South Wales region comprising Glamorganshire, Brecknockshire (Breconshire, south Powys) and Monmouthshire (Gwent).

Five of the circles have previously been considered in an astronomical context by the late Professor Alexander Thom (Thom, 1967). All five are located within the Brecon Beacons National Park in Powys, and they will now be briefly discussed.

At the Cerrig Duon circle in Fforest Fawr (SN 851 206) Thom suggested that the outlying stone (Maen Mawr) when viewed from the centre of the circle, indicated the rising of the star Arcturus in 1950 BC.

For the two circles on Trecastle Mountain (SN 833 311), Thom proposed three solar alignments, the most significant being to the midwinter sunrise. In the early 1900s, Lt-Col. W. Llewellyn Morgan also suggested that a row of four small stones leading from the smaller, South-western circle was aligned towards the early February and early November sunset, i.e. the Celtic Iron Age festivals of Samhain and Imbolc (Llewellyn Morgan, 1907-8, pg. 148). However, British archaeologist Aubrey Burl thinks it unlikely that this "miserable alignment" could ever have been used for astronomical observation; the low-standing row was so deeply buried in the moorland that Thom failed to notice it when he surveyed the site (Burl, 1976, pg. 262). Interestingly, the recent Royal Commission plan of the site shows an additional row of three stones running between the two circles, tangential to their South-eastern edges and roughly on the same alignment as the aforementioned row (RCAHMW, 1997, pg. 154).

For the two elliptically-shaped Nant Tarw circles situated south of the Usk reservoir (SN 819 258) Thom proposed four alignments, perhaps the most significant being between the centres of the two circles towards sunset on the Beltane/Lughnasa Iron Age festival days (i.e. early May/early August). A now fallen stone on the skyline, when seen from the North-western circle, indicates the rising point of the star Spica around 1900 BC. A similarly fallen stone on the WSW horizon, when viewed from the South-eastern circle, indicates a declination of -16°.8. Although Burl says this has no astronomical significance, it does in fact lie very close to the Samhain/Imbolc setting sun (Burl, 1976, pg. 260).

An astronomical alignment at the Gray Hill stone circle (ST 438 935) near Wentwood Forest, was first proposed by Fred J. Hando, a resident writer and artist (Hando, 1944). He suggested an alignment on the midwinter sunrise between two standing stones which he named the "First Piper" and the "Second Piper". However, this claim is disputed by Burl (personal communication, 1990) on the grounds that the line is inaccurate and that another stone adjcent to the circle has been overlooked in the assessment. The site is certainly ruinous and only the most rudimentary alignments can now be proposed.

The lonely circle at Ynys Hir (SN 921 383) on Mynydd Eppynt (now within a military training area) is an interesting circle with an apparently natural group of boulders occupying a wide gap at its South-eastern edge. Another wide gap occurs at the West of the circle. After excavation in 1940 the excavator thought that the most likely reason for the placement of these entrances was to accomodate two prehistoric trackways which intersected a short distance away from it (Dunning, 1943, pg. 178). One of the tracks was orientated East-West, and the entrances to the circle were similarly arranged, allowing easier access to the circle. However, when considering the deliberate inclusion of the natural boulders in the circle, he stated that "the long gap [at the South-east of the circle] suggests that the group [of boulders] was, for some reason or other, intentionally incorporated in the plan of the monument" (Dunning, 1943, pg. 177). The Royal Commission's recent inventory of the region states that these "glacial erratics were probably left there because they were too heavy to move" (RCAHMW, 1997, pg. 157). Could astronomy help to explain the inclusion of these stones? Although the centre-point of the boulders, when viewed from the centre of the circle, indicates sunrise in late November and mid January, the arc spanned by the boulders also takes in the midwinter rising sun - which may have been the builders' intended target.

The largest circle in the study area is the now barely discernible Blaen Digedi circle south of Hay-on-Wye (SO 239 373), also known by the names Hay Bluff, Blaenau and Pen-y-Beacon. It is particularly accessible since it stands beside a public car park on the road passing the Hay Bluff escarpment. Some recently placed boulders confuse the site somewhat, however the original circle was some 98 ft (30 m) in diameter, but only one original stone is now visible. This stone is of particular interest since, together with a smaller adjacent stone, it is set at right-angles to the circumference of the circle, the pair forming an apparent 'entrance' to the circle at the South-east (RCAHMW, 1997, pg. 160).

Finally a 'new' stone circle was officially recognised as such in 1993. Situated on open moorland to the South of Builth Wells, the Banc y Celyn stone circle (SO 050 463) is elliptical in plan, measuring 60 ft (18.5 m) by 49 ft (15 m) in diameter. There are 24 stones, three of which are clearly visible uprights, the remainder being partially visible or completely hidden beneath the vegetation. Like at Blaen Digedi, it has an entrance-like stone setting at the South-east (RCAHMW, 1997, pg. 158).

The presence of stone settings or wide gaps in the south-eastern quadrant of several stone circles in South Wales is potentially of considerable archaeoastronomical interest. Stone settings occur at the Nant Tarw western circle, the Trecastle eastern circle, Ynys-Hir, Blaen Digedi and Banc y Celyn. Curious gaps at the South-east are present at Cerrig Duon and Nant Tarw east, which may mark the former presence of similar stone settings. These sites certainly require further astronomical study.

Survey Results (Explanation of Data Table)

Stone Rows and Stone Pairs in South Wales
Neolithic Tombs in GLA and MON	Round Cairns and Round Barrows
Neolithic Tombs in BRE and HRF	Enclosures & Ringworks

BIBLIOGRAPHY

BURL, Aubrey

1976    The Stone Circles of the British Isles (Yale University Press, New Haven & London).

DUNNING, G. C.

1943    "A Stone Circle and Cairn on Mynydd Eppynt, Brecknockshire"  in Archaeologia Cambrensis (The Cambrian Archaeological Association, Cardiff), pgs 169-194.

HANDO, Fred J.

1944    The Pleasant Land of Gwent (R. H. Johns Ltd., Newport).

LLEWELLYN MORGAN, Lieut.-Col. W.

1907-8    "Three days with the Swansea Scientific Society" in Transactions of the Swansea Scientific Society, pgs 145-162.

ROYAL COMMISSION ON ANCIENT & HISTORICAL MONUMENTS IN WALES

1997    Brecknock: Later Prehistoric Monuments and Unenclosed Settlements to 1000 A.D. (Sutton Publishing Ltd., Stroud).

THOM, Alexander,

1967    Megalithic Sites in Britain, Oxford University Press (Oxford), Table 8.1, pg. 101.

Copyright Martin J Powell 2001, with minor revisions April 2006

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