with possible alignments towards
the Beltane/Lughnasa sunrise/sunset
by Martin J. Powell
Although prehistoric alignments towards the May Day/Lammas sunrise/sunset were suggested by Sir J. Norman Lockyer and F. C. Penrose as far back as 1901, it was Professor Alexander Thom who, in the 1960s, proposed an accurate and workable prehistoric calendar. Based on evidence gleaned from his surveys of some 300 prehistoric sites, Thom proposed that the prehistoric year was divided into 16 roughly equal parts, or 'months', based primarily around the solstices and the equinoxes.
The cross-quarter days (also called mid-quarter days) mark the points mid-way in time between the solstices and the equinoxes. These significant seasonal dates were celebrated by the Iron Age Celts of North-western Europe in the festivals of Imbolc (February), Beltane (May), Lughnasa (August) and Samhain (November). Falling either side of the summer solstice, Thom defined the May Day/Lammas dates (i.e. Beltane/Lughnasa) as occurring when the Sun's declination was +16º.67± 0.14 (Thom 1967, 110). In the current Gregorian calendar, this corresponds to dates around 6th-8th May for Beltane and 5th-7th August for Lughnasa (McCluskey 1989, S18).
The following table gives details of British and Irish sites dating from the later Neolithic and Bronze Age periods which are thought to include alignments towards May Day/Lammas. There are undoubtedly many more candidate sites, however the ones listed here are known to have been accurately surveyed and the astronomy thoroughly assessed. The alignments proposed by Thom are taken from Table 8.1 of his 1967 work. His 'Class C' alignments, i.e. those with the poorest indications, are excluded from this list.
Table listing British and Irish sites dating from the later Neolithic and Bronze Age periods which are thought to include alignments towards the May Day/Lammas sunrise/sunset (click for full-size table, 169 KB). The book references shown in the 'Source' column, and the reference numbers shown in the 'Notes' column, are listed in their respective sections below.
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1. Thom refers to the site as 'Usk River'.
2. Alignment is from Station Stone 91 to 93, two stones of a rectangle of 'Four Stations' positioned just inside the bank of the henge. Today, Stone 91 is prostrate and Stone 93 survives only as a stump, though all four stones were originally upright.
3. Alignment is from the geometrical centre of the flattened circle towards a cairn-circle known as 'Little Meg' 0.8 km distant (NY 576 374).
4. Alignment suggested by Barnatt and cited in Burl, 1983. The cist inside the circle has a cup-marked slab.
5. Alignment suggested in Meyn Mamvro magazine in 1991 and cited in Burl, 1993. The 244 metre long alignment of 85 stones ends at a cairn on Caradon Hill.6. Alignment is from the centre of the stone circle to sunrise over Rough Tor.
7. Also known as Tirghoil standing stone.
8. Alignment is from a tall menhir at the WSW of the stone circle to a cup-marked stone at the ENE of the circle. The name 'Beltany' is derived from 'Beltane'.
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1982 Prehistoric Cornwall: The Ceremonial Monuments, Turnstone Press (Wellingborough).
1976 The Stone Circles of the British Isles, Yale University Press (New Haven & London).
1983 Prehistoric Astronomy and Ritual, Shire Publications (Aylesbury).
1987 The Stonehenge People, Barrie & Jenkins (London).
1993 From Carnac to Callanish: The Prehistoric Stone Rows and Avenues of Britain, Ireland and Brittany, Yale University Press (New Haven & London).
McCLUSKEY, Stephen C.
1989 'The Mid-Quarter Days and the Historical Survival of British Folk Astronomy' in the journal Archaeoastronomy, Vol. 20, No. 13, Science History Publications (Cambridge).
MILLIGAN, Max & BURL, Aubrey
1999 Circles of Stone: The Prehistoric Rings of Britain and Ireland, The Harvill Press (London).
POWELL, Martin J.
1995 'Astronomical Indications at a Bell-barrow in South Wales' in the journal Archaeoastronomy, Vol. 26, No. 20, Science History Publications (Cambridge).
1967 Megalithic Sites in Britain, Oxford University Press (Oxford).
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Prehistoric Sites in England
Prehistoric Sites in Wales
Prehistoric Sites in Scotland
Archaeoastronomy in South Wales
Copyright Martin J Powell 2003
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