Sexagesimal Stonehenge – The Geometry of the Stonehenge Sarsen Trilithons.
Stonehenge is a mystery that attracts
explanations which range from the banal to the fantastic. To claim a new theory
is original, interesting, and credible is to set a high hurdle. This brief note
presents what is believed to be a new geometric design that is simple, elegant,
The positions of the five sarsen
trilithons of the inner horseshoe at Stonehenge can be explained by a simple
plan of chords based on the sixty points of the outer sarsen circle. This
layout provides an accurate geometry for aligning to all the solstitial
sunrises and sunsets.
The same geometry is exhibited by the
Bush Barrow Lozenge.
Stonehenge, Bush Barrow Lozenge, Trilithons, Geometry, Sexagesimal.
* January 2024
Preprint DOI: 10.13140/RG.2.2.16275.86560 License CC BY-SA 4.0
* January 2024
Revised Draft License CC BY-SA 4.0
* *Cannings Cross
Farm, All Cannings, Devizes Wiltshire SN10 3NP
* 750 Words
From the earliest surveys of Stonehenge,
the plans of the stone setting have attracted geometric speculation. From Inigo
Jones (1655), Stukeley (1740) John Wood (1747) and John Smith(1771) to the
innumerable modern speculators the arrangement of the stones has been attempted
to be explained by many different diagrams.
Figure 1 is believed to be most accurate plan of the present positions
of the stones.
Figure 1 Stonehenge Plan by Anthony Johnson, licensed under the Creative Commons Attribution 3.0 Unported license.
For ease of explanation, I have taken the
plan and turned it so the solstical axis is vertical. This is the alignment of
the Midsummer Sunrise and Midwinter Sunset that passes through the monument.
Figure 2 Modified
Stonehenge Plan by Tim Daw based on Stonehenge Plan by Anthony Johnson,
licensed under the Creative Commons Attribution 3.0
In “The Twisted Trilithon – Stone 56 and
its Skew”, Daw T 2015, it was argued that the central trilithon, Stones 55. 56
and 156, and the Altar Stone, 80 were originally positioned at an angle to the
perpendicular of the solstical axis described, and that this angle of about 80
degrees to the axis aligned them to the other solstical sunrise and sunset, the
midwinter sunrise and midsummer sunset. The calculated angle for this alignment
is ”80° 49' 25" in 2500BCE, very close to 81° “ (Banton S, Pers Comm
The outer circle of Sarsens can be considered to have had thirty standing stones and thirty gaps. There appear to be parchmarks where missing stones are expected, Banton et al 2014, and so it is justifiable to use a completed circle as the template. Taking the centres of these we can generate a familiar pattern of sixty marks in a circle.
Clockface image generated by Tim Daw
The diagram has every fifth mark
enlarged; this is purely for ease of understanding as it echoes the familiar
clockface. Also added are a central
marker and a central circle at half the diameter of the outer circle.
A geometric property of such a circle is
that a chord, a line across a circle that doesn’t necessarily pass through the
centre, can be easily drawn at 81 degrees to a diameter line. To use the
familiar clock idiom a line drawn from 42 minutes to 15 minutes is at 81
degrees to the vertical line. The same angle as the claimed additional
solstical lines of the stones 55-56 and the Altar Stone.
The Bush Barrow Gold lozenge found close to Stonehenge in Bowl Barrow Wilsford G5 as part of a rich assemblage of grave goods, now in the Wiltshire Museum, is based on the 81-degree angle. It dates from a more recent period than the construction of Stonehenge, but its use of the same angle suggests that the knowledge of its significance and method of recording it had continued.
Figure 4 The Bush Barrow Lozenge,
Wiltshire Museum Photograph, overlain with angled lines and clockface by Tim
The other four trilithons of the inner
horseshoe are also positioned on regular chords across the circle, to within an
acceptable accuracy of the plan and their present positions which have been
subject to movement and even re-erection.
They appear to be positioned so that the
centre of the flat inner surface of each trilithon is halfway from the outer
circle to the centre of the monument.
The proposed chords and as an overlay on the plan:
Figure 5 Clockface plan with chords generated by Tim Daw
Stonehenge Plan with chords. Based on figures 2 and 5
This simple diagram with the suggestion
that the architects of Stonehenge used the geometry of a sexagesimal circle may
form the basis of further speculation and insights.
Acknowledgement: The invaluable help from Simon Banton in sharing his knowledge, skills, and enthusiasm. This paper is self-funded.
BANTON, S, et al.
2014 Parchmarks at Stonehenge, July 2013. Antiquity. 2014;88(341):733-739.
2024. WhatsApp message 3 January 2024
2015 The Twisted Trilithon – Stone 56 and its Skew,
WANHM vol. 108 (2015 pp15-24)
JONES I, 1655.
The most notable antiquity of Great Britain, vulgarly called Stone-Heng on
Salisbury plain, London
SMITH, J. 1771. Choir
Gaur: The Grand Orrery of the Ancient Druids, Commonly Called Stonehenge on
Salisbury Plain, Astronomically Explained and Mathematically Proved to be a
Temple Erected in the Earliest Ages ... United Kingdom
STUKELEY W, 1740.
Stonehenge, a Temple Restor'd to the British Druids, London : Printed for W.
Innys and R. Manby, London
WOOD, John. 1747
Choir Gaure, Vulgarly called Stonehenge, on Salisbury Plain, Oxford