British Megalithic

see also Stone Circles, where some British circle geometries (proposed by Alexander Thom) are interpreted.

640px Stonehenge renderSarsen Circle (blue) within the preexisting outer circle of Stonehenge

It is important to see the practical problems faced by the builders of megalithic monuments.  By 3000 BC, Stonehenge was the ring now called the the Aubrey Circle, a set of postholes now thought sockets for bluestones brought from the Preseli hills in Wales. Other rings of postholes were dug in the centuries following, the Z and Y-rings, these perhaps containing 30 and 29 sockets for bluestones but not properly concentric with the Aubrey Circle or evenly spaced. Around 2500 BC, a new and complex design was carefully and concentrically placed within the area within the Y-ring. It has been suggested its design was influenced by the dynastic cultures of Egypt which had their own megalithism of pyramids and obelisks, employing faced masonry and stone joints but now in the British idiom of stone circles natural to higher latitudes. The Aubrey Circle came to be just as dynastic Egypt began whilst the Sarsen Circle was built in the middle of the second dynasty (Old Kingdom) (2625-2510). 

NE Cairn; half an hour before sunset [photo: Ian B. Wright, 2009] 

IBW Clava 6A bRight

Alexander Thom surveyed an unusual group of three cairns near Inverness, Scotland, and found significant alignments to the solstice sun on the horizon. The cairns were later carbon dated within a few centuries of 2000 BC. Since Thom significant further work has been published and Thom's astronomical alignments fell out of favour but are now making a (discrete) comeback. The plan below usefully shows artificially raised surfaces which allowed the kerb stones (holding the infill back) to be partially buried rather than set in fully dug holes. The 1997 plan appears to show magnetic rather than true North, 2.2 degrees west of North so I have turned the plan 2.2 degrees anticlockwise.  

BalnuaranCairnGroup RCAHMS1997

Figure 1 1997 plan of the Balnuaran of Clava with alignments to solar extremes 

 Bartolomeu Velho 1568 540The Geocentric Model of the cosmos with the earth at its centre, by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568 (Bibliothèque Nationale, Paris) [Wikipedia]. This mapping of planetary and other layers of time resembles the form of Neolithic henges (see figure 1 below).

Finding the right picture of important information requires ingenuity. Map makers, for example, use the technique of providing an inset showing a larger map at a smaller scaling (say of North America) and then a detailed map (of say the Gulf of Mexico) at the greater scale, so as to show cities and other features whilst still seeing the greater whole. Megalithic astronomy similarly generated maps, but of time periods, which were drawn geometrically, using lines and circles where units of measure represented every day which (for example) was an day to an inch or a day to a foot. In this and later articles we show how the megalithic built circular structures, henges and stone circles, to express major time periods. They had measured these periods using (a) alignments on the horizon pointing to sun and moon events and (b) counting time between events in metrological units of time.

I went to Thornborough some years back and was pleased to be shown English Heritage Research Report 174: Cult, Religion, and Pilgrimage: Archaeological investigations at the Neolithic and Bronze Age Monument Complex of Thornborough, North Yorkshire, ed: Jan Harding, (Council for British Archaeology: York) 2013, ISBN 978-1-902771-97-7.

ThornboroughHenges

The three henges are of similar size and design, a design most clear in what remains of the central henge. 

As usual with three slightly off-line objects, the parallel to Orion's belt has been made, and eventually this has become an acceptible interpretation (in this case) by the authors. One can see from the title of report 174, Cult, Religion, and Pilgrimage, religio-anthropological parallels are preferred by archaeology as a social explanation for the unique geography of riverine Yorkshire, east of the Pennines. However, astronomical alignments and the metrology within sites are dutifully ignored as a source of meaning relevent though to the widespread practice of horizon astronomy and counting using lengths of identical length (such as inches or digits).