Only two type-D stone circles (see figure 3) are
known to exist, called Roughtor (in Cornwall) and Seascale (in Cumbria). Seascale
is assessed below, for the potential this type of flattened circle had to
provide megalithic astronomers with a calendrical observatory. Seascale could also
have modelled the harmonic ratios of the visible outer planets relative to the
lunar year. Flattened to the north, Seascale now faces Sellafield nuclear
reprocessing plant (figure 1).
Stone Age astronomical monuments went through a
series of evolutionary phases: in Britain c. 3000 BC, stone circles became
widespread until the Late Bronze Age c. 1500 BC. These stone circles manifest
aspects of Late Stone Age art (10,000 – 4500 BC) seen in some of its geometrical
and symbolic forms, in particular as calendrical day tallies scored on bones.
In pre-literate societies, visual art takes on an objective technical function,
especially when focussed upon time and the cyclic phenomena observed within
time. The precedent for Britain’s stone circle culture is that of Brittany,
around Carnac in the south, from where Megalithic Ireland, England and Wales probably
got their own megalithic culture.
Around Carnac in Brittany the land is peppered with uniquely-formed megalithic designs. In contrast, Great Britain’s surviving monuments are largely standing stones and stone circles. One might explain this as early experimentation at Carnac followed by a well-organised set of methods and means in Britain. What these experiments near Carnac were concerned with is contentious, there being no appetite, in many parts of society, for a prehistory of high-achieving geometers and exact scientists. Part of the problem is that pioneers interpreting monuments are themselves hampered by their own preferences. Once Alexander Thom had found the megalithic yard as a likely building unit, he tended to use that measure to the exclusion of other known metrological systems (see A.E. Berriman’s Historical Metrology. Similarly, John Neal’s breakthrough in All Done With Mirrors, having found the foot we still use to be the cornerstone of ancient metrology, led to his ambivalent relationship to the megalithic yard. Neal’s interpretation of the Crucuno rectangle employs a highly variable set of megalithic yards, perhaps missing the simpler point, that his foot-based metrology is supported as present within the dimensions of the Crucuno rectangle; said by Thom to be a “symbolic observatory” of the sun: this monument was an educational device, in which Neal finds the geometry of “squaring the circle” which, as we see later, was probably the Rectangle’s main metrological meaning.