Archaeoastronomy in the British Isles - The Stones and the Stars: Building Scotland's Newest Megalith - page 89

F IG . 4.26 Arbor Low (Photo by Chris Stanley)
distant “foresights” until fully a thousand years after the circles
were created; what else went on is irrelevant to their argument.
However hard one tries not to have “a profound ignorance of the
archaeological facts,” it's hard to see how it can be anything but
“subjective and imposed by the observer” to suggest instead that
the circles are symbolic clearings in imaginary forests - forests
which, in mainland Britain, vanished centuries before, and which
in Orkney and Shetland apparently never existed at all!
The point about mensuration and Pythagorean geometry is,
logically, quite separate. The arts involved are not needed for the
positioning and layout of megalithic observatories, and whether
or not the builders had them is a quite separate argument - a by-
product, as far as this topic is concerned, of the astronomical one.
It arises because comparatively few of the ancient stone rings
are actually circles. From the air, Arbor Low, for example, very
clearly is not (Fig. 4.26 ), and neither is Castle Rigg in Cumbria
(Fig. 4.27 ).
Briefly, Thom claimed that his surveys of the internal layouts
of the stone rings, spirals and Carnac alignments reveal the exis-
tence of a common unit of length, the “megalithic yard” of 2.72 ft,
with a standard multiple, the megalithic rod (1 meg. rod = 2.5 MY),