Interpreting Lochmariaquer in 2012, an early discovery was of a near-Pythagorean triangle with sides 18, 19 and 6. This year I found that triangle as between the start of the Erdevan Alignments near Carnac. But how did this work on cosmic N:N+1 triangles get started?
Robin Heath’s earliest work, A Key to Stonehenge (1993) placed his Lunation Triangle within a sequence of three right-angled triangles which could easily be constructed using one megalithic yard per lunar month. These would then have been useful in generating some key lengths proportional to the lunar year:
the number of lunar months in the solar year,
the number of lunar orbits in the solar year and
the length of the eclipse year in 30-day months.
all in lunar months. These triangles are to be constructed using the number series 11, 12, 13, 14 so as to form N:N+1 triangles (see figure 1).
n.b. In the 1990s the primary geometry used to explore megalithic astronomy was N:N+1 triangles, where N could be non-integer, since the lunation triangle was just such whilst easily set out using the 12:13:5 Pythagorean triangle and forming the intermediate hypotenuse to the 3 point of the 5 side. In the 11:12 and 13:14 triangles, the short side is not equal to 5.
The word Alignment is used in France to describe its stone rows. Their interpretation has been various, from being an army turned to stone (a local myth) to their use, like graph paper, for extrapolation of values (Thom). That stone rows were alignments to horizon events gives a partial but useful explanation, since menhirs (or standing stones) do form a web of horizon alignments to solstice sun and to the moon’s extreme rising and setting event, at maximum and minimum standstill. At Carnac the solstice sun was aligned to the diagonal of the 4 by 3 rectangle and maximum and minimum standstill moon aligned to the diagonal of a single or double square, respectively.
It seems quite clear today that stone rows at least represented the counting of important astronomical time periods. We have seen at Crocuno that eclipse periods, exceeding the solar year, are accompanied by some rectalinear structures (Le Manio, Crucuno, Kerzerho) which embody counting in miniature, as if to record it, and it has been observed that cromlechs (or large stone kerb monuments) were built at the ends of the long stone rows of Carnac and Erdeven. Sometimes, a cromlech initiated a longer count,with or without stone rows, that ended with a rectangle (Crucuno). The focus on counting time naturally reveals a vernacular quite unique to this region and epoch. We have seen that the Kerzerho alignments were at least a 4 by 3 rectangle which recorded the 235 lunar months in feet along its diagonal to midsummer solstice sunset. After that rectangle there follows a massive Alignment of stone rows to the east,ending after 2.3 km having gradually changed their bearing to 15 degrees south of east. Just above the alignments lies a hillock with multiple dolmens and a north-south stone row (Mané Braz) whilst below its eastern extremity lies the tumulus and dolmen,”T-shaped passage-grave” (Burl. Megalithic Brittany. 196) called Mané Groh.
In 1973, Alexander Thom found the Crucuno rectangle to have been
“accurately placed east and west” by its megalithic builders, and
“built round a rectangle 30 MY [megalithic yards] by 40 MY” and that
“only at the latitude of Crucuno could the diagonals of a 3, 4, 5
rectangle indicate at both solstices the azimuth of the sun rising and setting
when it appears to rest on the horizon.” In a recent article I found metrology was used between the Crucuno
dolmen (within Crucuno) and the rectangle in the east to count 47 lunar months,
since this closely approximates 4 eclipse years (of 346.62 days) which is the
shortest eclipse prediction period available to early astronomers.
About 1.22 miles northwest lie the alignments sometimes called
Erdeven, on the present D781 before the hamlet Kerzerho – after which hamlet
they were named by Archaeology. These stone rows are a major complex monument
but here we consider only the section beside the road to the east. Unlike the
Le Manec Kermario and Kerlestan alignments which start north of Carnac,
Erdevan’s alignments are, like the Crucuno rectangle accurately placed east and