Erdeven Alignment’s counting of Metonic and Saros Periods

first published in March 2018

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.

Figure 1 The intermittent extent of the Erdevan Alignments, and associated dolmens

If we take the hint that the Kerzerho rectangle ([post2post id=”395″]) at the western extremity of the Erdevan alignments has the length 235 feet along its diagonal, and remember that terminating monuments often form a micro-site, a clue to the whole provided by an oral culture, like a textbook,then we can expect the Metonic of nineteen years within which 235 lunar months complete, to be present in the larger monument. We also know that the 47 lunar month approximation/reminder for 4 eclipse years was also involved since 235 =5 x 47, and the Crucuno count to the south, between dolmen and rectangle, was 4 by 3 with units of 47 feet.

Figure 2 The Micro-site of Kerzerho rectangle diagonal
whose outer dimensions were in units of 47 feet

It is possible that the alignments (figure 1), which were once “probably complete” (Lukis, 1888) and gaps now widened by agricultural necessity, sought to avoid the small hill of dolmen called Mané Braz whilst providing the alignments as a counting corridor-like cursus. Below the eastern extremity of the alignments lies the tumulus and dolmen of Mané Groh and one can see its bearing,on Google Earth, as being 18.4 degrees south of east whilst its distance, from stone left of the entrance to Kerzerho, divides by 235 feet 32 times. Thus, if a unit of 32 feet is used, then the distance to Mané Groh is 32 times the distance across Kerzerho’s diagonal and it too marks the Metonic period.

The angle to Mané Groh, at 18.4 degrees relative to east, is that of an 18-19-6 near-Pythagorean triangle and, since east and west are so accurately maintained at Crucuno and Kerzerho rectangles, then the 18 side can be assumed, there is no monument (today) at the right angle but one can see in figure 3, the 18 side can be taken down to area where the alignments terminate on the east, in their attempt to avoid the hill of Mané Braz whilst probably providing a counting corridor for the Saros period of just over 18 years.

Figure 3 Establishing the form of the whole Erdevan complex of counted and assumed dimensions of time

The Erdeven alignments were evidently a single monument including the dolmens necessary for marking out the triangle (Mané Groh), conducting the astronomy (Mané Braz) and the rectangles at the western extremity.

The Near-Pythagorean Triangle

There was a full article relating to two series of three Pythagorean triangles ([post2post id=421]) in which my discovery of a near-Pythagorean triangle with shortest side 6 units and longest side 19 units (the Metonic in years) leads to a base side of √(192 / 62) = 18.0278 units whilst the Saros period (of 19 eclipse years or 223 lunar months) equals 18.030 solar years, just 19 hours longer.

This means that the 18-19-6 triangle is a very excellent model of the Saros to Metonic ratio, of 223 to 235 lunar months, providing the 19 and 6 sides are integer: the 18 side will be longer by the required amount. Having counted 223 units of 32 feet directly east, one would reach the right angle of the triangle as shown in figure 3. So can one find (without looking too hard) the reference length of 223 feet within the Kerzerho rectangle? Figure 4 shows that we can and in this is both reminds me of the multiple square geometries AAK found associated with monuments around Carnac and directly illustrates it in the symbolism of Kerzerho.

Figure 4 Stacking of Triple Squares relative to east-west at Kerzerho rectangle.

Note the raised yellow length of 223 feet, between large stones A and B, crosses line of 235 feet, and it is the beginning of the 235 x 32 = 7520 foot alignment to Mané Groh

Two large stones define a length of 223 feet along the alignment to Mane Groh, which became the 235 months of 32 foot months, equalling 7520 feet in all. The starting stone A then defines the west-east line of latitude along which the abstract base of the larger triangle 32 times larger than the upper triple square length in figure 4.

The Metrology of 32 feet

The 32 foot units of length probably reveal something about the metrology practiced by the astronomers. At Crucuno ([post2post id=237]) I found a similarly large aggregate of 27 feet which, divided by 32/35 becomes 29.53059 Iberian feet. This means that one can use aggregate units of 27 feet to count lunar months, all the while able to also count days as individual Iberian feet within such months. In this case, of 32 feet, that length equals 35 Iberian feet since the 32 cancels leaving 35. In fact, 32 feet also equals 28 Royal feet (relevant in this context,having identified the royal cubit of 12/7 engraved upon Gavrinis’ stone C3). We are faced with the probability that such equivalences, between whole numbers of commensurate measures, may have been how measures were seen rather than, as we do today, see feet other than the English as a ratio of it.

The larger the unit of measure used to make a large count of lunar months, when applied to counts which consist of an whole number of lunar months (as eclipse cycles do), reduces the task to counting full or half moon’s within a smaller scale counting process, then to move on eclipse markers along a Saros encoded alignment. It would soon be found, within the frame of the Metonic’s 20 eclipse years (of 5 x47 lunations) lay the Saros period of 19 eclipse years. Easily then recognised as a superior eclipse period, repeating near identical eclipses at full moon, a very accurate value for the eclipse year (of two semesters) would emerge – far beyond what might be expected possible in the Neolithic period. Hence the significance of the Erdeven alignments to the history of humanity and of science. It was possible for an exact astronomical science to evolve before the historical appearence of exact sciences in the Ancient Near East.

The Related Design of Mané Groh

One would need an eclipse monument to process the pattern of eclipses over a long period so as to establish the consequences of the invisible invisible lunar nodes, where the moon’s orbit crosses the path of the sun during the year. The sun has to be at one of these nodal crossings for an eclipse to occur and, because the sun moves slower than the moon, the moon can often pass opposite the sun when it lies behind a lunar node. Having established there are 223 lunar months in a Saros and 235 in a Metonic, one can build the right angled triangle 235-223-(74.1) by recognising the Metonic as 19 solar years long and seeing the other sides as 18 years and 6 years, but also that 18 needs to a just that bit larger. The angle can be known as the diagonal of a three square rectangle and already, at Carnac, the single, double square and 4×3 rectangle were familiar.

To construct the needed larger eclipse monument to refine the Saros and eclipse year lengths, in days, the angle of a triple square was projected south of east in a count of 235 lunar months each equal to 32 feet, at which point the tumulus and dolmen of Mané Groh was built.

Figure 5 Design of Mané Groh as “micro-site” containing useful elements of the greater monument

The length of the corridor appears to be 32 feet and the symmetrical pairs of chambers which form the transcepts form part of a nested 4 by 3 design whose diagonal points to north relative to an otherwise non-planetary alignment to the southeast. The transcept design strongly mirrors the horizontal shape of the existing western extremity of the Kerzerho monument beside the road. If intentional, this may point towards that monument not having been encroached so much in the intervening periods. Conforming to the greater pattern of the alignments, indicate the main stones are in their original positions.

Another strange feature of 32 feet is revealed in having 384 day-inches within it. The triple square geometry relates eclipse to solar years as well as solar years to the lunar year of 13 lunar months (the “embolismic” year required to calculate Easter after the Synod of Whitby).

“Processional Walkways” or Corridors of Counting?

It is easy, since the romanticism of the 19th century, to talk of the megaliths as “rude monuments”, associated with tribalism, “rituals”, “sacrifices”, and “healing stones”. This indicates that when something significant goes beyond the event horizon of living memory or current ways of doing things, they enter the world of human imagination that whilst entertaining is completely wrong-headed. These monuments were actually pre-religious and highly technical in approaching astronomy without modern or even ancient numeracy.

If you are conducting a long count in which multiple objects mark past eclipses, one needs a long but not necessarily straight pathway on which to conduct the counting. To keep accurate track of the passing of the year, months, lunar orbits one needs alignments to the horizon exactly as one finds expressed in Mané Bras where the surviving dolmen point in various way to the horizon.

If you will not take into account the counting of time between horizon events, the use of exact measures and geometrical methods then it is the void then created that , in order to have any explanation of monuments, we are left with a primitive race and their rude monuments. How much better to see disparate monuments coalesce into a common purpose as at Erdeven and Crucuno.