Gavrinis 1: Its dimensions and geometrical framework

This article first appeared in my Matrix of Creation website in 2012 which was attacked, though an image had been made. Some of this material appeared in my Lords of Time book.

Gavrinis and Tables des Marchands are very similar monuments, both in the orientation of their passageways and their identical latitudeGavrinis is about 3900 metres east of Tables des Marchands but, unlike the latter, has a Breton name based upon the root GVR (gower). Both passageways directly express the difference between the winter solstice sunrise and the lunar maximum moonrise to the South, by designing the passages to allow these luminaries to enter at the exact day of the winter solstice or the most southerly moonrise over many lunar orbits, during the moon’s maximum standstill. Thus both the monuments allow the maximum moon along their passageway whilst the winter solstice sunrise can only glance into their end chambers.

From Howard Crowhurst’s work on multiple squares, we know that this difference in angle is that between a 3-4-5 triangle and the diagonal of a square which is achieved directly by the diagonal of a seven square rectangle.

Figure 1 The essence of difference between the winter solstice sunrise (as diagonal of 4 by 3 rectangle) and southerly maximum moonrise (as diagonal of a single square), on the horizon, is captured in the diagonal of a seven squares rectangle.

The best available plan for Gavrinis is that made by the AAK before the monument was taken apart and rebuilt by archaeologists. Some time back I managed to introduce a scale by comparison with another plan and estimate the length of the passage and chamber is close to 14 metres. Figure 2 below shows how I had placed 14 squares along and 2 across the AAK plan (vol.2) and to this has now been added the path of the sun and the moon along with a seven squares rectangle where the sun is its diagonal.

Figure 2 The AAK plan of Gavrinis with my own metre squares, arrows for sun and moon and seven squares diagonal. Note that the 14 metre squares correspond to the number and often the width of the 14 orthostats either side of the passageway. In the same manner, there are two end stones to mark the duality of Sun and Moon, thence 2 times 7 = 14 stones either side.

One notices that the left hand passage wall hugs the Moon for the first third and then the moon travels to the centre of the chamber’s end wall – around the junction between the two stones 45 and 46. Then it is the Sun’s arrow that hugs the left wall thereafter, all the way into the end chamber, having only just entered past the right doorjamb of the entrance. It seems true therefore that the distinctive serpentine form of the passageway is defined by the passage of light from either sun or moon at their extremes to the south, and the width of the entrance. The right hand wall of the passage seems to then be defined by the requirement to maintain a reasonably constant width of at least a metre, for human access and the display of engraved stones. The point where the sun and moon would cross is marked by the singular quartz stone numbered as seventh from the entrance doorjamb and apparently signifying the full moon

The designers appear to have used metres since 14 metres speaks of the sevenfold square within the design. However, 3/4 of a metre is the day-inch count for a lunar month and 14 metres times 4/3 gives the number of lunar months as 56/3 or 18 and 2/3rds which is close to the number 18.618 which defines the lunar nodal cycle. The hypothesis therefore emerges that this passageway and chamber embody a significant day-inch count and the  location of the first and second thresholds (seuils) appear to mark the day-inch count for the eclipse year of 364.6 days and half this, an eclipse season of 173.3 days. The quartz stone (number 7) lies six metres from the entrance and this would be eight lunar months from the entrance, the quartz signifying a full moon at the crossing of solar and lunar light.

The total intended length can then be corrected to being 29.53 times 18.618 day inches long, or about 13.96 metres. This length would represent:

the number of days for the moon’s nodes to move retrograde by the same distance (on the ecliptic) as is travelled by the sun in one lunar month of 29.53 days.

This is because the lunar nodes move 1/18.618 of the apparent movement of the sun. The nodes will always take 18.618 times longer than the sun, over ANY period of time. The length of time represented at Gavrinis turns the moon’s nodal period into a recapitulation of the solar year in that 12.368 Gavrinis lengths will add up to one complete nodal period of 18.618 years (6800 days). By measuring (somehow) the angular motion of the moon’s nodes and equating it to the lunar month, a long length of time has been created in day-inches that is 18.618 units long, each unit being 3/4 metre (29.53 day-inches). This measurement was possible to make and large enough to be accurate with regards to the difference between 18.666, 18.6 and 18.62. 

I would suggest that by embedding such a specific “symbolism” within Gavrinis, something of true significance was preserved: that at some stage an actual measurement of the lunar nodes was made over the same angular distance travelled by the sun in one lunar month. This gave the speed of the lunar nodes relative to the sun and identified the correct length for one complete nodal cycle of 18.618 years – since it is that exact ratio of nodal to solar motion which manifests as the nodal period’s length in years.

To conclude, I offer an edited version of a 2004 DuVersity.com tour visit to Gavrinis, filmed on DV by Anthony Blake and hosted by Howard Crowhurst. This film preceeded the film of Locmariaquer. We arrived in the nick of time to catch a feery to Gavrinis Island in a time when official tours were having lunch. We had a massive hamper made but had little time to eventually have a picnic near the pier. This is significantly reduced in length and introduced some of the questions about Gavrinis that can take years to digest.

Metrological note: the length of Gavrinis, at 14 metres, can be seen in terms of the AAK Pi cubit of 84 cm. This gives the length as 14/0.84 = 50/3 = 16 and two thirds Pi cubits. The Pi cubit is virtually identical to the vara of 33 inches so that there is an equation (29.53 day-inches =) 3/4 metre, times 18.618 equals 33 inches, times 16.3. The former gives more scope for interpretation than the latter. One can recognise that many such metrological equations, between units, could have been familiar within the specialists of that time but also, that some we might find were perhaps not known to them.

It seems mean to deny the builders a high level of astronomical meaning when they have been organising Gavrinis around the solar and lunar extremes with great accuracy. In conclusion:

The megalithic astronomers needed a metrology with which to build at all and, since they had developed it through day-inch counting (using a standard inch) then, when monuments were constructed, they were not only a means to an astronomical observation, but also a lasting monument forming an astronomical record for a pre-literate but technically accomplished civilization.