Bartolomeu Velho 1568 540The Geocentric Model of the cosmos with the earth at its centre, by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568 (Bibliothèque Nationale, Paris) [Wikipedia]. This mapping of planetary and other layers of time resembles the form of Neolithic henges (see figure 1 below).

Finding the right picture of important information requires ingenuity. Map makers, for example, use the technique of providing an inset showing a larger map at a smaller scaling (say of North America) and then a detailed map (of say the Gulf of Mexico) at the greater scale, so as to show cities and other features whilst still seeing the greater whole. Megalithic astronomy similarly generated maps, but of time periods, which were drawn geometrically, using lines and circles where units of measure represented every day which (for example) was an day to an inch or a day to a foot. In this and later articles we show how the megalithic built circular structures, henges and stone circles, to express major time periods. They had measured these periods using (a) alignments on the horizon pointing to sun and moon events and (b) counting time between events in metrological units of time.

A previous article about the Thornborough triple henge in North Yorkshire, looked at its likely metrology as a time-factored artifact. It consists of three henges oriented rather like Orion's belt of stars. Its Central henge is of particular interest here, in a way only mentioned in passing before.


A Henge is a circular structure with a ditch and raised ring. At Thornborough, the three henges each have three distinct concentric rings, and ditches or flat areas between. This design for a henge is the norm in Yorkshire's other henges, and these other henges are also of a similar size, implying both their size and their design was shared and significant. An outer ring defines the henge whilst two inner rings display a given ratio to each other, of around twelve to nineteen*** units. In other words when one looks at their diameters as a ratio, the nearest simple integer ratio that fits is 12:19. Since the rings are quite thick, their thickness can be variable due to erosion of damage, and so may deviate from what was originally built.

*** This ratio is very interesting since it can be normalised through division of the shared difference into each of the two numbers. 12/7 = 1.7143 which (in feet) is the Royal cubit
whilst 19/7 = 2.7143 which is the megalithic yard


CentralHenge Lunar Year

Figure 1 (right) the similarity in form and size of North Yorkshire's henges and (left) the integer ratio to be found between the inner and middle rings in Thornborough's central henge. [composite of sections of figures 3.18 and 6.4 of Harding. 2013]


From surviving engraved art near Carnac in Brittany, we can know that the megalithic counting of time (by 3500-3200 BC) had evolved inches to count days and the megalithic yard of 19/7 feet, the overrun of three solar years over three lunar years when counted in day-inches. In Gavrinis' stone C3 we see engravings using divisions of 12/7 inches, within an astronomical diagram. From the centre of C3, seven divisions (times 12/7 inches) show the (so-called) English foot as seven divisions of 12/7 inches, running downwards from the centre. Also shown are 5 extra divisions, culminating in a phallic design, to reach a radius of 12/7 feet, the (so-called) Royal foot of the Egyptians. The stone C3 appears as a whole to have been composed within a circular framework of 19/7 feet, the (so-called) astronomic megalithic yard.


Gavrinis C3 figure2

Figure 2 Stone C3 of Gavrinis annotated as to its metrology. [adapted from figure 5.10 of Heath. 2014]


We therefore find at Gavrinis two distinct measures within the engraved art, these measures related by the ratio 12 to 19, numerators of the Royal cubit and megalithic yard over their common denominator of seven. My brother and I have already demonstrated how these measures emerged of astronomical necessity, through counting three years in day-inches and because of the relative time lengths found when lunar months per megalithic yard are counted (instead of day-inches) when geometrically comparing the three periods: the eclipse year, the lunar year and the solar year.  This required a relatively simple step, of equating the lunar month to the megalithic yard as a length. The foot and the royal cubit naturally emerged from the fact that the solar year contains 12 and 7/19 lunar months (12.368), the lunar year 12 months and the eclipse year 11 and 12/19 months.


  • We know that the Saros period is made up of 19 eclipse years and this is because

19 x 12/19 = 12

  • We also know that the Metonic period is made up of 19 solar years and this because

19 x 7/19 = 7


The builders of the henges in figure 1, in building two rings in this proportion might have been referencing (a) the three years which are about twelve months long and (b) the Saros and Metonic periods which take nineteen of these years to complete.


Thornborough centralHenge fromHarding

Figure 2 Central Henge of Thornborough with 12 to 19 ratio employing a scale of feet to inches for days. The two sets of concentric red circles are (smaller) the eclipse, lunar and solar years and (larger) the Saros period, 19 lunar years and the Metonic period [adapted from Figure 3.18 of Harding. 2013.]


By this artifice of scaling in feet or inches per day it was possible for the years, and their anniversaries with the moon over nineteen years, to be shown in a single monument which could be used not only to store these time periods as lengths but also employ them for counting or geometrical purposes.



Thornborough Henge(s)



  1. Harding, Jan et al. Cult, Religion, and Pilgrimage: Archaeological Investigations Thornborough. Council for British Archaeology: York 2013.
  2. Heath, Richard. Sacred Number and the Lords of Time. Inner Traditions:Rochester 2014.