Author Archives: Robin

Stonehenge – Woodhenge (Part Three)




Part One and Two of this tryptych revealed an unexpected geometrical relationship between the location of Stonehenge and that of its sister henge monument, Woodhenge. These two monuments were shown to be connected, the locations of their respective centres marking two points that when joined define a line that, because of its azimuth angle , represents the ’13’ side length or hypotenuse of a 5:12:13 right angled triangle (a so-called Pythagorean triangle). The other two sides, the ‘5’ and the “12 side would therefore be aligned with the cardinal points of the compass. [The azimuth angle of the hypotenuse with respect to an east-west line is identical to the angle of geometry of a 5:12:15 triangle – 22.619 degrees.]

The distance or measurement between the centres of these two major monuments was seen to present the recogniseable and familiar geometrical and metrological patterns that have been found elsewhere within megalithic sites and connecting them. A map of the broader landscape around Stonehenge is shown below (Figure One), with the azimuths of the midsummer sunrise and major standstill moonset (e+i) marked for 2600 BC.

Figure One – The Landscape around Stonehenge

Part Three will now expand on this new evidence by comparing data from the megalithic landscape around Stonehenge/ Woodhenge with that from the megalithic landscape in and around the Preseli Hills of West Wales. This comparison provides a new type of connection linking the ‘bluestone’ culture of the Preseli Hills of West Wales with that of the Wessex culture, specifically the Stonehenge landscape shown above (but perhaps even Avebury and elsewhere).

The Bluestone Monologues

In 1923, geologist H H Thomas discovered that the bluestones originated from outcrops in the Preseli mountains in Pembrokeshire, Wales, some 135 miles as the archaeopteryx flies from Stonehenge. How they got to Salisbury plain remains somewhat contentious, some experts preferring glacial over human action. Neither camp can prove the case, and the whole argument has become mired through lack of the necessary discovery of any remains of a prehistoric boat, sledge or rollers!

Since the 1920s, various improved petrological analyses taken from outcrops on or near the main Preseli ridge have shown the local ophitic dolorite (feldspar-spotted bluestone to the layman) to provide a close match with many of the larger bluestones found at Stonehenge.

Other recent archaeological research has reversed the thinking of the past century by now suggesting what some other researchers, including myself and John North, had thought pretty obvious all along – that the 56 Aubrey holes may once have held a circle of bluestones. Archaeologists have accounted for over 80 bluestones within the later structures at Stonehenge, this would be more than enough to fill the Aubrey holes.

Closure on the bluestone argument, one way or the other, would be a big relief to many researchers into Stonehenge’s hoary history, and doubly so for the poor layman saturated with dull documentaries that fail to settle the matter one way or the other. However, the glacial flux/ human transportation argument is not the matter I am most interested in settling within this article. For my particular type of research concerning megalithic culture this hoary old argument is simply not relevant, and anyway it happens not to be the main question that needs answering.


Making such a comparison between the astronomical, geometrical and metrological similarities between megalithic sites in the Preseli region and those located on the Stonehenge landscape reveals a new and unexpected cultural link that once existed between the bluestone outcrop sites and Stonehenge. Those factions in archaeology and geology who presently have not been able to prove whether or not the bluestones arrived at Stonehenge by the action of glacial flux or by the intentional act of human transportation are thereby offered an independent and valuable new data source.

It remains the case that neither party in the glaciation/human transportation argument has yet provided the necessary evidence required to demonstrate how (or why) the bluestones appear to have been so crucial to the builders of Stonehenge. For at least ten years I have stood back from this debate, my developing methodology enabling me to effectively put aside the ‘bluestone question’ altogether. Instead, a developing methodology has shown that Stonehenge, Woodhenge and the Preseli Hills are connected through the same cultural ideology, the same cosmological model that developed through incorporating an identical megalithic technology, based on the same component sciences, into a transportable package, a moveable feast. This package could readily be taken anywhere in the megalithic world, and it did not necessarily need to involve moving large megaliths over unfeasible distances.

How the bluestones originated on site at Stonehenge is thus given a long overdue rest, and the question no longer stands in the way of understanding Stonehenge and its relationship with the bluestone outcrops in the Preseli Hills. The primary question should in any case always have been why and not how the bluestones arrived at Stonehenge, but no professional archaeologist has ever grabbed hold of this more pertinent question by the throat, let alone offered any credible answers.


I have a second purpose in introducing students of megalithic science to this comparison. It introduces a new and simply applied methodology that can be applied when undertaking megalithic research at any other major megalithic sites. By ‘reverse engineering’ the same methodology as appears to have been used by the original monument builders,  new channels for understanding the mind-set of the megalithic builders are opened, and this reveals their capabilities. Such a claim may be quite shocking for upholders of the present cultural model of Neolithic Europe. For everyone else, it will be found uplifting, reconnecting us to a long lost legacy from the Stone Age, connecting into the minds of prehistoric ‘megalithic scientists’ aka the astronomer-priests of 1970s archaeology textbooks aka the ‘Druids’ of Stukely’s day.

The methodology demonstrated here displays something of the megalith builder’s priorities, their methods and even their capability to reduce errors of measurement. As a side dish this offers the researcher a practical suggestion as to how useful and accurately made astronomical observations could have been stored over long periods of time.


There are six assumptions/ axioms that were adopted during the research programme. Some of these are not new.

1. That ropes and rods were used to measure point to point across significantly large distances overground between megalithic monuments.
2. That these distances were often ‘lengths of time’ and used to record time periods, such a the length of the lunar month or the solar year.
3. That the culture possessed accurate and easily applied techniques for measuring lengths.
4. That the end point locations were often marked or monumentalised with stone structures.
5. That the structures in 4 provided built in standards of key lengths in order to facilitate 1 to 4 above, such as to provide calibration methods to enable long term storage of astronomical or geodetic records, and absolute or reference measures.
6 That the measurable accuracy was accurate to 99.9% or 1 part in a thousand.

Some elaboration with regard to this listing may now prove useful:

1 & 2. Lengths of Time

It is first suggested that long ropes were employed by the megalith builders, together with shorter rods, and that these were marked up  with the key time periods of the sun, moon and lunar nodes, based on long-term observations. In other words, these ropes (and rods) were intended to represent lengths of time. The salient lengths required to facilitate and then record astronomical observations (taken over long periods of time, and sometimes over many generations) were then incorporated within the key structural features of the most significant temple monuments, to become their principal dimensions. The monuments thereby stored key astronomical constants as lengths, records that were memorialised or enshrined within the monuments themselves. Large stones endured where wooden posts and ropes would not endure.  The employment of megalithic structures marked immoveable locations which then offered the possibility of maintaining accurate standards of length for use within a far wider community over long periods of time.

2. Measuring lengths

All the lengths undertaken in the analysis that follows are ground lengths obtained from Google Earth, rounded up to the nearest foot unless stated otherwise. The azimuth angle between two sites is regarded as a straight line (originally a pegged rope) that connects two sites together. In the research, this line was draw on the landscape using Google Earth, and its length and azimuth angle recorded.

This method of determining lengths was chosen not only because it is simple and adequately accurate for the purposes in hand, but also because it can be checked and agreed upon by almost any educated modern person who owns a computer connected to the web. Google Earth has transformed the subject matter here because it removes the arduous and frankly tedious nature of surveying and measuring over often difficult territories. Direct point-to-point measurement is a fundamental measurement that is dependable over shorter distances where it can be accurately undertaken, independent of the effects of the size of the earth or its shape.

Accurate terrestrial measurement over larger distances – tens of miles – has to compensate slightly for the effects of the curvature of the earth and eventually even for the individual tiny changes from perfect sphericity that occur in different regions of the world. Mercifully, the distances involved in this research are small enough to render these effects negligible. In other words, because we are dealing with relatively small distances, there is no requirement to compensate for the curve of the earth, nor resort to using spherical geometry.

The now rather dated technique of taking latitude and longitude measurements of two points on an Ordnance Survey map and, from these, calculating their distance apart, is capable of delivering the same length as does direct measurement with long ropes, or the use of Google Earth. Often, however, it does not, and there are scientific reasons for this, beyond the scope of this article. The main reason for this discrepancy is that the geoid (the model of the earth’s shape) used by the OS to model the earth (OSB36) is a little different from that determined by Google Earth (WGS84). Important to note is that It has not been assumed in this article that prehistoric people were able to accurately measure latitude or longitude.

4. Determining end point locations

Where there is no clear positioning marker for one of the ends of a line connecting megalithic structures then the length given is the best estimate possible. Reasons for this include a monument being highly ruinous, or a standing stone having fallen or having moved from its original position. For example, a tree that grows between two stones is capable of pushing them apart before it dies, rots away and leaves no visible evidence of the once powerful forces it once acted on the two stones. Similarly animal burrows can tangible loosen the footings of a stone, eventually causing it to lean or topple. Frost and wind damage, separately or together, can break certain types of stone into pieces over time, and over time, rainfall can dramatically erode limestone and sandstone menhirs. Thom was quick to note that ‘the worst and most deceptive disturbances, however, are those produced by people who re-erect stones without leaving any record; the re-erectors have no knowledge of the original geometry and they have no survey. They simply replace the stone where they think it looks best; examples can be found at Seascale (L1/10, Callanish H1/1, and Killin P1/3‘ (Thom, MRBB, 1978, page 3).

Fully recognising that a priori bias may sway the selection of the ‘most likely’ end point, for these readings I took the precaution of asking for these readings to be taken by several people having no knowledge whatsoever of the subject matter of the ‘experiment’. In these cases an average value was chosen. An accurate ruler and the techniques to employ it correctly will always reduce the error incurred in measuring the distance between two ruinous megalithic sites whose exact original positions are not known with certainty. Such measurements are capable of delivering a more accurate estimate of the intended length (if there ever was an intended length!) than any intended length available from the ruinous monument(s) themselves. How this works in practice will be explored later, after an exploration of what one might expect from ‘accurate measurements’.

6. Accuracy

Accuracies from a perceived ideal or ‘perfect’ fit are (when appropriate) quoted here in parentheses, as percentage errors. Thus, 99% means the error is one part in a hundred. To demonstrate the true capabilities of a stone age culture to measure accurately, one must find examples that are way better than within 1% of any hypothesised value. I have always thought that examples of much better accuracy than ‘within one percent error’ are required to convince anyone that the data is not either coincidental, imagined or serendipidous.

99.9% is one part in a thousand, and this is less than, but approaches, the level of accuracy that Alexander Thom and his son Archie Thom were able to achieve in the field in order to refute the claims being made by some archaeologists during the 1970s that ‘it would be impossible to use wooden rods to measure with accuracy that we (Thom & Thom) claim for the megalithic yard‘.

This comment is quoted in a description of the Thom experiment within Megalithic Remains in Britain and Brittany (MRBB, Oxford, 1978, pp 42-43), where accuracies of one part in almost 3000 were realised with exceptional care, but without using specialised equipment. One part in 1500 could be readily achieved under all circumstances.

One part in 1500 represents an accuracy of better than 99.9%, and to place this in context within the lengths being considered in this article, this level of error in 2.722 feet, (Thom’s revised length of the megalithic yard), suggests an allowable range of measurements for this unit from 2.7193 feet to 2.723 feet.

Should the reader require more information concerning this aspect of the likely accuracies that can be achieved when measuring over relatively short distances using ‘megalithic’ equipment, then the introduction of Megalithic Sites in Britain and Brittany gives much useful information that sets the scene for this article (pp 2 – 4, [1.4 – 1.5]), as also does the biographical account of Thom’s life and work : Alexander Thom: Cracking the Stone Age Code (available from this website).

Finally 99.99% represents an error of one part in ten thousand, an accuracy which, over difficult terrain, would be hard to achieve with either modern or traditional surveying equipment and methods.

5. Absolute or reference measures

During the 1980s I used to lecture on instrumentation techniques.  My brighter students soon recognised that to connect the word absolute with measurement immediately presented an oxymoron. Even the most exacting experimental techniques and the best precision engineering skills will always deliver a minute amount of error in any length, area, weight or whatever other physical quantity that is being measured.  This phenomenon has a name. Coincidentally, it was first found to occur within quantum physics experiments during the very same year as the Cunninghams were excavating Woodhenge, and it has since become known as Heisenberg’s uncertainty principle, following its discovery by physicist Werner Heisenberg.



Some of the background evidence supporting the claims and suggestions that follow can be found in previous works, which I appreciate the more casual reader may not wish to peruse. Such readers may prefer to take note that the ideal kind of environment within which to lay out and compare very long ropes, being marked up with all manner of astronomical and perhaps meteorological time related events, would be a flat ‘runway’ marked out on the landscape by a bank and/or ditch that placed it out of bounds from anyone except those initiated into the knowledge required to operate, mark up and then ‘read back’ these ropes.

One well known and well defined Neolithic monument within the Stonehenge landscape meets these basic requirements very well. It has the name The Large Cursus, and it is nearly two miles long, sited a short distance north of Stonehenge, runs roughly east to west and is clearly visible on Google Earth (see below). A much smaller cursus is located still further to the northwest of Stonehenge and is ruinous, moreover it is far less visible on Google earth. The small cursus monument has therefore been ignored in this work.

Figure Two – The Stonehenge Cursus (courtesy Google Earth).

In the context of this article the large cursus cannot be ignored, for the following reasons:

a). The orientation of the cursus on the landscape aligns its eastern end to Woodhenge. Unfortunately, this interesting fact has been obscured because the eastern end of the cursus has quite recently been abruptly interrupted by modern military housing and recreational building works to the southeast of the army town of Larkhill.

b). The total length of the cursus from its westernmost end to Woodhenge centre is about 13,610 feet. This length may readily be confirmed using Google Earth, although regrettably, there is no convenient stone or marker to mark its westernmost end, just a boundary bank. It is not known where measurements, if any, were taken from. Ground radar may some day suggest that a row of small pegs or posts were once hammered into the chalk subsoil near the end boundary, but until then…well, in the meantime we will have to note that over such a large distance a few feet of indeterminacy at either end introduces only a very small error.

c). Were this length of 13,610 feet intended, (i.e. for the measurers to have achieved ±99.9% accuracy), the spread of measurements could span from 13,596 to 13,623 feet, a range of ± 14 ft.

d). The distance from the westernmost end of the cursus to the famous Cuckoo stone is 12,248 ft (The range at 99.9% is ±12 ft). From the Cuckoo stone to the tangential point of the perimeter of ring III at Woodhenge is 1,361ft in length and lies parallel to the line that connects Woodhenge centre to the westernmost end of the cursus.
There is even a large post hole at the tangential point coincidental with the line projected from the hypotenuse of the 12:35:37 Pythagorean triangle that Alexander Thom demonstrated had been used to define the complex geometry of Woodhenge’s coaxial rings.


It is now possible to identify a metrological thread that connects the cursus with both Stonehenge and Woodhenge.

Alexander Thom (1968) originally identified a metrological ‘family’ of units of length that emerged (were revealed) from his surveys at the various types of megalithic circles, stone rows and some more complex designs and landforms. Briefly, the chronology and chronicle of this work is given below:

In Megalithic Sites in Britain, (1968, Oxford) Thom used the not inconsiderable statistical talents of two of the greatest mathematicians of that time, independently of each other, to devise a statistical methodology that would take the data derived from his accurate surveying of over 200 megalithic rings in order to see what unit(s) of length had been employed by their builders, if any, the kind of simple question an engineer would ask, as a matter of course.

The outcome was that the data, taken from circles and rings throughout the length and breadth of Britain, revealed that a length of 5.44 feet having been employed as the ‘quantum’ length in the diameters of the data sample. Thom called it the Megalithic fathom. The unit for the radii of the circles was correspondingly half this value, and this became the notoriously controversial Megalithic yard of 2.72ft, as named by Thom.

Over the following ten years of further research and more survey plans, these units of length were minutely increased, following Thom’s several major surveys at Carnac, in Brittany, France, Brodgar, Stonehenge and Avebury. They were increased by 0.08% and their new values defined in Thom’s last major work, Megalithic Remains in Britain and Brittany (MRBB, 1978, Oxford, pp 40-43). Most of the research was published in a series of articles in The Journal for the History of Astronomy (JHA, various 1970-1975) by its far sighted editor, Mike Hoskins.

The table below lists these measures all linked within a ‘family’:

Megalithic Yard (MY = 40MI) 2.722 feet
Megalithic Fathom (2MY = 80 MI) 5.444 feet
Megalithic Rod (MR = 2.5MY = 100 MI) 6.805 feet
Megalithic Inch (100 MI = MR) 0.8166 inches

Table One. The Megalithic ‘Family’ of Measures identified by Professor Alexander Thom

The megalithic yard was now determined as being of length 2.722 feet, and comprised forty megalithic ‘inches’ of 0.8166 ‘standard or Imperial’ inches. The length of the megalithic inch was identified statistically (and independently) from an analysis of 57 examples of cup and ring marks found throughout the British Isles.

Two megalithic yards then became a megalithic fathom of length 5.444 feet while two and a half megalithic yards defined what Thom termed a megalithic rod (6.805 feet or 100 megalithic inches). The analysis of this ‘family’ of revealed megalithic units appears in chapters four and five of MRBB.

As one of Thom’s critics has pointed out, in All Done with Mirrors, (John Neal, Secret Academy Press, 2000) Thom’s nomenclatures for his claimed unit family were incorrect, misaligned from known ancient practice within metrology. Neal’s objection is valid but it presupposes that the system of ancient metrology was perfected, and up and running, during Neolithic times, which is presently not possible to establish.

However, Neal has a fair point. Had Thom better understood the ancient system of metrology he would have recognised that a ‘yard’ is always three times the foot from which it derives. Thus, because the eponymous megalithic yard is not three feet in length, being nearer two and half times its root ‘foot’ (just!), a multiplier (x 2.5) that, in metrology, is called a step. The megalithic fathom is then seen to be a pace (two steps).

To be correctly within the ‘bandwidth’ of the traditional length of Thom’s rod measure (16.5 feet) one must multiply its length by 2.42. Thom’s ‘rod’ is thus nowhere near the length of any traditional rod measure, and its naming is anomalous.


The length of the large cursus, between its somewhat indeterminate western end and the centre of Woodhenge, measures somewhere between 13,590 and 13,612 feet, and the upper value fits Thom’s units well, for,

13,610 feet = 5000 megalithic yards (MY)
= 2500 megalithic fathoms (MF)
= 2000 megalithic rods (MR),
and 2000 MR x 100 = 200,000 megalithic inches (MI)

Table Two. The length of the Large Cursus expressed in Thom’s family of units.

This length, 13,610 feet, therefore lies within 99.985% of fitting into all categories of Thom’s discovered ‘family’ of megalithic units, each an integer number multiplied by powers of ten.

The sole ‘experimental technique’ in this research has been to accurately measure various lengths, using Google Earth in lieu of the more traditional rods, pegs, ropes and calibrated rulers. The result suggests the cursus may itself have been a giant ruler, calibrated in the same megalithic units that Thom independently discovered elsewhere, in the diameters and perimeter lengths of stone circles, ellipses and rings. These units were revealed to Thom through hundreds of painstaking (and precise) surveys between 1934 and 1977, none of which included the cursus. So, can it now be reasonably proposed that this unexpected correlation presented above was intentional, part of the prehistoric design of this presently rather neglected landform?

It is helpful at this point to introduce another length, this being the distance between the western end of the cursus and the well known Cuckoo stone, a large sarsen boulder often visited and recognised as a component part of the Stonehenge landscape. That distance is 4500 megalithic yards, and this makes the distance from the Cuckoo stone to Woodhenge 500 megalithic yards. This measurement fits neatly within the other qualitative and quantative properties of the landforms discussed elsewhere.

Are these findings a bizarre coincidence, a serendipidous match, or do they represent an intentional quality of the cursus? I would suggest the latter option if only because the ensuing results appear, to an engineer, to be unlocking a design process. But what was that design all about, what was it for?

Thom’s original survey plan of Woodhenge gave perimeters for its ever increasing complex geometrical rings in integer values of megalithic yards, 40, 60, 80, 100, the absent ring 120 (whose sole representative on earth is that the apex of the defining 12:35:37 triangle lies on the perimeter of this ring,), and the two outer rings of perimeters 140 and 160 megalithic yards.

These above ring lengths form another set of smaller measurements relating to the cursus and Woodhenge and these also follow an initial sequence of small and related numbers, followed by a supply of convincing noughts after those simple leading numbers – multiples of ten. In other words, they too are similarly presented in integer lengths of megalithic yards raised by powers of ten.

This numerical arrangement does not resemble coincidence, does it? And neither does the 12:35:37 Pythagorean triangle that Thom identified as defining the geometry of Woodhenge’s complex design, whose unit length is its perimeter length (42 megalithic yards) divided by 12+35+37 (= 84), which is an exact half of a megalithic yard.


I believe that this kind of analysis has revealed a useful section of a one-time ‘service manual’ for the Stonehenge site. In Part One and Two of this article, the mean diameter of the Aubrey circle – or AMD – was shown to provide a common or ‘link’ unit between Stonehenge and Woodhenge, and it is helpful to our cause to note that this measurement is possibly the most accurately known dimension at Stonehenge, a datum measurement determined following a seemingly unlikely liason in 1973 between Alexander Thom (on theodolite and pipe) and the conservative traditionalist archaeologist Richard Atkinson (on cigarette holder, bayonet and resistivity meter). This duo determined the Aubrey circle’s mean diameter (AMD) to be 283.6 feet in diameter (Thom & Thom, JHA, 1974 op cit). They even became close friends- it can happen!

In Part One, the line connecting Stonehenge centre with Woodhenge centre was measured as being 10035 feet in length, and (because it appeared to have formed the length of the ’13 side’ of a 5,12,13 pythagorean triangle) this was subsequently shown to be ‘factorised’ such that,

10,035 feet = 13 x 2.722 x 283.6 feet.

This equation contains a highly significant detail that could be easily missed. The presence of 2.722 as a factor implies that the megalithic yard was a known unit of length and had been employed in the measurement. Rewritten, the equation is

3686.8 feet = 13 x 283.6 feet
1354.44 megalithic yards = 13 x 283.6 feet

The ratio 10,035 feet / 3686.8 feet = 2.72187 = the numerical value of the Megalithic yard

This ‘theme’ can now be taken further, because had the length of the cursus been intended to be 13,610 feet, (from its westernmost boundary to the centre of Woodhenge), then a similar equation to (1) above can be formed,

13,610 feet = 48 x 283.6 feet (to 99.994%).

or 5000 megalithic yards = 48 x 283.6 feet.

The Aubrey mean diameter (AMD) now makes its debut with regard to the metrology of the cursus, within an equation that contains a small integer number multiplied by 1000. It may be useful to note that the Aubrey mean diameter, expressed as inches, is 3403″, which, in day-inch counting or tallying, (or counting one inch for one day), is half the lunar node period (a time period which averages 6800 days). This is significant evidence, firstly because Fred Hoyles’ Stonehenge eclipse predictor relied on the lunar nodal axis being defined by the opposing Aubrey Holes, and secondly because in order to be able to predict eclipses in advance the lunar node period of 18.61 years (6800 days) has to be known (Hoyle, On Stonehenge , Freeman 1977, page 97). Hoyle was the cosmologist and leading astronomer of his day, and his book On Stonehenge he explicitly showed how the Aubrey circle, with its 56 holes (or markers) represents a ‘perfect’ minimalist design from which it becomes possible to monitor the positions of the sun and moon, and to predict when an eclipse may occur by tracking the lunar nodal axis.

Professor Fred Hoyle’s original assessment of the Aubrey circle was undertaken at the request by Glyn Daniel, then editor of Antiquity, who requested a review of Hawkin’s Stonehenge Decoded (Hutchinson, 1965), a book he loathed. Hoyle wrote back to inform Daniels that much of the astronomy in Hawkins’ book was both correct and very interesting. His review was subsequently published in Nature as a feature article, titled Stonehenge – An Eclipse Predictor (Nature, vol 211, pp 454-456). Hoyle had noted that 3 x 18.618 (years) = 55.854 (years), and this enabled a pair of ‘node markers’ to be used to track the celestial position of the lunar nodes within the 56 hole Aubrey circle [55.584 is 99.74% of 56]. The 56 markers also enabled the Aubrey circle to satisfactorily track of the celestial positions of the sun and moon. 

Harmonically, the numbers 56 to 48 form an exact 7:6 ratio]

Day-inch Counting and Eclipses

The length of the cursus, manifested as a marked up rope where one inch represents one day/night period, (a day-inch counting device), now is seen to represent 24 lunar nodal periods of 18.618 years, because,

18.618 x 365.2422 x 24 = 163,202 Imperial inches,

(18.618 x 365.2422 = 6800.079)”, the lunar nodal period, and

6800″ x 24 = 163,201.9 = 13,600 feet x 12 = 163,200 inches  = 200,000 Megalithic inches,

(to 99.999%)

It is surely now reasonable to suggest that the dimensions of the Stonehenge cursus are directly related to both Stonehenge and Woodhenge, and that this little understood monument (the cursus, although the nomination could equally well be applied to both Stonehenge and Woodhenge) was intentionally dimensioned to provide an astronomical computational system, based on rods and/or ropes that could ultimately predict eclipses, in addition to providing a workable soli-lunar calendar.


In addition to the Stonehenge cursus, the axis avenue at Stonehenge provides a second suitable location for the same kind of rope work outlined above and this monument has the advantage of lying on the Stonehenge ‘midsummer axis’, providing both a midsummer and midwinter ‘time check’. Using GPS, the avenue measures 1988 feet in length from the centre of Stonehenge to the point where it meets the centre of the path prior to it veering sharp right towards the river Avon. This same length is 730.5 megalithic yards, which is 365.25 megalithic fathoms (MF). On the Google Earth image below, the path off the right can be clearly seen just after the word ‘Avenue.’

Figure Four. The Stonehenge Avenue with its elevation profile (Courtesy Google Earth)

The length of the Stonehenge avenue can now be understood astronomically. By employing the megalithic fathom (MF), first named by Alexander Thom as a key unit in the design of stone circles and rings, the length of the avenue becomes 365.25 MF, which, as days, is the length of the calendar year (or solar tropical year to within 99.998%). Now, there’s something! The key fact is that:

The Stonehenge avenue was built aligned to that point on the horizon where the midsummer sun rose in and around 2700 BC and was made so that its length measured 365.25 megalithic fathoms, or one MF per day.

That the avenue was orientated to the midsummer sunrise has been known since 1740, when Stukely noted the fact that the axis of Stonehenge and the avenue leading from it are directed to the north-east ‘where abouts the sun rises when the days are longest‘. In his book Stonehenge, a Temple Restored to the British Druids he also quoted Plutarch, the Graeco-Roman Platonist who, along with other classical authorities from an earlier epoch, recognised the ancient practice of orientating temples to the position of the rising sun on their foundation day. A version of this practice of aligning temples was carried on, if somewhat disguised, well into medieval times and beyond as Christian churches were commonly aligned to the alleged birthday of the saint to whom the monument was dedicated or consecrated.

This great chronicler of his time, William Stukely, also noted a collection of regularly spaced stones along the banks of the avenue at Stonehenge. These stones have apparently vanished and no measured plans of these stones, by Stukely or anybody else, appear to exist. If ever stone holes were to be positively identified along the Avenue, these could provide further confirming evidence (or not) of the level of astronomical knowledge that was extant during the construction of the Avenue.


Something fresh can now enter the existing collection of Stonehenge stories. This new story draws far more on the fundamental data of measurement and far less on myths and legends. The key features at Stonehenge that relate or connected to observation of the length of the solar year is the Heel stone and the axis of both Stonehenge and its avenue. In old Welsh Ffriw yr Haul means ‘The ascending of the sun’, which goes a long way to explaining the origin of the somewhat unrealistic legend of the Friar’s heel, because the more modern appellation above is pronounced almost like the Old Welsh phrase. The fresh revelation is now that from the centre of Stonehenge to the right angled bend at the termination of the avenue measures 365.25 paces (Megalithic fathoms) in length, and that this unit of length was independently identified as being a megalithic unit within a family of megalithic units itself identified independently by Alexander Thom (1967, 1978).

How did we ever come to miss this wonderful connection for so long? Well, one reason could be because most archaeologists and even archaeoastronomers decided that Thom was completely wrong about his megalithic family of measures, and ignored them thereafter. It was, after all, Clive Ruggles, the man who held the only ever Chair in Archaeoastronomy in Britain, who pontificated in Astronomy before the Telescope (edited by Christopher Walker & Sir Patrick Moore) that,

There is no evidence for the use of astronomical observations for practical purposes such as determination of the time of year.’

The sad fact for anyone who ever believed this statement, or wanted to believe it, is not that the megalithic fathom reveals it to be untrue. It is that Ruggles pointed them away from even looking for such things. The lesson to be learned here is surely that ‘absence of evidence is not evidence of absence‘. Here we have found evidence:  the midsummer sunrise calendar connection, stored forever within that dead straight length of the Stonehenge Avenue, is also of an appropriate length that corresponds directly to the length of the solar year, in days. But this evidence keeps on giving, for no other unit but the Megalithic fathom reveals this match between the length of the solar year in days and the length of the Stonehenge avenue, originally aligned to the midsummer sunrise angle. The new evidence eloquently informs us that this was intentionally so.

This discovery informs the researcher that the builders of Stonehenge had deliberately used this known and human measure, that in modern metrology would be called a pace, (a pace is two 2.722 ft steps, or 5.444 feet in length,), in order to numerate the number of days between each summer solstice. The Avenue thus enabled them to pace the year, and create a space or ‘diary entry’ for each day in the current year. One wonder’s what they ‘wrote’ or recorded in that diary – astronomical events, may one dare suppose?

So, here is some really good evidence supporting ‘the use of astronomical observations for practical purposes such as determination of the time of year‘. It is Ruggles and his statement that ‘the idea that distant horizon features such as notches could be used to pin-point the motions of the sun and moon to within minutes of arc‘ that can now be discounted.

[It should be noted that if the cursus length were 13,600 ft (99.92% of 13,610 feet)) then compared to the 1988ft length of the avenue, it would be 6.841 times longer, which is also 3400/497 and that 6.841 x MY = 18.618. The number of days in half a nodal cycle is 3,400 days.
This connects, in simple metrological terms, the astronomy of the lunar node cycle of 18.618 years, with the cursus length.]

There are other important connections to come. To discover these it is necessary to understand how a different type of monument recently discovered in a different location connects directly with the above newly revealed relationships linking the various major component monuments of the Stonehenge landscape. The next stage of this story therefore involves a remarkable and previously unrecognised monument in West Wales, one that has survived in good enough condition to be measurable with great accuracy.


A Visit to the Preseli Hills

[Latitude 51*N 59″ 59″; Longitude 4*W 49′ 26″]

Figure Five. Carningli Summit

The most prominent visual feature within the Preseli Hills is undoubtedly that of the rocky summit of Carningli. This long extinct volcanic outcrop consists of a prominent long ridge whose axis is aligned northeast – southwest. At just 1070 feet AMSL, it is hardly a mountain, yet the rocky nature of the outcrop and its conical shape when viewed from the north or east of the Preseli Hills makes it appear much more impressive, more resembling a mountain than a mere hill (see photograph above).

Amongst the chaotic layers of volcanic rock along the summit ridge of Carningli can be found a anomalous flat seat or ‘throne’ that faces the north-east towards Cemaes Head (see Figure Five, above, where a white arrowhead marks its position). It is from this ‘throne’ that the observation of the St Davids Alignment is made (see Bluestone Magic, 2010), with Carn Briw, the dark ‘spike’ on the nearby horizon on the photograph (below, Figure Six) acting as a nearby foresight that indicates the notch between the twin peaks of Carn Llidi and Penberi (the grey peaks either side of Carn Briw)) near St Davids providing a distant foresight that once marked St David’s Day (prior to the calendar changes of the eighteenth century). Today, this alignment marks the setting sun on February 18th (in the spring).

Figure Six. The ‘Throne’ on Carningli Summit

I have observed this alignment over many years. From the ‘Throne’ it is possible to observe the track the number of days in the solar year. It also shows clearly, year on year, the quarter of a day that is added to the annual integer value of 365 for the (almost) true length of the solar year. Counting the number of days between observing this sunset one easily can observe the approx quarter of a degree shift between consecutive years, and that the fourth count always returns 366 and not 365 days. From this solar observatory it is perfectly possible to evaluate the length of the year as being 365 and a quarter days , or 1461 days in four years. This is as accurate as our current calendar.

One can identify many ancient sites along the length of this alignment, suggesting its continuation of use well into the late middle ages, when much of its length became embroiled and integrated into the once highly favoured and well trod Pilgrim path to St Davids.

[Latitude 52*N 02′ 28″; Longitude 4*W 44′ 06″]

The photograph below shows Carningli summit viewed from the trig point on the summit of Crugiau Cemaes, a second high spot renown in the area as a viewing platform, and recently being re-classified from a Bronze Age to a Neolithic site. In the late 1950s much of the site was seriously damaged by a local farmer using a tractor to demolish the tumps and thereby rid his land of rabbits.

Figure Seven (a).  Carningli Summit from Crugiau Cemaes

 This impressive elevated site is marked on the OS map as a view-point (sheet 145, Grid reference: SN125145). To visit the site, take the A487 trunk road from Cardigan towards Fishguard. After about 3 miles turn right to Nevern on the B4582. After a mile valley cuts through the hamlet of Glanrhyd, and a further 2 miles on, at the top of a long upwards hill, the monument is found located on the right, where a motley collection of barrows and an OS Trig station can be seen on the skyline. A car-park and lay-by are provided, and a gate leads to a public footpath, a three minute walk then takes the visitor to the summit and perhaps the most spectacular and often most elemental view of the Preselis and its coastline (see photograph above). The photograph below, taken from Ysgol Hen in Glanrhyd gives a good account of the visual prominence of the two main remaining ‘tumps’, the right hand one sporting its OS trig point.

Figure Seven (b).  The Tumps of Crugiau Cemaes. 

This site offers a view of the entire northern side of the Preseli Range of hills, from the eastern figurehead ‘mountain’ Frenni Fawr westwards to Carningli and beyond, to further smaller and less conspicuous outcrops, Carn Enoch and Garn Fawr. The prominence of Crugiau Cemaes was commented on by Pembrokeshire archaeologist Richard Fenton (1746-1811) who noted that the site could be seen from the coast at Aberystwyth, about 40 miles distant. On a clear day one can do a little better than this, as from Bardsey island both Crugiau Cemaes and Carningli can be discerned, at 50 miles range.

Site 3. LLECH Y DRYBEDD – the ‘big slab on a trivet’
[Latitude 52*N 03″ 16″; Longitude 4*W 46′ 18″]

Figure Eight.   Llech y Drybedd, with Carningli Summit in the background.

Llech y Drybedd is one of the most significant sites in the Preselis. Work on the astronomy of this site has revealed its axis of symmetry to be aligned to the midsummer sunset around the date of its construction, which currently is set at around 2,850 BC. This dolmen is also a backsite for observing the midsummer sunset over Lughnaquilla mountain, in the Wicklow Mountains in Ireland, which are occasionally visible at 90 miles range, when certain atmospheric conditions are suitable.

From the top ridge of Crugiau Cemaes, looking towards the coast, there is a second ridge, along which can be made out a significant dolmen, known locally as Llech y Drybedd, or sometimes Llech y Tribedd. It is at the same height above sea level as Crugiau Cemaes, at 612 feet.

When viewed from Crugiau Cemaes trig point, Llech y Drybedd marks the minor standstill moon set in the north, at an azimuth of 300.5 degrees, with Llech y Drybedd providing the horizon marker. A second henge site at Gaer, on the Felindre Farchog to Moylgrove road, provides the backsite for the major standstill moonset through Llech y Drybedd, the horizon foresight, at azimuth 319.5 degrees. I have personally observed, recorded both events over the past thirty years making the required corrections for the change of obliquity. There are archived web articles on this site and also on, as well as a fuller account of the astronomy of this remarkable dolmen site in my 2010 colour guide to the West Wales monuments, Bluestone Magic (Bluestone Press, 2010).

Figure NIne. Crugiau Cemaes viewed from Llech y Drybedd.


Using Google Earth, the lengths between these three sites can be easily and accurately determined. However, this was not how the importance of these sites was initially revealed. It was only after reviewing theodolite readings taken from all three summits over many years that suddenly the geometry that connects the three points was recognised, and suddenly made clear.

Firstly, a look at the original diagram, that followed my original survey, of the joined up sites – Carningli Summit, Crugiau Cemaes & Llech y Drybedd:

Figure Ten. The Carningli Triangle (the original 2013 diagram)


A. The three sites, Carningli summit (CI Throne), Llech y Drydedd (LYD) and Crugiau Cemaes (CC) form an accurate 5, 12,13 Pythagorean triangle.

B. The azimuth angles of this triangle, (obtained from a sun-shoot using a Wild T16 theodolite)) are

Azimuth of LYD from CI = 30* 27′ 00″
Azimuth of CI from CC = 233* 08′ 30″
Azimuth of LYD from CC = 300* 31′ 00″ (Minor moonset)

C. The internal angles of this triangle (measured using a Wild T16 theodolite), are

Internal Angle at LYD =90* 04′
Internal angle at CC = 67* 22′ 29″
Internal angle at CI = 22* 41′ 30″

[The ‘ideal’ internal angles of a 5, 12, 13 triangle are 22* 37′ 11″, 67* 22′ 49″ and 90* 00′ 00″].

C. The measured lengths between the three sites is as follows, taken from Google Earth:

Carningli Summit to Llech y Drybedd = 23,149 feet [12 side]
Llech y Drybedd to Crugiau Cemaes = 9646 feet [5 side]
Crugiau Cemaes to Carningli = 25,079 feet [13 side]

PERIMETER LENGTH (Σ P)=(23,149 + 9,646 + 25,079) feet
= 57,875 feet
UNIT LENGTH = (Σ P/ 30), [30 = 5 +12+13]
= 1,929 feet

This triangle is far too accurately defined (or configured) to be a chance coincidence of nature. The purpose of such a large landscape triangle connecting three summit points may by no means be clear at this stage. Nor is it clear if the unit length is significant or if that this length was purposefully chosen to fulfill an as yet unknown function. But it may be presumed that the accuracy of the geometry of this triangle makes it a vanishingly small chance that these sites came to be placed where they were placed by accident.

The data is largely presented in numerical form and, unlike almost all conventional archaeological data, it can be directly analysed and investigated by a non-specialist to answer such reasonable questions as;

Q1. Might the astronomical facts already established for these sites mean that somehow the triangle has a purpose relating to the solar year or to lunar cycles?

Q2. What unit of length were the designers of this geodetic shape employing in order to integrate or register solar and lunar cycles?

Q3. Is this triangle connected with the Stonehenge-Woodhenge triangle?

Q4 Is this triangle a lunation triangle (Heath, 1993 et al)?

Answers to these questions are forthcoming.

Answers to Q1 and Q2. There is indeed a connecting link between the unit length of this triangle, which is 1929.174 ft, and the lunar month of 29.53059 days. The ’12’ side of the triangle (23,149 feet) therefore happens to measure one lunar year in length, when measured in megalithic fathoms, and this is the lunar year of 354.4 days x 12.

1929.174 (feet) = Lunar year x Megalithic fathom
= 29.53059 x 65.3249
= 29.53029 x 5.444 x 12
= lunar month x meg fathom x 12
= lunar month x meg yard x 24
= lunar month x meg yard x 24

This equation both identifies and elucidates a connection between the unit length presumed chosen for the triangle (1929 feet) and the lunation period of 29.53059 days. If one day is here represented by one megalithic fathom, then the unit length of the triangle is one lunar year (354.36708 days x 5.444 feet)

The Lunar Month was perhaps the most important astronomical constant of all to the megalithic culture  – a twelfth of the time period of the lunar year of 354.36708 days. It is here found embedded within a prehistoric 5, 12,13 Pythagorean triangle that was designed using an independently discovered (by Thom) prehistoric system of metrology.

Next to the solar year and the four seasons, the lunation period provides the strongest rhythm, in the music of the sun, moon and earth system. It is a rhythm all living creatures on the earth dance to, synchronous with the earth’s tidal cycles, both telluric, chthonic and oceanic, and synchronous with the human menstrual cycle.

Answer to Q3. The Preseli 5,12,13 triangle is found to relate directly with the Stonehenge-Woodhenge triangle. Although no right angle point appears to be marked on the landscape today at Woodhenge, the ’13’ side is sloping at the exact angle with respect to an east-west line in order to define a 5,12,13 Pythagorean triangle. It is not incorrect to assume the intention that the Stonehenge-Woodhenge line was intended to form the hypotenuse of a 5,12,13 triangle. and not just for this single reason, as explained in part I and part II of this tryptych of web articles on the matter.

The Carningli triangle follows this set of rules, for its ’13’ side is angled such that it is coincidental with  the hypotenuse of a second triangle, a large 3,4,5 triangle, between Carningli summit and standing bluestones stones scattered around the farm at Pont Gynon, once the right angle point. Here, because the right angle point is not very clearly defined with the curtilage of the farm, the unit length is found from the hypotenuse alone, as 25,079 feet divided by five, which is  5016 feet, or 921.354 Megalithic fathoms This is therefore  2.600 times the unit length of the 5-12-13 Carningli Triangle.


A further significant factor remains to be discussed that seals the importance of the connections above. It is this: If completed, the perimeter length of the Stonehenge-Woodhenge triangle would have been identically matched to the length of the ’12’ side of the Preseli triangle, both at 23,149 feet. This makes the scaling between the relative sizes of the two triangles equal to 2.5 :1, or 5:2.

We here have powerful evidence supporting that these two triangles were the result of the same original cultural impetus.

Answer to Q4. Furthermore, the Preseli triangle still contains a well known megalithic monument within its perimeter that enables the construction of an inner 3,4,5 triangle to defines the 3:2 point. This is covered in detail with photographs within Proto Stonehenge in Wales (Heath, Bluestone Press, 2014), available via the book section of this website. This site, known as the Trefael stone provides, via a 3,4,5 geometry from Llech y Drybedd  supplies the required 3:2 point to identify the Preseli Triangle as once having been understood and therefore used as a lunation triangle. This is an extra twist on the lemon!

Earlier, the Stonehenge avenue was found to support another example of astronomical and metrological integration, that supported the already identified possible connections for which the Stonehenge – Woodhenge – Cursus complex provided key component parts. Had the builder’s intentions been to connect the centre of Stonehenge to the elbow in the avenue at 1988 feet, prior to it making a sharp bend to the right to the river Avon, then the simple act converting 1988 into units of megalithic fathoms in length reveals the length of the avenue as being 365.25 (days = MFs), where once again, one megalithic fathom is made to represent one day.

Length of avenue = 365.25 megalithic fathoms
= the solar year, calibrated 1 MF /day

The Stonehenge avenue revealed a second astronomical secret, for it was not only aligned to the midsummer sunset, but in the appropriate units of the day provided a daily or calendar diary along its length.


It appears likely that a 5:12:13 triangle connecting the centre of Stonehenge to the intended centre of a new (later) building, which became Woodhenge, may have been part of the process of ‘laying the bearings’ prior to Woodhenge’s construction, this later monument being erected following the first phase of Stonehenge had been constructed. In addition the so-called ‘Aubrey’ centre of Stonehenge was only possible to establish, i.e. available, between the time the Aubrey holes were originally dug and the later process of defining the station rectangle some three or four centuries later.

The 13th part of the length that separates the centre of Stonehenge from the centre of Woodhenge reveals the unit length of the triangle, in whichever unit of length one fancies to measure it. While it is possible to measure in the relatively new metrological ‘god’, the shiny and officially sanctioned ‘safe’ unit – the metre, this unit is mute when applied here, and only obfuscates what is going on, revealing absolutely nothing.

Use of the metre places an unnecessary and unwelcome fog between monument and researcher. In more appropriate metrological units the unit length is 771.9 feet, which is 283.6 megalithic yards, a unit handily provided by Thom (see earlier) that he also found to the unit of length that was employed during the design and erection of Woodhenge. The foot is suitably ‘hot’ in this application, the megalithic scientist /researcher can be completely comfortable when using these two unit at these sites, for,

771.845 feet = 283.6 MY
= (283.6 x 2.7216) feet

[283.6 feet = Aubrey mean diameter (AMD)]

This kind of analysis and its conclusions have previously been dismissed as entirely unrealistic within our modern culture, a culture that has forgotten, intentionally or otherwise, its prehistoric ‘megalithic’ past, or has dismissed any possibility of a science of megalith building founded on an alternative model of Neolithic capabilities, as outlined in the above report. The analysis, its suggestions and ultimately their authors (examples include Lockyer, Thom, Hoyle, Hawkins, Michell, Newham and many others, including this author) have instead been routinely banished into ‘Room 101’ of archaeology, that place reserved especially for those they do not agree with, and who they name the ‘Lunatic Fringe‘. This time honoured option has been far easier for archaeology than having to embrace the proposed alternative reality of prehistoric intentions presented by the evidence presented above. It is, of course, the lazy option, the ‘no-changes here’ stance.

However, the triangles described here make this easy option no longer available. One does not have to be an archaeologist to evaluate the data presented here, nor to understand its treatment. The evidence presented is unequivocal and clear in its presentation, emerging from several remarkably accurate artefacts, whose dimensions and other qualities reveal not only that the present model of prehistory is incomplete, but also that this model, as presently presented to the public by archaeologists, has failed to understand the true capabilities of the culture that built them. The model is woefully incomplete, and our true prehistory remains denied to us.

The current model of the prehistoric past is therefore of no practical use to modern times, and the recent stream of available evidence, some of which is presented within this report, suggests both how and why this model must now be radically redefined. The effort offers great rewards to anyone who really is seriously looking to understand our lost legacy from prehistory.

Robin Heath,
written between April – July 2018

The English Lake District Stone Circles

A New Perspective

by Robin Heath


The large number of stone circles found in the English Lake District of Northern Britain are among the oldest known, Aubrey Burl suggesting that the construction of Castle Rigg, its most visited ring as being ‘around 3200 BC’ [Burl 1995]. Many of these circles are in fact non-circular and most of the survivors are very large – over 100 feet in diameter. Their design geometry includes many of the ‘flattened circle’ geometries first discovered by Alexander Thom, [Thom, 1967], and which he named Type A and Type B flattened circles.

The Type A’s perimeter shape is based on hexagonal geometry, whereas the Type B is based on the division of a diameter line by three, which can be understood as based on a vesica piscis construction. The two types of flattened circle are fundamentally different, and rarely, a slight change was made to the standard design. One example of this is the Type D flattened circle, whose geometry will be explained later.

Only if one strays outside of the Lake District into the Scottish borders can one find the other familiar geometries. Borrowston Rigg, near Lauder, is the largest Type II ‘egg’ with a perimeter of just under 450 feet. The stones are small, but the geometry aligns very accurately to the egg design also originally discovered by Thom following his customary theodolite surveys. Another design of ring is Allan Water, near Hawick, which, despite its remaining upright stones now being used as scratching posts by cattle, similarly adheres well to the Type I ‘egg’ geometry, the internal back-to back pseudo – Pythagorean triangles dimensioned forming sides of lengths 11-13-17 in units of half megalithic yards. The perimeter of this stone ring is 151.3 feet.

I first began to take an interest in this collection of stone rings in 1992. Family connections in Scotland took me through the Lake District at least twice annually, and for some years I was living near Carnac in southern Brittany. In addition I had an old friend who lived near Ulverston. Each visit up to the family home would include a stop at one or several of the Lake District sites, often with a theodolite, ropes, tapes and pegs. I was particularly drawn to Grey Croft ring, also known as Grey Croft, one of the few Type D flattened rings. In this design, the inner forming triangle cuts the line OC a third of the distance along the line (at point E) rather than a half, as per the ‘classic’ Type A design (see Thom’s original survey plan, below).

Figure One. Seascale stone ring (also known as Grey Croft), a Type D flattened circle. 

Grey Croft also known as Seascale is today positioned on a Golf course adjacent to the Sellafield ex-nuclear power station and present day nuclear processing plant. Burl curtly and accurately describes this juxtaposition of an ancient and a modern power-point in just five words – ‘The stone circle is lovelier.’ [Burl 1995].

Work on this site was made difficult, due to security people hassling me about what my business was in bringing a theodolite into the area. However, Thom’s survey plan was checked over, and this was the first type D flattened circle that I had spent time with, often with the sound of waves breaking on nearby Silecroft beach. I have often since wondered if the conventional anglers that caught and ate mackerel off the beach at Silecroft thereafter glowed in the dark!

This period of my own megalithic ‘angling’ was researching large landscape triangles, particularly the 5-12-13 triangle I had proposed, in 1993, connected Stonehenge with Lundy island, to the monuments west, then up via the right angle to Carn Wen summit in the Preseli Hills, adjacent to the bluestone outcrops. The unit length of this triangle was 20,000 root megalithic yards, a unit minutely smaller than Thom’s 2.72 feet which I later named the astronomical megalithic yard (AMY), a length of 2.7154 ft. This length uniquely links the lunation period of the moon’s phases with the length of the solar year. [See The Measure of Albion, 2004, Robin Heath & John Michell, also available in a US facsimile edition, The Lost Science of Measuring the Earth (AUP, 2006)


The line from Lundy to Carn Wen when extended northwards, leaves the West Wales coastline a mile from Mwnt, just north east of Cardigan, and re-enters the Welsh coast near Aberdaron, (Castell Odo) on the Lleine peninsula. It then exits Wales from Holyhead, as does the present day Irish ferry, then, travelling ever northwards, it cuts the southern shores of the Isle of Man, near Castleton, where there are prehistoric burial grounds almost on the beach, and it leaves just north of Peel, en route for Scotland, where it passes near Ayr, Prestwick, through Troon and thence on and up to leave the British mainland at the tip of Loch Eriboll near Durness (shown below).

Figure Two. The Meridian Line from Lundy – Durness/Loch Eriboll

The British termination of the line is also the end of the recently revived Belinus line, whose modern champions are Gary Biltcliffe and Caroline Hoare. More recent landscape work undertaken by these two researchers and authors, based on Lewis’s work in the 60s, has since suggested that a line from the eastern tip of the Isle of Wight to Loch Eriboll and Durness point, formed what has been named the ‘Belinus Line’. This line has been duly explored extensively by these two authors, The Belinus Line becoming the title of a popular Earth mysteries book (published in 2012) in the style of The Sun and the Serpent (1989), by the late Hamish Miller and Paul Broadhurst. Both books are essential reading for those who wish to use an earth mysteries approach to understanding both geomantic effects and what humans have done with earth energies, consciously or otherwise.

The north-south meridian line from Lundy to Loch Eriboll passes through a well known site on the Isle of Man, a Neolithic cairn [a major site still referred to as a ‘Celtic Hill Fort’ in many tourist guides] right on the summit of South Barra. What first drew my attention to its possible significance was that a line drawn from the South Barra monument towards the Lake District to east to Burnmoor East (a Type A flattened circle) made an angle of 21.45 degrees degrees with respect to an east-west line, that was little over a degree of being the apex angle within a lunation triangle – 22.619 degrees.

A ‘little over one degree’ is nowhere near accurate enough to be worth pursuing any further in this line of work. But later I calculated that the line from South Barra, when taken up to Castle Rigg, passes right through both Castle Rigg and Long Meg stone rings. Bingo! The angle this line makes with respect to east is much more accurate (within a half degree over 90 miles) and is close to being the ‘Phi-angle’, 26.5651 degrees, the internal angle formed by the diagonals of a double square, a construction used to determine geometrically the value of Phi, via a simple construction involving the square root of 5 – the diagonal length, (the square root of five is numerically 2.236.. an irrational number).

A double-square is two squares that share a common side. A diagonal drawn across the squares from corner to corner has a length equal to the square root of 5 times the length of the square’s side length. Each individual square has a diagonal the square root of 2 times the length of the square’s side length. The diagram below shows this geometry.The geometry of a double-square.


[For the mathematically challenged or whose knowledge of such matters may approach homeopathic levels, the physical constant phi equals (1+root 5) / 2 , the irrational constant upon which governs so many processes on earth, and known as the ‘Divine Proportion’ or 1.618033989…..]


Figure Three. The line from South Barra summit to Long Meg via Castle Rigg.
Length 90.1 miles. Angle from e-w =  27.25 degrees. Double square angle = 26.565 degrees.



Over distances of above 25 miles, the earth’s curvature begins to need addressing in the measured angle using Google Earth. The straight line you see joining the three locations above is actually not straight at all. Due to the curvature of the earth, the start angle from South Barra has to be higher than the double square angle in order to pass through Castle Rigg and Long Meg at the doubles square angle. This can be checked out by drawing the line from Castle Rigg to Long Meg on Google Earth – which is 19.3 miles and gives an angle of 26.88 degrees with respect to an east-west line,. At just under 99% of the angle of a double square and now well worth pursuing).

The problem facing ‘ley hunters’ is that, over long distances, unless they possess a good grasp of spherical geometry as used in geodetic solutions to ‘straight’ lines on the landscape, they lay themselves wide open to announcing ‘ground-breaking’ discoveries that are simply not real. Fortunately for lengths less than twenty miles, this problem of distortion can often be neglected. The book that saved my bacon in this respect was The Astronomical and Mathematical Foundations of Geography by Charles H Cotter (1966, Hollis & Carter). If the very title gives you the hee-bee jeebies, then possibly your leyhunting research would be better confined to the investigation or discovery of shorter leys!

Google Earth was not yet available in 1992/3, it was OS maps that were checked and long hand and hard sums undertaken with a scientific calculator to be sure that the earth’s curvature was corrected for. This work was part of an experiment that was investigating the Lundy-Barra – Eribol line for having been part of a bigger prehistoric ‘National Grid’ of surveying points similar to the more recent trig points set up in Victorian Britain for similar purposes.

This Lake District experiment seemed to clinch the matter. Three major Neolithic sites, including perhaps the two of the best known stone circles in Northern Britain, were connected by a ‘straight’ line. The two large and very old stone rings, Castle Rigg and Long Meg were connected as the opposite corners of a double-square construction, to within 99% accuracy.

The Long Meg site gets its name from the large twelve foot high menhir that has always stood as an outlier to the south-west of the (later) ring . This very attractive red standstone menhir is inscribed with spirals and cup and ring marks. In recent centuries the ring has been known as Long Meg and her Daughters. Long Meg ring comprises the daughters part, no doubt once women turned into stone for dancing on the Sabbath in true anti-pagan Church tradition, while Long Meg herself has been somewhat downgraded to being an ‘outlier’, or, in earlier times, a Witch turned into stone.

The menhir and the ring are not the only surviving megalithic remains at the site. Within half a mile to the north-east of the ring can be found another ruinous circle, some 20 foot diameter and known as Little Meg. A mere shrimp compared to the 360 foot diameter of Long Meg’s daughters, even Little Meg has something to add concerning the geodetic qualities of this entire site. For example, it is interesting to note that the most accurate line (to the double square geometry) that can be drawn between Castle Rigg and the Long Meg site is that taken through the Long Meg menhir and up to Little Meg, as shown previously, (and below, figure seven).

Does all this indicate that prehistoric surveying had been employed in the siting of major megalithic monuments? It took me until 1994 before my work demanded that I revisit these sites to further address this question. I was asked by Helena Frances of the Hermes Centre in Surrey to prepare a week long course for her students that would include this research during three days of hard graft in the Lake District. Helena and I did a ‘reccie’ to prepare more surveys and check aspects such as intervisibility between sites. We surveyed the ruins of Orton ring, a few miles from Tebay services on the M6, and two other smaller circles. During this trip my old Watts theodolite went missing from right under our noses, never to be seen again.

In 1997, I visited all the above stone circles again with my partner, Trish. Ten years later, in 2007, we sailed to the Isle of Man on a 90 foot wooden sailboat, Keewaydin, with a small group of friends, and managed to visit various megalithic sites including S Burra and the Meyall Hill stone tombs above Port Erin. This latter site is the IOMs only stone circle, and is larger but has similarities with the monument Cerrig Y Gof (‘memorial stones’) near Newport in the Preselis.

Both sites have something of a stone circle about them, but mixed with a dash of dolmen, several capstones and rectangular chambers arranged in a symmetrical circular design around a central ‘henge’ or circular field. The Meyall Hill site has a quite splendid panoramic view to Ireland and, for that special apres site visit moment, a really good tea shoppe may be visited on the way down to Port Erin afterwards.


Later in 2007 that I was asked by a fellow megalithomaniac called Howard Crowhurst, to give a presentation or two at a gig he was organising in Plouharnel, near Carnac. Howard, a Yorkshireman, has lived in France since the 70s. The meeting with Crowhurst was brokered by my brother Richard, who had taken a group to visit Howard’s excellent megalithic museum and tour centre in Plouharnel some years previously.

The outcome of this necessary preamble is that Howard knew several sites within the major monuments at Carnac and elsewhere that had employed two-squares geometry in their design. This rekindled my interest in the lakes circles and led to further surveying visits to Castle Rigg, Long Meg and Burnmoor each and every summer from 2008 to 2011.


Once one superimposes the line from Castle Rigg to Long Meg onto the geometry of the Long Meg site, it revealed a fractal like similarity on a smaller scale to the double square between Castle Rigg and Long Meg (illustrated below, Figure four. Not shown is that the extension of this line – the diagonal between the menhir and the easternmost stone in the ring – cuts through the Little Meg ring.

Figure Four. A line from Castle Rigg cuts through the Long Meg menhir (Outlier) and then through the stone ring before passing through the centre of Little Meg.

Figure Five. A 2009 survey revealed that the geometric layout of the Long Meg site is  based on a double square, with three corners defines by the three largest stones comprising the monument, and a most interesting property in the light of this present research.

Another serendipidous event took place during a visit to Long Meg in early August 2010. A member of the Cumbrian Archaeological Society flourished a small map at me. This showed the wider extent of a recent archaeological survey of the entire Long Meg site, the details of which I have included here, based on a photograph I took of this somewhat rough map.

The smaller double-square of the previous illustration (figure six, below) now may be a fractal of the larger archaeological plan, where the rectangle has an identified Neolithic fort at top left and Little Meg at top right. Little Meg thus becomes integrated into the design of what one might term the bigger Long Meg landscape. The incoming line from Castle Rigg defines the lower left corner and passes through the menhir ‘outlier of Long Meg. Nothing at all has been identified on the lower right hand corner, just as for the smaller Long Meg rectangle. This point is located on heavily agriculturalised private land.

The top length of the enlarged rectangle is ten times the size of the ‘double square’ rectangle that defines the east-west diameter of Long Meg ring. Overall, these are satisfying results that support the argument for prehistoric surveying in the Lake District. The Long Meg site assumes an even greater significance.

Figure Six. Recent interpretation work by archaeologists of the Cumbian Archeological Societ, suggests the presence of a ‘Neolithic fort’, a prehistoric enclosure and some cursus ditches, a rather similar collection to the  contemporaneous work going on near Stonehenge and Durrington walls at this time.

Figure Seven. The overall ‘fractal’ structure of the wider Long Meg landscape compares with the  previously revealed double-square geometric construction of Long Meg, revealed through the application of  megalithic science.


During surveys undertaken between 2007 and 2011, I measured the east-west diameter of Long Meg ring with an accurate surveyor’s tape. This diameter is marked at each end by humungous blocks of granite, (see the photograph of the easternmost stone on page 14, at the end of this article) of a size that makes one ask: How could these ever have been moved or lifted through human effort?

The distance between the inside faces of these apparent immoveables measured most interestingly. At, 353.45 feet, and between their outside faces measuring 365.15 feet, to any astronomer this would immediately suggest that these distances represent the lunar and solar year, 354.367 days and 365.2422 days respectively, enshrined in stone such that one foot equals one day.

Here we have two of the most unmoveable, untamperable stones on the site. These two boulders define the geometry of the Long Meg site, which includes the Menhir stone, and they store within their placement, the length of the lunar and solar year, scaled at one day = one foot. The enlarged landscape rectangle depicted on the previous page is ten times larger, and its longer length consequently measures 3652 feet, or ten feet representing one day.

To find a similar connection between the foot and the astronomy of the Sun, Moon Earth system, it is useful to look at a well documented curiosity that occurred in China during the late Stone Age, which leads this inquiry into the area of megalithic science.


At first sight the history of human measure sounds like a dull subject to steer well clear of, which is exactly what the academic world did in the mid nineteenth century. This left a huge source of valuable information unavailable for future historians and archeologists. Having studied this subject for twenty years, I would suggest that dull is not the word, and metrology deserves to be studied by eveyone who wants to better understand prehistoric or ancient history.

The foot provided the root of all ancient systems of measurement. We know this extended back into the Neolithic period partly because Prof Joseph Needham, the Sinologist, without knowing it, found evidence supporting the possible ‘invention’ of the foot in defining the length of the year in Northern China, during the ‘Yellow River’ period, the earliest dynasties.

From 1954 onwards, Needham wrote a series of books entitled Science and Civilisation in China . These books are about the history of science in China and are very well regarded. During his travels, Needham discovered that the ancient Chinese astronomers divided up the equator into 365 and a quarter divisions. This matches the earth’s equatorial circumference to the earth’s orbital period around the sun – the solar year. The Time period became represented by a length, the circular perimeter of the equator. What Needham did not note is that if the equatorial circumference of the earth is taken to be 24,901 miles, the present figure, then this is 365.25 x 360,000 feet (or 365,250 x 360 feet).

Astronomers, navigators and surveyors now get the best of two worlds:

1. The first way of writing down the product of these two numbers, 365.25 x 360,000, enables the division of the equatorial circumference by the solar year. This represents the earth’s orbital period around the sun and it ‘stores’ knowledge of the length of the solar year in days as a length that relates directly to the earth’s principal dimension. This results in one day-degree around the equator being represented as a length of 360,000 feet or 69.177 miles.

2. The second arrangement 365,250 x 360 divides the equatorial circumference into 360 so that each (familiar) degree around the equator is then 69.169 miles or 365,214 feet. This turns out to be an average distance, because of variations to this figure that depend on latitude, due to the earth being flattened or oblate spheroid, but for navigators or surveyors anywhere on the surface of the globe, this figure of 69.169 miles for the length of one degree of travel will always provide accuracy to 2% [Clarke (1880)]

The equator is the only true circle within all the key constants of the geoid, the shape and size of the earth, and our present culture retains 360 degrees as the very convenient and highly factorisable number of degrees in a circle. It is therefore not unreasonable to question whether or not the foot length, which lies at the root of the structure of ancient metrology, was designated and dimensioned to provide this convenient astronomical, geometrical (in the sense of ‘measuring the earth’) and metrological arrangement, through the above relationship between the solar year and the size of the earth.

Whether you agree with this suggestion or not, the geodetic significance of the foot is not in doubt. The two numerical constants were fixed as 365.25 days leaving the remainder as a very nicely convenient and familiar 360,000 feet. This fixed the foot measure as the peculiarly enduring unit of length we still use today. It is hard to understand why until one understands and reckons with its ubiquity throughout all history of measurement.

It is probably why, in 1637, an Oxford professor, John Greaves, on visiting and measuring the Great Pyramid, inscribed a foot measure on the wall directly above the King’s chamber, with the message ‘to be observed by all nations‘. He then signed it, J Gravius. This act was no obscure professor-vandal indulging in some British nationalism via his graffiti message. Greaves’ measurements of ancient monuments throughout the ancient world later fed Sir Isaac Newton with the dimensions that enabled him to rediscover what the ancient world had known all along – the size and shape of the earth. From this came the understanding and laws of gravity.


It is now possible to expand on the identified geodetic fact that South Barra, Castle Rigg, Long Meg menhir and Little Meg all lie on or very, very close to a line drawn from South Barra to Little Meg. Some would call this a ley, or a ley-line, but recognition of the line’s angle also identifies that Castle Rigg and Long Meg define the corners of a ‘phi’ double square, which massively enlarges the significance of this geodetic arrangement.

Further work then hurried along apace with visits to other stone circles in the Lakes. Some of this work was usefully undertaken with a lightweight theodolite loaned to me by fellow megalithomaniac Andrew Davies. This instrument made it much easier to obtain rapid (if less accurate) basic data at sites.


Figure Eight. Three other major stone rings in the Lakes District – Grey Croft (Seascale), Burnmoor East and Swinside (Sunkenkirk) stone circles are located to mark out three corners of a square. The fourth corner (if it ever existed) now lies submerged under the sea off the Cumbrian coast.

The most significant factor in all of this work was that these three sites accurately replicate, in size and same orientation to the cardinal points of the compass, the dimensions of the Castle Rigg – Long Meg squares.

The Castle Rigg-Long Meg rectangle gives an average figure of 8.652 miles for the short side length. The three sites or Seascale, Burnmoor E and Swinside gives a measure of 8.81 miles.

Both geodetic squares possess side lengths that are very closely equal to one eighth of one degree in length, which averages at around 8.647 miles. This is 69.176 miles for the degree, a figure within a cool 99.99% of one degree (see previous paragraphs).

Suddenly, these two networks of massive stone circles become nodes that provide us with a rare commodity in this type of work – repeatable data affirming that a megalithic geodetic project once took place here in the Lake District.
The evidence presented here suggests that some kind of surveying process was being undertaken before 3000 BC, in the English Lake District. We might suggest that this had something to do with identifying the length of one degree across the surface of the Lake District.

If this is the case, then here is a wonder of prehistory, no less than Stonehenge, or Avebury, for it also suggests that our prehistoric forebears were familiar with the size of the earth, complex geometry, and the basis of counting and measuring angles, qualities that are entirely absent from our history books and particularly books on the history of science.

Our modern culture simply states that such things would have been impossible for people in the Stone Age to even comprehend, let along implement. This leaves us surprisingly biassed against the fair assessment of any new evidence that demonstrates just these very capabilities.

However, there have sometimes been high ranking and scientifically trained people who have kicked out at this attitude, by producing data that supports a much higher level of capability and knowledge in the people that built the thousands of monuments that have survived across the landscapes of Europe. Professor Alexander Thom, stated in a 1970 BBC documentary that, “In terms of their thinking abilities I think they (the megalithic builders) were my superiors”.

The same conclusions were also made concerning the abilities of those that originally built Stonehenge, by one of the most respected scientists of the twentieth century, Sir Professor Fred Hoyle (1915 – 2001), a Yorkshireman who had lived in and loved the Lake District. In the preface of his book, On Stonehenge (1977, Freeman), he wrote,

“The remarkable story discussed and developed in this book goes I believe beyond anything the casual visitor might guess, for it requires the men of the new stone age, men living 5,000 years ago, to have been meticulous observers of the night sky, to have calculated with numbers, and to have communicated sophisticated astronomical knowledge among themselves from generation to generation.”


The belief that only physical objects can survive from prehistory – not the ideas, beliefs or creative inspirations of the culture responsible for those objects – has made it all too easy for the more intangible ‘things’, such as angles and measurements, to become sidelined,neglected or forgotten, which is plainly what has occurred in our culture. However, these ‘other things’ are a type of artefact, other than the physical objects of present day archaeology, and here we see them speaking the universal language of number and science, taking the form of lengths and angles between megalithic monuments or the (latitude dependent) horizon angles of solstice sunrises or sets, and of major moonrises or sets.
A megalithic scientist looks for, works with and can find these ‘other artefacts’ within the landscape, and thereby gains access to the Neolithic mindset, a rich world that is revealing the true capabilities of Neolithic people and to which the conventional archaeologist or historian neither believes in nor has any means of access. This situation could, of course, radically change, and this article, one hopes, must go some way to encouraging such a change.


Castle Rigg to Long Meg = 102,079 ft      Sellafield to Burnmoor E = 46,840 ft
Top rectangle side = 91,078 ft                   Burnmoor E to Swinside = 46,734 ft
LH rectangle side = 45,786 ft                     Swinside to Sellafield      = 65,057 ft
Lower rectangle side = 91,378 ft (measurements from Google earth)


Figure Nine. The easternmost stone at Long Meg. Built to endure!

Copyright Bluestone Press 2018.               All rights reserved.               Robin Heath, June 2018

Note to the reader: This article, it is hoped, will be enlarged and expanded on, as time allows, weather permits and access to some other sites is obtained. RH


Wooden Books new compilation hardback, MEGALITH- Studies in Stone, was duly launched over the summer solstice celebrations at Avebury and at Stonehenge. The sun dutifully arose from a perfect azure sky at 4:52 am ( First Flash). Fabulous!!

So,  the new book’s out, and contains the revised and enlarged version of the earlier title Stonehenge (Wooden Books, 2000) available from the Wooden books website and their distributors (Central Books, and Amazon  plus many book shops, including the Henge Shop at Avebury (see website). Seven Wooden books, plus hard to find original Alexander Thom survey plans of Stone rings, all in enlarged format and within hard covers, priced at only £16.99.

Synchronous with the launch were substantial articles in the Daily Telegraph and Daily Mail (20th June)  The i,  (21st June) plus interviews with either John Martineau or Robin Heath on eight local radio stations spanning from Radio Scotland to Radio Jersey. These newspaper articles are all available on line, we are told, for a limited period.

Many thanks for all who contributed to make this event a happy and fun occasion. In particular, Hugh Newman, for generously letting us use his home as an brief overnight resting place and watering hole, – almost unique in being within visible range of Stonehenge; Will Gethin, PR whizz of Conscious Frontiers, for stimulating the media to take interest in the event and for organising me and John (like herding cats, I should think).To a dear friend, the Archdruid Rollo Maughfling, for giving the launch proceedings some extra gravitas.  And tor Dominique, Trudy and Jane at the Henge Shop, Avebury for laying on a lecture hall and providing many appreciated facilities within the Avebury ring.

Finally, to my wife Trish, who supplied a superb veggie lasagne late on solstice eve, and a greatly appreciated (and rapidly demolished) fried egg breakfast at 7:00 am on solstice morn.

Here are some photos of the event. No copyright, anyone can send any or all of them to whoever you llke.

I am now about to fall over through lack of sleep and having 400 miles driving under my belt in under 30 hours.

RH zzzz!

NB No-one was harmed in the production of this book launch.






Earth Light shoots out of Holy well

This photograph was mentioned during one of my presentations at Megalithomania 2018, in Glastonbury.
It is one of about seven photographs I took of a Holy well during a survey trip to Anglesey on 15th May 2011. I filed these and did not pick up on this particular photograph until 2016. Only one had this anomalous light, which appears to be a double or triple light source that is  leaving a diaphanous trail as it rises from the water source.

Make of it what you will, the photo shown here is exactly what emerged from the memory card in the digital camera, a Nikon 4300.




Fun for all the family!!

One month to go before the annual megalithfest at Glastonbury. It’s my first Megalithomania appearance since 2012. I have also been asked to act as some kind of tour guide on the Stonehenge special access visit on the Monday (14th May), my first since the old road was removed, the new Visitor’s Centre was completed, and I finally found an older, bigger analogue of the Stonehenge site in the Preseli Hills of West Wales. Surely not!?

I’m giving two presentations: the first is Aboriginal Stonehenge in Wales (May 12th) which will be an update on my recent work and will include the recent boisterous new research into the relationship between Woodhenge and Stonehenge, which many readers of this website will already be somewhat familiar with.

My first presentation is on Saturday 12th May, 2018, 4:00 – 5:00pm

Aboriginal Stonehenge in Wales 

Stonehenge as a later imitation.

Here is the official Megalithomania blurb:

In the 1970s, a motley assortment of leyhunters, dowsers and members of RILKO and IGR combed the Preseli hills of West Wales looking for evidence of a Preseli Zodiac. Support for their researches originated from ancient Welsh legends, and they almost found the original Stonehenge. For the past 33 years, Robin Heath has been living and working within this landscape, discovering that the landscape itself, together with the siting of several important megalithic monuments reveals the ‘zodiac’ that also formed the original design for Stonehenge. Robin’s illustrated presentation is the subject of a recently published book, Temple in the Hills.

My second presentation is on Sunday 13th May, 2018, 2:45 – 3:45pm

The 2018 John Michell Memorial Lecture

I have been honoured by being asked if I would give the annual John Michell Memorial Lecture (May 13th), entitled Keeping on the Old Straight Track. John was a very dear friend of me and my wife and we often walked miles of landscapes with John in search of evidence for prehistoric and ancient cultural evidence that supported the megalithic science of our ancestors. My own work was greatly accelerated by John’s energy and generousity.

Here is the official Megalithomania blurb:

 Keeping on the Old Straight Track

Applying John Michell’s legacy to new research.

John’s books and lectures reintroduced two generations to a global prehistoric science whose traces were still visible because they had survived into later Babylonian, Egyptian, Minoan, Greek and Roman times. Although the scientific establishment remains to be convinced of it, this ‘megalithic science’ (which John sometimes referred to as ‘spiritual engineering’) remains recogniseable to modern thought.

In order to demonstrate the effectiveness of the ancient sciences when correctly understood and then applied, Robin will revisit some of John’s favourite haunts, and pull a few new rabbits out of the hat.


Many website readers have asked when Part Three of the tryptych article will finally appear, and the answer is between this event and midsummer, during the launch of the new composite Wooden Book ‘Megalith‘. This new tome includes my own contribution to this marque, a rewritten edition of Stonehenge with much new material plus some of Sun, Moon & Earth, within a contents page to satisfy the desires of anyone interested in prehistoric culture and ‘Old Stones’.


Editor’s Preface                          1

Book I  Stone Circles                7

Hugh Newman

Book II  Carnac                        59

Howard Crowhurst

Book III  Stonehenge               127

Robin Heath

Book IV  Avebury                     181

Evelyn Francis


Book V  Stanton Drew          237

Gordon Strong


Book VI  Callanish                291

Gerald Ponting


Book VII  Ancient British Rock Art   355

Chris Mansell

Book VIII  Surveys of Stone Circles   419

Alexander Thom and Archibald S Thom

Index  487

At the time of writing this, the retail price for this bundle of joy is not available, but the other Wooden Book compilations have been set at around £14.99. Surely a whole lot of bangs for your buck at this price, with each separate WB’s priced at £6.99 this mammoth megalithic book is a hard bound bargain in a sparkly cover.

Go on (the WB website), because you’re worth it!!




Stonehenge & Woodhenge – PART TWO


Megalithic science claims to be able to provide a skill set whereby it becomes possible to understand the long-forgotten rules or lost prehistoric science needed to fathom out the purpose or function of a megalithic design that has stood there waiting to be understood for thousands of years. This experience can and often does confer an awesome sense of privilege, and it can connect a researcher directly to their far distant roots, seeing directly into the mindset of their ancestors. Once a few and quite simple rules are understood, the design rules, astronomy, units of length and geometry originally applied by the original architect(s) and/or builder(s) of a megalithic monument can be revealed. This methodology is presently and sadly not recognised by mainstream prehistoric archaeologists.

The various techniques and methodologies by which this recovery process is brought about has been described in many of my books and articles, and in many other works by other relevant researchers in this field.  The experiences which led me to be able to write on this subject are perfectly crystallized below, when  investigating the relationship between Stonehenge and Woodhenge.

Measuring the Distance between Stonehenge Centre and Woodhenge Centre

In Part One a single action began the process of investigation. I made a measurement of two physical realities : firstly the length of a line connecting Stonehenge centre to Woodhenge, centre, and, secondly, the angle of orientation that this line makes with respect to an east-west line, termed a co-azimuth angle. This second part of the article shows where that single action can lead a researcher into understanding presently unsuspected purposes within the designs of, in this case, Stonehenge and Woodhenge. A set of functions are revealed, functions or purposes which presently, no other technique being applied by archaeologists can offer.

I had measured the distance between these two henge monuments previously, and even the angle, in 2003, during the writing of The Measure of Albion (Bluestone Press, 2004, co-authored with John Michell (a facsimile is available in the USA under the title The Lost Science of Measuring the World, 2006, AUP). At the time this data became buried with a mass of other material had been gathered at the time. I had derived the length from the OS map coordinates, and this has since become the quaintly old fashioned way! Google Earth arrived soon after 2003, providing an astonishingly useful tool for this kind of work, although it can be fraught with dangers in this work unless backed up with site work on the ground. Google Earth, like the map, is not the territory. (adapted from Alfred Korzybyski, with apologies!). Researchers will need to recognise that the model of the earth (The Geoid) used by the British Ordnance Survey in making maps of Britain is coded OSGB36, whereas Google Earth uses WGS84 (World Geophysical Survey 1984.) Conversions from one system to the other are available on the web.

The 10033 feet measurement shown in the illustration above was taken centre to centre, using Google Earth.  For Stonehenge, the centre was assumed to be that location where the diagonals of the 5:12 station stones rectangle cross each other. The corners of this rectangle were originally occupied by moderately large stones. They were set a few inches inboard of the Aubrey circle perimeter and asynchronous with its hole spacing (see diagram below).

More detail: Stone 91 now lies recumbent next to its original stone hole and stone 93 is a large solitary stump over to southwest of Stonehenge. There are two missing stations, 92 and 94, but fortunately the location of their original holes has been established (Atkinson, et al). The centre of the Aubrey circle, marked as explained above, is depicted below, on a useful diagram that also indicates the principal solar and lunar orientations at Stonehenge and the direction of Woodhenge centre, which remains clearly marked by a solitary drab concrete bollard.

Stonehenge centre to Woodhenge centre = 10033 feet ( ± 3 feet)

It is estimated that this measurement, from centre to centre, is accurate to better than plus or minus three feet of the value given above.

Maxing the Factors

Now look what happens when one discovers the component factors present within this number,

10033 (feet) = 13 x 283.6 x 2.722 

The number 10033 feet can be represented by a tryptych containing three relevant numbers, each familiar to a student of megalithic science.

A).The number thirteen is inherently the numerical signature of the longest side length (hypotenuse) of a 5:12:13 triangle. 

B). The number 283.6 is the mean diameter in feet of the Aubrey circle, established by professors Alexander Thom and Richard Atkinson, during their 1973 survey of Stonehenge. Each Aubrey hole was located by Atkinson by probing and resistivity testing, and its centre established and marked with a survey pin (Thom & Thom, JHA, 1974, op cit, see Part One). 

C). 2.722 is the numerical value of the megalithic yard in feet, a unit that was originally discovered by Alexander Thom following two statistical methodologies prepared by the top Oxbridge statisticians of the time and based on analysis of the diameters of over 150 stone circles. (see Thom, MSIB, 1967, Chapter 5, and Thom & Thom, MRBB, 1978 , Chapter 4)

The point to point measurement of 10033 feet is also associated with an angle so similar to that of the apex angle of a 5:12:13 triangle that it may reasonably be  assumed to have been intentional, part of whatever process of laying out the bearings from Stonehenge took place, prior to Woodhenge’s construction. This tends to support the present archaeological view that Stonehenge was the first of these two henges to be erected.

But did Stonehenge come first? This is an important question that must not be hurried in the answer. The earliest known structures in the immediate Stonehenge landscape are those three massive post holes which incongruously became known as the ‘car-park post holes’ during the 1970s building of the now defunct earlier Visitor’s Centre and tunnel. Their locations were eventually marked with large white painted circles of concrete.

Whether the Woodhenge site may or may not have been later adapted throughout its long history, it remains true that the earliest known building work on this henge site included some very large post holes.The post holes for Woodhenge indicate that the posts would have been extremely massive, requiring similarly large retaining holes, particularly if the assumed wooden posts were long enough to support a roof structure. Evidence exists, for Cunningham’s excavators indeed found that there were ‘deep ramps to all the holes in Ring III‘. Thom also states (Thom, MSIB,1968, p 75) that ‘if the posts were 2.88 ft (in) diameter the inside of the structure would be a perfect fit‘ (to the sequence of perimeter lengths, discussed in Part One).

But what if those sixteen holes in Ring III were originally not intended for wooden posts? It is by no means a done deal that they were, is it? Their diameter is well matched to many of the eighty or so bluestones that remain on the Stonehenge site today. Might Woodhenge have once housed a bluestone circle during the five centuries gap that currently haunts researchers into the origins of the bluestones. Woodhenge has been somewhat neglected over the years, a wooden Cinderella to its stoney sister, Stonehenge. Viewed sideway on, at ground level, it may resemble a load of bollards, but Thom’s surveyed plan (and Part One and the diagrams here) suggest that Woodhenge is far more interesting than that.

The Unit Length of a Triangle

For any size triangle laid out in two dimensional space, the unit length can be found by dividing the measured length of the perimeter, in any chosen unit of length, by the number of ‘units’ in the perimeter. For a known and accurate 5:12:13 Pythagorean triangle, the perimeter units total thirty, the sum of the side lengths [13+12+5]. For the triangle under investigation, the perimeter length totals 23,153 feet and the unit length becomes that value divided by 30, (see below).

Because the apex angle is negligibly different to that of a 5:12:13 triangle, the unit length can also be derived simply by dividing the 13 side length by 13. But this answer assumes that the 5:12:13 triangle is exact, and geodetic triangles laid out on the ground are almost never exact. However, for this  example, on flat territory and over a small area, one would expect the unit length derived from the 13 side alone to be extremely closely matched to that derived from the total sum of all three lengths of this triangle, measured along the ground.

The two side lengths shown in red (on the diagram above) were measured using Google Earth. As an exercise, the reader may like to determine the difference between the unit length derived from the ’13” side alone and that determined from separate measurements taken of all three sides using Google Earth.

There is no substitute for being on site. Walking around this location shows that there is no surface sign that a right angle for this triangle was ever permanently marked, or monumentalised directly, although its location is strongly suggested by the geometry and metrology. A good place to dig, perhaps, but not, not ever, by other than qualified archaeologists who have the required blessings of EH and WHO.

For this example,  the best estimate for the unit length is that derived from the ’13’ side alone. The 13th part of that length separating the centre of Stonehenge from the centre of Woodhenge becomes the unit length of the triangle, in whichever unit of length one chooses to measure it with. In feet it is the product of 283.6  and 2.722 , which is 771.77 (feet).

Unit length of the ’13’ side of the triangle = 771.77 feet

But this is also 283.6 megalithic yards (771.77 feet / 2.722 feet), numerically the mean Aubrey Circle diameter expressed in the larger unit of the megalithic yard, instead of the 283.6 feet (mean diameter) of the Aubrey circle. The three factors revealed above can now reduce to just two, and the length 10035 feet is seen to contain 13 lengths of 283.6 megalithic yards.

The 10035 feet distance connecting Stonehenge (centre) and Woodhenge (centre) is thirteen ‘super-Aubrey’ circles… (if you like)!

10035 feet = 13 x 283.6 megalithic yards

The Perimeter Length  

The perimeter of a 5:12:13 Pythagorean triangle can be estimated by multiplying the length of the 13 side by 30/13, as shown above. This delivered 23,153 feet or 8,505.9 megalithic yards. The perimeter may also be measured using Google Earth for each of its three sides, and this presents an almost identical length, at 23,151.8 feet.

In Part Three, the consequences of this research will make it possible to recover yet more useful information from the designs of Stonehenge and Woodhenge, taken together. And we will then make a journey to the Preseli Hills of West Wales, where interest widens way beyond those outcrops that have proved to be the source of many of the Stonehenge bluestones.

Additional Notes : It is fortunate in this work that the foot and the megalithic yard have remained clearly defined and recogniseable units of length. Thom’s megalithic yard became recognised during modern times in Megalithic Sites in Britain (Oxford, 1967). Metrologist John Neal, in various metrological publications from 2000 onwards, proposed that the megalithic yard should more correctly have been named a megalithic step, being 2.5 times the length of the foot from which it derives within the traditional system of metrology, and not three times that length (a yard).

Neal identified the foot from which the megalithic yard derives to be the Geographical value of the Belgic foot (1.08617 feet). The root value of the root Belgic foot holds a ratio of 15:14 with the ‘root’ value of the English foot.

Similarly, Thom’s megalithic fathom (5.44 feet =  2 megalithic yards) would be better termed a pace, but Thom’s megalithic rod, (6.805 feet = 2.5 megalithic yards) sits comfortably within the canon, because a rod can be a double royal cubit, here based on a royal cubit whose single length is 3.403 feet.

In comparison, the inner and outer diameters of the sarsen circle accurately measure 28 and 30 double royal cubits at geographical value (3.4757485 feet), respectively.



Robin Heath, December 2017                      StoneAgeSurveys           





Stonehenge & Woodhenge – A Lost Legacy – PART ONE


Soon after the distinguished Welsh archaeologist Maude Cunningham and her husband finished work excavating the site we now know as Woodhenge, in 1929, the locations of each of the site’s many revealed postholes were marked with grey concrete bollards. The best that can be said of this action was that it ensured their original exact positions were recorded for posterity (see Alexander Thom’s photograph below, from 1958, courtesy of Eoghann MacColl).

Visually, Woodhenge is neither a pretty nor an impressive site, unlike its nearest neighbour, Stonehenge, some 1.9 miles to the southwest. VIsitors to Woodhenge tend not to linger around this site, and soon slope off to nearby Durrington Walls, to the north, or Stonehenge, to the southwest. This article claims to lift the present Cinderella status afforded to this Neolithic class II henge and timber circle monument, by identifying a previously unrecognised significance in its geodetic placement with respect to Stonehenge.

 The Brief History of Woodhenge’s Discovery

Originally, what became Woodhenge was first discovered in modern times during the first half of the nineteenth century, as ‘earthworks’ thought by some archaeologists of the time to be a disc barrow. It had been named Dough Cover, surely the first reference to the site’s henge shape.  In 1926 Woodhenge’s discovery was amongst the first triumphs of the new science of aerial photography, and the site was first positively identified from an aerial photograph taken by Squadron Leader  (later Group Captain) Gilbert Insall, VC, in 1926, during a survey of Wessex by Alexander Keiller and OGS Crawford.  Keiller later undertook the pioneering restoration work at Avebury, during the 1930s, and Crawford was Archaeology Officer for the Ordnance Survey and later became the editor of Antiquity. Having recognised the importance of the site,  renowned archaeologists Maud and Ben Cunningham immediately began work excavating the site, and by 1929  their survey report confirmed that it was indeed a henge.

In 1958 and again in 1973, Alexander Thom undertook a survey of the Woodhenge ‘bollards’,  a simplified version of his original plan of the site appearing in Megalithic Sites in Britain (Oxford, 1967, p74) site. His original site plan is reproduced below.

Thom wrote that a ‘very careful survey’ of the site, ‘using steel tape and theodolite, was made of the concrete posts which the excavators placed in the post-holes in the chalk’. He then linked the site with Stonehenge astronomically by  pointing out that the axis of the site aligns to ‘the point on the horizon where the midsummer sun first appeared about 1800 BC’.

The calculated ‘first flash’ azimuth is indeed 49.2 degrees when the given figures for the latitude of the site and horizon altitude are entered into the standard formula (see below).

A hawk-eyed reader may spot that on the plan published in MSIB  the solstitial sunrise is given a declination of 24.2 degrees, which corresponds to a date around 4800 BC, far too early for all dating estimates of Woodhenge.  The original plan (above) gave the declination in Thom’s own handwriting,  at 23.9 degrees, and a theodolite measured horizon altitude of 0.5 degrees. 


QUICKAZ – Finds azimuths in a flash!

1. Determining solstice sunrise at Woodhenge, circa 1800BC (dec 23.9 degrees)

The proposed sunrise is in the NE quadrant.

Epoch 1800BC, Declination = 23.914, Latitude = 51.2, Horizon Altitude = 0.5 degrees

Correction for Earth’s Curvature = 1.37197E-06, Parallax Correction = .002 degrees,

Refraction Correction = 0.55 degrees

                                                          ^         ^         ^

********- horizon -****^****^****^**********

First Flash =                              49.20144 degrees

disc half risen =                                49.61157 degrees

disc on horizon =                                   50.42171 degrees

The same formula run with 24.2 degrees declination (4,800 BC) give the following rise azimuths for the sun:

2. Determining solstice sunrise at Woodhenge, circa 4800BC (Dec 24.2 degrees)

                                                               ^       ^       ^

********- horizon -****^****^****^**********

First Flash =                             48.64856 degrees

disc half risen =                                    49.06212 degrees

disc on horizon =                                             49.8788 degrees


Program by Robin Heath, Stone Age Surveys, 28th November 2017

The geometry of Woodhenge is shown to be one of a family of designs which mostly occur on the western side of Wales (Castell Mawr and Hirnant), and in Brittany. The various arcs are struck from the points of a triangle, usually of integer side-lengths and Pythagorean (right angle triangles). Sometimes the ‘blunt end’  is semi-elliptical (Castell Mawr) rather than semi-circular (Woodhenge). The plan of Woodhenge given above shows the design to be based around a 12:35:37 Pythagorean triangle, from whose corners the various arcs are struck to define the perimeter. The arcs at the blunt end share a common centre at A, whilst those at the sharp end share a common centre at C. The measured distance between  A and C is 6 megalithic yards (2.72 feet), which makes the triangle 12:35:37 in units of half a megalithic yard.

From point B the flatter arcs are struck to then complete the perimeter.

Woodhenge consists of a set of concentric arcs struck from each point of the triangle, with one gap (see plan). It is the perimeters which reveal the true nature of the design. While the radii are not integral multiples of the megalithic yard, the perimeters turned out to be of lengths close to 160, 140, (gap), 100, 80, 60, 40 megalithic yards. For each ring the radius of the arc at the ‘sharp end’ is 1 megalithic yard smaller than that struck from the ‘blunt end’ (MSIB Table 6.5 shown below, author’s commentary in brackets).

Ring           Perimeter (My)          R1(My0         Major axis    P(actual)

I                      160                            24.02              53.04          161.0

II                     140                            20.84              46.67          138.2

III                    100                            14.47              33.94          104.2

[The same perimeter as the Aubrey circle diameter 283.6 feet = 104.188 feet]

IV                      80                             11.29             27.58            79.9

V                       60                               8.10             21.21            61.3

VI                      40                               4.92            14.84             39.4

Thom noted that there were deep ramps to all the holes of ring III, and that the holes averaged at 2.88 feet diameter (7.839 feet). He concluded that very large posts had been used, ‘carrying perhaps a platform or roof‘ [or maybe a bluestone or two?]. He further noted that the ring was 4 per cent larger than expected, and that holes of the above larger diameter would assure ‘the inside of the structure would be a perfect fit‘.

Neglecting ring III, Thom applied his statistical methodology, designed by mathematician and statistician Dr Simon Broadbent, to find from the values of P(actual), the value of the megalithic yard which best fits Woodhenge. This turned out to be about 2.718, a value so close to his later value for the megalithic yard ( 2.722 feet) as ‘to show that we can be quite certain we are using the identical geometrical construction to that used by the builders‘.

To briefly digress, when I was staying with the Thom family in preparation for writing the biographical account of Thom’s life and work (Alexander Thom: Cracking the Stone Age Code, Bluestone Press 2007) the full nature and extent of the excoriation this pioneering archaeoastronomer had endured from the negative reaction to his work from many mainstream prehistorians and archaeologists was laid bare in front of me. This became known within archaeology as ‘Thom bashing’ and ‘Thomfoolery’. However, some of the leading prehistoric archaeologists of that time (Atkinson, Burl, Case, MacKie) were both amicable and quite accepting of his work and studied the implications of accepting the claims Thom had made concerning the capabilities of Neolithic megalith builders. What was also painfully true was that many of his most vehement critics were neither equipped nor qualified to assess the numerical nature of Thom’s findings. Interested readers can glimpse the nature of this energetic debate – a fascinating vignette of a true pioneer who arrived on the scene during the most turbulent time in the recent history of archaeology – by watching the archived 1970 BBC ‘Chronicle‘ documentary, Cracking the Stone Age Code,  available on the web (search ‘BBC archive Chronicle Thom’). They do not make documentaries like that any more.

What happens when Stonehenge and Woodhenge get together

Thom first surveyed Woodhenge in 1957-8 while he was still professor of Engineering at Brasenose College, Oxford. By the time of the 1973 Stonehenge surveys he had retired and moved back to the family farm (The Hill) in Dunlop, Ayrshire. He enjoyed full assistance during that work from his son, oceanographer Dr Archibald Thom,  professor Richard Atkinson, Stonehenge custodian Major Lance Vatcher and members of the Survey Branch, Royal School of Artillery. His report first appeared in the Journal for the History of Astronomy, Vol 5, part 2, No 13, June 1974), and a version of this paper later appeared in Megalithic Remains in Britain and Brittany (Thom and Thom, Oxford, 1978).

It  dawned on me while working on the relationship between Stonehenge and Woodhenge that Alexander Thom is probably the only individual who has ever undertaken an accurate survey of both monuments. I was particularly aware of this during a trip to the Stonehenge landscape with John Michell in 2003. While setting up a theodolite on an anonymous barrow some 3700 feet from Stonehenge, I noted that all three sites lay on a straight line connecting Stonehenge with Woodhenge. When I returned in 2014 (with a better theodolite) I had more time to study this linearity and its relationship with the sky and landscape.

The centres of the two henge sites are spaced 10033 feet apart. Defining the centre of Stonehenge is rather harder to estimate than for Woodhenge, due to each phase of the former monument having a slightly different centre than the others (Thom, JHA 1974, op cit). I used the crossing point of the two diagonals of the station stone rectangle, as shown below ( lower left). The measurement is from Google earth, and estimated to be accurate  to within two or three feet, based on a normal surveying practice of defining a previously laid out base line, in this case the measured distance between the eponymous Cuckoo stone and Woodhenge centre, some 1350 feet in length, and using Google earth to compare the accuracy of that already known length with the length delivered by GE for the unreachable (out of bounds) centre of Stonehenge!

The azimuth or bearing of this line, looking from Woodhenge to Stonehenge, is 247 degrees and  23 minutes, obtained from a sun-shoot. Looking up the line from Stonehenge, this azimuth angle (the angle between north is 67 degrees and 23 minutes’, and the angle from the white east-west line (illustrated above) is therefore 22 degrees 37 minutes). This is significant, for it is uniquely the acute angle of a Pythagorean 5:12:13 triangle. It means that the two thin white lines above, each aligned to the cardinal points of the compass, for the ’12’ side and the ‘5’ side of the triangle, and have lengths, according to Pythagoras’ theorem, of 9261 feet and 3858 feet respectively. There is no sign of any monument at the point where these lines meet, at the right angle, although a dig there may prove fruitful for anyone up for the task and who has permission from the custodians of this World Heritage site!

Here’s where the application of megalithic science begins to deliver big dividends. There has so far been no digging, no invasion of the site, no massive expense and yet already this investigation is able to change the way we look at these two henge monuments, separately and as a pair. And there has been neither the harming of any archaeologists, nor employment of loony fringe ideas. Just one angle and one length accurately measured using precision instruments up to the task.

There is already an existing 5:12:13 triangle implied within the 5:12  station stone rectangle, once described by Aubrey Burl as ‘near perfect’. The diagonals of this construction are 13 of the same units that make up the known and measured ‘5’ and ’12’ sides, and the three measurements are 108.8 feet  261.2 feet and 283.6 feet, respectively. It is the 13 side of a 5:12:13 triangle that is our measured length from Stonehenge to Woodhenge,  measured as 10033 feet.

As they say on the sport news, look away now if you don’t want to see the result.

Now for the good bit –  10035.47 feet = 283.6 x 13 x 2.722 feet.

Alternatively 13 x The Aubrey circle diameter (expressed in megalithic yards) = 3686 megalithic yards

[99.98% of the measured value, using the later value for the megalithic yard determined by Thom during the 1973 Stonehenge survey (Thom, JHA,1974, op cit) and confirmed by the Avebury survey of 1975 – 6, (Thom & Thom, MRBB 1978, op cit, pp 36-43)].

Thus it appears, based on this first step in investigating the relationship between Stonehenge and Woodhenge, that these two henges relate to each other, through a fundamental measurement of the Aubrey circle, namely its mean diameter (Thom, 1974, JHA, op cit), which is fundamentally and intelligently incorporated into the distance that separates their two centres.

That is enough for the first part of this article. Result.


Robin Heath                                           StoneAgeSurveys                                       3rd December 2017