03 March, 2009

24. Systematic Irregularity: Why almost nothing in the Celtic world was square

There are some things that are so obvious that nobody notices, and they pass without comment or explanation. About twenty years ago I noticed that almost nothing in the ancient Celtic world was square, so I named the phenomenon “systematic irregularity”, and published it, but ironically nobody noticed that either. [1]

So second time around, and now in colour, I give you Systematic Irregularity, a phenomenon which can be observed in many aspects of the prehistoric Celtic world, which is a problem, as I can’t show you everything that isn't square; but you can trust me – I’m an archaeologist.

We are all familiar with the restless flowing curves characteristic of Celtic decoration, particularly the Iron Age La Tène Style, exemplified by pieces like the Battersea Shield [left], not a place you would really expect an unnatural shape like a square; however, it goes much deeper than this.
Viewed from the air at certain times of the year, and in certain light conditions, the ditches of fields and enclosures dug by previous generations magically appear as cropmarks in the countryside. A great deal of what we know about prehistory has come from mapping and excavating these cropmark sites, which can often be tentatively identified from size and shape alone. On this basis, anything square is probably Roman or later.
The Late Iron Age enclosure at Orsett, Essex: A: Primary enclosure. B: Secondary enclosure, with double outer ditch system enclosing both, probably built in response to the Roman Invasion in AD43.[1]

I first noticed there was something was odd about Celtic enclosures when I was writing up the excavation of the late Iron Age site at Orsett ‘Cock’. It had two phases of overlapping enclosures, surrounded by as double ditch system enclosing both.[1] The enclosures were roughly the same slightly irregular shape, with two parallel sides and two right angles: technically trapezoidal, almost square, but with one corner misplaced.

This concerned me. Why did both enclosures have a similarly irregular shape? Clearly, ditches may have to respect topography, existing structures, and even trees, and you would naturally expect hillforts to be hill shaped, but Orsett was a gravel terrace.


Quadrilateral Iron Age enclosures: A: South Lodge Dorsett (Bronze Age?) B: Portsdown Hill, Hampshire. C: Aldwinkle, Northhamptonshire. D: Scrooby Top, Nottinghamshire. E: Casterley Camp, Wiltshire. [2]
As I looked at other sites, it became clear that trapezoidal (2 parallel sides), usually with 2 right angles, enclosures were quite common, and that some even had 2 sets of parallel sides and no right angles, like a pushed over rectangle or square, a parallelogram or a rhombus respectively (more rich pickings for the pub quiz). Everywhere I looked, nothing was quite square, regardless of scale, not even quite small enclosures such as that surrounding an important building within the Hillfort at Hod Hill.
A small enclosure within the Hillfort at Hod Hill in Dorsett [3]
Surely it can’t all be related to topography. So were they were just rubbish at surveying?

An irregular four-post structure from Orsett, Essex [1]
However, I became really suspicious that something strange was going on when I started looking carefully at the buildings from Orsett, in particular the small square structures with four posts, thought to be granaries. I noticed they weren’t square either; one corner was always out, not by much, but enough so you would notice. It appeared that the post was placed fairly precisely next to its appropriate geometric position. This really was concerning! Irregular fields are one thing, but buildings that are not square -- that is quite another matter! Being on the level and square are essential prerequisites of building (as any Freemason will tell you!), and to find that these cardinal principles were being messed about with by people who, as we have demonstrated, were very competent builders and architects! [5]
Four-post structures from Little Woodbury. The numbers are posthole depths, and note how each phase of structure has consistent foundation depth. [6]
When I looked further afield, I realised that the four-post structures at Little Woodbury, where the form was first defined, were also trapezoidal. Something was definitely going on! Builders, just like the people laying out enclosures, were either incompetent, or deliberately avoiding squares in their structures.
Small structures from the South Cadbury Hillfort [7]
The more I looked at four-post and other small structures from other sites, the more it became apparent that nothing was quite square. Either prehistoric southern England was a land of botchers and bodgers, or they were doing it deliberately and systematically. I chose the latter option and called the phenomenon “systematic irregularity”.
For an archaeologist concerned with understanding the built environment, this had several important implications, not least for finding and identifying buildings. Faced with the large number of postholes sites often produce, the first thing that most archaeologists will look for is circular structures and small square ones. As I have discussed previously, the most important factor associating postholes of the same building is depth, as the Little Woodbury examples perfectly demonstrate, but this is not widely appreciated, and structures are often identified by overall shape alone.
Some excavators have even used computers to find ‘square’ structures and associated postholes. This was tried at the important Iron Age fort at Hengistbury Head, with the computer looking for squares with an accuracy of 150mm, and while posthole size was also considered, the postholes' depth, as such, was not.[8] Systematic irregularity suggests the computer would better have looked for structures with an ‘inaccuracy’ of about 300-400mm. In the end, the actual results were generally discounted, confidence in the computer being somewhat undermined by its habit of using the same posthole in more than one structure.

So our search for buildings and structures in posthole palimpsests is slightly more complicated than anticipated, but builders are unlikely to have compromised their building because of this, so any irregularity would probably not affect the roof. Noticing which post is misplaced may actually give us a vital clue about the superstructure it supports.

The square structure from Heathrow in Middlesex, thought to be a temple or shrine. [9]
As always, there is a glaring exception that rather proves the rule: ‘Celtic’ or ‘Roman-Celtic’ temples. These small buildings were clearly intended to be square, and first came to light at Heathrow in Middlesex during the war, and have subsequently been recognised at important sites like Danebury and South Cadbury.

Square structures with Danebury Hillfort, Hampshire [4]
However, not all religious buildings were square. At Hayling Island in Hampshire, the central structure was circular, but what is important is that it is set in a square enclosure, an arrangement that continued when it was rebuild in the Roman period.

The two-phase religious centre at Hayling Island, Hampshire [10]
This suggests that the square marked the division between sacred and profane space: that anything within a square is sacred, which is why it is avoided in a secular context.
As a structural archaeologist, my interest in the phenomenon ends here. I‘ve got a plausible explanation for why Iron Age structures aren’t perfectly square, and I now know that looking for structures that are may be counter-productive, so I’m happy. But a toe has been dipped into the dark reflective waters of the ritual pool, and the ripples spread wide, and questions are bound to be asked:
  • How far does the phenomenon extend geographically?
  • In what other aspects of Celtic culture does it manifest?
  • What does it tell us about Celtic culture, belief, and religion?
  • When does it appear and disappear?
  • What happens when the Celts interact with cultures like the Romans, where squares are not similarly regarded?
To be frank, it’s not my problem! I’m a buildings man, and in that respect, being aware of systematic irregularity is enough. But I have been thinking about this for some time, so I will share some initial observations.


A plan from the Iron age cemetery at Fin d'Ecury, N France [11]
Religion and burial are usually linked, but Iron Age burial practices were quite varied. Although both cremation and inhumation were practiced, there’s actually a bit of an archaeological mystery as to where all the bodies went. But that’s another story.[12] However, roughly square burial mounds are known, particularly in Yorkshire, such as Barton Fleming.[13] I am particularly struck by a plan from a cemetery at Fin d’Ecury, in the Marne region of northern France, showing square enclosures, one containing cremations, another contained inhumations, and a third enclosing a systematically irregular four-post structure.[11]
The symbolism of a square is based on the balance and regulation of four elements, or two opposing pairs, such as the points on the compass, or the four ‘elements’: Fire, Water, Earth, Air. A square is more often female in association, because of its relationship with the earth, as is the case in Hindu and Chinese symbolism. [14]


The central motif of the frontispiece to a Quran. Look carefully and you will see that the artist has placed a 14-sided figure in the middle of a 12-sided geometric scheme, preventing it from being perfect. [15]
In the Islamic world, where only God is perfect, art and architecture is obliged to be imperfect. The most intricate of decoration will contain deliberate imperfections for this reason, although this may only have been apparent to the craftsman.

This provided a good example where religious belief impacts the way craft is practiced, and it is important to note that this is no way detrimental to the quality of the finished article. The imperfections being subtle, they have no significant effect on form or function.

I am unsure as to when systematic irregularity first appears. In the Neolithic, sacred spaces are assumed to have been defined by circular structures such as stone circles and henges. People are thought to have lived in rectilinear houses, and were buried in communal long barrows. By the Bronze Age we see roundhouses, and round barrows, and sacred space presumably became square at, or after, this point.
I have found systematic irregularity in buildings from the late Bronze Age, but the prehistoric built environment is very poorly understood, so it is not the easiest place to look. Most classic trapezoidal enclosures date from the late Iron Age, along with the square temples.

Religion can be a difficult business. Gods, rulers, and people can be fickle, so quite what became of systematic irregularity when parts of the Celtic world came under Roman control is difficult to judge. In this context it is impossible to avoid mentioning the druids, who, according to the Romans, were responsible for such things when they got there. Julius Caesar tells that the druids were staunchly against writing and literacy. As presumed keepers of the oral history and laws of the people, they had considerable vested interest in illiteracy. It may be that systematic irregularity was another practice that served to help differentiate the Celtic culture from the destructive forces of the Classical world.

It is clearly difficult to demonstrate that a phenomenon like systematic irregularity is real, let alone prove the theory that it was rooted in the belief that sacred space was defined by squares, but it works for me as an explanation. The apparent alternative, that Celtic surveyors and architects, our ancestors, were serially incompetent, is not something I am prepared to believe.

References and further reading:[1] G. A. Carter, 1998: Excavations at the Orsett ‘Cock’ enclosure, Essex, 1976. East Anglian Archaeology Report No 86.
[2] Illustration cobbled together from: A. Chadwick, 1999: “Digging Ditches, but Missing Riches? Ways into the Iron Age and Romano-British Cropmark Landscapes of the North Midlands,” in Northern Exposure: Interpretative Devolution and the Iron Ages in Britain, B. Bevan, ed. Fig 10.3, p153 [Scrooby Top]. B. Cunliffe, 1978: Iron Age Communities in Britain: An Account of England, Scotland and Wales from the Seventh Century BC Until the Roman Conquest. 2nd edition. Routlage & Kegan Paul. Figs: [11.6] Aldwinkle Northhamptonshire, [11.5] Casterley Camp, Wiltshire, [11.14] Portsdown Hill, Hampshire, [2.4] South Lodge, Dorsett
[3] Ibid [13.26] Hod Hill, Dorsett
[4] Ibid [15.7] Danebury
[5] http://structuralarchaeology.blogspot.com/2009/02/23uncovered-prehistoric-building.html
[6] G. Bersu, 1940: Excavations at Little Woodbury, Wiltshire. Part 1, the settlement revealed by excavation. Proceedings of the Prehistoric Society, 6, 30 -111
[7] Taken from: Downs, Jane, 1997: The Shrine at Cadbury Castle: Belief enshrined. In Adam Gwilt and Colin Haselgrove, eds: Reconstructing Iron Age Societies. Oxbow Monograph 71, Oxford, 145–152
[8] B. Cunliffe, 1987: Hengistbury Head Dorset. Volume 1: The prehistoric and roman settlement, 3500BC–AD500. Oxford University Committee for Archaeology. Monograph No. 13
[9] W. F. Grimes and J. Close-Brooks, 1993: Caesar’s Camp, Heathrow, Middlesex. Proc Prehist Soc 59, 299-317
[10] A. C. King & G. Soffe, 1994: The Iron Age and Roman temple on Hayling Island, in A. P. Fitzpatrick and E. L. Morris, eds.: The Iron Age in Wessex: recent work, Salisbury: Trust for Wessex Archaeology, 114-16
[11] S. Piggott, 1965: Ancient Europe, Edinburgh University Press: Fig131, p 233
[12] See: J. Collis, 1977: Pre-Roman burial rites in north-western Europe. In R. Reece, ed., 1977: Burial in the Roman World. CBA Research Report 22, London
[13] I. M. Stead, 1971: ‘Yorkshire before the Romans: some recent discoveries’, in R. M. Butler, ed.: Soldier and Civilian in Roman Yorkshire, 21–43, Leicester
[14] J.E Cirlot, 1971: A dictionary of symbols 2nd edition, Routlage & Kegan Paul
[15] From Figure 5: http://www.geometricdesign.co.uk/perfect.htm Taken from: Martin Lings, 1987: Splendours of Qur'an Calligraphy and Illumination ISBN: 0500976481 Interlink Pub Group Inc.

6 comments:

Amol said...

Good post, I stumbled it...

Unitof1 said...

Hello Buildings Man, Unitof1 here, banished of BAJR, out looking for distractions from the report that I should be writing-currently a very grotty buildings survey.
I have noticed certain traits of yours-all justifiable devices: reaction to the Out of Africa paradigm in your blog which is unfortunate as I am a seventh generation expat currently based in Nigeria, the disregard of string, love of the Triatholon joint and in this theme the resort to dipping toe in ritual pond.

And was thinking- what about the use of forked sticks for your four posters. Seems to me that in amongst the mud huts I have seen the device of the forked stick to support the wall plate often results in a less than satisfactory post profile standard and so a disarray of posthole alignment to accommodate the subsequent cunning balancing acts. Indeed it is my contention that such is the mystic reverence for the fork of the forked stick, is it its ridged joint strength that draws the eye, that there is an almost perverse disregard for the post bit. This might be unfair but merely the result of giving in to the probability of matching forks in your forestry arrangements.

Not sure of your use of the myth of the Muslim perfection, Its hard to see where it would end.

Cut, cut, fill, fill.

Geoff Carter said...

Thanks for the comment.
On the subject of forked sticks; if your building requires only 2 major posts it is conceivable you might use one, however, in reality it is much easier to find lots of straight bits of wood of the required length, than to find straight bits with a appropriate fork in the desired position. Posts by and large connect to more than one piece of timber in the superstructure to ensure rigidity in all directions. Mortise and tenon joints allow more than one piece of wood to be joined to the head of post.

Unitof1 said...

I apologise at the outset in presuming that you imagine that the misaligned four posters that you have presented in the blog, attach to the rest of the superstructure through mortise/tenon joints –and that you are suggesting that the celts use the tenon joints but deliberately misalign the wall plate and so carry on the misalignment into the roof shape. Where as I am suggesting if the celts were fixated with having a forked stick, they would have to accept that you probably wont find them all attached to straight bits and they would make up for it by playing around with the post hole positions but still be able to create a reasonably proportioned wall plate and roof/platform structure –they might even throw in a few stake hole forks as well.. Type in African granary into google images and see where it takes you. Surely this is why the four posters were interoperated as granaries……

Not sure about your use of-in reality it is much easier to find lots of straight bits of wood-I think that you might have to create a very self assured silviculture with 50 to a hundred year cropping regimes first. Is there a possibility that forked sticks can for the same height and strength be produced from younger wood. Quite often here I see what are little more than stake sized forked sticks being used to hold substantial wall and tie beams. Also after the easy bit of finding the wood there is not much left to do to a forked stick…

Cut, cut, fill, fill.

Geoff Carter said...

I assume that the distortion in the plan would be done in such a way as to have no effect on the structure, and certainly not on the roof. I will be getting on to this, but in terms of the Orsett Post structure illustrated above, the first set of timbers would be a pair running up and down in terms of the plan, this would support a cantilevered base, [thus avoiding the distortion].

Granaries are remarkably similar the world over, and in Britain the basic form remains the same into the medieval period, though the posts are replaced by shaped ‘saddle’ stones.

I have hundreds of straight coppiced & standard oaks (quercus petraea), growing in woodland on my Farm, as most farms and estates would have had in the past, but I would have to go look for one with a symmetrical fork at the base of the crown.

I can think of no conceivable reason why forked sticks would have been used in post and lintel architecture; the four–poster at Orsett was built in the 1st century bce, at the end of a tradition already 5000 or 6000 years old in Northern Europe.

Unitof1 said...

Conceive. Is your use of systematic necessary with irregularity? Possibly aren’t you after cultural, traditional, ritual or…., for instance I am not sure that the four post form of construction would demand symmetrical forks or even those from the base of the crown. Almost any branch will do and paradoxically provide Celtic culture with your Systematic Irregularity from the fact that almost no two forks are exactly same.
http://www.hikingwithchuck.com/Downloads/OakSapling20070318.JPG
I think that you can find forks all over the oak tree-from little acorns and all that it must be the gods. Even in a coppice there are rouges and wolfs. I suggest that forks would have much more obvious uses in round houses as well.

You seem to be envisioning some theory of opposites, of either ors within a symbolised landscape centred on a circular home of the Celtic mind within a roughly squared enclosures evolved from an earlier Opposite type Neolithic but soon to be overtaken by the Cadastralist and doing so as a history of the tenon joint. How can the tenon be relevant, is the tenon joint made unsymmetrical in one system but not in another. But, like the joints at Stonehenge hidden, beneath a roof made right. Maybe what we are seeing is the evolution of no-mans land. The celts educated in round houses refute Pythagoras (still a common problem with most ground worker setting out foundation), they have a problem with setting right angles-what’s the problem of a few degrees here or there when they have mastered the circle.

Sorry I can feel myself going off into that other place (the pub).

Looking forward to your series of cantilevers

Cut, cut, fill, fill