I’m guessing most readers are familiar with the classic ringed or Celtic cross: originally large, standing stone crosses with what many have described as a stone ‘nimbus’ around the arms.* These standing crosses ranged in height from about 3m to 5.5m. Here’s a generic vector drawing to illustrated what I mean:

Vector drawing by Petr Vodicka of an original in the public domain

There are now millions of these nimbused crosses in miniature: on tattoos, t-shirts, and tarot cards; woven in hanging cloths, painted on Christmas cards, and hammered from bronze and pewter and silver and gold and hung on neck chains. There’s lots of rumination among academics, religious, antiquarians, and historians about where and how that so-called nimbus developed. Perhaps it comes from the cosmological cross, an “important motif in Coelius Sedulius‘s poem Carmen Paschale,” composed in the fifth century and, according to Wikipedia, “known in Ireland by the 7th century.” (You will forgive me if I call bullshit, or at least an unseemly stretching of probability.) Or maybe St Patrick combined the cross with pagan symbols (such as the Neolithic and Bronze Age wheel cross—see footnote) to appeal to the heathen. (We have absolutely zero indication of this, but, hey, anything’s possible.) Or, gosh, it could represent Christ’s dominance over the sun god. (Well of course it could; it could represent a prescient seventh-century mystic’s representation of a lunar module on top of Apollo 13.) And on it goes. It’s always been clear to me that all these pedantic old white men were basically talking through their beards.

So I was absolute delighted last month when I read an article in the September issue of Current Archaeology, “Iona’s Archetype,” that gave a much more likely explanation: the shape is a useful accident resulting from at least two sets of damage and an eight-century repair. And for this eminently sensible suggestion there is some evidence—circumstantial, of course, but something tangible.

On the island of Iona (that Hild knows as Hii) there were several large standing stone crosses. Most now standing are replicas, or are in pieces—or parts of a larger, reconstructed whole—in museums. One, the eight-century St Martin’s cross, still stands in its original position on Iona:

St Martin’s cross. Original mounted photograph annotated by Erskine Beveridge ‘ St Martin’s Cross Iona – (from east)’. From the RCAHMS Society of Antiquaries of Scotland Collection MS/36/209.

Note how short the arms are, how small the upper surface area is relative to the width of the long central arm. Iona is a windy island. Any top-heavy structure, especially if the top part has a large surface area, will be prone to being blown down. My guess is that the size of those arms explains the St Martin’s cross’s survival.

The Current Archaeology article, though, examines St John’s cross, originally 5.3m tall (about 17.5′), carved in the early eight century and apparently the progenitor of all Celtic crosses. Here’s what the partially reconstructed cross looks like.

Photo via Canmore

This is very high and very top-heavy. That central boss and outstretched arms would have acted rather like a sail, tipping the top-heavy thing over. The stone, particularly the arms, would most likely break under its own weight—and in fact there’s evidence of more than one such break and subsequent repair. There’s also evidence that sometime after the cross fell over it was re-erected, this time jammed into the central slot of an old mill stone to provide stability.

More interestingly, from my perspective, the circle appears to be a latter addition, introduced during one of the repairs, along with an extra piece at the top and at the neck—the shaded bits in the diagram below.

Here’s a more detailed look at the structural repair and stability improvement.

Photos again courtesy of Canmore

It is an elegant solution.

So, that beard-tugging rumination about the origins of the circle in the Celtic cross? Just-So stories resting on wishful thinking.

Finally, just for grins, here’s a photo of the concrete replica of St John’s cross that stands today on Iona.

It must have been an awe-inspiring sight, particularly if it was painted. Was it painted? We don’t know. I’m not aware of evidence of polychromatic decoration but, there again, I’m not aware of any evidence that they weren’t. And why would you go to all the time, trouble and expense of creating such an amazing thing and then not make it as striking as possible? Maybe we should have a colouring competition…

*I am not talking here of the white supremacist hate symbol, usually with four equal arms rather than the long vertical axis of a standing cross. The hate symbol very possibly could be a direct descendant of the wheel cross—which is a cross inside a circle (and if you break that circle just before its join to the cross you get the beginnings of a swastika)—but it’s also just possible it could be connected to the nativist national origin myths that neo-nazis love to co-opt.