Science Spin January 2007

Irish bogs reveal bodies and books

By Shane Leavy

Perhaps one dark night around 800 AD a monk hurried over Faddan More bog away from his monastery with a gang of raiders closing in behind him. In his arms he grasped an expensive Psalter, a book of psalms, handmade with intricate detail on vellum. Finally he stopped to catch his breath, dug a hole in the peaty soil and inserted the book on its spine into the gap. The monk piled sphagnum moss over the hole and hurried away, never to return.

Faddan More had then already long been a bog and over the next 1,200 years or so, another metre of peat would grow up over the treasure. Bogs are formed when dead vegetation, in particular sphagnum moss, is unable to fully decay due to acidic conditions and so accumulates as peat over the centuries. Buried under this wet, acidic soil, the vellum decayed very, very slowly."The low levels of oxygen present also inhibit decomposition," says Eamonn P Kelly, Keeper of Irish Antiquities in the National Museum of Ireland. Without oxygen material can be preserved for decades, centuries even.

Around the world

Irish peat bogs are not the only ones to have preserved historical artefacts. The Windover archaeological site in Florida is a "muck pool" where remains of 160 individuals were recovered in the peat at the bottom of the water. Dating from 6000 to 5000 BC, these bodies were so well preserved that brain tissue was sampled and DNA from the finds has been sequenced.

Bog bodies have been found in Britain, Germany, Sweden, Holland and Denmark. In one case in Scotland's Cladh Hallan, archaeologists think that a man who died around 1600 BC and a woman from around 1300 BC had both been buried in a peat bog for six to 18 months to deliberately mummify the bodies, before being exhumed and set permanently inside a house.

One forensic technique used in Cladh Hallan was based on the fact that when an individual dies, the bacteria in their gut start to attack the skeleton of the body, riddling it with holes. Archaeologists took a piece of bone, measured its volume and placed it into a container of a known volume. Mercury was then forced into the container under pressure and filled these tiny holes. After measuring how much mercury has entered the holes, scientists could tell that the bacteria must have been only eating for a day or two before being stopped by the sterile bog conditions.

Peat bogs are not the only places with naturally preservative conditions, though they may be the best known. "The very high levels of preservation at Wood Quay (Viking site in Central Dublin where the city's Civic offices are now located) result from the fact that there is an iron pan layer which has built up on top of the subsoil which has inhibited drainage," says Eamonn Kelly. "So you have conditions which mirror those in bogs to a certain extent. In fact in the 19th century some of the writers of the period wrote that Dublin was built on a bog, but what they were commenting on were the preserved archaeological deposits of medieval and Viking Dublin, which they presumed to be bog."

The inks

As the Faddan More vellum very slowly decomposed, something strange happened to the letters written on the pages.

As Rolly Read, Head of Conservation at the National Museum explains, the ink was prepared from iron and oak galls. Oak galls are marble-sized growths produced by trees in response to an insect parasite. Apart from their use in making ink, oak galls were also used for tanning leather. "So we think that the letters have partially been tanned by the ink and preserved, while the vellum around them has rotted. The letters are floating in a mush."

Other inks did not fare so well. Any green ink would have come from unstable copper sulphate which washes out in an acid environment. The reds have become discoloured. A golden colouring called orpiment which comes from yellow arsenic sulphide has been discovered in letters on the front page.

Buried under a metre of peat, the Psalter remained for over a millennium until workman Eddie Fogarty noticed it falling open in the bucket of his bulldozer while working in the bog. Thus began another task - the retrieval and conservation of this remarkable find.

Recovery and bog bodies

As soon as he had noticed the book, Eddie Fogarty carefully covered it with moist peat. This was not the first time that artefacts had been dug out of Faddan More bog and he immediately recognised that it was of importance. A leather satchel and a wooden keg, discovered in 1999 and 2002 respectively, came from a similar time period as pollen core tests showed.

The pollen core shows what major plant types were growing and releasing pollen in Ireland at the time that the layer of peat was laid down and can be compared with other samples to determine a rough date for each stratum of peat.

"There is a good level of consistency between what is happening in one part of the country to another," explains Eamonn Kelly. "So by looking at the pollen cores, you can say, 'Well that looks like the Bronze Age horizon, that's the Iron Age horizon' and so on. The present material in Faddan More is all coming out of the same sphagnum horizon which is turning up early medieval material."

Rolly Read and Carol Smith supervised the safe removal of the manuscript, wrapping the whole artefact plus peat in cling film before bandaging it in plaster-of-Paris to form a protective, waterproof shell for transporting to the Collins Barracks laboratory. Here the manuscript is now being kept in refrigeration in 100 per cent humidity. Eventually it will be dried out under carefully controlled conditions.

The National Museum has another example of a bog discovery whose unwise dehydration caused the artefact serious damage. In 1821 the Gallagh Man was discovered in a Galway bog in"exceptional" condition. However, the experts of the day simply dried it out to conserve it, causing it to shrink and distort.

The Gallagh Man is just one of many corpses discovered in Irish bogs. The tanning action which helped preserve the vellum manuscript also affected these bodies to an extraordinary extent. Skin, hair and even stomach contents are maintained. Tissue samples taken from the bodies have been used to estimate the normal diet of these men and women.

"Literally speaking you are what you eat," points out Eamonn Kelly. "Your hair and your fingernails contain the residues of what you eat so by examining the molecular structure of the hair it can indicate whether you have been dining on a high-protein diet or a high-vegetable diet. If your diet changes through the year and you have a sufficient length of hair to examine, we can see the fluctuations in diet."

The bodies are often found to have been brutally murdered and dumped along the boundaries of different regional territories, leading historians to believe that they had been ritually killed as part of pagan ceremonies.

One, the Old Croghan Man, had identifiably manicured fingernails and the condition of the hands told archaeologists that this was not somebody who had to engage in manual labour - a member of royalty perhaps? His nipples had also been mutilated, a symbolic gesture perhaps since the sucking of nipples had been a way of showing fealty. Archaeologists were even able to tell that his final meal had been wheat and buttermilk by observing the preserved contents of his stomach.

Though of a later era, the Faddan More Psalter is also being looked at with somewhat of a detective's eye for clues as to its origin. "We think the book was deliberately concealed in the bog, with the intention of recovery: whether by a monk fleeing from a monastery under attack, or by a raider with a posse of angry monks in hot pursuit - we can't really say," says Eamonn Kelly. "But it would have been a very valuable object. It takes a lot of dead calves to make one of these books, so it indicates a certain level of wealth. Also the materials used in making the book are costly, as are the time and training to make it."

Conserving the Psalter

"The problem is that nothing like this has ever been found before, so there are no parallels," says Rolly Read. "Normally when we're preserving things in an archaeological context there is always something that has been found before that is similar. We know how different things have been treated and what the results have been like. But in this case we're dealing with something without any precedence."

The conservation team will have to invent totally new techniques to conserve the Psalter. One example is the series of preserved letters who have lost their vellum matrix upon which they were written. This is a completely unique problem, but one Rolly is already considering.

"I suspect we are probably going to end up facing the letters up while they are still damp with some sort of very flexible, very strong material, maybe something like goldbeater's skin (the treated outside membrane of the large intestine of cattle used in the repair of vellum manuscripts) and then lifting each layer off one by one. It's going to be a very, very complicated task."

Before the team goes anywhere near such tricky problems they are systematically recording it and working out a work plan.

"At the moment we have the Psalter in cold storage. We're restricting access and making sure it stays in the fridge to keep mould growth out of the picture," says Rolly Read. "We are fully recording it and doing some basic investigations on it so that we know exactly what we have and that we have squeezed as much information as we can out of it.The next stage, when conservation starts, is almost like an archaeological excavation of the book, in that the process is destructive. To be able to take the book apart to conserve it, we have to destroy the way that it is currently bound. The type of binding that it is in is not one that has ever been found before in an Irish context, because practically no Irish books survive with their original binding. We will probably get it scanned, and we are getting it 3D photographed."

Over the next few years Irish archaeology will be experimenting with totally new scientific techniques on the Faddan More Psalter. The research will involve a diverse team of specialists from around the world. In any case, the find is practically miraculous, courtesy of the preservative effects of Irish bogs.

"We always had a joke within the museum: 'What'll we do when the illuminated manuscript turns up?,"laughs Eamonn Kelly. "Certainly, when I got the phone call saying that a book had been found in a bog, I thought it was a leg pull. It was only really after I spoke to the landowner and he said, 'Oh yes, it's like the Book of Kells' that I realised...Nobody has ever faced this precise situation before there will be a high level of creativity in the process. They will need to see what works and they will pretty well need to get it right first time."