Raising the Roof: Comments on the recent Newgrange ‘roof-box’ controversy

This is not a typical blog for this page. Instead of discussing recent site visits or photographs we’ll be looking at a recent controversy sparked by comments about the reconstruction of Newgrange and, in particular, three claims made in the media by an Irish archaeologist; 1. That the “roof-box” at Newgrange may not be an original feature, instead it was “fabricated” and has “not a shred of authenticity” 2. That two vitally important structural stones, both decorated with megalithic art, from Newgrange were lost after the excavation and 3. That the photographic evidence that backs up the existing restoration is either inaccessible or never existed at all. I hope to show why we can be sure none of these claims are sustainable and that in fact the winter solstice phenomenon at Newgrange is an original and central feature of the tomb.

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Winter Solstice at Newgrange. Today two beams of light, one from the doorway and one from the roof-box, illuminate the passage.

December 21st, 2016: The Winter Solstice falls on the traditional day on which the largest crowds, various VIPs and the media gather in front of the great passage tomb, situated on the brow of a ridge overlooking the Boyne River and its fertile floodplain. At 8.58am, if a stubborn cloud bank on the southern horizon had dissipated, those lucky few people who had the privilege of waiting inside the chamber within would have observed one of the most ancient, spectacular and moving displays of all prehistoric archaeology. One which magically combines engineering, artistry, drama and spirituality like few other constructions before or since.

The discovery of the alignment towards the rising sun on the shortest day by the excavator of the tomb, Michael J. O’Kelly (known to friends and associates as Brian), in 1967 had caused a sensation. Not only did the passage of the tomb face directly at the point at which the Winter Solstice sun rose above the horizon at the time of its construction, circa 3200BCE, the builders had also installed at Newgrange a unique and ingenious device through which the sun could illuminate the floor of the chamber 19 metres (60 feet) distance within the mound, even when the massive door-slab sealing the tomb was in position. O’Kelly’s discovery was surveyed and assessed by Patrick, the results being published in 1974, demonstrating that the probability of an alignment towards the rising sun on the Winter Solstice was extremely high, enough to conclude it was deliberate (Patrick, 1974). This claim was subsequently strengthened by Tom Ray in his own 3D analysis (Ray, 1988). It has been suggested that other passage tombs may originally have had a similar feature, though such a construction has thus far never been found in situ elsewhere. Claims that a roof-box had been constructed at Cairn G at Carrowkeel in Co. Sligo are difficult to prove, the supposed opening, which is much narrower than at Newgrange, is in fact very similar to those over the three recesses in the chamber and may simply reflect the preferred building method of the builders.

O’Kelly named the feature the ‘roof-box’. The front lintel of it protrudes through the grassy mound in historical photos and artist’s representations of the monument. Workers under the direction of Richard Burchett tried unsuccessfully to shift it using crowbars in 1874. There was speculation that it indicated the entry point to an undiscovered passage, or was a receptacle for offerings to the dead within. What O’Kelly found on removing the covering cairn however was remarkable.

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The Newgrange roof-box, viewed from the exterior of the tomb. In front of the roof-box is the first roof-stone of the passage, RS 1. Below the decorated lintel is what O’Kelly called the ‘Back Corbel’ and behind that is Roof-stone 2 (RS 2).

The Newgrange monument was built on the narrow crest of the ridge, to the front the passage sloped downwards from the chamber towards the entrance and at the rear it also followed the fall-off in the ground level, covering an earlier turf mound in the process. As you walk through the passage and enter the chamber you are also climbing this slope, a height difference of some 2m. The overhead roof-box that you pass beneath on entry is now at the level of your feet. A slight bend in the passage and the constraining effect of the upward slope combine to restrict ambient light from the entrance reaching the chamber and so the chamber remains almost totally dark throughout the year.

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An unforgettable moment: Winter Solstice Sunrise illuminates the floor of the chamber of Newgrange in 2010. Viewed here from the chamber floor you can see the roof-box directly ahead. Due to the slope of the passage the roof-box and entrance are not visible while standing in the chamber.

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Illustration of the Winter Solstice illumination of the chamber and passage. As can be seen, before the restoration, the slumped position of RS 2 and RS 3 would have prevented any  light reach the chamber. Illustration: Vallancey 2016, after Stout & Stout 2008.

On this particular day, unfortunately, the sun would not appear in the chamber. Instead of the iconic warm glowing pictures of light on the chamber floor, Newgrange was making headlines in print and across social media for a totally different reason. In the December 21st edition of the Irish Times journalist Lorna Siggins had a different take on the spectacle we had waited over-optimistically for. Quoting archaeologist Michael Gibbons, Siggins made a bold claim: the famous spectacle made possible by the roof-box, which had put Newgrange on the world map, was a “fabrication” with “not a shred of authenticity”. The remarks formed part of a report on a paper published by Michael and Myles Gibbon describing possible Iron Age features at Newgrange that may represent significant cult activity at the site during this period, connected with events in Roman Britain.

In further comments on Irish radio, Gibbons suggested that the roof-box we know today was in disarray when O’Kelly found it and it was an imaginative interpretation that saw it end up as a special opening that allows the solstice light to strike the chamber floor. It was, Michael said, like picking up the pieces of a broken bottle and fitting it all back together with a mixture of old and new pieces.

In his view, it is impossible to say what the structure was like in antiquity, the excavation report did not contain enough detail and photographic evidence to back up the modern reconstruction. The archive, we were told, was not publicly accessible. Worse still “two of the key stones from it went missing, they’ve been lost, I’d love the minister to tell us what happened to those stones” therefore we can no longer test whether the reconstruction ever matched what was there originally.

Are any or all of these claims based on fact? Archaeologists and other interested parties were quick to address the claims. Within the articles themselves, archaeologist Robert Hensey disputes them and later gave a detailed reply on the Moncrieff show on Newstalk Radio,the Office of Public Works issued a brief statement with accompanying photographs of the lintel and partially uncovered roof-box in the early 20th century and in a letter to the Irish times, four prominent figures in Irish archaeology, all former students of O’Kelly, strongly disputed the assertions.

What has been lacking, however, has been a demonstration of the case supporting the current roof-box reconstruction, supported with excavation photographs and illustrations which help prove the entire roof-box was found intact and was restored with the highest possible precision. Gibbons does raise a valid point in that the excavation report published by O’Kelly has few detailed photographs of the roof-box structure. It must be borne in mind, however, that while O’Kelly may have known his restoration was controversial, he probably did not foresee claims that major structural elements were fabrications, so the provided illustrations may have been seen to be adequate at the time.

Let’s examine the evidence for each assertion in turn and hopefully along the way test some of the claims and rumours that surround the authenticity of the solstice event at Newgrange.

Claim 1: The roof-box was “fabricated” and had “not a shred of authenticity”. It was made higher and wider to allow the sunrise light reach the chamber.

This claim seems very difficult to sustain, early photographs and drawings show the lintel of the roof-box in what seems to be an identical height and position behind roof-stone 1 (RS 1).

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Photo c. 1880 by R. Welch, note the decorated lintel set behind and above the passage entrance, just as it appears today.

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The opening of the roof-box as photographed in 1935, photo provided by the Office of Public Works

In the rarely seen photo below, we can see the roof-box uncovered as the cairn stones around the passage are in the process of being removed. We know this was taken before the reconstruction or the straightening of the passage orthostats because the base of the original cairn is still in place and the concrete walls that run the length of the passage, and which stand taller than roof-stone 1, are absent. A large cutting down to the old ground level had been made during the excavation to allow the orthostats to be restored to the vertical, this was completed before the roof-box had been re-assembled (O’Kelly, 1982, pg. 89). Note the height of roof-stone 3 (RS 3), the long capstone running behind the roof-box, it will become important later.

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The roof-box as originally uncovered during the excavations. Note the position of the rear large roof-stone (RS 3) at almost the same level as the forward large roof-stone (RS 1). The concrete walls built later along the rear of the passage orthostats is not seen in this photo and the cairn behind has yet to be removed. Photo from Michael J. & Claire O’Kelly – Partnership in Prehistory.

Below are just a small selection of the numerous photos of the Roof-box and passage capstones being fitted back in position according to exact measurements and with reference to large scale drawings (O’Kelly, 1982, pg. 112) visible in the bottom right photograph (Michael J. & Claire O’Kelly – Partnership in Prehistory n.d.).

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Reconstruction of the passage capstones and Roof-box under the direct supervision of O’Kelly, using detailed large scale drawings. Photos from Michael J. & Claire O’Kelly – Partnership in Prehistory.

In the excavation report itself (O’Kelly, 1982), two photographs were presented of the uncovered roof-box, plates 41 and 43. Plate 43 is from a downward angle and shows the first few metres of the passage. The roof-box is visible, but due to the angle it is difficult to judge with certainty if the structure had collapsed in on itself. Plate 41 is a tightly cropped photo of the entrance and roof-box taken from a position in front of the entrance. It shows the supporting stones beneath the decorated lintel and the back corbel but due to the lack of context around the structure it could be hard to tell if this was before or after the reconstruction. The caption, however, indicates it was after the removal of the surrounding cairn.

Below is a comparison of the appearance of the external Roof-box structure before and after reconstruction. Compare each block supporting the corbel slabs that in turn support the back corbel and decorated lintel. Each stone is identical, the original stones were re-used in the re-building of it. The height and the width of the roof-box also appear to be identical. Click the photo to enlarge.

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The Roof-box before (left) and after reconstruction. Compare the size and shape of each of the visible stones supporting the upper components of the Roof-box. The height and width of the opening looks identical before and after. Pre-reconstruction photo after O’Kelly.

Claim 2:  “two of the key stones from it went missing, they’ve been lost.”

This claim, also from an interview with Matt Cooper on Today FM, is the easiest claim to settle, the two stones that formerly supported the roof-stones and back of the roof-box are in fact exactly where O’Kelly stated they were, in the National Museum in Dublin. Here they form the interior of a mock-up passage tomb built into one corner of the museum and are available for public viewing. See the drawings of the carved stones below, and photos of the stones as photographed by me in the museum in 2011. Click on the photos to enlarge.

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Incidentally, one of the corbels (Right Corbel 3) has a wonderful example of the unique ‘water grooves’ cut into the roof-stones of the passage to drain excess water out from the passage into the surrounding cairn. All of the other examples in the monument itself are hidden from view within the cairn or purpose built tunnel. Special permission is required to view these.

EDIT 28/12/16: Michael Gibbons has since asked to clarify that the two lost stones he was referring to were quartz blocks that O’Kelly believed were used to block the roof-box before and after the solstice.

However, only one such stone was found during the excavation, where it had fallen into the opening of the roof-box. A second stone was never found but O’Kelly inferred from scratch marks on the top surface of RS 1 that a second had been present and both were repeatedly moved to allow light enter the chamber (O’Kelly, 1982 pg. 96). The quartz block that was present was not a structural stone and would not demonstrate if O’Kelly’s reconstruction of the roof-box was legitimate or not. The current location of this quartz block is apparently unknown.

Claim 3: The excavation remains mostly unpublished and there is no publicly available photographic evidence to back up the restoration of the roof-box.

The O’Kelly archive is in fact accessible to any member of the public, an appointment is necessary to view it however. This was clarified in the press statement made by the OPW following the publication of the article and has been the case for several years now. Contact the National Monuments Service Archive for more information.

So if the roof-box was in good condition when found and was restored faithfully, there is then no reason to suspect the illumination of the chamber was an original feature that guided the construction of the tomb? Not quite, there is one further objection that is sometimes raised to the restoration and the resulting beam of light that, in c3,200BC, would have lit up the very rear of the terminal chamber.

Behind the roof-box there are two roof-stones, RS 2 and RS 3 that are not currently in the position that they are drawn from the pre-excavation surveys. They are both significantly higher. If they had been in the lower positions originally, no light may have reached the chamber at all.

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The passage pre-excavation, note the low positioning of RS 2 and RS 3 and also the section drawings that show the slipping and compression of the dry-stone corbelling that supported the roof-stones. Illustration after O’Kelly

O’Kelly describes the reasons for this in the published excavation report: the corbels that were once seated above the orthostats had slipped under the weight of the massive cairn above them and now rested behind the orthostats, helping to push them inward to create the very tight passage that earlier visitors struggled to squeeze through. The section drawings above also show the corbels splayed out so the inner wall of the corbelling was significantly compressed. O’Kelly notes the same effects can still be seen today further along the passage in the area where the overlying cairn had not been removed (O’Kelly, 1982 pg. 96). When the passage orthostats were straightened and the corbelling reinstated to their positions above the orthostats, the resulting lift clears the path for the solstice light to penetrate the chamber.

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The reconstructed passage and roof-stones, note that RS 2 and RS 3 and now higher and the resulting gap allows the beam of light to reach through the passage. Illustration after O’Kelly.

It is clear that, if the alignment was to function, both RS 2 and RS 3 had to have been higher in the original construction. If one or both were significantly lower then the phenomenon simply would not work. Another of the unusual engineering techniques used by the Neolithic builders simplifies this problem somewhat, the gap between RS 2 and RS 3 had originally been sealed by  a putty made of burnt clay and sand which prevented water from passing through. This putty was suitable for radiocarbon dating and the resulting dates matched those found further along the passage, where the roof rises to meet the chamber. The presence of this putty in this position strongly suggests that both stones were originally fitted together, if one is lifted by the reinstatement of the corbelling, then the other must move in tandem with it to preserve the original relationship. If only one had slipped, the putty seal would have been ruptured and the traces likely washed away. If both stones had not been laid in close proximity originally, the putty seal between them would not have been required.

The photo below of the reconstructed outer passage shows the position of the front  edge of RS 3, it is approximately 20cm above that of RS 1, which rests directly on top of the outermost orthostats. Because there was no corbelling in this outer part of the passage, we know the height of RS 1 has to be original. In the section drawings in O’Kelly’s book, the front edge of RS 3 is shown practically level with RS 1. Therefore, it only needed to be raised by 15-20cm for the Roof-box to project light onto the floor of the chamber. Even by a conservative guess, judged by the extent of the lean of the orthstats and the compression, the combination of the lift provided by straightening the passage orthostats below RS 3 and the reinstatement of the corbelling is more than adequate to facilitate this size of a gap and would certainly have allowed the angle of  the light to illuminate the chamber floor, if not the back wall of the rear chamber, both after the original construction of the monument and today.

If, on the other hand, the reconstructed roofing of the passage had turned out to be too high, this would have had no effect on the phenomenon visible in the chamber as the maximum height of the beam is determined by a particularly low lintel further along the passage and the pronounced lean still present at orthostat L20.

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Looking from the passage outwards through the entrance and roof-box, December 2015. Note the gap, measuring about 20cm, between the front edge of RS 3 and RS 1 in front of and below it.

The reconstruction methods used by O’Kelly, however archaeologists today judge their appropriateness by current standards, ensure the slippage and compression that previously blocked the Winter Solstice light should not recur. We can reasonably expect this phenomenon to occur and be witnessed by many generations into the future.

References:

O’KELLY, M. J. & C . N.D. Michael J. & Claire O’Kelly – Partnership in Prehistory. Retrieved from http://www.worldheritageireland.ie/bru-na-boinne/educational-resources/ Accessed December 2016

O’KELLY, M.J. 1982. Newgrange: Archaeology, art and Legend. Thames and Hudson

PATRICK, J.D. 1974. Midwinter Sunrise at Newgrange. Nature 249. 517-519

RAY, T. 1988. The Winter Solstice Phenomenon at Newgrange: Accident or Design? Nature 337. 343-345.

 

Winter Solstice Report – Newgrange, December 21st 2013

Winter Solstice sunrise shines through the roofbox above the door of Newgrange and along the passage floor

Winter Solstice sunrise shines through the roofbox above the door of Newgrange and along the passage floor

Click the ‘Play’ button below to start a slideshow. You can also click this link  to view larger in a new window, or if you are using a mobile device.

There’s a really special atmosphere at Newgrange on a sunny winter solstice morning, especially so this year since there hadn’t been a clear sunrise here on the 21st of December since 2007. This morning was surely one of the most memorable and welcome sunrises in recent years. Most of the people who had made their way to the ancient passage tomb had come prepared for the worst, it seemed unlikely that the thick cloud and driving rain would ever clear. As dawn approached, however, a clearing to the south west began to spread east, sweeping the horizon ever closer to the point on the opposite ridge where the sun was soon to appear.

The sun finally breaks over the low cloud and lights up the river valley

The sun finally breaks over the low cloud and lights up the river valley

The moment of sunrise passed, a stubborn bank of cloud sat just where the disc of the sun rises above Red Moutain. Within 15 minutes or so the window within which the sunrise can reach the chamber down the long passage would pass and the chamber would remain in darkness. The drumming and chanting from the crowd grew louder and louder, then all of a sudden a dazzling burst of light reached across the river valley, turning the white quartz facade of the 5,000 year old passage tomb a glorious golden orange. Accompanied by a loud cheer, the sun finally stretched across the floor of the chamber within the tomb, much to the delight of the lucky children and adults who had won places to witness the event inside the chamber.

Sunlight bursts through the specially designed roofbox constructed to admit light to reach deep inside the tomb

Sunlight bursts through the specially designed roofbox constructed to admit light to reach deep inside the tomb

The great passage tomb at Newgrange is over 5,000 years old, built in the Neolithic or ‘late stone age’ by local farming communities. For much of that time it had stood in ruin, its passage compressed inwards by the sheer weight of the mound and the ingenious ‘lightbox’ above the door filled in with rubble. It was during the excavations and conservation of the monument from the 1960’s through to the early 1980’s that the secret of its astronomical function was revealed. The phenomenon was first witnessed by the excavator, Prof. Michael O’Kelly of University College Cork, at midwinter of 1967, he described it thus:

‘I was there entirely alone. Not a soul stood even on the road below. When I came into the tomb I knew there was a possibility of seeing the sunrise because the sky had been clear during the morning.’

‘I was literally astounded. The light began as a thin pencil and widened to a band of about 6 in. There was so much light reflected from the floor that I could walk around inside without a lamp and avoid bumping off the stones. It was so bright I could see the roof 20ft above me.

‘I expected to hear a voice, or perhaps feel a cold hand resting on my shoulder, but there was silence. And then, after a few minutes, the shaft of light narrowed as the sun appeared to pass westward across the slit, and total darkness came once more.’

Gathering outside the monument has become a yearly tradition and it’s always great to old faces and new, catch up with the year’s events and look forward to the Christmas holidays and New Year ahead. The staff from the Office of Public Works deserve huge credit for the warm atmosphere and smooth running of the event each year, alongside all the other organisations and volunteers who help keep the event a family friendly affair. It’s great to see the smiling faces of the children emerging from the passage after witnessing something they may remember for the rest of their lives. Having seen their wonderful art hanging in the visitor centre, it was surely a very well deserved prize! Congrats to all the winners of the school art competitions and well done to everyone who took part.

Megalithic Art at Midnight: King’s Mountain, Co. Meath

The decorated pillar under the midnight sky

The decorated pillar under the midnight sky, March 15th 2013

Down a narrow track off a minor country road, the pillar at King’s Mountain sits upright in a field like a beautifully decorated standing stone. This stone however is quite special, being the solitary remaining roofstone or lintel of a long destroyed passage tomb type monument which had been built around 5,500 years ago. Just five kilometers away is one of Ireland’s greatest passage tomb cemeteries from the Neolithic or Late Stone Age, the Loughcrew complex of decorated chambered tombs. These are also visible against the sky from this spot.  Meath is a relatively low lying county so even though the hills at Loughcrew are not particularly high, they do dominate the lowlands for many miles around.

Though they had been noted by a Miss Beaufort in 1828, the passage tombs at Loughcrew were first formally described by Eugene Conwell in 1864 and presented as ‘The Tomb of Ollamh Fodhla’ in paper read to the Royal Irish Academy in 1872. A cairn is marked near this location on an estate map of 1798. When he visited King’s Mountain, it was sadly just a little too late to record exactly the nature of the monument that stood near this spot:

“On its present site up to a few years ago, stood a tumulus, which the proprietor of the field caused to be carried away for top-dressing; and in the centre of the mound this stone was found, covering in a chamber formed of smaller flagstones and filled with bones, all of which have disappeared, the covering stone alone excepted” (Conwell, E.A. 1872)

The night sky above the spiral covered solitary remainder of a destroyed passage tomb.

The night sky above the spiral covered solitary remainder of a destroyed passage tomb (click to view larger)

The decoration on the bottom three-quarters of one face of the stone consists of spirals of various  sizes with both clockwise and anti-clockwise turns, joined by arcing lines. The dominant spiral has also been enlarged with penannular circles. These have been integrated into one larger design across the face of the stone more consistent with the mature ‘plastic’ style of megalithic art found at the Boyne Valley passage tombs of Newgrange and Knowth than the more haphazard and wonderfully energetic freestyle of depictive art found at the Loughcrew tombs. (Shee Twohig, E. 1981, Herity, M. 1974)

The site is located down a maze of local minor roads, miles from the nearest village or town and is about as good a dark-sky location as anywhere on the east coast on very clear nights. Some light pollution from Oldcastle was dimly visible while I was taking pictures, giving an orange tint to some of the longer exposure photographs. Seeing as it was heading into the St. Patrick’s festival weekend, I thought it would be worth rummaging around the bottom of the camera bag for some Strobist gels to add a festive green tint to the stone, I’m not normally a big fan of using different coloured effects with flash but here’s the slightly more subtle results using a fluorescent correcting light shade of green over the handheld flash unit:

Lit up green for the St. Patrick's Festival!

Lit up green for the St. Patrick’s Festival! (click to view larger)

The site is located on private land down a narrow track, see Knowth.com for more information. Click here if you would like to purchase a print, please specify if you would like image 1,2 or 3 from this page.

References:

Conwell, E.A. 1864. On ancient remains, hitherto undescribed, in the County of Meath. Proceedings of the Royal Irish Academy (1st series) 9, 42-50.

Conwell, E.A. 1866. Examination of the ancient sepulchral cairns on the Loughcrew Hills, County of Meath. Proceedings of the Royal Irish Academy (1st series) 9, 355-79.

Conwell, E.A. 1872. On the identification of the ancient cemetery at Loughcrew, Co. Meath; and the discovery of the tomb of Ollamh Fodhla. Proceedings of the Royal Irish Academy (2nd series) 1 (Literature), 72-106.

Herity, M. 1974. Irish passage graves: Neolithic tomb-builders in Ireland and Britain, 2500 BC. Dublin: Irish University Press.

Shee Twohig, E. 1981. The megalithic art of western Europe. Oxford: Clarendon Press

Equinox Dawn, Loughcrew, September 2012

Equinox Dawn, September 22nd, 2012, looking east past Patrickstown Hill towards Slane where the sun rises over the Irish Sea.

For three days around the Equinox, which occurs roughly around the 21st March and September each year, the Office of Public Works allow access to the chamber of Carin T, the central passage tomb on Carnbane East, Loughcrew, Co. Meath. Cairn T is also the largest on this central hill of a small chain of hills which are conspicuous from many miles around due to the low lying farming land in this part of the country. Within its passage and chamber, the passage tomb is highly decorated with a type of carving described as megalithic art, made by chipping away the surface of the stones that make up the structure that sits underneath a massive cairn or stones.The passage tombs on Carnbane East have not been scientifically excavated though the style of construction and decoration suggests that they are probably contemporary with, or even earlier, than the great passage tombs of the Boyne Valley at Newgrange, Knowth and Dowth. Knowth and Newgrange have produced radiocarbon dates from the late neolithic for the main construction phase, indicating the main focus of passage tomb activity dates back to around 5,000 years ago.

Catching the sunlight on the backstone of the rear chamber of the passage tomb

The weather reports for the weekend suggested that the morning of the actual astronomical Equinox, the 22nd, would be the best chance to see some light inside the chamber. Although there were clear skies when I left Wicklow at just before 5am, as I travelled north the cloud began to build over the eastern horizon. Though a large cloudbank above the clear horizon can lead to some spectacular colours, it did also limit the amount of time the sun would shine inside the chamber. On a clear morning the Fsun may be visible in the back chamber for almost a full hour, on this morning we had a much smaller window of about 20 minutes. As the event has become publicised more widely, so the crowds have grown larger each year. This September there was a crowd of about 150 people qeueing from before dawn, since the chamber can only accomodate six or seven people, inevitably only a lucky few would see the full display of light.

Megalithic Art Illuminated by the Dawn Sunlight

Click  the ‘play’ button on the slideshow below to view a selection of photos from the equinox event or click here to view a larger version of the slideshow on the website, should also work on the iPhone/iPad and other mobile devices.

Summer Sunrise at Bryn Celli Ddu, Anglesey, Wales.

Bryn Celli Ddu Sunrise

Bryn Celli Ddu (pronounced approximately ‘Brin Kethlee Thee’) is a restored passage tomb on the island of Anglesey on the north Wales coast. Built on top of a destroyed henge and stone circle, it is a late example of the type of chambered tombs built during the Neolithic, between 5-6,000 years ago. The restored mound is a fraction of its original size, but the passage and chamber are much the same as they would have been originally.

In 1906, Sir Norman Lockyer published one of the first systematic studies of megalithic astronomy. Based on observations made at Easter, he predicted a summer solstice alignment at Bryn Celli Ddu. This idea was not take seriously at the time and the notion fell into obscurity until archaeologist Steve Burrow came across Lockyer’s book. In 2005, he was able to make observations that proved Lockyer correct. The discovery was widely publicised at the time and a video of the sunrise can be viewed in the museum in Cardiff. Click here to read the BBC report.

Sunbeam in Chamber of Bryn Celli Ddu

During an otherwise very cloudy and damp holiday on Anglesey this summer, I was fortunate enough to have one very fine, clear morning. A very early start at 4.20am was well rewarded with a spectacular light show inside the chamber, click to play the slideshow below:

Click here to view a larger version of the slideshow on the website, should also work on the iPhone/iPad and other mobile devices.

Although the morning I was in the chamber was a couple of weeks after the solstice, the rising position of the sun moves so slowly during the solstice period that the phenomenon changes only slightly over the weeks before and after the ‘standstill’. See the diagrams below to see how the sun’s angle at sunrise changes over a couple of weeks. The length of the passage is also quite short compared to Newgrange or Knowth, which also extends the window of of time during which the light beam can be observed.

The yellow lines depict the angle of the sun at sunrise on each of the dates, compare where the line passes through the buildings in the farmyard. Screenshots are from the excellent Lighttrac app for the iPad

Sunrise at Bryn Celli Ddu on 21st June 2012

Sunrise at Bryn Celli Ddu on July 2nd 2012

Laser Scanning the Great Tombs of the Boyne Valley

Marcus sets up the instrument to begin a 360° scan of the chamber and passage of Knowth East, collecting an astonishing 500,000 data points approx. per second.

As one of Ireland’s foremost heritage landscapes, the great neolithic passage tomb complexes of Newgrange, Knowth and Dowth, collectively known as Brú na Boinne, attract hundreds of thousands of visitors every year. The chamber within Newgrange, the most famous of Ireland’s many passage tombs, welcomes a steady stream of tourists who crouch and shuffle single file up the long passage, literally rubbing shoulders with some of the finest megalithic art in Western Europe.

In the 5,000 or so years since it was first constructed, the settling of the mound’s layered bulk had caused many of the uprights lining the passage to lean and tilt inwards, making parts of the passage difficult to negotiate. This was remedied during the excavations and renovations led by Prof. Michael J. O’Kelly between 1962 and 1975 so that today the chamber is readily accessible. At Knowth and Dowth however, the chambers remain largely out of reach for most visitors due to a mixture of structural obstacles, site management and safety concerns.

At Knowth East, the passage orthostats nearest the chamber lean in so heavily that the only route through is on hands and knees along a wooden plank. At the time of the chambers discovery in 1967, the excavator, Prof. George Eogan, actually entered by crawling above the passage orthostats, eventually managing  to reach the chamber floor below by lowering himself down along the two metre high portal stones.

The situation is not much different at Dowth North, here the only means of access to the passage is a rather claustrophobic and uncomfortable crawl down a 20 metre long souterrain that was probably constructed between the 9th-11th centuries A.D. The lighting fixtures that had been installed decades ago are now flooded and defunct, the chamber now lies in damp and eerie silence.

With the sophisticated technology and expertise offered by a team from the York Archaeological Trust however, it is hoped that ‘virtual visits’ may be offered in the future through the medium of 3D virtual reconstructions and interactive ‘fly through’ videos of these unique and remarkable sites. The incredible level of detail and realisitic textures captured in this project will also allow researchers, whether within Ireland or abroad, to continue to study and analyse the construction and decoration of the tombs from their desks.

Over several days in May 2012, Dr. David Strange-Walker and Marcus Abbott meticulously scanned, photographed and logged GPS co-ordinates for both Knowth and Dowth in an exciting project organised in conjunction with UCD. Dr. Steve Davis of the School of Archaeology in UCD was one of the main co-ordinators of the project and both he and David were interviewed inside the chamber of Knowth for a piece on RTÉ News, broadcast on the 15th May:

Phillip Bromwell of RTÉ meets the team at Knowth.

I was delighted to be given the opportunity to meet the team and check out the work going on within the chambers of Knowth and Dowth and am very much looking forward to seeing the results of the surveys and scans, particularly the megalithic art. Having firsthand experience of how difficult it can be to record and in some cases even access the sheer number of decorated stones, it will be very interesting to see how technological advances along with the talent of people like Marcus and David can bring this collection of some of Europe’s finest pre-historic carvings to life for everyone to enjoy.

In the meantime, below are some images from my short visits to see the team in action. This was of course a very challenging environment to work in. Not only are there extremely low light levels within the chambers, but due to the scale of  the project it was not exactly practical to stop the work in progress and set up some atmospheric environmental portraits, not to mention the need to regularly find the nearest hiding place and sit still for several minutes while the scanner was collecting data! All of the shots therefore were taken handheld at exceptionally low shutter speeds mostly combined with very high ISO settings to increase the sensitivity of the camera just to avoid blurring as Marcus and David went about their various tasks.

Marcus secures the scanner to its low-level base where the passage meets the chamber in Knowth East.

It’s very much a case of ‘watch your head’ and ‘watch your step’ in the eastern chamber at Knowth.

Marcus checks the location and visibility of the targets which will allow the different scans to be combined later with sophisticated software.

The large basin stone in the rear chamber, Knowth East.

Marcus checks the settings on the scanner before it begins a 360° scan of the chamber and passage.

David Walker sets up the camera to capture the texture and colour of the surfaces that have been measured by the laser scanner.

The scanner set up in the right hand recess of the main chamber of Dowth’s northern passage.

The chamber in Dowth North is normally in permanent total darkness, the lighting arrangements are ‘bring your own’.

The very talented Marcus Abbott (left) and David Strange-Walker pictured in the eastern chamber of Knowth.

For more information on laser scanning and past projects using similar techniques, the wonderful website of the Nottingham Caves Survey project is very much worth a browse. Other exceptional case studies are featured on Marcus Abbott’s site. Special thanks are due to Dr. Steve Davis for arranging access for both myself and the team over the ten day period and particularly to the OPW for their time and co-operation in facilitating the work.