Why read this
Engineers are helping recreate the journey of a stone monolith from Wales to Wiltshire
Civilisation has put obstacles in the way
The journey covers land, sea and a canal
In the steps of Stonehenge
Stone Age man moved 80, 4t monoliths from a remote Welsh hillside to the barren expanse of Salisbury Plain to form part of Stonehenge. Next week sees the start of an attempt to replicate the epic journey. Andrew Mylius reports.
Some five millenia ago, long before the invention of the wheel or the domestication of draught animals, a ring of 'bluestone' monoliths was erected on Salisbury plain. Neolithic man had hauled them 350km from the hills of Wales to form the outer ring of what is now known as Stonehenge. Centuries later an inner ring of much larger sarsen stones from the nearby Marlborough Downs was erected, again using human muscle power only.
Next week, on St David's Day, a corps of Silicon Age men will set out to replicate the astounding Stone Age feat. Using the technology of five millennia ago a 4t obelisk will be moved from the same rocky outcrop that yielded the henge's stones. The stone is 2.5m long and tapers from a 900mm by 900mm base to a 450mm by 450mm tip. Providing it survives a perilous voyage across the Bristol Channel, it should reach Stonehenge itself by the autumn equinox on 23 September. The journey will demonstrate just how sophisticated our ancestors really were.
The venture, code named 'Millennium Stone', is being championed by community action group Menter Preseli. The group has enlisted help from engineering consultant Whitby & Bird.
'We are not archaeologists, we're well-meaning amateurs,' cautions Menter Preseli project co-ordinator Philip Bowen. Changes in the landscape mean it would be incredibly hard to replicate a Neolithic journey with complete fidelity: sea level was 1m lower 5,000 years ago; there were more trees but no fields or hedges. Ancient Britons did not have to contend with roads. And, Bowen suspects, health and safety now has a higher profile than it did. Operation Millennium Stone wants to avoid blistered heels and crushing volunteer rock-pullers is out of the question.
Whitby & Bird associate Nick Price observes: 'This isn't meant to be a serious piece of archaeology. It's about highlighting awareness of archaeology. If it works, great. But if it doesn't work it's still great - the project shows how difficult the feat really was.'
Price has been looking for ways to move the stone effectively over the land-bound legs of the journey and at optimum methods for transferring the stone between land and water. 'Key principles are simplicity, practicality and safety,' he says. 'Really, we haven't done anything that requires a degree. Everything is being carried out at a craftsman level. The operation must be done using methods available to Stone Age people while recognising we're not in a Stone Age ourselves.'
Chemical analysis shows all 80 Stonehenge monoliths were sourced from a craggy outcrop at Carm Meini in the Preseli hills of north Pembrokeshire. The spotted dolerite stones occur naturally - no quarrying or shaping is required. Locals still attach mystical significance to them and the Preseli hills are swathed in folklore. It is at Carm Meini that the Millennium Stone project will get under way.
Moving the stone on log rollers is out of the question, says Price. Stone Age engineers would have appreciated that logs large enough to overcome irregularities in the ground would be hugely heavy and difficult to handle. Life may have been cheaper than it is today, but our ancestors were not suckers for danger. And, Price notes, 'progress would have been very stop- start as logs were moved from back to front. You'd also have problems with control. It would be simpler to use something like a present day sledge.'
Sledges run superbly over grass. It is possible Neolithic logistics experts favoured winter conditions for the stone shifts, when frozen ground would have been slippery but hard enough to support the sledge, speculates Bowen.
Bowen, a native of the area, scoured the countryside for an optimum route - Wiltshire County Council has helped by doing route reconnaissance on Salisbury plain. Challenging gradients mean much of the journey could not be contemplated off-road and the sledge will be dragged along B-roads. This is no cop-out, though, Price contends.
'Roads are designed to have a high co-efficient against skids' - far harder going than open grass-land, he claims. Friction-reducing technology is called for. Price carried out friction tests and found that Netlon - a polythene mesh commonly used to support climbing garden plants - out-performed carpet, reinforced polyester, polythene sheeting or oiled plywood. Better still, it is cheap, hard wearing, easy to handle and visually unobjectionable. At 3mm it is just thick enough to prevent the sledge runners scraping the road surface.
The sledge itself is to be a simple affair. Because the stone is uneven along its length, it is to be supported by only two cross-members. These will be lashed to a pair of elm runners. 'I'm sure the ancient Britons would have known their timbers - elm is very abrasion-resistant,' Price notes. Nonetheless, plastic shoes are to be fitted to the runners.
Ropes will either be attached to a third cross-member uniting the runners at the very front of the sledge, or to the stone itself. Eight to 10 people will be needed to pull the sledge along the flat and up to 20 up gradients, Bowen believes.
'We'll be doing trials to find out how far we can drag the stone,' he says. 'But we reckon it will be less than 1km a day.' The Welsh overland leg is 30km long; the stone will have to travel another 10km over land to Stonehenge in Wiltshire. Vitally important, notes Price, 'is to keep the sledge moving - 10 minutes sliding at a time rather than short spurts. Dynamic friction is in the order of two thirds of static friction.'
Bowen is still in the throes of liaising with the local council, police, the Highways Agency and local farmers over road closures, but the route is finalised and secured.
The stone will be transferred from land to water at Blackpool Mill on the eastern branch of the River Cleddau. It will be transported down river to Milford Haven on a catamaran made of two 10.5m long currachs joined by a wooden deck. A currach is a Stone Age boat made of pitch-sealed canvas over a lightweight wooden frame. Construction of two 10.5m currachs is starting this week.
To load the currach catamaran a narrow jetty made of stone filled wicker gabions will be built out into the Cleddau, which has a tidal range of just 500mm. The catamaran will be positioned so its deck rests on the jetty at low tide.
The stone will be slid from the sledge, down a pair of stout poles onto the catamaran deck. And at high tide, with slack water, the currachs, deck and stone should float clear to start the voyage towards the Bristol Channel. If the catamaran fails to float clear of the jetty 'we will simply demolish it', says Price. Traversing the notoriously hazardous Bristol Channel, the currach catamaran, crewed by 10 oarsmen, a lookout and a helmsman, will be accompanied by a flotilla of craft taking part in the nautical festival Celtic Voyage 2000. They will journey together from Milford Haven to Swansea and Cardiff, before crossing the Channel to Bristol. Local pilots have been tapped for advice on navigation.
'The currach is capable of four knots in up to gale force 4 in the open sea,' says Bowen. Stone Age boats expert at the University of Bangor Owain Williams has been involved in the currach's design and a 7m model has been tested.
At Bristol the stone will be transferred to a punt-like barge. This operation, conducted in the harbour with the aid of a Victorian steam crane, is full-on cheating, Bowen concedes. But the barge itself is a faithful replica of the Neolithic specimen preserved in a peat bog at Ferriby, Yorkshire. The 6.6m long, 2.4m wide, 900mm deep vessel will be towed by a single currach up the River Avon to Bath, and along the Kennet & Avon Canal.
At Honeystreet, just past Devizes, the stone's aquatic journey will come to a halt. Price has designed a low level crane for lifting the stone out of the barge and placing it on the sledge once again.
A rock pivot, set in a giant wicker gabion basket for support, will be topped by an 8m lever arm. The stone will be lashed to one end of this and counter-weighted with stones until it slowly lifts.
Menter Presli contact is Philip Bowen, (01437) 766664. E-mail philip@menterpreseli. freeserve.co.uk