About 70 meters west of our avenue trench, Colin was digging a small square trench just five meters across. He was hoping to find evidence for the shaping and dressing of the stones before they were taken the last few hundred yards to the stone circle. His enthusiasm for molehills, generated all those years ago as an evening-class student, has never left him. Every time we stroll around this field in front of Stonehenge, he gets everybody to look in the small heaps of loose soil. Immediately east of the visitor center, Colin had found sarsen chippings brought to the surface by those moles. When he returned year after year he was able to see that a very extensive area in front of Stonehenge was producing chippings from the stones. The density of chippings is greatest on the field’s west side, where it was plowed during the 1970s.
Colin consulted the records of the parking-lot and visitor-center excavations in 1935 and 1967. Although they had dug carefully, Young and Newall, and the Vatchers had found very few stone chippings—though it’s clear from their records that they had been looking for them.13 In contrast, Mike Pitts had found loads in his cable-trench excavation in 1980 on the other side of the road.14 Kate Welham carried out a resistivity survey in the molehill field, the results of which were great. We could see a skirt-shaped zone of high resistance stretching westward from the beginning of the avenue to the area plowed in the 1970s, close to the visitor center. We were sure that this high resistance was being caused by a pavement-like spread of broken stone. We could hear the crunch of metal hitting sarsen as Mike Allen cored a series of auger holes across the spread, from which we picked out tiny chips.
We were sure that we’d found the stone-dressing area where the sarsens were worked. They must have been dragged here from the quarries, already roughly shaped but awaiting their final smoothing. Perhaps they were also lined up on their wooden cradles and their dimensions checked, to make sure that lintels would fit on top of uprights. Then they would have been hauled on their sledges through the wide northeast entrance into Stonehenge. To demonstrate beyond doubt that this was a stone-dressing area, we needed to put a trench here.
We proposed a 15 meter by 10 meter area for the trench. This would be just big enough to reveal the silhouette left by the stone debris lying around the edges of at least one sarsen. But the National Trust wasn’t having it: It would allow only a much smaller hole five meters by five meters. We had no choice—and at least we’d been given permission to open a trench here at all. This was the only completely new area in the avenue field we were allowed to dig; all our other trenches re-opened old excavations.
Beneath the turf in Colin’s trench, he came down on to a classic worm-sorted topsoil. This had not been plowed in thousands of years, if ever. Beneath it was a small piece of the Stonehenge Neolithic landscape that had survived the ravages of erosion for four or five millennia. Just as Colin had predicted, there was a carpet of sarsen chippings across the surface of the chalk bedrock. To Mike and Charly’s satisfaction, the periglacial stripes here were very narrow and shallow, confirming that the oversized stripes beneath the avenue are unique.
The shape and position of each stone chip as it lay in the ground was drawn on a detailed plan and then the chippings were lifted in half-meter squares for counting, weighing and careful analysis. We needed to establish that this was “primary refuse”—that the chips lay where they had fallen from the activities of stone-dressing, and that these stones had not been collected from somewhere else and dumped here in heaps at a later date.
Colin’s team included Ben Chan and Hugo Anderson-Whymark, who are experts in worked stone—whether flint or sarsen. With all the stone chips laid out across the floor of a giant agricultural barn, they found from patient trial and error that some of the pieces fit together. The pieces that fit were found lying close to each other, suggesting that they lay where they had fallen from the stone. One half of the trench had very few chippings in it, with a very obvious and straight north–south line dividing this area from the part of the trench with masses of chippings. We were looking at the silhouetted edge of a stone, where a sarsen had been laid on its back and all its surfaces, apart from its underside, pounded smooth. Had we been allowed a bigger trench, we could have seen the entire shape of the stone that had been dressed here.
Computer specialists Lawrence Shaw and Mark Dover (standing right) visit Colin Richards’s trench immediately north of Stonehenge. Here the sarsen stones were dressed (shaped and finished) before they completed the last step of their journey.
Colin, Ben, and Hugo counted and weighed 6,500 sarsen chippings from this one trench. They also found fifty hammerstones, many of which were fractured and broken. These fist-sized hammers are made of hard quartzitic sarsen, in contrast to the generally softer stone of the uprights and lintels of the stone circle. Most of the hammerstones are round but some have been roughly flaked to make simple hand-axes, their edges battered from repeated contact with the rock. The process must have been exceedingly tedious and damaging: Anyone could have contributed to this sort of work—men, women and children—but hour upon hour of bashing hand-held rocks against the huge stones would surely have injured their wrists and fingers. Larger hammerstones, termed “mauls,” were also used in stone-dressing. Gowland, Hawley, and Atkinson all found examples of these used as packing around the bases of sarsen uprights. Perhaps these larger hammers were salvaged from the dressing zone when they were needed to pack the holes of the raised sarsens.
Colin Richards and his team plotted every stone chipping found in the trench. The distribution shows the straight edge where a sarsen once lay while it was being dressed.
Colin has spent a long time, during various visits inside Stonehenge, looking at the minute details of the finished product. Some surfaces of the sarsens have been hammered smooth, while others are speckled with tiny pockmark-like holes. Some stones have wide grooves separated by low ridges. No stone is dressed exactly the same as another.
A closer look also reveals that the inside faces of the stones, in both the outer circle and in the trilithon horseshoe, have been dressed, as have their thin sides, whereas their backs (facing outward) are either unmodified or have been dressed to about head height only. When the sarsens lay in the dressing zone, the stone-dressers would have been unable to get at the stones’ undersides. The sarsens would have then been brought into the construction area, presumably on wooden sledges or cradles, and each maneuvered to the outside edge of its stonehole before being erected. They would have been raised from the outside of the circle toward the inside, like petals closing on a flower. The back of each stone (on which it had been lying) would have been inaccessible until the stone was raised; final dressing of the back could then be carried out, but only to head height.
This finally explains why the inner faces of the sarsen circle are better dressed than their outer faces, a feature first noted by Stukeley three hundred years ago.15 It may also help to shed light on the curiously small size of one of the sarsens in the stone circle. Stone 11 stands upright but is not much larger than a lintel. It is far too short to have ever been a support for a continuous line of lintels from Stone 10 to Stone 12. In 2005, Mike Pitts was faced with the dilemma of how to reconstruct its lintels. The television company Channel 5 was building a full-sized replica of Stonehenge in polystyrene. Since Stones 10 and 12 have tenons (knobs that project from the top of the stone to fit the cup-shaped mortise holes of lintels), they were definitely designed to support lintels. A double-length stone lintel bridging the gap over Stone 11 would not have been stable but a wooden substitute might. Mike’s solution was to use a timber lintel over the top of Stone 11.
Looking again at the surfaces of Stone 11, I could see that its inner face never received the same dressing treatment as the other sarsen uprights. Perhaps this little shorty was not part of the main build. Maybe it was added later, taken from one of the stoneholes of the Station Stones or from one of the two stoneholes next to the Slaughter Stone. Perhaps there never were lintels here. Stone 11 lies on th
e axis of the south entrance to Stonehenge. Maybe the tenons on all the sarsen uprights were shaped in the quarry or the dressing area in a standardized production-line fashion, before anyone realized that the stones in this part of the circle would not need mortise-and-tenon joints. Interestingly, a former bluestone lintel lies close by (now mostly buried below ground)—perhaps this is the remnant of an entrance through the bluestone circle at this point. Only further excavation can reveal whether Stone 11 is part of the original build or a later addition to the sarsen circle.
Supervisor Chris Casswell stands with a scale behind tiny Stone 11 at Stonehenge. It is clearly too short to have supported a lintel and has not been dressed in a similar fashion to the other stones of the sarsen circle.
In strong contrast to the number of sarsen pieces found (6,500), only forty bluestone chippings were found by Colin in his five × five-meter trench. There were more bluestone chips in the avenue trench but only just over a hundred. Why are there so few fragments of bluestone outside the stone circle, when excavators digging inside Stonehenge have found many more bluestone chips than sarsen chips? It is most likely that the dressing of bluestones took place inside Stonehenge. That certainly makes sense if the bluestones were already there, in the Aubrey Holes, ready to be rearranged in the Q and R Holes. Not all the bluestones have been dressed: Of the forty-three survivors, only seventeen have been worked to create smooth surfaces.16 Although moved around several times, presumably the bluestones have never left the premises since their arrival around 2950 BC.
The builders had to think very carefully about how to position the dressed sarsens. The lintels had to fit neatly on top of the uprights. The difficulties of getting a perfect fit would have been compounded by the slight slope of the site. At Durrington Walls the ground was terraced flat before the construction of the Southern Circle, but at Stonehenge the architects chose to retain the natural slope even though they wanted the lintels on the stone uprights to be horizontal. To compensate for the slope, the uprights had to be shorter upslope to the southwest and taller toward the northeast.
The puzzle of how Neolithic people built such a complex structure has occupied many minds for centuries. Around 1640, Inigo Jones thought it was so precisely built that it must once have been a completely symmetrical monument with Classical proportions as set out by the Roman architect Vitruvius.17 However, although Jones,’ stylized portrayal of Stonehenge’s ground plan is accurate to within 5 percent, his desire for it to be perfectly symmetrical led to his adding an extra, sixth trilithon that never actually existed. William Stukeley was the first to try to work out what unit of measurement had been used.18 If it was the Roman foot of 0.96 feet (0.293 meters), then Stonehenge was Roman, as Jones had thought. Stukeley was convinced that the ancient Britons who had built it “knew nothing of Vitruvius” and, after taking 2,000 measurements, deduced that Stonehenge’s base unit of measurement was 20.8 inches (1.73 feet or 0.528 meters).
One of the reasons why William Flinders Petrie was determined to make an accurate plan of Stonehenge in 1872 was that he, too, hoped to work out the units of measurement used by its builders.19 He found that the inner diameter of the sarsen circle amounted to 100 Roman feet (his calculation of the Roman foot was slightly longer than Stukeley’s at 0.973 feet, or 0.297 meters). He also deduced that the outer features—the ditch, bank, and Station Stones—were laid out using a completely different unit of 1.873 feet (0.571 meters).
In the 1960s, Alexander Thom stunned the world of archaeology by claiming that many megaliths, including Stonehenge, had been built by astronomer priests to measure astronomical events. He also claimed that they had all worked to a common unit of measurement, in use across the whole of Britain, to construct these monuments. This he called the Megalithic Yard of 2.722 feet (0.830 meters). In 1988, Thom and his son published their finding that the average center-line diameter of Stonehenge’s sarsen circle is 37 Megalithic Yards.20 Although Thom’s work still has something of a following today among the wider public, archaeologists have never accepted wholeheartedly his concept of the Megalithic Yard (although it may be relevant for megalithic monuments in northern Scotland, where he first formulated the idea).
Most recently, archaeologist Tony Johnson proposed in 2008 that Stonehenge could have been planned without a unit of measurement, simply by laying out series of intersecting circles.21 Using computer-aided design (CAD) methods, he showed how the Aubrey Holes could have been laid out in twelve moves. The positions of the seemingly unsymmetrical trilithons could have been established by marking the intersections of two sets of concentric circles, one centered between Stones 1 and 30 and the other between Stones 15 and 16. These are then combined with circles centered on Stones 1, 11, 20, and 30 of the sarsen circle to arrive at the positions of the trilithons. Johnson is able to show that the inside edges of the ten trilithon uprights (and the external edges of the great trilithon’s two uprights) can be plotted at chosen intersections of the six circles. Johnson calls this intersection of the two concentric circles a “diffraction grating.”
A few months later, John Hill, a research student at Liverpool University, demonstrated that Stonehenge could be laid out much more simply using lengths of rope, the sun’s shadow, and basic counting on fingers.22 To show how easy it could be, he enlisted the help of school-children from Northcote Primary School in Walton to lay out Stonehenge’s ground plan at the university sports ground.
I had always kept my distance from the complex issue of Stonehenge’s geometry. It was quite clear that there were all kinds of different ways of solving the same problem, and each originator was convinced that his solution was the correct one. How could anyone decide which was the actual solution used by Stonehenge’s designers and which were attractive possibilities but no more than that? For John Hill, the principle of Occam’s razor applied: They would have been most likely to choose the simplest solution. For Tony Johnson, a decider was the fact that his method could reveal that the great trilithon upright, restored under Gowland’s direction in 1901, has been re-erected in the wrong place, 60 centimeters from its original position (though this is exaggerated; for the midpoint of the stone’s face, the distance by which it is mis-set is actually about 30 centimeters).
Then my colleague Andrew Chamberlain took a look at the problem.23 As a specialist in human osteology and paleodemography, Andrew works with mathematical problems all the time. We had worked together some years before on Saros cycles (lunar-eclipse cycles) and their correlation with the timing of construction of Iron Age timber causeways; Andrew worked out how to compare dendrochronological dates for tree-felling with Saros cycles of full lunar eclipses. Here was a new challenge. Thom’s Megalithic Yard value of 37 for the sarsen circle’s diameter, for example, did not seem particularly convincing to Andrew. Had Thom come up with not one but a series of whole number measurements, with regular intervals in measurements—such as 40, 50, 60—for different parts of the Stonehenge plan, then the likelihood of the Megalithic Yard as a base unit would be more persuasive.
Instead of starting where everyone else had, with Stonehenge itself, Andrew looked at the ground plans of all the timber monuments at Durrington Walls, Woodhenge, and the other Wessex henges. These could provide an independent test of any concept of a Neolithic base unit of measurement at Stonehenge.
Since we knew that the wooden circles were laid out around the same time as Stonehenge, it should be straightforward to identify shared regularities in design. Andrew started with the Southern Circle, for which we now had a complete circular plan, at least for the larger posts. He employed one key principle from the beginning. When laying out the positions of planned features, people are likely to choose their centers and not their edges. To dig a ditch or raise a bank, it’s simpler to mark out the mid-line rather than the edges. The issue is even more important for uprights. A simple parallel is the erection of fenceposts in the garden—if you’re going to nail a trellis to the posts, you must try to get the distances right. You de
cide where you want the middle of one post to fall, and then measure off to where the middle of the next post will be; if you measure between the edges of the posts it will go wrong, and it’s no help at all to measure the distance between the edges of your postholes.
We know from excavations of postholes and stoneholes that it’s not always possible to control the erection of an upright so precisely that it fits exactly where it was intended to go. People didn’t measure to the edge of an imagined corner of a future post or stone that was going to be put up; they measured to roughly where the center of the upright would be and could thus mark the center of the hole to be dug for it.
Measuring the six concentric circles of posts of the Southern Circle’s second phase from the centers of the postholes, Andrew found that the diameters of the outer four circles can be matched with regular and incremental multiples of an ancient English unit of measurement called the “long foot.”
The distances came out as 70 to 90 to 110 to 120 “long feet.” The figures are not precise, with deviations varying from six centimeters to 50 centimeters, but Andrew thinks that this can be attributable either to imprecision in construction or, of course, to imprecision in archaeological recording during excavation. Nevertheless, he had identified a possible unit of measurement that could be tried out on other monuments.
Stonehenge—A New Understanding: Solving the Mysteries of the Greatest Stone Age Monument Page 26
