Stonehenge Solved Its Three Observatories, Who built them, How and Why

The returning party must have given a positive report because another set sail for Britain. It is likely the two worked together to produce the design of the Stone henge and decide upon the construction process. The aim-design would have been subject to fine tuning in the light of the impending ultimate, on-site survey results. The work provided the basis for the choice of equipment to be taken, the number of men required and their skills, and in turn, the number of ships. However, the ships required for this first tour could not be determined without first estimating the number required for completion of the whole project, and the total number of tours, this taking into account what was felt to be a tolerable duration away from home, Clearly, there must have been an overall project team in Egypt, which suggests the presence of a powerful benefactor.

The number of tours decided upon was four, and because the first inevitably would have to do preparation work for those following, its number of men and hence ships would have to be greater than the others. Additionally, not only would they have to take an adequate number and range of implements and tools, and measuring and surveying equipment, but also a significant supply of rope and cord; they could not rely on what the Bretons and Britons were able to do about flax in their absence. Crucially cord and rope would be needed in the construction process at the outset, long before the latter was needed for operational use, but this action would not have precluded taking rudimentary rope-making aids.

All these requirements, plus conveying Bretons to and from Britain, would have resulted in a larger number of ships than the three the Reconnaissance party needed, perhaps seven, or eight, with crews having a different mix of skills. These would have embraced craftsmen and surveyors able to train and supervise the local people, and manage the project. This, it will be recalled, included technical assistance for the Britons' augmentation of the flood refuge at Silbury. The larger number of ships was also necessary to provide enough towing capacity for transporting bluestones from the Presceli peninsular to the head of Southampton Water. The essential resources they did not have to plan for were timber, the availability of axes, and the skills of using them.

The first step on arrival at the site was surveying the Moon's apparent paths in the dome of the sky. These determined the centre line of the installation, which was to be aligned 51 degrees east of true north, together with the positions and heights of the five masts, Figs 37 and 38. These governed the positions of the observation windows. Marking out the site was done as follows. A stake was secured in the ground at the assessed centre of the Early henge ring of spoil heap vestiges, now covered in vegetation. With the aid of cord, a circle of radius 84 cubits (28x3) was scribed on the ground, and on this was dug 56 (28x2) equally spaced small pits. Each of these hosted the butt of a pole, secured by its backfill. The poles were set at various appropriate angles enabling study of their shadows cast in the light of the Moon's passages.

The installation's internal base circle of 28 cubits radius for the intended sarsen stone circle was then scribed on the ground, but when the positions of the masts were scribed, it was discovered the position of upright 56 in mast 156 coincided with a 1.2m (4ft) deep pit shaped like half a pear, cut facing upwards. (The details of this and the following mention of insecure ground, were noted in chapter 3 (i).) This difficulty was solved by finding at the quarry a stone 1.2m (4ft) longer than they had planned for, thus enabling them still to meet the need for an adequately deep foundation.

However, close to this pit on the prospective site of fellow upright 55, the ground was insecure for some reason, and a second compensating, extra long stone, could not be found. Fortunately an alternative was discovered in the form of a stone of the planned length, but unusually having a protrusion at one end, at right angles to its flank, this forming a potential foot. With the underside face of this made smooth, when standing upright the stone's weight would be distributed over a larger area, thus decreasing the ground loading per square metre. But by itself this measure was judged to be insufficient and was supplemented by drawing the intended upright away from the offending area. This was done by shifting the entire layout of the installation: the centre stake was relocated 60cm (2ft) to north northwest and the whole plan was marked out on the ground all over again. In combination, these two measures were anticipated to result in a stable foundation for stone 55, but as we shall see, in the event a third step was ultimately taken.

Stone 96, the so-called Heel Stone, was the first of six tall ones to be erected by the team and it was unique because it was the only one of all the uprights of all lengths arriving on site completely unworked; all the others had one flat, smooth face worked at the quarry (ii). It is possible the Britons transported it in their customary fashion and the Egyptians thought this took far too much time and effort bearing in mind the total number of stones to be moved. The advantages of the worked face were twofold. Firstly, it enabled transportation by sliding it along, possibly on a track of half-logs set in the ground in a manner akin to railway sleepers in ballast, the stone being propelled by men each side with levers and fulcrums. Secondly, on erection it enabled accurate positioning of an upright on the scribed line of its marked out position, regardless of its otherwise rough surfaces. Because of the absence of a flat face, in the event stone 96 was not used.

A second stone of the same dimensions, brought to the site by the Egyptians' transportation method, was erected close to it, one each side of the straight way SU 0637-1, Figs1 and 39. The pair had two functions: to act as contingency spares, or reserves, to cover possible trouble at some later stage when erecting a mast; and in the meantime act as a signal, beckoning those ascending the way through the scrub from the northeast. As spares, their heights were at least equal to those of the uprights in the taller masts 154 and 158, but not those of 156, which were planned to be special as described.

The construction phases are seen to have been the erection of masts 158 and160, followed by the entrance and stations each side in its immediate vicinity. Because the quarries were on the Marlborough Downs the stones' approach from the north would have been facilitated thereby, especially those of the masts' uprights, the position of mast 152 was marked out for the following party. The method of erecting a mast is explained in chapter 16, that for a ring upright and beam, in chapter 15. The stones erected at the entrance were: the sarsen circle uprights 28 to 03, beams 129 to103, and bollards 46 to 31a. On completion of this work, a path was laid between the entrance and the straight way at the Heel Stone and its fellow, thus creating a distinguishable approach for visitors from the northeast. Completion also enabled the setting up and operation of three low-elevation observation stations. But it is unlikely they saw immediate routine operational use, partly because of the limited observable apparent paths of the Moon, and partly because they would have been an inconveniencing obstruction. More likely they, along with the other completed work, were intended to be models of quality standards, and a demonstration of how things should be done, for the following parties. Hence the names assigned to this first construction team: the Model Team, and Model Sector.

With this much done the Model team withdrew and returned to Egypt but not before insignia were carved on two circle uprights: a 'trellis' and three axes on 03, and a 'torso' on 29. On mast upright 57 was carved one large and one small 'panel', or 'shield'. It was the practice of construction work groups in Egypt to identify themselves in this way, and here these may reflect there being two groups, one each side of the entrance. The standard nominal depth of the foundation for an upright, contemporaneously, was 3 cubits (160cm, or 5ft). After adding to the spoil thus generated, the spoil of the bollards, plus that of the unbackfilled construction equipment holes Y and Z, a large quantity needed to be disposed of. It was dumped on the surrounding, now verdant, Early henge spoil heaps, turning them into a white bank. The topsoil of the site was thin, trampled by feet and damaged by equipment when not torn from the chalk. Often it would have been slippery, a hazard mitigated by leaving stone dust and chips where they fell, when not spread about. The Egyptians departed a dishevelled site.

The strategy of the Model team was not only to provide standards of workmanship for subsequent teams to follow but also set up the working methods at the quarries and for the transportation to and fro. Contingency spares reflect forward thinking. However, blots on their record could be firstly, the foundation of upright 60; here it would seem the stone fractured during erection and a large piece fell away from its butt; this was resolved by propping it up with a pile of sarsen boulders. Secondly, the bearer of mast 158 seems excessively long; a potential problem for the fourth team. Thirdly, the foundations of mast 158 were untypically shallow, perhaps stones of adequate length could not be found.

None of this work could have been achieved in the absence of construction equipment, principally timber as we shall see, and crucially the Bluestones, a generic term, all but two of which came from Presceli (iii). If one excludes more than one deployment for some of these stones, approximately 100 were required, 75 as bollards in the design, notionally 56 for the circle stations and19 for the masts, the rest as construction aids. The groups concerned with the early stages of procuring the bluestones loaded up their ships with most of the rope and sailed west. Like the Reconnaissance party they progressed up Milford Haven to East Cleddau and on the way noticed an interesting sandstone outcrop at Mill Bay and another useful looking outcrop of different stone 5km (3m) further upstream on the opposite bank at Llangwm.

On reaching the prospective quarry they first set up camp and in the light of what their predecessors had told them, reconnoitred the area and discovered the viability of sailing round St David's Head and using Newport Bay Sands as their trans-shipment point. The transportation method employed was to bring a stone, or stones, on an 'A' frame sledge, downhill to the beach and rest it on the waterline at low tide, Figs 36 and 40. On the rising tide a raft of tree stems was floated above the loaded 'A' frame, to be secured there until the next falling tide lowered it on to the stones, enabling them to be bound together. The following high tide floated them off the foreshore for towing to Totton. It is likely two ships were employed for this, one to tow, the other for servicing the tug during the voyage: providing sleeping and resting quarters for shift working, going ashore for provisions and carrying out maintenance work. Because of the lengthly duration of the voyage and the necessary return with the raft, possibly four pairs of vessels were employed for this shuttle. At Totton the trans-shipment procedure was reversed. 'A' frame sledges carried the stones once more, the route being north to the flood plain of the River Avon. Following this necessitated three small, simple bridges at Downton, Salisbury and Lake village. From Lake a curving, gentle gradient brought the loads to the construction site from the south, over Normanton Down, 48km (31m) in all.

Not all of the stones needed to be transported by 'A' frames; at the quarry four of them, the largest, were fashioned to have smooth slightly curved sides about 65cm (2ft) square with rounded corners resulting in a cushion-like cross-section; and slightly tapered down their lengths, one pair 4.3m (14ft) long, the other 3.5m (12ft), the former weighing over 4 tons each. As we shall see, these were continually used in construction of the circle after their ends had been dressed on site ready for use. Their smooth surfaces not only facilitated their handling when used, but also enabled them to be dragged over the ground more readily than with an 'A' frame beneath them.

On leaving the quarry for their return journey, the first group to arrive at Preseli retraced its route down Milford Haven and took the opportunity of taking a stone from each of the outcrops they had seen previously, they were not to leave 'empty handed'! That from Llangwm was fashioned to be 1 cubit x 2 cubits in cross-section and possibly 10 cubits long at least, and weighed 7 tonnes. A part of its attraction for them was its high content of fragments of mica which glisten brightly when the stone is first fractured. Shortly after the Model team's arrival at the construction site, when enough other stones had arrived to allow it, this one was raised up, to rest on the dressed flat and level tops of the Heel Stone and its fellow, forming an arch, Fig 39. Visitors approaching the installation would not have seen anything like it, and thus it functioned as a dramatic beacon for them, as well as serving as a third contingency spare.