Stonehenge: Neolithic Man and the Cosmos

As for Aldebaran and Altair, which seem to be indicated by the Ridgeway, the southernmost pair of scaling posts is suited to the marking of Aldebaran’s setting in one direction around 4144 BC,

and the rising of Altair in the other, around 4190 BC.

An azimuth of 21.0° north of east and south of west is assumed here, taking the posts to have been centrally seated in their holes.

This spread of dates is not very satisfactory. The posts are of course too close together to allow very accurate dating, but it is a fact that if we assume the post in the southeastern hole displaced to make the azimuth 19.5°, the two alignments bring the named stars more or less into agreement in time, with Aldebaran at 3984, Altair at 3970, and alpha Crucis (as before) at 3940 BC. While this may seem to be a very devious move on our part, there are arguments in its favour. First, it makes for consistency with yet other dates, that are to be derived in a different way from the first barrow, but only after an analysis of its successor. And second, as an examination of the excavator’s drawing reveals, the hole in question is oval, unlike the others, and the required shift leaves the post well within the oval. In short, the first barrow can be provisionally placed at, say, within a century of 3965 BC.

In reporting on the excavation, Atkinson noted that the posts south of the main chamber must have predated it, since the northeastern post hole was covered by the sarsen slab leaning inwards at that point. This offers support for our view that what we are calling ‘scaling posts’ were destined to be discarded after they had been used to ensure a correctly aligned mortuary house, and were not for use after its completion. Fussell’s Lodge offers comparable evidence.

There is more to be said about potential sightings over the first mortuary house, but the way to discovering them is through an examination of the later barrow. The neat trapezoidal form of this will provide evidence that risings and settings were observed by people standing in the ditches flanking it, and will lead on to a realization that the first structure had very probably already been used in the same way. Parts of the ditches will prove to have been for continuing ritual use, and other parts to have been of use only at the design stage, like the scaling posts.

Wayland’s Smithy II (#ulink_08f01715-02a8-5ea5-9aac-98914fc2a530)

It will be seen from Fig. 13 (#ulink_4bbb2ada-441e-590b-886f-2f07595b45e0) that the ridge line of the old mortuary house at Wayland’s Smithy was in one direction more or less the line of the eastern wall of the new grave chamber, while in the other direction it passed through one vertex of the trapezoid. Apart from a very slight shift in orientation, there was an evident awareness at the new barrow of the traditions by which the old was planned. The precise form of the new barrow, however, is something about which we are not yet in a good position to speculate. On the face of things, the line linking the two structures could not have been the line of a ridge running all of its length, since that would have made the surface slope too steeply at its northwest corner. Reasons will be given for thinking that the ridge was displaced very slightly from the perfect line to the northwest vertex.

Judging by the higher end, the angle of view from the ditches could hardly have been less than eight degrees to the horizontal and is unlikely to have exceeded 15°. Taking this as starting point, consider then which important stars could have been seen from the two ditches, on the assumptions (1) that viewing was at right angles to the long edges of the barrow, whether the near or the far side, and (2) that viewing from opposed positions in the two ditches set the same altitude for viewing.

What seems to have been a constant concern for creating features at right angles to the ditches at many long barrows—for instance here and at Fussell’s Lodge, but in quite a different way there—offers superficial support for (1), while (2) is underwritten by the near-symmetry of the flanking ditches of most long barrows, especially of their inner edges. Accepting these principles provisionally, potential lines of sight of a typical pair of observers are shown in Fig. 12 (#ulink_da851d40-f55e-5408-b0be-96eb99bc0284). The assumption in the case illustrated is that the perpendiculars are to the near sides of the barrow. The lines are chosen to pass over the northeast corner of the new sarsen chamber, which it will be recalled lies on the line through the old D-posts. This point would have been at the same distance from both observers. Assuming that the section across the barrow was reasonably symmetrical at its high end, we have all that we need.

FIG. 12. It is wise to keep an open mind over the question of whether viewing was at right angles to the far edge (or far ditch) of the barrow, or to the near edge (or ditch). There seems to be no evidence that a right angle was taken with an intermediate ridge.

FIG. 13. The long barrow, Wayland’s Smithy II. Observations were made by people standing in the ditches, for example at B, using the barrow as an artificial horizon. The barrow set horizons of identical altitudes to observers in opposite ditches, but the directions (azimuths) were not the reverse of one another. Another potential observer stands on level ground at A and looks up the ridge of the barrow. The dimensions given to the chamber are only approximate, and are for the outer surfaces of the stones.

Since the joint principles (1) and (2) will be invoked on many other occasions, a defence of their great naturalness may be offered here. It is easy to believe that a perfect arrangement was regarded as one in which the rising of one star exactly opposes the setting of another. There would have been times when this was found over open ground, but if the horizon was to be set by a barrow, then the simplest and most appealing arrangement would surely have been a parallel-sided barrow in ridge-tent form, with the observers square on to it and at the same distances. Granted that the observers are at the same level and equally distant from the ridge, the two stars would have had equal altitudes. (There is no suggestion that the person observing them was necessarily conscious of viewing at right angles to any particular feature, or that the altitude of view was a significant angle—although evidence will be gradually accumulated that the latter might have been the case.) The stars would almost invariably have failed to cooperate in this ideal scheme, however. While not all of these conditions could in general have been met, the barrow could nevertheless always have been built with (a) the direction of one star perpendicular to the ridge, the same ridge being used for the other star, observed obliquely now (that is, not at right angles to the ridge) from exactly the same distance. Alternatively, the two observers could still have looked along lines perpendicular to the ridge, and yet view at different altitudes, either by (b) standing at different distances from the ridge, or (c) varying the levels of the ground on which they stand. Judging by the structural features of barrows, options (b) and (c) seem to have been generally disliked. There are exceptions to this rule, but even a cursory survey of styles of ditching round long barrows shows that if viewing was indeed from them, then there was a preference for symmetry of viewing position—in distance and in level. Even when a barrow runs along a contour on steep ground, so that one side is appreciably higher than another (it will later be seen that this was so at Giant’s Hills, Skendleby, Lincolnshire), this ambition was evidently aimed at and achieved in ingenious fashion, by stepping the ditch edge.

It appears that oblique viewing was usually preferred to (b) and (c); but that having sacrificed directly opposed viewing, their architects managed to preserve viewing at right angles to a new ridge, or at least across a new edge. Our double principle ((1) and (2) together) is in fact an extremely natural way of preserving monumental symmetry; and if, on a plan, ditch symmetry seems to be absent, then that is likely to be because one or both of the ditches is parallel to an edge that is not obvious. The directions of ditches offer important clues as to the directions (azimuths) of viewing, but here there is a difficult decision to be made—one to which allusion was made in an earlier section. Is viewing to be at right angles to the local ditch or to that on the other side of the mound?

FIG. 14. Lines of sight (altitude 11.7°) from the eastern ditch over the crossing in the burial chamber at Wayland’s Smithy. The vertical lines in the ditch (terminating in points corresponding to the observer’s eye) represent two possible viewing positions that share the same line of sight. The broken lines are suggested limits to the cross-section of the mound at this place. The stones fronting the mound (not shown here) would all have fitted under the sight-lines, and in the case of three out of the four surviving stones, the fit would have been rather precise. Only one (at extreme left) would have failed to fit under the three-part broken line.

The most natural solution at first sight is one that puts the right angle near at hand. At the Beckhampton Road long barrow—which will be placed in the thirty-fourth century BC—it was seemingly there the far edge that counted. The scaling posts at Fussell’s Lodge and Wayland’s Smithy are ambiguous, but the placing of the ditches in relation to the latter will turn out to fit better with the idea of viewing at right angles to near edges. All told, we are left with little choice in the matter: every example must be worked out for both possibilities, and the solution preferred that is more consistent, internally and with radiocarbon dates.

All possible angles of view are considered until a pair of declinations is found that were simultaneously held by two bright stars at some likely period of prehistory. This is done on both assumptions concerning the right angle, whether it is with the near or far side. There are two qualifying objects that seem most likely to have been observed across the barrow at Wayland’s Smithy, namely the Pleiades (setting) and Spica (rising). (The position of the Pleiades will always be taken as that of the brightest star in the cluster, Alcyone, then of magnitude 2.86.)

First for a near-side perpendicular: for viewing at an altitude of 11.7°, a pair of simultaneously valid declinations is derived. The Pleiades (at azimuth 247.7°) would have had declination –4.14°, and Spica (azimuth 76.3°) declination 17.47°. These values are appropriate to dates in the neighbourhood of 3670 BC. The altitude of 11.7° is close to a gradient of 1 in 5. Whether the true ridge was visible from the ditch depends on the precise shape of the barrow. If viewing was from mid-ditch, the distance to the ridge (17.4 m) would imply a maximum height for the barrow of about 3.6 m, again depending on the form of the cross-section. This is the height above the observer’s eye, but judging from the only relevant ditch section available to us, the eye must have been very near to ground level (see Fig. 14 (#ulink_9bccf35a-7aa2-5da1-a954-dd3f4cea31b5)). The height of the top of the stone covering of the chamber is approximately 2 m, which is well below the required maximum.

If this solution is to be accepted, with more than a metre’s depth of soil above the stone capping, then at least it fits with the greatest problem in viewing the Pleiades—their high extinction angle (about 4.4°). The mound, on this hypothesis, would have set an appreciably higher angle of view.

FIG. 15. Three potential solutions (marked by small circles) for the viewing of stars across the Wayland’s Smithy long mound. Continuous lines are for viewing at right angles to the far edge of the barrow, broken lines for the near edge.

Repeating the calculation for a set of azimuths perpendicular to the far edges, other dates are obtained, in one case with very different implications for the form of the barrow. The stars are the same (Spica and the Pleiades), the date 3710 BC, but the angle of view is only 5.35°. The lines of sight would in this case not have been high enough to clear the chamber, and so this is rejected, but another two solutions present themselves on this second hypothesis. Both are for the thirty-sixth century. One pairs the settings of Procyon and Regulus (around 3581 BC, altitude 11.70°), the other the settings of Procyon and Capella (around 3549 BC, altitude 11.85°). These various solutions are shown graphically in Fig. 15 (#ulink_810a443a-17a8-51b0-9e33-2273b92a6cab).

Which of the three viable solutions are we to favour? All the dates derived fit comfortably into the range found from the radiocarbon dating of a branch or small trunk that the excavators linked with the operation of clearing vegetation from around the previous barrow by fire (2820 ± 130 bc, or 3620 ± 180 BC). This is an ill-starred situation, and other evidence must be brought to bear on it.

Procyon and Capella are both brighter than Spica, and they and Regulus are much brighter than the Pleiades. If one inclines to the Spica–Pleiades combination, it must be for other reasons. Independent dating from other possible alignments might offer us a way.

FIG. 16. The stone mortuary chamber of Wayland’s Smithy II, showing how rays from the brightest stars of the Southern Cross, when rising, fell diagonally across the chamber, grazing carefully shaped stones. (The blocking stone at the entrance, used to seal the tomb, is omitted. The places of missing stones are not indicated, but should be obvious.) The faces of the large stones at the ends of the transepts are likewise carefully placed so as to parallel the sides of the mound, and so would have aligned on alpha Crucis and Deneb before the mound covered them. If the arrangement indicated is not an illusion, then it is plain that religious conceptions were more important than astronomical observations. The upper plan covers the entire mound, and shows how beautifully the geometry of the chamber is related to that of the mound. The details hardly need to be spelled out.

The tomb begs to be considered as an artificial horizon for a view of the southern sky over the length of the barrow. The slope of the barrow was evidently small: judging by its dimensions, known and inferred, the angle set by it to an observer standing at ground level was a little under 2.36°, depending on its form. The massive central stones at the southern end would have been hidden to an observer at the north. Now it so happens that during the period in question the only reasonably bright star in anything approaching the required direction was the rising alpha Crucis, which has an extinction angle close to this figure. The star could have been seen over the chamber by an observer standing at the northeast corner along a line exactly parallel to the western long side. This was very precisely true around 3750 BC, assuming an extinction angle of 2.42°. (It has to be remembered that estimates of extinction angles are not absolute. To give an idea of potential uncertainties: bringing the angle down to 2.1° would in the present case advance the year by a century.) Alternatively, an observer standing at the northwest corner would have seen the same star rising at the same altitude, as if it were coming out of the large sarsen stone at the southwest corner. (This stone is unfortunately now missing, but was probably higher than the corresponding stone on the other side.)

There are interesting resemblances between old and new chambers: the internal measurements of the stone chamber were such as to bring in the ray from the rising alpha Crucis to the northeast corner of the chamber at this time. (With an estimated azimuth of 167.8° and an extinction angle of 2.35°, a year of 3640 BC is obtained.) There is, however, a new and quite unexpected alignment with the other main diagonal of the chamber, this time on the rising of beta Crucis.

As in the other case the line is uncertain—they are estimates for standing observers rather than prone skeletons—but an azimuth of 150.1° and an extinction angle of 2.42° suggests a period around 3680 BC. The west ditch is just long enough to accommodate that same alignment over the crossing point in mid-chamber (see Fig. 16 (#ulink_d198fe47-3fb9-5630-ba2b-e4f662b35db1)).

In sum, taking these additional dates into consideration inclines us to take the Spica–Pleiades combination, with its earlier date (3670 BC) and its more intuitively acceptable style of viewing at right-angles to near edges. Doing so, moreover, brings us to the middle of the radiocarbon range. All the dating is subject to error. For the time being, all too little is known of the ditch floor, but one thing at least seems probable, albeit based on only two sections: the floor falls gradually towards the north, as the ditch is pulled in to the tail of the barrow. This is surely how the angle of view was preserved, while lowering the height of the barrow. (Note that the principle of viewing at equal altitudes was generally implemented by having opposed sections at equal levels. It does not require level ditches, although they were indeed usually level.) When the ditch is completely excavated, the barrow’s form will be better known, but even now one can say—on the basis of ditch sections at the transept and at mid-mound—that the barrow was falling over this stretch at a gradient of about 4.3°. This gradient would have brought it down almost perfectly to ground level at its very tail, but perhaps the gradient was levelled out towards that end, so that the tail retained some height.

FIG. 17. The central area of the next figure.

This analysis has an important consequence for the sequence of building. For those who reject an astronomical interpretation, it makes little difference whether the mound preceded or followed the chamber. The precise astronomical alignment of the stones of the chamber, however, makes it seem certain that they were set up first, rather as the scaling posts for the older barrow had been.

Some people have seen the massive sarsens flanking the entrance to the surviving barrow as male to the right and female to the left. Alpha Crucis has a natural partner, beta Crucis, then slightly brighter, and to be seen on the side of the ‘male’ stones flanking the entrance. (One might equally say that it illuminated the ‘female’ side of the interior, and it would take a Jungian psychologist to decide on the more probable interpretation.) The two stars might well therefore have been regarded as male and female. Was gamma Crucis (magnitude 1.63) their child? The fourth star making up our cross is relatively feeble—but a second child, perhaps?

FIG. 18. A general view of the planning of the mortuary house and its ditches at Wayland’s Smithy. For lettering, see the previous figure, and for a detail, see the next figure.

FIG. 19. A detail of the previous figure, showing the shape of the shallow pitched roof of the earliest mortuary house at Wayland’s Smithy. No attempt is made to show constructional details. Hatching is added simply to make the pitch (and the ridge) more evident.

Frame and Form at Wayland’s Smithy I

What has now emerged about potential uses of the later barrow at Wayland’s Smithy reflects back in an important way on the earlier phase of activity on the site. All the evidence of scale rules out the idea that observation of risings and settings of stars across the earlier structure was done by people standing at ground level, which would have required a higher central edifice than the later barrow. But what if Spica and the Pleiades were observed from the ditches, as it seems likely that they were with the second barrow?

An artificial barrier of wood or chalk or stone over the mortuary house would then have provided the horizon. Only two or three of the edges defined by what is known of the monument are acceptable for the purposes of observing the two stars, on the hypothesis that viewing was at right angles to the edges. They are the lines labelled KB and JA (or parallels to them) in Fig. 18 (#ulink_a295d917-5c64-5947-bcac-1a7c6d7618eb), and they set azimuths (measured from north) of 73.2°, towards the rising of Spica, and 246.9°, towards the setting of the Pleiades, at an altitude and period as yet undetermined.

Note that whereas the second direction represents a shift of less than a degree from what was set by the later monument, the other direction differs from its later equivalent by three degrees. This alone should lead one to expect an appreciable time interval between the two monuments.

Applying exactly the same argument to the first phase of the barrow as that applied earlier to the second, perfectly consistent results are obtained only around the year 3940 BC. The two stars—the only bright stars with the property of being seen as stipulated over the right spread of centuries, would both have been observed at an altitude of 10.4°, when the Pleiades’ (Alcyone’s) declination was –5.59° and Spica’s was 18.58°.

Since Procyon, Capella and Regulus offered alternatives with the later mound, it is worth mentioning here that the dates they yield, whether on the assumption of viewing at right angles to near or far edges, are either much too early or too late (4555, 3490, 3415 BC).

However implausible it may seem to claim that we can make such a precise statement (overlooking small uncertainties in the azimuths) about a monument that has left hardly more than two-dimensional traces of its existence, there is much circumstantial evidence for our conclusion, as will appear in the course of the following suggested reconstruction of the procedures adopted by its builders:

The holes were prepared for the split trunks N and S, and N was erected. Scaling posts were set up at D and A, aligned with the eastern edge of N on the star Deneb. (Post d was also used along the same line, but for mechanical reasons and not geometrical, so that here it will be passed over in silence.) The opposition of Aldebaran’s setting and Altair’s rising was well known at the site, as was the fact that their directions over a natural horizon were almost perfectly at right angles to the Deneb line. Post B was set up to provide the requisite Aldebaran—Altair line. Some fine trimming in the position of A was needed, hence the oval hole. Post C was next placed so that it yielded a right-angle DCB, needed for the ‘viewing at right angles’ rationale of the monument. Once the lines of the artificial horizons had been so defined by the scaling posts AD and BC, the experimental part of the operation began. Beams were tied across those posts (see Fig. 18 (#ulink_a295d917-5c64-5947-bcac-1a7c6d7618eb)), the first of them perhaps to d too, and carefully adjusted in level and height (always kept equal) so that the rising of Spica and the setting of the Pleiades was always viewed across them at right angles. This was easily arranged: they simply used the uprights, C with D and A with B, to define the direction in conjunction with the appropriate beam. But viewing now had to be precisely done from a definite height, ground level, and the ditches were dug accordingly. Viewing was later going to be by people standing more or less in the ranges UV and XW of the ditches. The UV area was dug first, and the ditch extended to a point (E) suitable for observing the Pleiades. There was to be no wasted effort: digging was to be done as far as was needed, and no further. The same was true for a point G in the western ditch. (But later the ditch was extended to F so that an overland sighting of Spica was possible.) Care was needed to ensure that E and G were at precisely the same distances from their respective beams. At last the requisite height of the beams was found (it was about 1.09 m above eye level), and the roof of the mortuary house could be erected.

This was in the first place a wooden structure, and its being pitched would have aided the run-off of water, although it was only at a shallow angle of 10° or so. The perfect pitch for observing the stars was 10.4°. It was the two edges that were really crucial, and these were defined by marks cut into the split trunk N and by the short posts flanking S. These short and puny posts did not bear any load: they were levelling posts, each hammered into the chalk until level with the edge of the corresponding beam. The nearby sarsens bore the weight of the roof ridge.

By an unhappy circumstance—heavy sarsens in the ditch-fill—the inner ditch sections were not always excavated to the bottom, and never where they are of greatest interest to us. However, the inner ditch gives every sign of having been a normal viewing ditch, flat-bottomed and within a few centimetres of 1.65 m below the thin chalk soil (rendsina) under the cairn. (The estimated heights of eight adult males in the tomb yield an average of 1.70 m, and the average eye-level of the tallest three would have been about 1.65 m.) This has important implications for the astronomical argument. Clearly the remnants of the later cairn must allow for the idea that the viewing angle did not greatly differ from 10.4°. This they do, but the two sarsens at the southern D-post—which on our reconstruction supported the roof of the earlier wooden chamber—if set upright in the (known) stone holes from which they came, set a more reliable criterion. Each would have been almost exactly 1.05 m above the floor. The viewing angle requires the ridge at this point to be a minimum of about 1.20 m, and for more comfortable viewing 1.30 m, so that there is ample leeway for a (probably solid) roof of 15 or even 20 cm thickness. Trunks of this diameter could have provided a frame for the roof, bringing it up to the right height. The need for waterproofing might be thought to argue for a covering of turf or even compacted chalk, but solid trunks, split, trimmed to shape, and calked in some way would have been better.

The shallow ridge of the roof runs from K to I. What might easily have been taken as a sign of incompetence on the part of the builders, who might have been thought simply incapable of positioning one massive trunk precisely opposite another, is now on the contrary seen as testimony to genius of a high order. The trapezium outline of the horizon-roof is very much the same as the shape of the later long barrow, and no doubt its pitches were much the same. Furthermore, there is an exact analogy between the placing of the stone mortuary house within it, to the side of the central line, and the mortuary house under the roof between the split trunks (compare Figs. 13 (#ulink_4bbb2ada-441e-590b-886f-2f07595b45e0) and 19 (#ulink_a3e547c6-5c55-5360-9374-2d4fc558f9a8)). In other words, the great barrow at Wayland’s Smithy was very probably a replica of that original roof, in all but the fine details of the angles, which the precession of the stars had altered.

The observing ditches were dug so that the ranges XW and UV were equidistant from the roof edges, just as G and E had been from their beams. Each range had space for six or seven people standing side by side. (Could they have been three men and three women, like the sarsens fronting the barrow?) Each person probably had a place-marker, say a ridge cut in the chalk. Note that the chalk at X was dug so as just to accommodate a viewing position, but with little more expenditure of energy than was necessary. Later extensions to the ditch took it up to other viewing positions L, M, and Q—and again took it no further than was necessary—from which the stars under discussion here could have been seen in different ways. Which stars they were will be appreciated without further comment, if Fig. 18 (#ulink_a295d917-5c64-5947-bcac-1a7c6d7618eb) is examined for parallels to the lines of sight already discussed.

Fussell’s Lodge Revisited (#ulink_5fa9d78c-39c9-57d3-8d22-248ec2d7aa88)

In possession of our several new principles, it is possible to re-examine the first chamber at Fussell’s Lodge, here previously dated at around 4235 BC on the basis of individual stars—Aldebaran, Spica, beta Crucis, and beta Centauri. The broad principles embodied in the use of scaling posts, whose positions are at Fussell’s Lodge known fairly accurately, are now taken to be the same as at Wayland’s Smithy; and these provide a pair of directions, across which it will be supposed that viewing was at right angles. Examining them for stars at low altitudes, no qualifying pair emerges at all, but as the altitude is increased it becomes clear that the setting Arcturus to the north

and the rising Betelgeuse or Bellatrix to the south

are possible candidates.

FIG. 20. Two possible forms of roof for the Fussell’s Lodge mortuary house, seen from different viewpoints. The first form, anticipating the shape of the barrow, is favoured here.