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). 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.
Which of the three viable solutions are we to favour? All the dates derived fit comfortably into the range found from the radiocarbon dating