The long cairn in question is one of a pair, in a field known as Barrow Ground, 13 km east of Cheltenham and about 45 km west of Oxford. Many other long mounds are nearby, including Notgrove, Belas Knap, and Burn Ground (Hampnett). Hazleton North is on a bedrock of limestone, rising gently to the northwest. It is well placed for viewing over reasonably distant horizons in the southern half of the sky. It lies east–west and is fairly unusual in one respect, for its highest part was to the west—although it was once thought to be otherwise. In common with so many others in this, the finest English group of stone chambered tombs, it was being steadily destroyed by ploughing. The rescue excavation, for which several groups had been pressing hard, resulted in one of the most meticulous Neolithic surveys ever carried out. It revealed traces of human activity on the site before the mound (cairn) was erected. Tentatively grouped with this phase in the estimation of the excavators were a number of post holes and stake holes beneath the mound. Some of these follow the line of one of the transverse internal walls so closely (Figs. 50 and 51 below) that they were almost certainly aligned on the same astronomical event. Some of the posts involved were too substantial for merely staking out the mound, however, and their arrangement roughly resembles that of post holes bounding burial areas on the sites of earthen mounds. For want of more surface detail, they are not discussed further here, beyond the remark that if used for viewing over the natural horizon, the heavier posts might possibly have been aligned on the rising of alpha Crucis a little before 4000 BC. Early or late, the fact that they all come so close to the line separating cells U and S suggests that the mound was deliberately related to them.
FIG. 49. The general arrangement of the dry-stone walls that gave the Hazleton North cairn its form (after the much larger plan in the excavation report by Alan Saville). For the quarries, a scale, and a key to the lettering used in the text, see Fig. 52.
The arguments offered for the West Kennet chamber’s having been set up before the surrounding mound was begun might have been applied here, had the upright stones been more precisely tooled. As it is, one can only say that there are certain significant directions that they seem to define—for example, the longest side of the north chamber probably aligned on the rising Pleiades, and the spine on the setting Pleiades. If this is not an illusion, then once more it can be said that the alignments would not have been possible had a significant part of the mound preceded the uprights. One would naturally expect any viewing of stars across the finished mound to have taken place opposite them, if nowhere else; and in fact the quarry-ditches to north and south are best suited to such activity opposite the middle of the mound. Those quarries have never been extensively excavated, but their estimated outlines are as shown in Fig. 52. The floors of quarries, by the nature of things, are mostly very uneven, but since in the act of quarrying the builders reached down to marl at some points—especially in the central areas—they had at their disposal two flat areas from which to view. The inner area marked on the figure, namely the south quarry, the better excavated of the two, was extremely flat and level. As in the case of chalk ditches, levels are virtually identical to both sides of the barrow. To the south, small ‘islands’ of stone were left in place that could have been used as steps. One of these, opposite the south chamber, would have brought the adult male observer’s eye to the level of the base of the mound, but there is no way of knowing whether such a step was used—an unfortunate fact, for it would have allowed us to estimate the height of the finished mound. The excavator’s discussion of heights was inconclusive. The favoured reconstruction suggested a maximum height of around 2.5 m, while analogies with other cairns seemed to hint at a somewhat higher figure. While our earthen barrows have shown us that analogy is an unreliable guide, the angle of view to be derived shortly (11.85°), taken together with the symmetrical viewing positions marked Y and Z on the figure, imply a height of about 2.9 m—or about 25 cm more than this if the eye had been precisely at the level of the mound base.
FIG. 50. A detail of Fig. 52, showing the relation of the posts to the division between cells U and S.
FIG. 51. The stake holes and post holes under the Hazleton North cairn.
The astronomical argument proceeds exactly as before. The possibilities are considered of viewing at right angles to near and far edges and—as justified by the perfect level of the quarry floors—at equal altitudes. In the half millennium centred on the many radiocarbon dates known from the site, the only stars that offer themselves are the setting Vega and the rising Sirius. Viewing perpendicular to near edges, the date derived from the azimuths assumed (340.3° and 171.8°) is 3870 BC, and the viewing altitude 11.85°. (If the principles on which it is found are accepted, then the date is unlikely to be in error by more than half a century.) Surprisingly enough, taking far edges instead, the date is only put back to 3950 BC, but the viewing angle becomes 9.6°, and the known facts of the structure seem to rule this out conclusively. Once again, therefore, the orientation of cell divisions seems to be a misleading guide to viewing direction. In fact the pattern of these divisions is extremely interesting: at the head, perpendiculars are to the axis in the middle, the business area, they are to far sides; and at the tail of the mound one of each sort, near and far, crossing the entire mound. This seems to suggest that if there was no perfect pairing of stars across, and perpendicular to, the line of the axis, then the mound was used as a ‘precise’ artificial horizon only across its middle region. In fact as far as can be seen there was no other reasonable option.
There remains the possibility that stars were observed along the line of the barrow, as found elsewhere. The barrow sloped upwards to the west, and on our estimate of heights (2.9 m over the chamber and 0.5 m at the tail, 32 m distant from it) it did so at an angle of about 4.3°. Although this working is very approximate, the figure is so close to the extinction angle of the Pleiades that it comes as no surprise to find that indeed the Pleiades cluster could have been seen setting over the mound by an observer at the lower end, looking along the spine (estimated azimuth 256°) in the thirty-ninth century BC. (Taking the extinction angle, the year comes out at 3870 BC, but the uncertainty is of the order of two centuries.) This finding fits the other evidence so well that it comes hard to modify it. The ideal arrangement would have been with the observer’s eye at or below (depending on distance) the tail edge of the barrow. Our estimate of the mound’s overall shape is shown in Fig. 53, for which the line of sight is the right-hand half of the white line along the ridge. In short, we should expect some sort of pit or quarry beyond the tail edge of the mound. None was found, although the excavation did not extend very far in this direction. Of course the Pleiades could still have been observed setting in this direction, but they would have vanished from view somewhat above the ridge, rather than descending into the mound. The Pleiades might have been observed ritually by a large number of people, in the course of setting over the natural horizon along the same direction.
FIG. 52. The proposed cell structure of the Hazleton North mound, with construction lines drawn at right angles to the south or north mound edges or to the axis.
FIG.