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Prehistoric Sites in Wales (1 of 5)

Archaeoastronomy in South Wales

Neolithic Tombs in South Wales

Astronomical Alignments

at the Crick Barrow

in Gwent, South Wales

 by Martin J. Powell

[This article first appeared in its original form in the journal 'Archaeoastronomy', Vol. 26, No. 20 (1995) published by Science History Publications Ltd and available to read (in pdf format) here]


With the arrival of the Bronze Age period in Britain (ca. 2500 BC), the burial practice of constructing large megalithic tombs had been replaced by that of generally smaller, circular earthen or stone mounds (barrows or cairns).  Unlike the communal burials of the Neolithic long cairns, round barrows were often built solely for one person, and whilst many contained inhumations placed in a crouched position, cremation became increasingly practised.  The round barrow tradition was introduced by the mysterious 'Beaker Folk' of the late Neolithic, so named because of the decorated pottery often found alongside their burials.  The Beaker culture also introduced metal-working into Britain, hence giving rise to the Bronze Age.

Nowhere in post-Beaker Britain was round barrow design more diverse than in the relatively wealthy region of Southern England referred to as 'Wessex' (Wiltshire, Dorset, Hampshire and Berkshire counties).  The most common form was the simple bowl-barrow, but several distinct barrow types emerged from the Wessex culture.  They were the bell, the disc, the saucer and the pond-barrow, the main distinguishing factor being the relative sizes of the mound and, where it existed, the berm surrounding the mound.  Wessex barrow burials were often accompanied by rich grave goods, e.g. elaborately decorated metal daggers, stone battle axes, and ornaments of gold and amber.  The type of barrow constructed appears to have been dependant on the sex of the deceased in question.  Bowl-barrows were built for both men and women, but bell-barrows were usually built for men and disc and saucer-barrows for women.  Barrow cemeteries also developed, which often contained a variety of barrow types.  Good surviving examples can be seen at Winterbourne Stoke in Wiltshire and at Lambourn Seven barrows (96 KB) in Berkshire.

Figure 1  General location map of the Crick bell-barrow: within Wales (15 KB) and within South-east Wales (click on thumbnail for full-size image, 91 KB). Other prehistoric sites of various types are also marked. Contours are shown in metres above Ordnance Datum and are based on the 1:50,000 scale Ordnance Survey map of the region.

Of particular note in the present context is the bell-barrow, perhaps the most visually imposing of all the barrow types. Although the vast majority are found in the Wessex region, the bell-barrow concept did spread further West.  Examples of bell-barrows can be seen in Dartmoor, Exmoor, the Mendips and in South Wales.

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Barrow Details

A Welsh bell-barrow is situated near the village of Crick, in the county of Monmouthshire (formerly part of Gwent), about 2 km north-east of the town of Caldicot.  The barrow is in a field just West of the village, beside the main A48 road (Ordnance Survey Grid Reference ST 48440 90257; see also location maps in Figure 1, 91 KB and Figure 2, 133 KB).  To date, the Crick Barrow is the only bell-barrow to be identified with certainty within the Welsh principality, although a further example is suspected at Crug-yr-Afan in the Rhondda Valley, Mid Glamorgan.

The Crick Barrow in its local setting, based upon the 1:50,000 scale Ordnance Survey map (133 KB)Figure 2  The Crick Barrow in its local setting, based upon the 1:50,000 scale Ordnance Survey map (click for full-size image, 133 KB). Contours are given in metres above O. D., with land above 50m uniquely shaded. The foresights of Parkwall Hill and Crown Hill are marked.

Prior to excavation, it had been thought that the Crick barrow might have been of Roman date, since it is positioned beside the Roman road leading out of Caerwent (Venta Silurum).

The barrow's true nature was however revealed during excavation in 1940 by the late Dr. Hubert N. Savory, who was then working as an assistant in the Department of Archaeology at the National Museum of Wales.1  The following account summarises the main findings from his excavation.

The barrow mound was typically circular, averaging 31.7m in diameter.  It was surrounded by a berm originally 3.5m wide, which was itself surrounded by a 'V'-shaped ditch about 3m wide and 1.5m deep.  It was uncertain from the excavation evidence whether or not the ditch completely surrounded the barrow, or whether an outer bank surrounded the ditch, as is the case with some of its Wessex barrow counterparts.

The mound was found to cover two cremations, both of which were located in pits a short distance from the barrow's centre.  The primary burial is believed to have been of a young woman; the sex of the secondary was not determined.  The barrow was dated, through the finding of two plano-convex knives, to the Early Bronze Age Period III (circa 1750 to 1450 BC).2  The barrow would therefore be roughly contemporary with the later phases of construction at Stonehenge in Wiltshire, which lies at the heart of Wessex.

Plan of the Crick bell-barrow, reproduced after H. N. Savory (69 KB)Figure 3  Plan of the Crick bell-barrow, reproduced after H. N. Savory (click for full-size image, 69 KB). The lines running through the barrow are the excavation trenches. The 'key boulders' are shown solid and the loose stones of the 'crude walling' are shown in outline. The astronomical alignments to the cup-marked boulders are shown through the points of greatest cup-marked concentration. The elevations (h) and declinations (Greek letter δ) refer to an observer standing on the pre-barrow surface (main plan reproduced from the journal 'Archaeologia Cambrensis', XCV, 1940, available online at the National Library of Wales website).

Beneath the mound was a stone ring 28m in diameter (Figure 3, 69 KB).  The ring comprised what Savory called 'key boulders', of conglomerate sandstone, with an average height of 0.7m, interspersed with a 'crude walling' of small stones held together by clayey earth.  The ring was considered too unsubstantial to serve the obvious purpose of providing a revetment walling for the covering barrow.

Two of the 'key boulders' were unique in one respect: they had been decorated with numerous carved circular or oval depressions, known as cup-marks.  One of these boulders occupied the south-eastern quadrant of the circle.  It was the largest boulder in the ring, measuring 1.7m long by about 0.6m wide, with 23 cup-marks on its outer face.  They were mainly clustered on one half of this face, with diameters ranging from 3.7 to 7.5cm, and depths of between 0.8 and 1.9cm (see excavation photo Plate 1, 90 KB).

The second decorated boulder occupied the north-eastern quadrant and was smaller, measuring 0.7m long by 0.5m wide.  Its upper surface had 17 cup-marks, which were also clustered on one half of this face.  They varied in diameter from 2.5 to 5cm and were between 0.6 and 1.2cm deep (excavation photo Plate 2, 95 KB).

The South-eastern cup-marked boulder at the Crick Barrow, with 23 cup-marks (90 KB)___The cup-marked boulder in the North-eastern quadrant of the Crick Barrow, with 17 cup-marks (95 KB)

Plates 1 and 2  The two cup-marked boulders contained within the Crick bell-barrow (click on thumbnails for larger versions, 90 KB and 95 KB). (Left)  The South-eastern cup-marked boulder, with 23 cup-marks and (Right) the cup-marked boulder in the North-eastern quadrant of the stone ring, with 17 cup-marks on its upper surface (both plates are reproduced from 'Archaeologia Cambrensis', Vol. XCV (1940), available online at the National Library of Wales website).

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Astronomical Alignments

Having examined Savory's excavation plan, I believe the two cup-marked boulders in the stone ring may have been astronomically aligned by its builders.

When viewed from the centre of the ring, the mid-points of the larger and smaller boulders lie at azimuths of 130.7 and 63 respectively.

If a prehistoric observer were standing at the centre of the ring and at the surface level of the barrow, i.e. before the mound was constructed, the line of sight over the mid-point of the south-eastern boulder would cross an almost level hill about 1.4 km distant (Crown Hill) with an angular elevation of 1.1.3  Since the boulder spans an arc of some seven degrees when viewed from the centre of the ring, the declination indicated ranges from -21.4 to -25.1; a range of 3.7, with a mid-point value of -23.2.  Where the cup-marks are at their greatest concentration (at an azimuth of approximately 132.5) the declination is -24.2.  This is very close to the midwinter Sun's lower limb declination around the period of the barrow's construction, i.e. when the Sun's centre had a declination -23.8.4

The alignment through the South-eastern cup-marked boulder, as it would be seen from the centre of the stone ring by an observer standing on the pre-barrow surface (57 KB)Figure 4  The alignment through the South-eastern cup-marked boulder, as it would be seen from the centre of the stone ring by an observer standing on the pre-barrow surface (click for full-size image, 57 KB). Sunrise is shown for the winter solstice in the Early Bronze Age Period III, with the Sun at a declination of -23.8. Note the apparent clustering of the cup-marks in relation to the sunrise position.

The line of sight across the smaller, north-eastern boulder faces a gently sloping hill 1.8 km distant (Parkwall Hill), although the line is now obscured by a railway embankment.  The angular elevation of the hill at the mid-point of the stone is, however, around 0.5.  The boulder spans an arc of 3.2 when viewed from the ring's centre, so the declination indicated varies from +15.6 to +17.4; a range of 1.8 with a mid-point value of +16.5.  This is very close to the Sun's lower limb declination at the cross-quarter days in early May and August, i.e. the days marking the mid-points between the summer solstice and the spring/autumnal equinoxes.  The declination at the greatest concentration of cup-marks is +16.9, which is exactly the Sun's upper limb declination for the same calendar dates.  Evidence of the recognition of these days in Bronze Age times seems to have survived in the form of the Beltane and Lughnasad festivals of the Iron Age Celts.5  Through his own detailed examination of dozens of Bronze Age sites, Professor Alexander Thom determined the centre-disk declination of the May and August cross-quarter days as +16.67 0.14.6  The two astronomical alignments through the boulders are shown diagrammatically in Figure 4 (57 KB) and Figure 5 (41 KB).

However, since the highest points of both boulders stand considerably below eye-level, they would appear well below the skyline when seen from the observer's location at the ring's centre.  The tops of the south-east and north-east boulders would appear about 3.7 and 4.4 below the skyline respectively.

The alignment through the North-eastern cup-marked boulder, as it would be seen from the centre of the stone ring by an observer standing on the pre-barrow surface (41 KB)Figure 5  The alignment through the North-eastern cup-marked boulder, as it would be seen from the centre of the stone ring by an observer standing on the pre-barrow surface (click for full-size image, 41 KB). Sunrise is shown for the cross-quarter days in early May and August (Celtic festivals of Beltaine and Lughnasadh), with the Sun at a declination of +16.7.

It is interesting to examine the manner in which the cup-marks are patterned on both boulders.  On the south-eastern boulder, there is a horizontal line of cup-marks across its centre, with an arc of cup-marks towards its southern edge, where the greatest concentration of markings occur.  One could argue that this pattern was a symbolic representation of a succession of sunrises leading up to midwinter's day, the arcing pattern mimicking the actual rising path of the sun.  A similar arcing pattern occurs on the north-eastern boulder.

Observations after Mound Construction

When the mound was raised, it covered the stone ring.  One would assume from this that the astronomical lines could no longer be of any practical use.  However, it appears that this was not the case.  In his excavation report, Savory believed that the outer casing of the covering mound did not originally cover the top of the larger, south-eastern boulder, which was taller than the other stones in the ring.  In other words, the boulder had been left exposed and was intended to be seen by an observer standing outside the barrow.  Clearly this boulder must have held a special significance to the barrow builders.  Savory thought it unlikely that the smaller north-eastern boulder had ever been left exposed in the same manner, since this would have considerably altered the profile of the covering mound at this point.

Evidently, only the the exposed south-eastern boulder could have been observed astronomically after the mound was constructed, the north-eastern boulder having been obscured by it.

The covering mound was originally dome-shaped in profile and was constructed using successive layers of sandy and clayey earth.  During excavation, the mound was found to survive to only 1.6m in height.  Its original height above surface level can only be guessed at, although Savory suggested that it "must have exceeded 12ft" (3.65m).  If the original height was close to this, it would have been at least theoretically possible for an observer standing at the top of the mound to have seen the exposed surface of the south-eastern boulder.

The effect of an observer viewing across the boulder from the top of the mound would be to reduce the elevation of the distant hilltop by at least 0.1.  The declination at the mid-point of the boulder would then reduce to -23.4 and through the point of greatest cup-mark concentration it would reduce to -24.3, which is still significantly close to the midwinter Sun's lower limb declination in the Bronze Age.  The precision of the line would be considerably reduced, however, because the top of this boulder would then appear a sizeable 18 below the skyline.

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Accuracy of Sight-Lines

The observation of the astronomical alignments is clearly dependant upon how accurately the centre of the ring or mound can be located.  According to the plan, the mound is not perfectly circular but is very nearly so, its diameter varying by no more than 0.6m from its average diameter.  Similarly the stone ring is somewhat flattened on its Northern and Western sides but nevertheless its diameter varies by no more than 0.5m from its average diameter.  The centre positions of both mound and ring would therefore have been recoverable to within 0.5m or so.  If an observer were to stand as much as 0.5m away from the true centre of the ring, it could have caused the azimuths of both boulders to shift by up to 2 either way, thereby significantly affecting the resulting astronomical alignments.   Therefore, locating the true centre of the ring would have been an important factor in ensuring the effectiveness of the astronomical lines.

A speculative reconstruction drawing of the Crick bell-barrow, viewed from the South, based on evidence gleaned from H. N. Savory's excavation report (75 KB)Figure 6  A speculative reconstruction drawing of the Crick bell-barrow, viewed from the South, based on evidence gleaned from H. N. Savory's excavation report (click for full-size image, 75 KB). The barrow is shown at the moment of midwinter sunrise, with a man shown beside it for scale. The south-eastern cup-marked stone can be seen protruding through the mound, facing toward the sunrise. The gap in the surrounding ditch is pure guesswork and is not based on any known archaeological evidence.

Today a visitor to the Crick barrow will most likely be disappointed to witness its poor condition (Figure 8, 135 KB), the mound surviving to less than a metre in height and having few visible surface features.  The south-eastern cup-marked boulder can still be seen through the much denuded mound (Figure 7, 165 KB) but it is immediately evident that the barrow itself is not in a surveyable condition.  Consequently, I have taken the aforementioned azimuths directly from Savory's excavation plan on the assumption that his North point indicates True North.  I contacted Dr Savory in 1990 in order to clarify the situation but unfortunately, he was unable to confirm from his notes whether or not this is the case.

The South-eastern boulder, as it appears today (165 KB)Figure 7  The South-eastern boulder, as it appears today (click for full-size image, 165 KB). Two cup-marks are visible just above the grass-line, highlighted above in red. In the main photograph they have a slightly pinkish hue.


In Savory's opinion the stone ring concealed beneath the mound was in all probability a purely ritual feature, as opposed to a structural feature such as a revetment walling.  He reached this conclusion on the basis of three factors:

Given these factors, perhaps it is not surprising to find evidence of astronomy-related practises within such an apparently futile structure.

Prehistoric alignments towards Beltane / Lughnasadh are rather less well attested and more contentious than those of the Winter solstice, which are far more numerous. The following tables list British & Irish sites of the later Neolithic & Bronze Age period which are thought to contain such alignments:

Beltane/Lughnasadh Alignments

Winter solstice Alignments involving decorated stones

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The astronomical lines could only have been set out before the mound was constructed.  Perhaps the stone ring was used as a ritual site in itself before the barrow was completed, although the excavation revealed no clear evidence to support this notion.  As has been shown, less precise observations could in theory have continued solely to the south-eastern boulder once the mound was raised.

Neither of the boulders were able to provide accurate astronomical lines because of their low standing heights and the rather wide angles they would have spanned when viewed from the centre of the ring.  Furthermore, there are no significant horizon features indicated by these boulders, such as 'notches' or hill intersections (referred to by Thom as 'indicated foresights'), hence further reducing the precision of the lines.  It is not therefore possible to determine whether the intended observing target was the Sun's centre or its upper or lower limbs.

Consequently, a ritual rather than calendrical function should be assigned to these alignments.  Perhaps the astronomical lines were never actually used for solar observation, but were simply incorporated into the design of the monument as a ritual feature; hence the hiding of the north-eastern boulder by the covering mound.  Stones with hidden decoration are known at other prehistoric sites in Britain and Ireland.

The Crick barrow as it appears today, looking towards the North-west (135 KB)Figure 8  The Crick barrow as it appears today, looking towards the North-west (click for full-size image, 135 KB). The South-eastern boulder is just visible to right of centre.

The Crick barrow is one of the few sites in Britain which contains an alignment towards the Beltane/Lughnasadh festival dates, and is currently the only known site in Southern Britain to do so using cup-marked stones. A May Day alignment exists between two of the so-called 'Station Stones' at Stonehenge, some 50 miles (80 km) to the South-east of Crick.  The 'Four Stations' are thought to have been erected between 2200 and 2100 BC, several centuries before construction of the Crick barrow.  Winter solstice alignments are also present at Stonehenge, involving the horseshoe of giant trilithon stones.7

As Savory points out in his report, given its proximity and easily accessible terrain, it is not surprising to find the coastal strip of South-east Wales strongly affected by ideas emanating from Wessex. This concept no doubt also applies to the religious practises and beliefs relating to the celestial bodies, evidenced at numerous Wessex sites and from earlier sites across the British Isles.

The Crick barrow is also a rare example of monument that may support the link between cup-marked stones and solar observation.  Such a relationship has been suspected at prehistoric sites in Scotland and Ireland,8 but they are insufficient in number to reach any positive conclusion on this point.  Cup-marked stones are uncommon in Wales and few round barrows have been excavated in Gwent county, so there are currently no similar sites available for comparison.9  Similar sites might be revealed during the course of future excavations, but in their absence it appears that, hidden beneath the mound at Crick, we find further evidence that significant seasonal days were recognised and revered during the British Bronze Age some 3,500 years ago.

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I am grateful to Dr Aubrey Burl and the late Dr Hubert N. Savory for their kind help and encouragement in the production of this article.

[A short account of the life and work of Hubert N Savory (1911-2001) can be seen on the Cardiff Naturalists' Society website]


1.  "A Middle Bronze Age Barrow at Crick, Monmouthshire" by H. N. Savory in Archaeologia Cambrensis XCV (1940) (Cambrian Archaeological Association, Cardiff), pgs 169-191.

2.  At the time of excavation Savory assigned the plano-convex flint knives to the early Middle Bronze Age.  Under the current, revised chronology the barrow is assigned to the Early Bronze Age Period III.  A photograph of a flint arrowhead found during the excavation is included in the People's Collection Wales website.

3.  The horizon elevations given have been determined from Ordnance Survey 1:25,000 scale maps (Sheets ST 48/58 and ST 49/59) and the values are therefore subject to error.  It is unlikely, however, that the error in elevation exceeds 0.1, with a resulting declination error of around the same magnitude.  The horizon is assumed to be free of vegetation cover and the observer's eye height has been taken as 1.55m (5ft 1in).  All declinations given have been calculated taking into account the necessary allowances for refraction.

4.  Due to an effect called precession of the equinoxes, the tilt of the Earth's axis in space (called the obliquity of the ecliptic) varies in a cycle lasting 25,800 years.  During this time the obliquity varies between its extreme values of 21.9 and 24.3.  In the middle Neolithic (ca. 3500 BC) the obliquity had a value of 24.07, reducing to 23.89 by the Early Bronze Age around 1700 BC.  The present value (2000 AD) is about 23.44.  Where precision solar alignments are thought to occur at prehistoric sites, it is important that this effect is taken into account.

5.  The modern derivative of Beltane is May Day, and Lughnasad is often associated with the Christian harvest festival of Lammas.  However, Ronald Hutton points out that "the Anglo-Saxons had their own festival to open the harvest, Loaf-mass or Lammas, which fell on the same day [as Lughnasad] ... which sometimes makes it very hard to distinguish from the Celtic feast."  See Hutton's The Pagan Religions of the Ancient British Isles (Blackwell, Oxford, 1991), pgs. 176-9, 182-3.  Stephen McCluskey's fascinating study relates Lughnassad with the Christian feast of St Anne, held on 26th July, or possibly St Oswald, on 5th August.  See McCluskey's The Survival of British Folk Astronomy in the journal Archaeoastronomy, Vol. 20, No. 13 (Science History Publications, 1989), pgs. S1-S19.  On the Internet, the history and practices of Beltane are detailed in an article by Rowan Moonstone.  The festivals of the Celtic year are described at the Sacred Fire website.

6.  Megalithic Sites in Britain by Alexander Thom (Oxford University Press, Oxford, 1967), pg. 110, Table 9.1.  In fact, Thom refers to the Crick Barrow in Table 5.6 of this work, when discussing his determination of the Megalithic yard.  He makes no reference to any astronomical alignments at the site, however.

7.  The Stonehenge People by Aubrey Burl (Barrie & Jenkins, London, 1987), pgs. 145-7, 191, 204.

8.  For example, see The Stone Circles of the British Isles by Aubrey Burl (Yale University Press, New Haven & London, 1976), pgs 162-3, 165-7, 178-9, 198-9, 252, and From Carnac to Callanish (Yale University Press, New Haven & London, 1993), pgs 170, 173-5, 181, 190, 195-6, 201.  For Irish examples see The Stars and the Stones by Martin Brennan (Thames & Hudson, London, 1983).

9.  The round barrow at Carrow Hill (St Brides Netherwent) (ST 4330 9035), which lies 3.2 miles (5.2 km) west of the Crick barrow, was excavated in 1860 and also in 1975.  The barrow was found to cover a much robbed ring-cairn, but it did not contain any significant boulders or decorated stones.  Other findings from the excavations included an ogival grooved dagger, a whetstone and a flint arrowhead.  Apart from "traces of burning", no definitive burial was found.

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The Crick Barrow (Desktop Site)

Prehistoric Sites in Wales

Archaeoastronomy in South Wales

Neolithic Tombs in Glamorgan & Gwent

Copyright  Martin J Powell  1995/2003

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