3 General description

Descriptive records of stone circles are known as early as the 16th century, but the classification of stone circles into their constituent types is more recent. Aubrey Burl offered the first synthesis of current knowledge of stone circles, including concentric stone circles, in the British Isles in 1976. The most recent study by Barnatt (1987) does not include concentric stone circles as a separate class.

Key excavations for evidence of dating, origin and function of the monuments have taken place at Stonehenge, Avebury and The Sanctuary in Wiltshire and at the Druid's Circle, Birkrigg, Cumbria.

Concentric circles usually comprise a double ring of stones, although the Shapbeck stone circle, Cumbria has three rings and Yellowmead in Devon has four rings. The rings are either all regular or irregular, though in ruined examples it is difficult to tell.

Stone pillars of the outer ring number between 20 and 97 stones ranging in height from o.9m to 2.2m. The megaliths are variably spaced depending on whether the circle is quite regular or not, averaging between 3m and 5m apart. Occasionally the stones are graded in height, for example at the Druid's Circle, Birkrigg, Cubria the tallest are in the North and South-west. The stones of the inner ring(s) were often lower and always fewer. The stones were not always of local or volcanic material. The bluestones at Stonehenge phase II may have been transported part by glaciation and/or part by man from the Preseli mountains of South- west Wales. At Druid's Circle, Cumbria, one of the megaliths of carboniferous limestone had been sculptured into a shape resembling the head of a sperm whale. At Stonehenge carvings of daggers have been added to the stones at some stage in their history. At Stonehenge some of the pillars were actually constructed as trilithons or were lintelled. This may have been the case elsewhere, but they do not survive.

The dimensions of stone holes have not generally been well recorded, but excavation has shown the method of erection of the megaliths using clay and packing stones to support the stones in the holes.

Inner mounds occur singly in several concentric stone circles, inside the smaller circle. They vary in diameter from 7.4m to 15.85m, depending upon the size of the circle by which they are contained.

Embankments are noted at two concentric stone circles in Derbyshire which are now destroyed. At Park Gate, the inner ring 13.7m diameter had its uprights on the inner edge of a 1.8m wide rubble bank which stood 0.3m - 0.7m high.

Avenues occur especially in Wiltshire. At Avebury there were two avenues, at Stonehenge there is an earthen avenue.

Outlying standing stones, sometimes larger than the stones of the circle, occur at several concentric stone circles. It is questionable if outliers are always contempoary with the circle. It has been suggested that such stones acted as waymarkers either to or away from the circle.

A centre stone is known at Avebury in the south ring within the outer ring. There is also an internal rectangular stone structure of unknown purpose here.

In the northern concentric ring at Avebury there is a cove. This may be related to the henge monument rather than the stone circle.

Pavements are recorded in three phases at Birkrigg, Cumbria within the inner circle. Each was constructed of cobbles of "blue rag", a stone not indigenous to the area. They may occur elsewhere, but have yet to be found, though there is some evidence for cobbling at Shapbeck stone circle, Cumbria.

Burials occur in all excavated concentric stone circles either as inhumations, unurned or urned cremations. Sometimes all three types of interment are found at the same site, as for example at Birkrigg, Cumbria.

Four types of concentric stone circle have been identified on the basis of component features and the number of rings:

Avebury is complex in having an outer very large stone circle, contemporary with the henge which surrounds two circles, one in the north which may be a double concentric, type A and one in the south which is a single large irregular stone circle. The northern circle is seen as concentric by Burl (1976) but Smith, in her analysis of the excavations there by Alexander Keiller found no evidence for an inner circle. It is possible that the north and south inner circles represent an earlier or later structural phase than the bank and ditch and the outer ring, but there is no supporting evidence. Without formal phasing of the site it is difficult to determine what classes of stone circles are present. For the moment the whole monument is classed as one complex concentric stone circle.

Stonehenge has been phased following its excavation by Atkinson. However, this phasing is now considered doubtful. It is followed here only until a new phasing is produced. Phase II is a double concentric stone circle, Phase III, a lintelled circle around an inner horseshoe of trilithons has been classed as a double irregular concentric circle and IIIb, a double ring of 60 bluestones has also been classed as a double concentric circle, type A.

See Figure 1 for plan of the main types of concentric stone circles.

It is possible that The Sanctuary, Wiltshire, had a double concentric timber predecessor, although excavation has not disproved that the post-holes between the stones of the inner megalithic circle were not contemporary. These may have represented a building. In all, four phases of occupation/construction have been recognised at this site. At Stonehenge there are three phases, the last being itself subdivided into three. At Birkrigg, Cumbria, three phases of construction were revealed by excavation and there are at least two phases of building at Avebury. Whether the function of the monuments changed over the periods of modification and reuse.

Burl has suggested that the Wessex concentric stone circles are different from those elsewhere, including Cumbria, where the concentirc rings are very like the chamber and kerbstones of a passage-grave before it was hidden under its cairn or barrow, an appearance which could account for the frequent scatters of stones or cobbles as "paving" in the inner ring as figurative representations of the cairn. He sees their derivation in the chamber tomb tradition, whereas those in Wessex may be megalithic skeuomorphs of timber settings. He sees evidence of woodworking techniques at Stonehenge in the deliberately fashioned sarsens with their joints and rebates. The rings were certainly used for burial but the larger rings in Wiltshire were almost certainly also used for communal ceremonies, judging by the effort involved in their construction. At Druid's Circle, Birkrigg, Cumbria various "ritual" objects were found between the stones of the circle including pear-shaped stone, oyster-shaped stone and red ochre.