geophysical surveys of bury walls hill fort, shropshire

Archaeological ProspectionArchaeol. Prospect. 10, 249–263 (2003)Published online 6 October 2003 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/arp.216

GeophysicalSurveysofBuryWallsHillFort,Shropshire

RUTH E.MURDIE,1* ROGERH.WHITE,2 GLYNNBARRATT,2

VINCEGAFFNEY2 ANDNEILR.GOULTY3

1 Schoolof EarthSciences andGeography, UniversityofKeele, Staffordshire ST5 5BG,UK2 Institute ofArchaeologyandAntiquity, UniversityofBirmingham,BirminghamB15 2TT,UK3 Department of GeologicalSciences, University ofDurham, SouthRoad, DurhamDH13LE,UK

ABSTRACT ThehillfortofBuryWallsinShropshirehasbeensurveyedextensivelyby topographicalandgeophysi-calmethodswith theaimsof recoveringevidence foroccupation, characterising theuse of thehill fortand clarifying the chronological development of the site.Topographic surveys delineated the currentextentofthefortanditsmassivefortifications.Resistancesurveysshowedseveralinterestingfeaturesinsidethefort, includingextensiveuseofthegeologytomakeflattenedledgesinanotherwisequiteun-even fort interior, apossible crossdyke, interiorroadsand tracesofpossibledwellings.Magneticgra-dient surveys again showed clearly the possible cross dyke. Additional geophysical surveysattempted to define the depthsof these features foundin the resistanceandmagnetic gradientmaps.Thisstudy, althoughnot fullyansweringtheoriginalaims, providesausefulbasisfor futureexcavation.Copyright�2003 JohnWiley&Sons,Ltd.

Keywords: IronAge; hill fort; geophysicalsurveys; topographicalsurveys; Shropshire

The site

Bury Walls hill fort in Shropshire, England islocated at OS grid reference SJ 576 275 betweenShrewsbury and Whitchurch. It is one of themost impressive Iron Age hill forts in theMarcher counties (Figure 1), and has been desig-nated by English Heritage as Scheduled AncientMonument no. 01139. The interior of the fort isnow under pasture and the fortifications aredensely wooded (Figure 2). It relies for defencearound much of its perimeter on its strategicposition, utilizing to maximum effect a well-defined spur of land that juts out southwardsfrom higher ground to the north (Figure 3). The

massive ramparts of the fort arc east–west acrossthe neck at the northern end of this landform toannex the spur. Hence the site could be regardedas a promontory fort (Cunliffe, 1991), but itsoverall size of some 10 ha is unusually large.For most of its perimeter, the site is univallate,but across the northern end, which is the side lesswell defended by the topography, there is adouble rampart with medial and outer ditches.The top of the massive inner rampart is 13 mhigher than the bottom of the medial ditch. Anunusual feature of the site is that it has a naturalspring within its defences.

Motivation for the survey

Prior to the Roman invasion and occupation,Britain was divided into areas inhabited bydifferent tribes. These tribal societies were

Copyright # 2003 John Wiley & Sons, Ltd. Received 11 January 2003Accepted 15 July 2003

* Correspondence to: R. E. Murdie, CTBTO, Vienna Interna-tional Centre, PO Box 1200, A-1400 Vienna, Austria.E-mail: [email protected]

associated with a variety of settlement types,predominantly small enclosures but also someunenclosed settlements (Whimster, 1989). Apartfrom small farms, settlement was associated withmassively defended hill forts or, in some areas,

with extensive proto-urban sites called oppida.Bury Walls is situated within the area inhabitedby the Cornovii, a tribe about which very littleis known, who probably inhabited an areaequating with the modern English counties ofShropshire, Cheshire and Staffordshire (Whiteand Barker, 1998). Pre-Roman settlement seemsto be linked with a variety of small farmsteadsand a number of substantial hilltop forts. Untilnow, there has been little evidence that the tribehad a complex social structure and it has beensuggested that it was a cantonalized groupingwith no central authority (Millett, 1990). There isno evidence that the Cornovii opposed theRoman occupation and it is likely that the regionwas annexed with little violence. Here, as else-where, the Romans founded a new tribalcapital called Viroconium Cornoviorum, situatedat Wroxeter, Shropshire.

The motivation for the geophysical survey ofBury Walls was thus to explore the ‘native’component prior to the Roman occupation atWroxeter. If, as is likely, the bulk of the popula-tion of that city was derived from the local land-scape, where were the centres of population inthe immediately preceding Iron Age? In lookingat Iron Age Shropshire, it is difficult to see wherea large population group could be drawn from.

Figure1. The location of BuryWalls in relationship to other no-table Iron Age enclosures within the Cheshire^Shropshirearea. The position of the Roman town of Wroxeter is alsomarked.

Figure 2. Aerialphotographof thesiteasit is todaywithwoodlandcoveringmost of therampartsand the centralportionof the fortleft forgrazingandoccasionalmowing.

250 R. E. Murdie et al.

Copyright # 2003 John Wiley & Sons, Ltd. Archaeol. Prospect. 10, 249–263 (2003)

The city cannot have derived its populationentirely from the surrounding countryside as itwould not have been able to support itself. Thus,we must look to the only large-scale sites weknow for that period: the hill forts. Of these, BuryWalls is both the closest to Wroxeter physicallyand is also of a type of settlement that is likely tohave supported a large population. However,very little was previously known about the site.Only a single Iron Age sherd of pottery has beendiscovered on the fields around Bury Walls(Evans, in press). Additional aims of the surveywere to determine the nature of the settlementwithin the site, its degree and quality of survival,and whether settlement continued after theestablishment of the Roman capital at Wroxeter.

There is evidence that the site was used in thelate Roman period, either for ritual purposes oras a ‘refugium’. William Camden, the great six-teenth century topographer visited the site andnoted that: ‘on a spot of ground a small city oncestood, the very ruins of which are almost extinct;but Roman Coyns, with such bricks as are usedin building, are evidence of its antiquity andFounders.’ During the 1930s, a small excavationwas carried out on the site by Mr E. W. Bowcock

(Morris, 1932), who located a large stone build-ing which he thought to be medieval, althoughno evidence was recovered to confirm this date.The report of these excavations (Morris, 1932)mentions a plan of the site that is not reproduced.However, the original plan survives in Rowley’sHouse Museum in Shrewsbury and study of itsuggests that the building may be Roman in dateand possibly a late Roman temple such as thetemple at Lydney, Gloucestershire, rather than amedieval building (Wheeler and Wheeler, 1932,1936). Numerous examples of Roman templeslocated within Iron Age hill forts are knownthroughout Britain (Woodward, 1992). Further,there is consistent evidence, in the west at least,for the continued occupation and use of theseshrines and temples into the late Roman period(de la Bedoyere, 1999).

Although the Bury Walls site today is underpasture, the owner of the land has collected anumber of Roman finds including pottery andValentinianic coins (AD 364–378), suggesting thatthe site was occupied in the late Roman period(Gaffney et al., 2001). Late Roman artefacts havebeen found on other Shropshire hill forts too,such as pottery from Nesscliffe (Home and Jones,

Figure 3. Adigitalelevationmodelof the site showing the steep escarpments surrounding the site to the south.Note that thever-tical scalehasbeenexaggerated.

Geophysical Surveys of Bury Walls Hill Fort 251


1959). This suggests that Shropshire’s hill fortscontinued to play a role in society until lateRoman times, albeit perhaps largely a religiousone.

Survey objectives

The Bury Walls survey was undertaken follow-ing the very successful geophysical survey ofWroxeter (Gaffney and Gaffney, 2000) to extendthe work of the Wroxeter Hinterlands Project(Gaffney et al., 2001). That project had sought tocharacterize the development of the landscapearound Wroxeter in relation to the foundationand growth of the Roman civitas capital at Vir-oconium Cornoviorum. A programme of extensiveand intensive field surveys was undertaken withthe aim of determining the spread of Romanmaterial culture into the landscape. In order tointerpret the results, however, it was also vital tocharacterize the culture and settlement patternof the preceding Iron Age to determine whateffect the introduction of Roman culture hadhad on the tribe.

The work of the hinterland project, and itsinterest in the character, social and culturaldevelopment of the Iron Age peoples of theregion, has coincided with a wider reassessmentof the Iron Age in Britain (Haselgrove, 1999;James, 1999). This recent work has often soughtto question the models of Iron Age culture devel-oped in Wessex and epitomized by the work ofCunliffe (1991), in particular. The conventionalparadigm tends to emphasize developments inthe south and east of Britain as being at the ‘core’,with the remainder of the country becomingmore and more peripheral to the mainstreamdevelopments in the south and east. It charac-terizes Britain as dominated by strife betweencompeting warlords who, nonetheless, remainfrustratingly elusive in the archaeological record.The south and east is seen as demanding, orseizing, resources from the more fragmentedcommunities at the periphery, who are oftencharacterized as weak or disunified. In particu-lar, the undoubted similarities between theapparent settlement character of the Wessexarea and the Welsh Marches (‘the hillfort-dominated landscape’ (Cunliffe, 1991, figure

14.38)) has led to neglect of the archaeology ofthe Welsh Marches as being no more than a paleand weaker imitation of Wessex.

Increasingly, scholars have become dissatis-fied with this picture of the Iron Age in the WelshMarches. Matthews (1996), working in Cheshire,has shown that far from being peripheral in theIron Age, there was considerable contact with theoutside world via the port at Meols, and Morris(1985) has mapped the extensive distribution ofCheshire salt over much of the northern part ofWales in addition to the northern Marches. Thecontrol and organization implied by this tradesuggests that the Cornovii were not as weak ordecentralized as they have been characterized todate. The excavations on the hill fort at theBreiddin (Musson, 1991) have shown that hillfort development was early in date and inter-mittent in character in the region. The totalexcavation of the nearby lowland settlement atCollfryn (Britnell, 1989) has demonstrated thecharacter of lowland occupation in the area.Such settlements are now known to dominatethe occupation of the region in the Iron Age(Whimster, 1989), and thus it becomes increas-ingly difficult to see the hill forts as the mostimportant element in the Iron Age community.In the light of such work, it might be concludedthat the Iron Age Cornovii were much morecentralized than at first appeared—evidencedlargely in their control of the extensive salt tradeand in the construction of their numerous hillforts. If this is indeed the case, then it is pertinentto ask whether this tribe, too, was movingtowards ‘enclosed oppida’ hill forts (Cunliffe,1991), even without the stimulus of direct contactwith the continent. If so, then only two hill fortsites in Shropshire would offer the potential forsuch developments: Old Oswestry (Hughes,1996) and Bury Walls.

The suitability of these two sites to oppida-style occupation rests on two factors. Firstly, theyoccupy plateau-like sites that have massivedefences. Secondly, their defences enclose exten-sive areas—over 8 ha at Old Oswestry and 10 haat Bury Walls—suitable for a large population.In the case of Bury Walls, there is the addedincentive to population and livestock manage-ment of a permanent spring within the ramparts.Unlike many of the other Shropshire hill forts,



they do not occupy dominant and exposed hill-tops, yet both dominate their immediate sur-roundings. In contrast, many of the hill forts ofthe Cornovii may be characterized by their loca-tion at elevations above 200 m, commonlyexposed and highly visible positions. The sum-mit of The Wrekin, for instance, is at an elevationof 407 m, and the site is extremely exposed. Yet itis often characterized as the principal hill fort ofthe Cornovii, the evidence for this coming fromthe suggestion that it was from this site that theircivitas capital was named (Rivet and Smith,1979). There is little in the excavations that havebeen carried out on the site to confirm the pres-tige nature of the occupation (Kenyon, 1943;Stanford, 1985), and its exposed position begsthe question whether it was habitable all yearround. Other hill fort sites, such as TitterstoneClee or the Breiddin, were certainly occupiedeven though exposed, but where evidence forprestige occupation is found, as at the Breiddin,it is early in date, belonging in the late BronzeAge (Musson, 1991; Lynch et al., 2000).

The archaeological objectives of the survey,therefore, were twofold. Firstly, the full geophy-sical survey of the interior aimed to recoverevidence for occupation and to characterize theuse of the hill fort. Secondly, it aimed to clarifythe chronological development of the site andpin point and further elucidate the buildingfound in the 1930 excavations in the interior(Morris, 1932). Another important aim was toprovide a detailed topographic survey that couldbe used to provide information for the manage-ment of the site in the future.

Field surveys

In total, five types of survey were undertaken. Inaddition to topographic, resistance and magne-tometry mapping surveys, depth soundingresistivity and seismic refraction profiles werealso acquired in order to obtain a more three-dimensional picture of the features detected.

The main area of interest was the landenclosed by the fortifications. However, attentionwas also paid to a field adjacent to the fort, as itappeared that part of the fortifications hadexisted within that field and had now been

flattened. The topographic survey was mostdetailed over the fortifications and over a rockcutting in the cliff face on the eastern edge ofthe escarpment. Coverage of the mapping sur-veys and locations of profiles are shown inFigure 4.

Topography

The planimetric and topographic survey under-taken was carried out to control points estab-lished by high resolution GPS tied into OScontrol coordinates. All subsequent groundsurvey was undertaken using reflector or reflec-torless Total Stations supplied by Leica Geosys-tems UK, with data logged in digital form intothe Penmap logging system. The mixed wood-land and dense undergrowth covering the ram-parts and the precipitous nature of the rampartsmade all survey work difficult, even to theextent of necessitating the use of safety ropes inplaces. Where it was not possible to obtain pointsby conventional prism/infrared reflector TotalStation recording, the red laser reflector-lessmode of the Leica TC307 was used to infill spotheights. The survey work undertaken wasdesigned to complete a digital topographic dataset of the interior of the site and of the hill fortdefences.

Resistance mapping

Resistance mapping was carried out over thewhole of the inside of the fort and also in theadjacent field. Surveys were carried out in gridsof 20 m� 20 m, with sampling intervals of 0.5 malong traverses spaced 1 m apart. About half thework was completed using a Geoscan RM15 withautomated logging and the rest using a GeoscanRM4 with manual logging.

The data were then read into Geoplot (GeoscanResearch software) and processed using stan-dard routines: despiking, mean and edge match-ing between grids and finally a low-pass filter.The data quality was fairly consistent, althoughon repeating some particularly poor grids, it hasbecome apparent that some of the older RM4machines were not performing to the quality ofthe RM15. However, the data have been reason-ably well integrated.



Magnetometry

Four Geoscan fluxgate magnetic gradiometerswere used to cover the interior of the fort withmagnetic surveys. The sample spacing was thesame as that for the resistance mapping surveys.

The data were read into Geoplot and the follow-ing processes were applied: despiking, traversemean removal (in this case to remove instrumen-tal drift) and edge matching between grids. Thedata quality from this survey is variable. Longgrass and inexperienced operators were partly thereason, but in some grids, there was no explana-tion for the speckled nature of the data.

Resistivity depth sounding

Resistivity depth sounding was carried out alongspecific traverses with the aim of finding thedepth of features identified by the topographicand resistance mapping surveys. A Wennerarray of electrodes was used and the resistancemeasured using a Megger Earth Tester. Initially,the electrode spacings inside the ramparts were

chosen to be 0.1 m, 0.2 m, 0.4 m, 0.7 m, 1.0 m,1.5 m, 2.0 m and 4.0 m. Later the 0.1 m and 1.5 mspacings were dropped and replaced by spacingsof 7 m and 10 m.

Measurements of resistance from the field datawere converted into apparent resistivity valuesby the standard geometric conversion: apparentresistivity¼ 2�� electrode spacing� resistance.These values were then displayed as pseudosec-tions and also inverted using Res2Dinv (Geoe-lectrical Imaging software) to produce a modelof the features in the ground and show therelationship of the resistive features with thetopography.

Seismic refraction

Eleven seismic refraction lines were acquiredwith a spread of 24 single geophones. Insidethe fort, a geophone spacing of 0.5 m was usedand outside the fort a spacing of 1 m was used.The source was a hammer impacted on a metal orrubber plate. Data were recorded on Terralocand Smartseis enhancement seismographs.

Figure 4. Extent of the surveys carried out inside the fort.



Results

Topographic results

The topographic surveys were superimposed onOS Panorama data of the site. The vantage pointof the site above the surrounding plains canclearly be seen in Figure 3. At the northeasterncorner of the fort, the massive inner rampartalong the northern side of the fort bends sharplytowards the south. Close to the scarp, it termi-nates abruptly to form the main entrance to thehill fort. The medial ditch, outer rampart andouter ditch all fade out at the northeastern cornerof the fort, although there is still a depression inthe topography, which follows the expected lineof the outer ditch almost to the scarp. At thenorthwestern corner of the fort, the massiveramparts along the northern side of the fortterminate some 5 m short of the top of the scarp(Figure 5). It seems probable that this gapbetween the ramparts and the scarp around thespur is original, and probably represents a smallsecondary entrance.

The ramparts survey provided valuable infor-mation on the construction of this major compo-nent of the hill fort. Clearly, without excavation

of the ramparts, it is impossible to be certain ofthe details of construction. In particular, it isimpossible to determine whether there wereany earlier phases of occupation. The interiorrampart is a truly massive construction, whichremains today a formidable barrier. It standssome 5.1 m high on its interior (southern) side,and falls a formidable 13.7 m from its summit tothe bottom of the medial ditch to the north(Figure 5). The sides of this rampart remainwell defined with little evidence of slumping.They seem to have been constructed throughoutas dumped earth retained in places by a dry-stone wall made from the local bedrock, whichis Upper Mottled Sandstone of the TriassicSherwood Sandstone Formation. The UpperMottled Sandstone beds are laminated by currentbedding, which allows quarrying and dry-stonewalling. It can be split in rough planes to allowsuch construction with relative ease. In places,notably near the eastern termination of the innerrampart near the main entrance, a roughly builtwall is visible in the rampart, which presumablyrepresents an internal constructional wall.Indeed a short length of original revetment wall-ing is exposed on the outer face of the ramparttowards its eastern end. A high stone content is

Figure 5. Adigital terrainmodelof the insideof the fort and the flattenedramparts to thenortheast.The cross-section through theramparts shows the full extent of theheight differencebetween the top of the rampart and thebottomof the ditch.



also revealed in places along the rampart top,where stone concentrations are exposed, havingthe appearance on occasion of a possible wallstub. This use of large quantities of stone in therampart construction is consistent with the prob-able quarrying revealed by the geophysical sur-vey of the site interior. The construction materialappears to have been quarried in the interior andpiled outwards. The glacis is accentuated by theexcavation of the medial ditch, the material fromwhich was presumably piled outwards to formthe much lower outer rampart. This survives asan equally well defined, if slighter structure,4.8 m high on its interior south side and 5.9 mon its outer north side. On the outer bank of thenorth ramparts, a carefully constructed stonewall built of Upper Mottled Sandstone wasfound. The purpose and date of this was notclear, but it seems more probable that it relates toeighteenth century activity rather than Iron Agework. If it was of such late date, it might relate tothe later work-creation schemes of the formerowners of the site, the Hills of Hawkstone, whosemost famous creation was Hawkstone Park, afew hundred metres from Bury Walls (Stamper,1996).

The medial ditch and outer rampart along thenorthern side of the fort run parallel to the innerrampart. Today the outer rampart stands above awell-constructed stone walled revetment, whichfalls to an outer, wet ditch that is about 5 m wide.The outer ditch here could be an original feature,but the state of preservation and coursed natureof its construction may indicate that it was latermodified as a landscape feature, likewise possi-bly associated with Hawkstone Park. Around theeastern quarter of the inner rampart, for approxi-mately 100 m, later agricultural use has obliter-ated the medial ditch and greatly reduced theouter rampart and outer ditch. The outer rampartappears to have been pushed into the medialditch, which is today overlain by the course ofthe farm track into the hill fort interior. All thatremains of the outer ditch here is a wide, shallowdepression, 1.1 m deep, which rises 1.3 m to thenortheast at its outer edge.

The topography suggests that in its originalform the outer rampart and outer ditch rancontinuously, parallel to the inner rampart, toend by the main entrance on the steep natural

slopes which fall to the south. In that case, theywould have prevented access from the easyapproach along the higher ground to the northof the hill fort, so the main approach would havebeen from the wetlands to the south and east,climbing up the quite steep terrain of the scarp.Today a terraced pathway does climb from thisarea towards the main hill fort entrance, passingthrough what is a well worked U-shaped cuttingthrough outcropping sandstone. Pick marks inthe sides of the cutting and deep grooves in itsrock floor, the latter probably a result of erosionby heavy wheeled transport, indicate that thepresent form of this cutting may have beenaltered by later landscaping. Indeed, its form isvery similar to garden landscape features visiblein Hawkstone Park. Even so, it may be a rework-ing of an Iron Age approach to the fort.

Another possible Iron Age approach route wasfrom the southwest, because there was a gap inthe ramparts here and related outworks at thiscorner consisted of a platform 30 m long juttingout into the adjacent valley. This presumablyacted as a lookout post. There are further terracesbelow the platform and, at the same level, acauseway seems to have been partly built acrossthe valley. None of these features was investi-gated comprehensively and the area was notincluded in the topographic survey, but thepossibility of an entrance here certainly needsconsideration.

What does seem certain is that the massivemain rampart, possibly stone revetted and sur-mounted by a stone wall, is designed not only asa formidable defence against any possible attackfrom the north, but also as a powerful statementof prestige, power and communal wealth. Thesheer size of the defences here remains impress-ive today, and it seems likely that approachingthe site would have been a very intimidatingexperience for anyone visiting the site, for what-ever purpose, at the height of its power.

Geophysical results

This turned out to be an unusual site in thatresistance mapping showed many more featuresthan the magnetic gradiometry mapping. Theseresults are shown in Figures 6a and 7a withinterpretations in Figures 6b and 7b.



Figure 6. (a) Resistancemapof the interiorof the fort.The lower section shows the resistance drapedover the topography, high-lighting thepositionof the terracing.Thewhite drapesat the edgesare the ramparts, whichhavenot beenassigneda resistance.They are partially shown because they would otherwise have obscured the view into the interior. (b) Interpretation of the resis-tancemap.See text fordetails.



The resistance map divided the interior intotwo parts of unequal size. The larger, northernpart was dominated by a concentric pattern,roughly ovoid in shape, of alternately high andlow resistance. The centre of this pattern lay atthe highest point of the hill and it is clear fromoverlaying the topographic survey with the resis-tance results that these concentric rings coincidewith distinct terraces cut into the outcroppingsandstone bedrock. The purpose of these terraceswill be considered further below. Three terraceswere noted in all: the highest, at the summit ofthe hill was about 30 m wide. The other twoterraces varied in width from 45 m on the westside to 20 m on the east side. It is thought thatthese rings of high and low resistance have beencreated by differential accumulation of topsoilbecause the accumulation will have been greater

within the region of deepest excavation. Here theground appears to have drained more easily,hence giving higher resistance readings. Theseterraces show up in the depth-sounding resistiv-ity as shallow patches of varying depth of higherresistivity (Figure 8a). The depth of the region ofhigh resistivity appears to be in the region of 0.4–1.0 m. These terraces can just be picked out in theseismic refraction profiles (Figure 9), but not wellenough to define the extent of the terracesclearly. It is possible that these terraces are sim-ply a geological signature. The bedrock of UpperMottled Sandstone dips gently towards the northand hence would produce outcrop in a patternsimilar to that shown by the resistance map.However, the scale of the features would implythat the terraces are not entirely natural, but thatthe geology has been exploited to ease the crea-tion of level areas for habitation or other pur-poses.

Cutting across these terraces from east to westis a continuous linear feature of high resistanceinterpreted as a cross dyke. This ran from anatural notch in the east side to a similar butless pronounced notch on the west side, an effectnot dissimilar to the more pronounced notchingcaused by the earlier defences on Maiden Castle,Dorset (Sharples, 1991, figure 33). This featureappeared too in the magnetic maps, although itdoes not extend to the ramparts (Figure 6a). It issuggested that this feature may be the line of anearlier defence that was subsequently slightedwhen the ramparts that remain today were built.A possible entrance in the cross dyke is visibletowards the western edge of the second terrace.This feature is marked in the magnetic map by areverse in polarity and clutter in the data oneither side of the break. The feature appears tobe very shallow, indeed much shallower than theterrace features, showing up as only about 0.5 mdeep in the depth-sounding plots (Figure 8b). Itis possible that the high resistance feature couldactually be a wall. However, there is very littlesoil coverage on top of the hill and any builtfeature would probably have been removed byploughing. The date of the cross dyke is impos-sible to determine without excavation. Its rela-tionship to the terraces would help indetermining if it were a later or younger feature.The fact that it apparently cuts the terraces,

Figure 6. Continued.



rather than the other way round, suggests that itmight relate to later occupation, after the hill fortfell into disuse. If this is the case, then it may becontemporary with the building excavated in the1930s. Unfortunately, this building was notlocated in these surveys. Its position was to thesouth of the cross dyke according to the locationmarked on the contemporary plan of the excava-tion. Possibly the slight remains that existed inthe 1930s have been ploughed out by now.

A further 100 m south, there is a much fainterlinear feature in the resistance map that isroughly parallel with the cross dyke. Where itis not seen in the resistance map, it is visible inthe magnetic map, and hence appears to traversethe whole of the fort. It cuts across the southernend of the lowest terrace at a point where thetransition is made to the generally level southernend of the site. The purpose of this relatively

slight feature is not clear. It is difficult to see it asanother cross dyke but it may have been a lightpalisade or ditch for penning livestock in thenorthern part of the hill fort, away from thepresumed concentration of population withinthe southern end of the fort.

Another feature that is visible in both resis-tance and magnetic maps, but which is not read-ily explicable, is a banana-shaped anomalylocated in the northwest part of the upper ter-race. This shows as both low and high resistancefeatures in the resistance map and as an area ofenhanced magnetic readings on the magneticmap. The narrow parallel linear marks trendingeast–west just to the north of this feature arethe tracks caused by farm machinery enteringthe hill fort. The remaining features in the re-sistance map within the northern part of thefort can all be attributed to glacial activity, with

Figure 7. (a) Magneticmapof the interiorof the fort. This shows the difference in totalmagnetic field between the topandbottomsensor. (b) Interpretationof themagneticmap.



ice-wedge polygons dominating the results inthe western and southeastern parts of this endof the site (Williams, 1973).

The southern part of the hill fort is generallymuch more subdued in terms of features on theboth resistance and magnetic maps, and there arefew clear anomalies that may be attributed tohuman activity. Yet this is almost certainly the

part of the site that was the most densely inhab-ited because it is level and is sheltered from theworst effects of the weather by the ramparts andalso by the terraced northern part of the hill fort.Despite this, traces of houses or other humanevidence are difficult to detect. This may beexplained by the results from the seismic sur-veys, which show that the layer of soil and rubbleis slightly greater here, around 1.5–2 m deep asopposed to 0–1.5 m deep in the regions of higherelevation. Some faint signs of possible roundhouses may be seen in the southwestern tip ofthe area, and further possible structures arevisible on the eastern side of this part of the hillfort (Figure 6a).

Adjacent to these latter features can be seen astrong linear feature in the resistance map thatparallels the line of the rampart, yet lies 10–20 mfrom the present rampart profile. This feature isalmost certainly a road running around the inter-ior of the rampart. It is the same width as thecutting immediately to the south of the main

Figure 8. (a) Resistivity profile across the terraces. (b) Resistivity profile across the crossdyke.

Figure 9. Depth to the refractor as determined by seismic re-fraction profiles shot W^E across the crown of the interior ofthe fort along the sameprofileas the resistivitydepth sounding(Figure 8a).



entrance and would possibly have been linked.Such features are common in Iron Age hillforts, as best demonstrated in the excavations atDanebury, Hants (Cunliffe and Poole, 1991). AtDanebury, the rampart road was lined on bothsides by round houses, pits and other structures,mostly four-post granaries. The feature is visibleonly on the eastern side and fades away in thesouthwest corner, yet it is possible that it runsalong the western side of the fort as well. Here,contact for the resistance probes was extremelypoor, with many voids detected in the under-lying rubble. The rubble is tumble from theramparts that has presumably buried any roadsand other structures. It can be seen clearly as alayer of high resistivity in the depth soundingplots (Figure 8a) and in the seismic data as athickened top layer (Figure 9). Such deposits willmake the slight evidence of roundhouses andfour-post granaries that might be expected verydifficult to detect. An alternative view is that theroad stopped at the suggested southwestern gateand that the hill fort thus had diagonallyopposed entrances, another common feature ofsuch sites.

The geophysical profiles in the outer fieldshowed unequivocally that the outer ditch didnot extend to the cliff edge, but stopped a fewmetres short of it (Murdie et al., 2003). Presum-ably the outer rampart and medial ditch alsoterminated in parallel, allowing access to themain entrance from the more level ground tothe north of the fort.

Discussion

The surveys have demonstrated that the upper(northern) part of the hill fort has been heavilyterraced. The terraces may have been cut quiteearly on because they are apparently crossed by alater dyke. The terracing may have had severalfunctions but two are perhaps more obvious thanothers. It would have created level areas thatmay have been used for habitation, and it wouldhave generated a large volume of rock that couldhave been used to create the massive rampartsthat define the site, especially those to the north.

The construction of these terraces and theramparts implies the mobilization of a workforce

of considerable size and a society with the orga-nizational skills to achieve such ambitiousworks. Both conclusions conflict with the conceptof the Cornovii as a society relatively impover-ished and fragmented in nature. Rather, we arelooking at a sophisticated and organized society,perhaps under the control of a religious or mili-tary elite that was able to mobilize a workforce ofsufficient size to achieve these operations.

The location of the site was presumably chosenfor its relative impregnability—it is defended bysheer cliffs on three sides, with an extensivemarshland, Top Moss, at the foot of the cliffs—but also because it was ideal for human habita-tion. Its domination of the surrounding country-side is all too obvious, despite the trees thatobscure the site in the present landscape,although sadly its relationship to the manyenclosures in the vicinity is not at all clear. Theimportance of the site seems to have lasted intothe Roman period, or at the least to have beenreasserted in the late Roman period, by theprobable construction of a religious buildingwithin the interior. The cross dyke may havebeen an associated feature whose intention wasto delimit a temenos around the structure. Alter-natively, it may have been an earlier, smallerdefence across the narrowest part of the promon-tory that was destroyed at a later date when thefort was enlarged. Enlargement of the fort wouldthen have opened up the main hill in the area forterracing and habitation and provided the mate-rials for the new ramparts.

This survey has shown the usefulness of com-plementary techniques in a geophysical surveyto obtain depth profiles of structures as well asposition. Although the additional techniqueshave not ultimately answered all the questionsposed by the standard resistance and magneticmapping, it has helped define what type offeatures we are looking at. The lack of featuresseen in the magnetic mapping is puzzling: thecross dyke shows up very clearly, so it is surpris-ing that other features do not show up clearlytoo. From the resistance mapping, we know thatthere are features under the grass, so presuma-bly the magnetic susceptibility contrast betweenthese features and the bedrock/soils is not verylarge. It seems certain that some features havebeen lost owing to the ploughing of the site. This



may well have removed signs of a busy habi-tation area as, owing to the shallow topsoilcoverage, foundations to structures and pitsthat did not involve excavation of bedrock alsowould have been very shallow.

Future work is required to test these resultsthrough limited excavation designed to answerspecific questions. These might include investi-gation of the depth and nature of deposits imme-diately behind the rampart to see whetherstructures have been more deeply buried here.Another priority would be to examine the crossdyke and the terraces to see what their relation-ship is and to attempt to determine their absolutedate. Finally, a test excavation of the 1930s build-ing would also be carried out to determinethe date and nature of this structure, if it stillsurvives.

Acknowledgements

The authors are extremely grateful to ArthurFox and his family for allowing us access toBury Walls hill fort. We thank Earthwatch UKfor largely funding the fieldwork, and we aregrateful to the hardworking and interested indi-viduals who took part in the project as Earth-watch volunteers. We would also like to thankthe many students from the universities ofBirmingham and Keele, without whose hardwork this survey would not have been possible.We thank Liverpool University and StaffordshireBorough Council and Staffordshire County Coun-cil for the loan of various items of equipment.

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geophysical surveys of bury walls hill fort, shropshire

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