157_Dimitris_Theodossop

Transcription

The Achievement of Structural Stability in the Drystone
Iron-Age Broch Towers in North Scotland
Dimitris Theodossopoulos
University of Edinburgh, Edinburgh, Great Britain
John Barber, Graeme Cavers, Andy Heald
AOC Archaeology Group, Loanhead, Midlothian, Great Britain
The sophisticated brochs of Northern Scotland
are the most prominent and monumental variant
of what archaeologists call Complex Atlantic
Roundhouses (Harding 2004): domestic structures of complexity both in plan and elevation,
always in drystone masonry, which flourished in
the Scottish Iron Age [roughly fifth century B.C.
to fifth century A.D.]. Structurally, they are characterised by a thick base [galleried in various
degrees] of relatively wide diameters [13-18 m]
that tapers to considerable height [9-13 m], and
the established scheme comes from the sole intact
case [Mousa, Shetland]. The intriguing size and
internal features are evidence of the high technological capacity and culture of the masons or communities, and this will be explored here through
the examination of hypotheses of how stability in
this scale was achieved.
The fabric shows complexity beyond plain,
repeatable construction processes, which combined with a repetition of patterns and key
features (Fig. 1) poses an obvious quest for a
structural scheme that may have been diffused
among masons. Architectural typological studies (MacKie 1975; Martlew 1982; MacKie 2002;
Theodossopoulos at al. 2012) have given spurious
results as they are based on a limited number of
variables or they are highly dependent on the diffusionist pattern chosen (Harding 2004).
It is more meaningful therefore to explore
such a scheme through the construction process that enabled the masons to build on such a
scale, rather than the structural performance of
the finished form. The stonework for example
[masonry bonds or course sizes] is variably related
157_Dimitris_Theodossop_PC_CS5_.indd 1
Fig. 1: The interior of the entrance area in Dun Telve, Glenelg.
to the availability of local material [like flagstone
or metamorphic igneous rocks]. Important elements such as intra-mural cells [often corbelled],
staircases, or enigmatic features like the internal
stacked openings, required skills or at least guidance by someone who could plan the process as
in-situ experience showed (AOC 2011). The use
of scarcement ledges to support internally the
upper timber platforms also indicates efforts in
planning, while classifications using the percentage of the wall base [PWB] or main configura-
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2
Technology / Foundations & Masonry
tions [solid, galleried] and their variations have
shown relation to stability and the presence of
upper floors (Fig. 2).
The relation between such features and structural form is debatable due to the paucity of
remains above the ground floor in the vast majority of surviving brochs, like the emblematic case
studies [Mousa, Dun Telve, Dun Troddan, Dun
Carloway, Gurness]. There are however, modern
scientific archaeological reports from excavations
that arguably reached a floor level that is considered “original” [Dun Mor Vaul, Dun Vulan,
Dun Bharabhat], and which have provided some
information on construction sequences, albeit that
this remains sketchy.
Finally detailed information of the current state
of the fabric and the vectors of degradation, which
may relate to ongoing or new failure processes,
is obtained from condition surveys [Clachtoll,
Caisteal Grugaig]. All this factual material is discussed without making chronological, regional or
stylistic connections. Additionally, direct insight
to the processes has been gained by building models that allowed the construction process (Early
Architecture Project in Spittal, AOC 2011) and
structural performance (Thew et al. 2012) to be
monitored.
These tests showed the substantial strength
of these structures against the main structural
actions [dead load, settlement]. It is however
local damage, starting around the more vulnerable
opening or the wallhead that initiates a process
of failure, exacerbated by degradation or lack of
maintenance. This work proposes to review the
patterns of construction in relation to notional
structural schemes and proportions, using architectural and engineering analysis. The choice of
monuments for discussion here was based on the
Fig. 2: Plans of brochs A) Dun Troddan, Glenelg [solid base and internal post-rings]; B)
Nybster, Caithness (AOC Archaeology); C) Dun Mor Vaul, Tiree [galleries and hearth]
(MacKie 1974); D) Midhowe, Orkney (RCAHMS 1946).
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D Theodossopoulos / Drystone Iron-Age Broch Towers in North Scotland
amount of archaeological information available
[including information on material culture] and
the ability for direct overview and assessment. The
literature has shown the potential contribution
that the field monuments can make to our understanding of brochs and ultimately, this consideration of the methods developed by the masons to
achieve stability is expected to enrich our insight
into their technological culture and achievements.
Geographic and cultural context
More extensive studies have been published
about this context [for example Ballin Smith and
Banks 2002; Armit 2003; Harding 2004] to discuss the distribution of brochs primarily along
the north and west coastlines (Fig. 3) and their
relation with their immediate settings. It is interesting to note that this area corresponds to the
Fig. 3: The location of the major known brochs (V. KondratievPopov, from Theodossopoulos et al. 2012).
3
Atlantic arc of Scotland and Britain and its maritime routes which can link to building traditions
in other parts of Atlantic Europe. Chronologically
however there is no reasoned basis upon which
to establish connections with apparently similar Mediterranean prehistoric towers (Nuraghe,
Talaiots, Girna), because, with the exception
of some of the Nuraghi, they were built in the
Bronze Age or earlier; more than a millennium
before the Scottish Iron Age. There are few studies on the influence of maritime transport routes
of the period (but see Cunliffe 2001 and 2008
or Henderson 2007), but for the size of boats of
the time, procurement and transport of building
materials was unlikely and in any event, the geographic culture of materials was highly local, with
the exception of timber for the island brochs procured on the mainland: sedimentary of fluvial origin and clearly laminated flagstone in areas like
Caithness, Orkney, Shetland, adjacent to igneous
metamorphic areas [gneiss in Lewis] or purely
igneous [Mull and Skye] with intermediate and
mixed areas [Sutherland, Glenelg].
Various hypotheses have been formulated about
their use but their massive character, with only a
single low entrance passage and no other openings, was not solely a consequence of a defensive
purpose but rather the outcome of the quest for
height and monumental stature. With reference
to a technological culture, they are more plausibly considered the product of communal building efforts managed, perhaps trained by itinerant
master masons (MacKie 2002). Further functions
have been proposed, like beacons or warehouses
[storing barley or hosting metal-working activities
for example] of the communities, though these
are likely to be incidental to their primary function as homes. This importance may explain the
care taken with their appearance and the control
on the tapered profile (Figs. 1 and 7), but the
compacted bond in coarse rubble and relatively
smooth finish avoiding sharp edges indicates preparation for human residence especially in the cells
or galleries [see the staircase in Dun Troddan or
the corbelling in Edin’s Hall].
The period of occupation and therefore the
expectations for durability by the masons is difficult to ascertain because of the very few scientific
excavations. In any case, there is no trace of any
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4
interior fittings in timber, apart from few charred
remains indicating the possible end of the broch
by a fire [Dun Bharabhat in Lewis, radial arrangement in Langwell Dun in Sutherland]. The latter offers a chronology of inhabitation (Harding
2002), using dating of timber, material finds and
the stratigraphy of layers of occupation: the primary roundhouse construction and occupation
started around 520 B.C. and consequently the
secondary occupation ended presumably with
the destruction of the broch by fire in ca. 30
A.D. Similar dating for Dun Mor Vaul in Tiree
(MacKie 1974) showed the broch was built 70-40
B.C. and was used until 250 A.D., presumably as
a communal fort initially [with added living space
provided by raised internal timber platforms] and
then in the domestic use of a single family [when
the posts were removed]. It is possible that the
upper part of the broch was dismantled by the
occupants once the upper fabric was not used,
as likely happened at Jarlshof, where blocks from
that area were found carefully piled outside.
The monumental scale and apparent continuity
in the complexity of features above ground level
indicate a degree of planning that goes beyond the
vernacular. When viewed alongside hypotheses of
a similar complexity in circulation and functions,
brochs emerge as architectural structures designed
perhaps to enhance spatially and culturally the life
of their inhabitants and their territory. The possible need for platforms may have preconditioned
certain attributes, such as the overall height and
the form of the staircase, although not specifically others, such as the vertical slots. Apart from
charred timbers, the presence of internal platforms
has been deduced from post-holes and scarcements, the c. 30 cm recess found in many brochs
at around 1.5-2 m above ground level. Brochs built
however on a slope, like Caisteal Grugaig (AOC
2010), challenge the very functionality of platforms
as the doorway for the intramural staircase would
have been blocked by a continuous timber platform. Study of possible circulation arrangements in
a reconstruction project of Architecture students in
Placement (Fig. 4) indicated that by stepping back
the platform in line with probable post locations,
a ladder could expand circulation, limiting the circulating distance between levels (Theodossopoulos
et al. 2012).
Fig. 4: Circulation and cross section in Caisteal Grugaig
(J. Henry and X. Zheng, from Theodossopoulos et al 2012).
Shortage of suitable [straight, strong and durable] timber for roofing and platforms in the
far northwest and north of Scotland is widely
accepted, even at those times when temperatures
may have been slightly higher, although sources of
suitable timber could have been secured, including from driftwood. A level of technical capability in timber has been demonstrated in Iron Age
communities in other domestic structures but
the hypotheses for the roof are uncertain [single
pitch or conoid]. Clearly, the form of the timber
superstructure is determined by the stone building
beneath, but there may be promising avenues of
research that explore brochs as the surviving elements of an even more complex and ambitious
structure, built in stone, timber and other organic
materials that do not survive.
Construction characteristics
There are some fundamental aspects to be investigated in any construction made of local materials, like the degree the buildings integrate with
the environment or whether they are assembled
rather than designed (Clifton-Taylor 1972). The
scale of brochs make the second aspect important
and will be explored initially from bond patterns
26/04/2012 18:15:23
of the drystone masonry and assessment of the
construction process [in this section] towards the
discussion of structural performance and the possibility of “design” or a Kantian structural schema.
Drystone construction is conditioned by the
degree of contact and friction between the stones,
the need to avoid continuous vertical joints and
as a consequence the interlocking of blocks in the
longitudinal and transverse directions. These conditions guide the eye of the builder in the selection and location of stone or the use of tools to
adjust the blocks when the fit is not tight. Using
relatively flat or laminar stone, like Caithness
flagstone [which characterises a big proportion of
brochs] results in a sort of masonry bond (Fig. 5)
or at least this is a scheme to assess the efficiency
of the stonework [see the tight bond in Mousa,
Dun Telve, Keiss]. Squared rubble is the next best
attempt to ensure good interlocking and transfer
of loads between the blocks and this is linked with
a possible better use of stoneworking tools [Dun
Carloway in Lewis, Caisteal Grugaig in Glenelg,
Dun Mor Vaul in Tiree, Dun Vulan in Uist].
The more irregular joints are filled with a variety
of pinnings or smaller blocks in triplets, which
good practice requires to be added during completion of each layer to create a flat base for the next
one. The creation of layers even as horizontal construction breaks, or the extent to which stonework
was dressed can be an indication of technical skill
(Harding 2004) and sophistication in planning.
Fig. 5: Patterns of layering Caithness flagstone in a full-scale
model at a quarry in Spittal (Early Architecture Project, AOC
2011).
5
The availability of stone or the “eye” of the
masons for its selection can creates different building patterns even within the same building. The
well preserved Dun Telve demonstrates an ideal,
regular and tight masonry bond in continuous
layers, even if not of constant thickness (Fig. 6).
Tiles are used regularly throughout with some
areas filled with “triplets” [blocks of three or four
stones for the vertical joints] or wedges [horizontally]. The section shows the effort to arrange the
blocks alternatively as inband/outband, as the
experience in models in Spittal showed to be good
practice (AOC 2011). The bond shows experience, care and above all consistency and control, which is not typical for all brochs. Mousa,
the most complete one, is maybe too robust (Fojut
1981), both in structure [plan, section] and construction: variable flagstones are used everywhere,
with a plethora of sophisticated details and a continuous staircase extending to the wallhead at c.
12m. The fabric is not as compact as Dun Telve,
because of the stone used, and so many pinnings
have been used to fill voids and improve contact,
rather than establish layers.
The type of stone used seems to “dictate” the
masonry patterns, in terms of materiality and also
of construction process. The availability of laminar stone [flagstone] guides the masons to create
layers [Keiss Road or Nybster in Caithness] or
at least to create some regularity even where the
blocks are not very flat [Yarrows in Caithness] or
laminar [Grugaig]. In areas of rocks of volcanic
or metamorphic origin, as in the Western Isles,
the blocks may be dressed square or very large,
Fig. 6: Aspects of stonework in the exterior of Dun Telve [left]
and Clachtoll [right].
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6
and they constitute almost the entire ground level
[Dun Carloway]. In some cases the blocks are
closer to boulders [Dun More Vaul, Clachtoll],
with a case like Dun Dornaigil in the geologically mixed area of Sutherland standing somehow
in between.
The construction is brought to levels every few
courses rather than at each one and occasionally a
larger, square stone is included [Dun Telve]. This
may have also been a sort of construction break,
perhaps between building seasons rather than
days. Building a full-scale model broch (AOC
2011) showed that the construction of a quarter
of the ground floor of a broch [largely replicating
the geometry of Clachtoll] may take five adults
up to four weeks. Stepped construction process
creates ramps that facilitate access during building
so a closer study of the monuments may reveal
evidence that the masons planned their work carefully. Usually this can be identified where joints
step [N side of Dun Telve] or align [Caisteal
Grugaig], but a more detailed study will have
to done, based on practical experience or simulations. In this respect, it is interesting to contrast the Scottish monuments with the Irish Stone
Forts of broadly comparable age, all of which display evidence of systematic building breaks.
Aspects of the global behaviour of the brochs
as were directly appreciated by the builders will
be discussed in the next section, but some effects
of structural performance and stability would
have become immediately apparent during construction. Unbalanced or insufficiently supported
blocks and lintels can partially fail during erection
of the upper sections but the block can quickly
wedge against adjacent blocks, transmitting the
load upon them through an arch effect (AOC
2011). Observation would teach the masons the
importance of tight containment of stones, which
is another aspect that has to be planned for, especially at higher levels in the structure.
Cells constitute a micro-structure in which the
masons can combine learning through experience
with some guidance, especially where such cells
will have to appear in higher levels [see Dun Telve
around the entrance]. Some cells were roofed by
corbelling [Clachtoll], where overlapping of joints
between courses and balance of the back half are
essential (Fig. 5); where the drystone bond is
tighter then the walls can be vertical and the cell
is roofed with long, flat flags [Yarrows]. In most
cases, the wallfaces are smooth, a proxy indicator of human occupation and the angular cut of
the corbelled stones in Edin’s Hall [East Lothian]
shows an advanced understanding of the importance of making spaces habitable.
Finally, the use of deliberately decorative elements that do not affect the fabric, especially triangular plates above the entrance instead of a flat
lintel, a sort of relieving triangle, show that the
masons had some familiarity with the possibilities and expression of the system and were able to
see the less functional and more tectonic aspects.
The plate in Clachtoll for example is quite thin, in
a form that needs to be carefully dressed or even
imported, which is an indication of the importance of such elements for the broch builders.
Structural features and overall scheme
Due to scale, the structural scheme of these
Complex Atlantic Roundhouses goes beyond the
summation of their parts or the extension of the
plain roundhouse in height, a further indication
of a sort of a design. Unfortunately only a few
brochs survive to anywhere near their original
height, but some were repaired or rebuilt, without
record. The poor sample is further undermined by
the paucity of archaeological reports (Curle 1916;
MacKie 1974 and 2002; Harding 2002; Gilmour
& Cook 1998), condition surveys (AOC 2009
and 2010) and even measured surveys.
When assessing the plan, the variety (Fig. 2)
relates to the location of cells or the placement on
the ground, especially at uneven promontories like
Dun Carloway or Grugaig (Fig. 4). Analysis of
the plan of the latter, using laser scan data (AOC
2010), shows a perfect circle which was, curiously,
planned not on the slope but on a virtually horizontal plane. This would have been difficult
to achieve on the ground, unless the structure
were planned from a platform. A study by Euan
MacKie (1975) aimed to show there were principles of circular design or even evidence of a “broch
yard” of 0.839 m., discussing further circularity as
an intuitive scheme to achieve structural stability.
A way to classify the proportions of the combined thickness of the walls to the overall diame-
26/04/2012 18:15:25
ter is by the Percentage of Wall Base [PWB]. The
first interesting observation is that Mousa is way
outside the average PWB, as its proportions are
too robust, a possible reason for its survival (Fojut
1981). Study of the support strategies and ground
conditions shows further advanced construction
skills, especially in the way the natural bedrock
is prepared [Clachtoll] and incorporated into the
structure [Dun Carloway, Caisteal Grugaig]. The
distinction between ground-galleried [mainly
Gurness] and solid-based brochs is not clear-cut
and has some structural significance albeit not a
regional one, though they are more common in
the Northern Isles than elsewhere. The distinction
should not be exaggerated, since preservation can
skew classification, and typological analysis has
limitations in prehistoric environments (Martlew
1982; Harding 2004). Dating problems mentioned earlier, furthermore, make any hypothesis
on development from a prototype based on diffusionist criteria uncertain, at best.
The elevation shows further sophistication in
the resolution of the profile, plan changes, juxtaposition of cells etc, as also in the incorporation of elements with structural impact: staircases,
galleries, tapering at wallhead and disturbance by
internal openings (Fig. 7). Typically, the interior
wall is cylindrical and the exterior one is tapered,
separated with a gallery that thins up almost at
Level 2 [as exemplified in Dun Telve]. In the case
of Mousa however, the profile becomes straight
once again in the top third, apparently to accom-
Fig. 7: Comparison of profiles A) Dun Telve, B) Mousa, C)
Dun Mor Vaul, D) Caisteal Grugaig [drawn at the same scale].
7
modate the staircase which is the only one that
survives up to the wallhead [possibly also at the
less well preserved Dun Carloway]. Tapering is
an essential feature that developed from intuition
and, very probably, from techniques developed in
much earlier chambered cairns to provide stability. Its acceptance as a characteristic of the Iron
Age built environment is manifested in brochs
built with squared rubble where the facing blocks
are tilted or dressed at the angle of the slope [Dun
Carloway, Dun Dornaigil].
It is difficult to maintain the slope constant throughout, as the irregularities in Mousa
demonstrate. All brochs standing beyond ground
floor show a consistent attempt to follow a geometry that visually and intuitively was shared among
communities and masons as good practice, probably in a manner similar to advancements in
Gothic architecture. The use of stoneworking tools
of course it is not an innovation of this period.
However, whilst there is limited evidence of the use
of stone tools, the very quarrying of the stone in
the first instance clearly required a significant tool
kit. The discussion of the case studies, at any scale,
shows how the scale of the enterprise and sophistication of the internal arrangements reflects the
new social structures of the Iron Age: groups working increasingly together on a common project, the
broch [or even living together as the external settlements or the few hill forts show], which becomes a
residence but even a beacon or communal facility.
The examination of brochs as architectural
structures, even at very early stages (Barber 2009;
Theodossopoulos et al. 2012; Romankiewicz 2011)
can bring further insight to the use of buildings
with a solid interior and softer tapered exterior.
The gallery for example can be seen to function as
a modern ventilated cavity that protects the internal leaf against humidity. The environmental conditions [daylight and thermal comfort] have been
assessed by very basic tests on a model of Caisteal
Grugaig (AOC 2010; Theodossopoulos et al.
2012) and highlighted the crucial role of the roof
in controlling natural daylight and the conservation of heat from a central hearth. Further tests of
this nature are planned to explore the hypotheses
formulated by archaeologists.
It is worthwhile focusing on structural performance briefly to explore how far the builders
26/04/2012 18:15:25
8
so other actions like gradual decay due to neglect
or stone-robbing could cause deterioration during their lifetime. Actually, danger from falling
debris from the edge rather than structural collapse may have forced the inhabitants to resize
them once they became unusable at their original
heights [Dun Mor Vaul, Jarlshof ].
Structural stability and construction
culture
Fig. 8: Collapse of a model simulating Gurness due to forced
subsidence (Thew et al. 2012).
understood a structural scheme or what they may
have learnt from partial failures. Stability was
immediately necessary for dead load [resisted by
corbel action, two-point support and friction] and
secondarily for long-term settlement [Dunbeath,
Dun Bharabhat]. Tests on 1/15 scale models replicating Dun Telve and Gurness (Thew et al.
2012) focused on settlement (Fig. 8), which can
also trigger the shear-type failure observed in Dun
Telve or Dun Carloway. Failure occurred as the
frictional strength between the stones was overcome until a discontinuity between parts was
formed, which remained intact with further settlement, reproducing how some brochs may have
collapsed gradually following localised failure.
The split in the ground-galleried model focused
on the axis of rotation (Fig. 8), while in the solidbased model spread in wider area, as the solid base
up to a third of the broch height forces the two
walls above to collaborate and the combined centre
of gravity to stay within the base of the footing for
longer period, distributing the forces more evenly
within the wall. The tests show brochs can withstand large amounts of settlement before collapse,
The discussion of archaeological literature, surveys and experimental analysis structured around
the construction process and structural performance of the field monuments provided evidence
of sophistication in planning and construction.
The surviving brochs examined, at every scale,
show continuity of complexity in the higher
levels, variations in creating layers in drystone
masonry, the importance of tectonics at the elevation, the ability to reach and control a large
scale of construction, etc. Experimental assessment proved a valuable tool to get direct insight
into the masons’ methods in building tight bonds
and controlling building quality throughout.
This architecture, in contrast to later “historic”
achievements, combines effectively technique and
style, is an expression of a group endeavour and
most probably a result of common experiences
between patrons and builders (Ousterhout 1997),
although the latter can be further investigated.
This study has probably provided more questions
than answers about the technological culture and
achievements of the period, about the construction sequences in individual monuments (Dun
Telve and variations in the neighbouring Dun
Troddan, or interpretation of imperfections in
Mousa), and about comparisons of cross sections,
statistical analysis of layers and their horizontality etc. However, it represents a first coherent
attempt to places these matters on the archaeological research agenda and opens a new area of
collaboration between professionals in architectural engineering and in archaeology that holds
the promise of enriching our understanding of
these fascinating structures.
26/04/2012 18:15:25
9
Reference list
AOC Archaeology, 2009. Archaeological appraisal and
conservation proposals for Clachtoll broch, Sutherland.
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Armit, I., 2003. Towers in the North: the brochs of Scotland. Stroud: Tempus.
Ballin Smith, B. and I. Banks, 2002. In the shadow of
the brochs: the Iron Age in Scotland, A celebration of the
work of Dr. Euan MacKie on the Iron Age of Scotland.
Stroud: Tempus.
Barber, J., 2009. Towards an improved understanding of
the engineering of brochs. Broch Special Interest Group.
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Heald, A. and A. Jackson, 2001. Towards a new understanding of Iron Age Caithness. Proc. Soc. Antiquaries
Scotland 131.
Henderson, J.C., 2007 The Atlantic Iron Age. Oxford:
Oxford University Press.
MacKie, E.W., 1974. Dun Mor Vaul: an iron age broch
on Tiree. Glasgow: University of Glasgow Press.
MacKie, E.W., 1975. The brochs of Scotland. Recent
Work in Rural Archaeology. P.J. Fowler (ed.). Bradfordon-Avon: Moonraker Press.
Mackie, E.W., 2002. The Roundhouses, Brochs and
Wheelhouses of Atlantic Scotland C.700BC-AD500
– Architecture and Material Culture Part 1 The Orkney
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Cunliffe, B., 2002 Facing the Ocean. Oxford: Oxford
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Mackie, E.W., 2007. The Roundhouses, Brochs and
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Southern Mainland and The Western Isles. BAR Series
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Cunliffe, B., 2008 Europe Between The Oceans 9000
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Martlew, R., 1982. The typological study of the structures of the Scottish brochs. Proc Soc Antiq Scot, 112.
Curle, A.O., 1916. An account of the ruins of the broch
of Dun Telve, near Glenelg, excavated by HM Office of
Works in 1914. Proc. Soc. Antiquaries Scotland 50 (19151916).
Ousterhout, R., 1999. Master builders of Byzantium.
Princeton: Princeton University Press.
Clifton-Taylor, A., 1972. The pattern of English building. London: Faber and Faber.
Fojut, N., 1981. Is Mousa A Broch? Proc. Soc. Antiquaries of Scotland 111.
Gilmour, S. and M. Cook, 1998. Excavations at Dun
Vulan: a reinterpretation of the reappraised Iron Age. Antiquity 72, 276.
Harding, D.W., 2002. Dun Bharabhat, Cnip : an Iron
Age settlement in west Lewis. Edinburgh: University of
Edinburgh.
Harding, D.W., 2004. The Iron-age in Northern Britain: Celts and Romans, natives and invaders. New York:
Routledge.
RCAHMS, 1946. Twelfth report with an inventory of the
ancient monuments of Orkney and Shetland. Edinburgh.
Romankiewicz, T., 2011. The complex roundhouses of
the Scottish Iron Age. Brit. Archaeological Reports Brit.
Ser. 550. Oxford: Archaeopress.
Thew, I., A. Sutherland and D. Theodossopoulos,
2012. Drystone Technology and Stability in Iron-Age
Brochs. Paper on course of publication at Structures &
Buildings, ICE.
Theodossopoulos, D., J. Henry, X. Zhen, V. KondratievPopov, R. Sedgwick, D. Walker and A. D’Auria, 2012.
Caisteal Grugaig broch study report. Placement Project,
University of Edinburgh.
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157_Dimitris_Theodossop

Transcription

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