Proc Soc Antiq Scot, 111, 1981, 220-228 Is Mousa a broch? Noel Fojut* ABSTRACT e BrocTh f Mousao h n southeri , n Shetland s lonha ,g been considered typicae formeth f o lr appearance of most brochs. However, its impressive architecture may not be representative of the whole class. Recent field survey makes it possible to demonstrate that Mousa is quite atypical, and to quan- tify this abnormality. As mousa has frequently been cited in attempts to understand both the functions origine th d f thesso an e much studied monuments t followi , s that these finding havy ema s considerable archaeological significance. INTRODUCTION BROCE TH : H CONCEPT specialisee Th d drystone fortlets know brochs na s have bee objecn na mucf to h investigation eved an n more speculation, almost sinc earliese eth t awakenin f antiquariago n zea Scotlandn i l . From time to time summaries of the current state of knowledge have appeared, from the Archaeologia Scotica of 1890 onwards, with notable contributions from Curie (1927), Graham (1947), MacKie (1965, 1971) and, most recently, Hedges and Bell (1980). The long-awaited publi- excavatione catioth f o n t Gurnesa s s broch, Aikerness, Orkney will understande w , , includea majo review ne r whicf wo publishee hth d view summar a f Hedget so bu Bel d e san lar y (Hedges, in preparation). In the recent paper Hedges and Bell note, correctly, that a number of brochs have been excavated in the recent past, and that while most of these still await publication, the information already available from these excavations make t appareni s t that broch studiee sar once more enterin perioga revolutionf do whicn i , h long-held view reconsideree sar lighe th tn di of fresh data. As forerunners of this revision may be cited Caulfield's recent case for the signifi- cance of quern replacement in the chronology of broch evolution (Caulfield 1978) and Barrett's attempt (this volume o re-absort ) e brochth b s inte mainstreath o f e buildinIromo Ag n g types. Hedges and Bell (1980) published dates for the construction phase of a solid-based broch- like structure at Bu, Cairston, Orkney, which plainly show that massive sub-circular dwellings of a similar scale to brochs were being constructed in Orkney by the mid-lst millennium be. With the dates currently available, this gives strong support to Caulfield's advocacy of a northern, rather than a western, origin for the brochs. Although Bu is a site of great significance for many reasons, not least the internal fitments, it is without doubt the dating evidence which will arouse most initial interest, awakening the dormant debate surrounding broch origins and spread. In particular sequence ,th evolutiof eo n propose MacKiy db e apparentls i (1971 ) 8 g fi , y brought into doubt. In this sequence, the broch was seen as evolving from the galleried dun, through the D- shaped semi-brochs of Skye and environs, into a ground-galleried type of broch, which then evolved into the solid-based form when the broch idea spread from the west to the north. The SDD(Ancien* t Monuments), 3-11 Melville Street, Edinburgh. FOJUT: is MOUSA A BROCH? | 221 situatio furthes ni r confuse recene th y dtb wor MacKif ko semi-brochsn eo , whic produces hha d dates consistent wit hypothesis hhi s (MacKie 1980 becomin,s i t 55)I . g clear tha 'answere th t o t ' broch origins is as far as ever, if not further, from a definitive resolution. Hedge Beld san l (1980 mak) commoe 88 , eth n assumption that Mous typicaa s ai l brochy ,b citin dimensions git thoss snormaa a f eo l specimen, while simultaneously warning againse th t dangers of taking either Bu or Mousa as in any way typical. The authors take care to avoid div- ision of brochs into two categories, and indeed, no evidence is presented to show that Bu is repre- sentative of one particular group of structures. To complete this picture, it remains for the present articl demonstrato et e that Mousa ,t representativ alsono s i , groua f e o simila f po r brochss i t bu , in fact sui generis in both detail and dimensions. There may well be a spectrum of brochs ranging examplciten fro e coula loftyu squae b e s just m t B dth squath a a s dbu o no ,f a tt e o t brocho s , Mousa should not be cited as an instance of the taller forms. e samth en I year that Scott advance hypothesie dth wida f o se variet f brocyo h forms, heights and functions (Scott 1947), Graham published an alternative view, in which all brochs were held to have been built to a considerable height (Graham 1947). While Scott's case rested upo notoriousle nth y unreliable measuremen e basith f so f rubblo t e volumes t gaini , s support from the evidence at Midhowe, Orkney, for the erection of an over-heavy superstructure on an inappropriate foundation (Callander & Grant 1934), and from Bu (Hedges & Bell, 1980), Cross- kirk, Caithness (Fairhurst forthcoming) and Howe, Orkney (Bell pers comm) for the apparent adaptatio relativela f no y slight structure increasiny ,b wale gth l thickness mako ,t t suitablei r efo bearing a heavy wall. Graham's argument was based upon the proposition that, because all brochs (albeid ha definitiony b t ) wall foundation massivo to sexplainee b o et defency db e alone, then height of wall was the only explanation. Since this was the case, Graham argued, tall walls must have been built in every case. In the absence of any evidence touching upon the degree of toler- ance allowed for incalculable stresses by the builders, this argument must be suspect, founded as upos iti implicie nth t mode Mousf unconscioulo e th s aa s ideal towards whic broch-builderl hal s strove. MacKie (1971, 40-1 advances )ha dschema developmenf eo t which envisage graduasa l refinemen brocf o t h design allowing progressively taller tower constructede b o st , culminatinn gi structures suc Mousas ha . This startine vieth ws i gpresene pointh r wides fo tt ha study t -i r fo , spread implications, particularly affectin positioe th g f Shetlanno d durin broch-buildine gth g episode. MOUS BROCD AAN H HEIGHTS Three lines of evidence can be pursued in reassessing the status of Mousa: original height, foundation dimensions and minor architectural details. The first of these considerations is least well served by surviving sites. Even allowing for a modest completed height for most brochs, only a handful could be said to stand substantially intact. It is interesting that the tall-standing examples t easilno ye ar explaine laca latef y kdo b r settlement hencd an , e stone-robbing botr fo , h Mousa and Dun Carloway, Lewis, stand close beside later habitations, yet are less disturbed than many brochs in remote glens, which now lie in total ruin. It must be a distinct possibilty that the brochs which stand tallest today were in fact among the best-built, so that their very height and solidity has acted as a deterrent to later destruction. This might be complicated by the fact that a tall broch collapsingn i , , would ten hido dt foundations eit s more effectively tha nmora e modest structure, thus concealing the nature of the resulting mound from identification as a broch. A survey of Shetland recently completed found that the greatest difficulty in measuring dimensions of ruined broch-like structures occurred on sites where stone-robbing had been most extensive, and 222 | PROCEEDINGS OF THE SOCIETY, 1981 that generaln i , largee ,th moun e rth d was easiee identifications ,th rwa . This still leave possie sth - bility of mounds so substantial as to escape being identified as non-natural, but there are few candidate thir sfo s categor Shetlane th n yi d landscape. tallese Th t broch Scotlann si listee dar Tabln di e 1. TABLE 1 Mousa Shetland 13-26 m Telvn Du e Inverness-shire 10-03 m Dun Carloway Lewis 9-15 m Dun Troddan Inverness-shire 7-62 m Dun Dornaigil Sutherland 6-70 m This group of five stands well clear of the next contenders. In the absence of any signs of an upward continuatio staire th t musf i ,n o assumee b t d that Mousa's uppermost surviving level originae th representf o lp structurto e sth e (Paterson 1922) narrowin.A highese th f go t preserved gallerie t botsa h Carlowa Telvd yan e suggests that these, too close ar ,thei o et r original stature. These are, however undeniabll al , y towers Mousd an , a canno singlee b t t mereldou y becauss i t ei the tallest, since one example of any class of monument must always survive best. MOUSA'S DIMENSIONS IN A SHETLAND CONTEXT A recent survey of all known and suspected broch sites in Shetland (Fojut 1980, 160-9) make t possiblsi t Mous contexe pu neighboursth s o et it n a i f o t , since detail grounf so d plae nar availabl site5 7 se classeeth f froo probabls 7 mda 2 e brochs. This represent greatesa r concentration of data from one area than has previously been available. Further, it must be noted that, since ground plans are recorded for about one-third of Scotland's five hundred broch sites, a greater degree of reliance can be placed on conclusions drawn from a comparison of plans than upon those base survivinn do g heigh r architecturao t l details, since these aspect foundee r sar fa n do fewer examples.