Conservation of marine archaeological objects

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  • Journal of Archaeological Science 1990,17,469%472

    Book Reviews

    Conservation of Marine Archaeological Objects. Edited by Colin Pearson. 1987. 297 pp., 69 figures, 68 plates. London: Butterworths 05.00. ISBNO-408-10668-9.

    UNESCOs long-standing committment to the field of conservation studies and practice, dating from the foundation of the International Centre for the Study of the Preservation and the Resto- ration of Cultural Property (ICCROM) in 1959, has resulted in an outstanding corpus of technical monographs and handbooks. The volume under review is among the most substantial of these, and perhaps the most original too. Thirty years ago marine archaeology was, in the words of an earlier UNESCO publication, a nascent discipline. The 1628 Swedish flagship Vasa, though by then discovered, had yet to break the surface of Stockholm Harbour, while 28 m below the eastern Mediterranean a young classical scholar, George Bass, viewed in awe the remains of a ship which went down in Homers time. Since then the discovery and exploitation of cultural material underwater has burgeoned throughout the world.

    In spite of the sound methodology established by the pioneers-+specially Bass-much of this subsequent work has been inexcusably destructive. Few governments have come to grips with the problems of treasure hunting, while persuasive (and generally misleading) images of sunken riches have clouded public perceptions of the undersea heritage. More insidiously, perhaps, well- intentioned excavators-many of whom are amateurs-have often found themselves overwhelmed by the sheer evidential richness of underwater sites, and the consequent demand on post- excavation resources, especially conservation. Far too little of the work done to date has been brought to a sound conclusion and still less adequately published. Straight archaeologists might therefore be forgiven for regarding the whole business as peripheral, and even slightly disreputable.

    By focussing on the wide range of material which can be preserved in the undersea environment, and addressing the formidable range of problems encountered in conserving it, this book should go some way towards redressing the balance. It is a multi-author work and its editor, Colin Pearson (who is himself a major contributor), has clearly been at pains to select people who are not only distinguished scholars but also have extensive and successful track records in practical conservation. Close collaboration and strong editing are revealed by the way in which the component papers, though differing widely in approach and content, fit together to form a cohesive whole. The fact that six of the eight authors are either Australian or Canadian reflects no imbalance on the contrary, it underlines the sensitive and effective policies towards the undersea heritage which in both these countries has encouraged the development of conservation resources and expertise.

    The first part of the book deals with the physical, chemical, and biological factors which change and sometimes preserve submerged materials. This is followed by two chapters (by Pearson and Leskard) on the problem of extracting such materials and transporting them safely to the labora- tory. The remainder of the book is devoted to a practical review of recipies and techniques appropriate to the various categories of materials and artifacts previously described.

    Florians two introductory chapters discuss the nature of the underwater environment and the deterioration of organic materials other than wood. Conservation techniques appropriate to these materials are considered by Jenssen in Chapter 8. Grattan devotes the third chapter to describing the nature of waterlogged wood before combining (in Chapter 9) with Clarke for a lengthy and compre- hensive review of available treatment methods and their practical implications. In Chapter 4 North and MacLeod consider the chemistry of metal corrosion, which North then develops in conservation terms in Chapter 10. Pearson does the same (in Chapters 5 and 11) for ceramics, glass, and stone. Finally Jenssen and Pearson combine, in a short but useful closing chapter, to summarize long-term environmental considerations for storage and display.

    469 0305-4403/90/040469+04 tO3.00/0 0 1990 Academic Press Limited

  • 470 BOOK REVIEWS

    Much of the content is highly technical, and it is in the nature of such studies that not all of it will find universal acceptance. Nevertheless it is notable that the contributors avoid over-emphasis of those techniques with which they have been most directly associated (often, indeed, which they themselves have developed), and fully describe alternative methods and approaches where these appear to have merit. This book is essential reading for any conservator who has to deal with submerged finds; it should be required reading for anyone contemplating raising such material; and it is recommended reading for archaeologists at large. For the latter it will serve to underline the potential, as well as the pitfalls, represented by the undersea heritage.

    CoIin Martin University of St Andrews

    Tree-Ring Studies of Wood Used in Neolithic and Bronze Age Trackwaysfrom the Somerset Levels. Edited by R. Morgan. 1988. 2 Volumes. 169+249 pp., 156 figures, 51 tables, 8 appendices. B.A.R. British Series 184 (i +ii). Oxford. E24. ISBN 0 86054 526 1.

    This volume constitutes a review of Ruth Morgans work, on wood remains from the Somerset Levels, from 1973 to 1988. It represents a subtle blend of dendrochronology and tree-ring studies.

    To begin with the layout, the volume comes in two parts with the text separated from the tables and figures. Some people will find this tedious to work with as there is constant reference from the text to the numerous figures-I for one have never mastered the art of holding two books open at once.

    The text is divided into seven sections, I-VII, which can be grouped into three broad units. Unit 1 (comprising Sections I and II) is the background which looks at previous work in the general field of dendrochronology. There are chapters on tree-ring studies in Europe and Britain and an introduc- tion to the geology, vegetation and archaeology of the Somerset Levels. Morgan notes the particular importance of the Somerset Levels with its confined geographical area and its uniform archae- ological context which offers the advantage of limiting variables and enabling comparisons and contrasts to be made. As is clear from the conclusions it is essential to limit variables as far as possible.

    The second half of this introductory unit covers general information on wood and woodworking practices. It stresses the importance of sapwood for interpretive purposes. Thereafter there are descriptions of the basic processes relating to dendrochronology and tree-ring studies under the headings sampling, measuring, recording and cross-matching. Incidentally, it is well worth noting the list of questions which have been pursued in this volume on pages 2 and 3 of the introduction, and referring to these when reading the conclusions.

    The results of the various wood analyses fall into two broad units which Morgan identifies as Part A (Section III) and Part B (Sections IV, V and VI). Part A represents the results from the timber tracks-Sweet, Meare Heath and Tinneys Ground. These are tracks where substantial oak timbers were preserved and where a classic dendrochronological approach was possible. The tour-de-force is the study of the timbers from the Neolithic Sweet Track and indeed this is the backbone of the volume. It begins with an analysis of the large number of oak timbers, mostly riven planks, which were used in this important, early, trackway. A tree-ring chronology is produced covering 410 years and various attempts are made to place this chronology precisely in time. Suffice to say that in the 1970s and early 1980s there were no tree-ring chronologies against which to attempt dendrochrono- logical dating, while now, when chronologies exist in both Ireland and Germany, it is still impossible to prove a definitive match. So far the precise date of the Sweet Track is unknown.

    Radiocarbon dating was applied to the same problem and a number of dates were obtained from the Harwell laboratory in the mid-1970s. These dates make interesting reading in themselves with one replicate sample giving ages 860 radiocarbon years apart. Even allowing for the fact that rootlet and insect contamination were noted it is hard to believe that the laboratory gave out such diverse dates. However, the main point is that using six regularly spaced, and replicated, radiocar- bon samples it was thought valid to wiggle match these Sweet dates against the bristlecone pine calibration. This was carried out by Dr R. M. Clark and produced a suggested calendar range for the recent end of the 410 year chronology, of 3685-3415 Cal-nc. Morgan seems not to have taken

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