This volume investigates the circumstances and conditions under which trade/exchange, direct access, and/or mobility best account for material conveyance across varying distances at different times in the past.

This volume is the third in the Advances in Archaeological and Museum Science series sponsored by the Society for Archaeological Sciences (SAS). The purpose of this series is to provide summaries of advances in various topics in ar chaeometry, archaeological science, environmental archaeology, preservation technology, and museum conservation. The SAS exists to encourage interdisciplinary collaboration between archaeologists and colleagues in the natural and physical sciences. SAS mem bers are drawn from many disciplinary fields. However, they all share a common belief that physical science techniques and methods constitute an essential component of contemporary archaeological field and laboratory studies. The series editors wish to thank the reviewers of each of the chapters in this volume for their excellent comments and suggestions. We also wish to thank Chriss jones for her invaluable assistance in the preparation of the texts for submission to the publisher. xi Preface As noted in the introductory chapter, this volume is the second major review of research progress in the study of archaeological obsidian. An earlier book, Advances in Obsidian Glass Studies: Archaeological and Geochemical Perspectives, appeared in 1976. A comparison of the treatment of topics reflected in this earlier work and that contained in this volume not only highlights important advances in the quality and depth of research on archaeological obsidian over more than a quarter of a century but also illustrates more generally some characteristics of developments in the archaeological science field in general.

The last 20 years have witnessed a proliferation of new approaches in archaeolog ical data recovery, analysis, and theory building that incorporate both new forms of information and new methods for investigating them. The growing importance of survey has meant an expansion of the spatial realm of traditional archaeological data recovery and analysis from its traditional focus on specific locations on the landscape-archaeological sites-to the incorporation of data both on-site and off-site from across extensive regions. Evolving survey methods have led to experiments with nonsite and distributional data recovery as well as the critical evaluation of the definition and role of archaeological sites in data recovery and analysis. In both survey and excavation, the geomorphological analysis of land scapes has become increasingly important in the analysis of archaeological ma terials. Ethnoarchaeology-the use of ethnography to sharpen archaeological understanding of cultural and natural formation processes-has concentrated study on the formation processes underlying the content and structure of archae ological deposits. These actualistic studies consider patterns of deposition at the site level and the material results of human organization at the regional scale. Ethnoarchaeological approaches have also affected research in theoretical ways by expanding investigation into the nature and organization of systems of land use per se, thus providing direction for further study of the material results of those systems.

In this unique volume, archaeologists examine the changing economic structure of trade in North America over a period of 6,000 years. Organined by geographical and chronological divisions, each chapter focuses on trade in one of nine regions from the Arachiac through the late prehistoric period. Each contribution explores neighboring areas to llustrate the complexity of North American exchange. By charting the econmic structure of these regions, archaeologists, economic anthropologists, and economic geographers gain greater insight into the dynamics of North American trade and exchange on a continental wide basis.

This volume emphasizes one aspect of scientific method: units of measure and their construction as applied to archaeology. Attributes, artifact classes, locational designations, temporal periods, sampling universes, culture stages, and geographic regions are all examples of constructed units.