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Prediction plays an essential part in the building of models of geographical systems: it exposes weaknesses in our concepts, checks our credibility and encourages model reformulation. Despite this centrality, the notion of system predictability and the way it fits into model building is often weakly developed in the geographical literature. The nature of predictions is illustrated here by the attempts to build geographical models of the spread of epidemic waves. Three types of spatial models are explored and illustrated: (i) descriptive models of a spread process, (ii) predictive models of the future extent of spread and (iii) interdictive models which show how spread may be curtailed. From this review, the wider role of prediction and predictability in other areas of geographical model-building is explored.

Carl Sauer's Bowman Lectures to the American Geographical Society were given forty years ago. Although Sauer remains a major and much cited figure in geography today most of the attention is focused on his historical and environmental writing. This paper looks at the legacy of the Bowman Lectures through the two editions of Agricultural origins and dispersals2 and relates them to a different contemporary problem of origin and dispersal. The emergence of new epidemic diseases in the last two decades raises afresh the question of where and when diseases originate and how they then spread around the world. As for agriculture, the origins of most diseases lies too far in the past to be resolved, while spread can be accurately tracked only over recent centuries. It is argued that Sauer's approach to his problem contains lessons that can be drawn upon in today's approaches to disease origins.

Seven alternative models of an epidemic diffusion model are compared using a binary autocorrelation statistic. The study area consisted of 28 local areas within an English county reporting measles ...

The older part of the coffee belt of south-eastern Brazil provides a classic case of a land use cycle: from primary forest, through crop and pasture, to secondary forest. Coffee {Coffea arabica L.) was, at the beginning of the nineteenth century, confined to the coastal lowland around Rio de Janeiro, the Baixada Fluminense, but by 1850 it had crossed the Serra do Mar and had become well established in the foothills flanking the Paraiba river. Sergio Milliet (1939) has mapped the 20-mile wide swath of forest felling and burning through which the coffee frontier advanced for some 200 miles along the Paraiba to within a short distance of the city of Sao Paulo. Within another generation the coffee frontier had moved north-west to Campinas and Ribeirao Preto and with astonishing rapidity the plantation tract along the Paraiba collapsed: the coffee groves {cafesals) were abandoned to weeds and cattle, and the plantation houses {casas grandes) and slave quarters {senzalas) to decay and encroaching forest. This dramatic collapse of a social and economic system has caught the imagination of Brazilian novelists like Monteiro Lobato (1943), and such historians as Taunay (1939-45), Milliet (1939) and Simonsen (1940) have woven a web of theory and counter-theory over the complex causes of failure. Stein (1951, 1953, 1957) has summarized these views and brilliantly documented the rise and fall of the plantation for one Paraiba county, Vassouras. Land use cycles have, however, less spectacular but no less interesting effects on the physical landscape. In a paper titled 'Land use and sediment yield' given at the 1956 Wenner-Gren symposium on Man's role in changing the face of the earth, Dr. L. P. Leopold indicated the linking of land use regimes with sedimentation cycles in the western part of the United States (Leopold, 1956). For the coffee cycle in the Serra do Mar foothills there is enough contemporary evidence to suggest that an investigation of this topic in a tropical area might reveal similar linkage. On crossing the Paraiba river near Entre Rios in June 1867, Richard Burton observed that

There are few sins in which geographers indulge with more relish than generalizing our field fi dings at a local level over the whole of an adjacent re ion. The writer was made keenly aware of this commission in returning in 1962 to travel more widely over the south-eastern part of Brazil. Speculations on the persistence of forested zones based on localized field-work in the Taubati area (Haggett, 1961) were only partly sustained when the survey was extended, via sampling methods over an adjacent area some hundreds of times larger. In this paper the results of a localized study based on a small 100-square-kilometrearea are reported alongside those of a wider regional study. It is shown that not only is the distribution different at the two levels but that the appropriate pattern of study changes in sympathy. Data available at one level are unobtainable at another, levels of measurement possible at one level are too fine at another, and statistical tests appro? priate at one level are inapplicable at another.

Since 1951 Cambridge University has used Madingley Hall for summer residential courses to bring teachers into contact with the newest ideas in the various professional fields. In 1963 RichardJ. Chorley and Peter Haggett, both then lecturers in geography at Cambridge, were the directors of a course for geography teachers in training colleges, grammar schools, and similar institutions. In this book the seventeen lectures given by fifteen British geographers are published, and the whole symposium is summarized in a "retrospect" by the editors. Chorley and Haggett were careful to avoid laying down a "party line" to by followed by the lecturers, or to do any editing that would give a false sense of unity to the published chapters. The differences and contradictions characteristic of a rapidly changing field of study are presented just as they were expressed. If the teachers in the audience were anything like teachers elsewhere they were probably somewhat bewildered and frustrated by the lack of a unified point of view. Scholars the world over take a certain pride in the special quality of their own insights which must, therefore, be expressed somewhat differently from those of other scholars. But the teachers who come to seek guidance find that in the end each must make his own decision between the regional and topical approach, between insisting on field study or depending on some one else's field observations, between approaching geography as a descriptive art or as a rigorous science-or even between teaching any kind of geography or no geography at all. As in similar books produced in other countries, there are contradictions and differences here, some fundamental and some arising from a failure to agree on word meanings. The book is divided into three parts. The seven chapters in Part 1 deal with the changing philosophy of geography, and the new concepts in geomorphology and climatology, in population, social, economic, and historical geography. The six chapters in Part 2 deal with techniques, including quantitative techniques and field methods. The four chapters in Part 3 deal with teaching, in the older universities and the newer universities, in training colleges and technical colleges, and in the schools. The final chapter, by Haggett and Chorley, suggests the elements of unity that can be found in the symposium, offers a forward look at the possibility of greater use of theoretical models in the teaching of geography, and outlines the problem of the lag between the newer ideas of the scholars and the outmoded content of many geography courses. The editors identify seven major themes, each of which is touched on in several of the chapters. The first is the regional theme. E. A. Wrigley disposes of regional geography by defining it as the description of local associations of people and place, as exemplified by the work of Vidal de la Blache and the French regional school. The industrial revolution, says Wrigley, makes the examination of the local interconnections of a rural society with its habitat irrelevant, for now the regional differences are related to the varying accessibility of places to major markets. According to this definition the functional region is not a region, nor can the varying patterns of accessibility be measured regionally-which is a kind of verbal subtlety that might not come through clearly to the ordinary teacher. On the other hand, D. Timms says that "the recognition of valid regions is the basis of geographical research," and Haggett provides a challenging discussion of the importance of scale, or 443

ALTHOUGH GEOGRAPHERS are traditionally concerned with the description, analysis and explanation of areal distributions of phenomena, much of the most vigorous development of new techniques in this field has come from outside geography. The harnessing of the vast potential of computer systems to mapping problems has been pressed forward both in subjects like meteorology where mechanical graph-plotters, line printers, and cathode-ray tube displays are being used to map directly the output of digital computers (Sawyer, 1960; Wippermann, 1959), and in botany where field information on the occurrence of vascular plants are being rapidly processed and printed out (for example, the 1,623 maps of the Atlas of the British Flora (Perring and Walters, 1962)). The most striking adaptations of computer technology to traditional mapping problems are being employed in the earth sciences, however: for example, in geophysical prospecting, structural mapping and sedimentary petrology (Krumbein, 1958). Here the most fundamental developments in mapping techniques lie less in the automation of traditional techniques (a field reviewed for geographers by Tobler (1959)) but in the evolution of new ways of extracting more information from map data. This paper reviews developments in one of the most promising of these techniques, trend-surface mapping, and attempts to assess its significance for, and applications in, the wider field of geographical research.

(1967). Locational Analysis in Human Geography. Economic Geography: Vol. 43, No. 3, pp. 276-277.