The Urban Hierarchy: An Air Passenger Definition

S geographers in recent years L/\X have turned their attention A7XX.. toward the organizational as well as the formal aspects of spatial phenomena, they have shown an increased interest in the linkages between cities. I n particular, the idea of a hierarchy of urban centers has received considerable attention since its early theoretical formulation by Christaller. One might tentatively separate the approaches to this idea into two categories. In one, the actual linkages between cities are examined. In the other, the sizes and economic activities of cities are categorized or examined for evidence of discreteness of level. The bus hinterland studies of F. H. W. Green and Sven Godlund emphasize the manner in which the actual pattern of linkages reflects the hierarchical structure of English and Swedish cities.' In the work of Brush, Smailes, Philbrick, and others, categories are established for size and economic activities, and the distribution of these is examined for particular areas.2 Berry and Garrison subjected the idea of discreteness of level within both a size and functional hierarchy in Snohomish County, Washington, to rigorous statistical proof.3 Charles J. Stewart, Jr., and others suggested the importance of scale of observation in any attempt to ascertain the discrete or continuous nature of the distribution of city size and functions.4 The apparently continuous nature of these distributions (rank-size rule, etc.) for larger areas might be due to a fitting together of a number of more-hierarchical distributions for small areas. In a number of the above studies, both the actual