ABSTRACT
This chapter concentrates on a very special type of diffusion, that of an idea or concept through the academic landscape. Urban models of the distribution of cities by Christaller and of internal patterns of cities by Burgess, by Hoyt, and by Harris and Ullman have played roles in urban geography. Edward L. Ullman pursued the study of amenities as a factor in regional growth of transportation and of spatial interaction. Many of the reproductions of the urban models cite the original publication, but many have been taken from later intermediate sources, as revealed by various markers such as the form or year of the citation provided or the diagram submitted in the request for permission to reproduce. Collections in urban sociology also played major roles in diffusion of the models. Linguistic boundaries apparently were bridged more easily in geography than in sociology. The paths of diffusion sometimes occurred through several stages, though these may be difficult to trace with certainty.
