(y-axis) is plotted against a measure of connectivity, the Beta (B) index (x-axis); as connectivity increases, so does the Beta index. Highly developed countries like France have large connectivity indices for their railway system, while underdeveloped countries like Nigeria have low connectivity indices. In the second graph (Figure 3.19B) another measure of development, gross national product per caput (y-axis), is plotted against a measure ofnetwork shape, the T index (x-axis). Again, France with its high shape values (approximating to a circle) stands in sharp contrast to Nigeria with its elongated system. In both graphs there is a consistent relationship which is statistically significant and strongly suggests that the geometry of some route networks may be very closely allied to the general development of regional resources. Should this be so, we must slightly modify Cooley views the importance of purely on political factors: we suggest that while such factors may have a dramatic eff on individual routes, the major pattern suggests the importance of more purely economic considerations. Network analysis using graph theory has also proved useful for the analysis of the position of particular places on a route system. Using one measure of accessibility, Garrison (1960, 131-5) was able to analyse the relative pp. of 45 in the southeastern part of the United States which places accessibility were linked together by the Interstate Highway System (Figure 3.20A). The places were defined partly on urban size criteria and partly on their topological position (e.g. at the end of Atlanta turned out to be a route). the most accessible point on the network, and may be compared with St Petersburg 0, which is the least accessible of places. Part of the reason among for this contrast lies in the fact that graph theory concentrates on the property of the network, its connectivity, rather than on its dimensions. Kansky (1963) has reminded us that, from the topological point of view, the railways of Sardinia do not look like Figure 3.20B, but more like Figure 3.20c. The advantages that this more abstract model confers from the viewpoint of analysis must, of course, be weighed against the loss of other significant detail