SHARABLE INPUTS,PRODUCT VARIETY,AND CITY SIZES*

In this paper, I investigate some of the causes of city formation in spatial economies. A model is proposed in which an intermediate differentiated input shared by more than one industry is the cause of the formation of diversified cities. The desire of both the traded-good and the local-good industries to employ a variety of inputs from the intermediate industry provides the reason for the agglomeration of the three industries. In addition, the paper contains a comparative-statics analysis of the model in an open and a closed-city framework. It is demonstrated that the larger the city, the more variety of intermediate inputs the city can provide and the more specialized it is in the production of the traded-good. Moreover, the model suggests that different industrial structures will result in different city Sizes.     

SOURCES FOR VALLEY-FILL ALLUVIAL SEDIMENTS: BELLA COOLA RIVER BASIN, BRITISH COLUMBIA

Changes in the grain-size distribution and the lithologi-cal I mineralogical properties of sandy-gravel sediments are used to discriminate between sources for the alluvial valley-fill of Bella Coola River, coastal British Columbia. Spatially variable bedrock sources, ranging from highly resistant quartz monzonites to easily weathered basalts, yield sediments that reflect parent rock characteristics. Local increases in the D₉₅ fraction of bulk gravel samples and the D₅₀ fraction of sand samples can be related to inputs from steeper, heavily glaciated tributaries, or those underlain by fractured basalts of the Fraser Plateau. Where there are similarities in the grain-size properties of the source and the sampled deposit, however, grain-size information alone cannot be used to discriminate between sources. The lithology of Bella Coola alluvium shows a close correspondence with the general distribution of rock types in the basin, suggesting proportional contributions from most tributary sources over the long term. However, sand samples from the floodplain have a mostly volcanic affinity, indicating the dominance of sediment derived from headwater tributaries underlain by this rock type. Admixture of plutonic source sediments is evident in lower Bella Coola River adjacent to alluvial fans, heavily glaciated tributary creeks or rock walls comprised mainly of quartz monzonite. Les changements dans la granulometrie et les proprietes lithologiques et mineralogiques des sediments de gravel sablonneux servent d differencier les sources des depéts alluviaux de la Riviere Bella Coola sur la céte de la Colombie-Britannique. La variation spatiale des sources fondamentales donnent des sediments qui refletent les caracteristiques de la roche-mbe variant des quartz rnonzonites très résistants aux basaltes superficiellement altérés par les agents atmospheriques. Les augmentations locales dans la fraction D₉₅ des echantillons de gravel et la fraction D₅₀ des echantillons de sable peuvent être reliees la contribution des tributaires aux pentes plus escarpees et fortement glaciaires ou ceux qui traversent les basaltes fractures du Plateau Fraser. Cependant, quand il y a des similitudes dans la granulometrie de la source et le dépôt-échantillon, l'information granulometrique seule ne peut pas 6tre employee pour differencier les sources. La lithologie des alluvions de Bella Coola montre une correspondance avec la distribution générale des types de roches dans le bassin, suggérant des contributions proportionnelles des sources tributaires a long terme. Cependant, les échantillons de sable des plaines sujettes à inondations ont en grande part une affinité volcanique, indiquant que la dominance du sédiment provient des tributaires qui traversent ce type de roche. Une addition de sediments de sources plutonique est evidente dans le bas de la Riviere Bella Coola adjacent aux eventails alluviaux, aux ruisseaux tributaires affect& par une forte glaciation, ou aux murs de roches qui comprennent principalement des quartz monzonites.