Effective hydration temperature of obsidian: a diffusion theory analysis of time-dependent hydration rates

An estimate of effective hydration temperature (EHT) is needed for chronological use of obsidian hydration data. This paper describes a method for calculating EHT by the practicing archaeologist, replacing three techniques that are in general use today: estimates based on mean temperature, numerical integration of models of diurnal and annual temperature variations, and use of temperature cells. The hydration (or diffusion) coefficient of obsidian is a function of temperature and thus is time varying, while the classic quadratic law of hydration is not valid for time-varying diffusion coefficients. This paper presents a mathematical solution to the case of a time-varying hydration coefficient, based on diffusion theory, with a concise definition of EHT. It is shown that the results are not affected by concentration dependence in the diffusion coefficient. A computer program to compute the rigorous solution is described, and data are presented to explore the resulting range of variation. That use of the Lee equation to compute EHT is not appropriate for obsidian hydration studies is evident from the data presented. The effects of paleoclimatic variation are estimated, and an algebraic best fit equation and worksheet are provided as practical aids to the archaeologist.     

New East Manchester: Urban Renaissance or Urban Opportunism?

In this paper we ask how a shrinking city responds when faced with a perforated urban fabric. Drawing on Manchester's response to its perforated eastern flank —and informed by a parallel study of Leipzig—we use the city's current approach to critique urban regeneration policy in England. Urban renaissance holds out the promise of delivering more sustainable—that is more compact, more inclusive and more equitable—cities. However, the Manchester study demonstrated that the attempt to stem population loss from the city is at best fragile, despite a raft of policies now in place to support urban renaissance in England. It is argued here that Manchester like Leipzig is likely to face an ongoing battle to attract residents back from their suburban hinterlands. This is especially true of the family market that we identify as being an important element for long-term sustainable population growth in both cities. We use the case of New East Manchester to consider how discourses linked to urban renaissance—particularly those that link urbanism with greater densities—rule out some of the options available to Leipzig, namely, managing the long-term perforation of the city. We demonstrate that while Manchester is inevitably committed to the urban renaissance agenda, in practice New East Manchester demonstrates a far more pragmatic—but equally unavoidable—approach. This we attribute to the gap between renaissance and regeneration described by Amin et al. (Cities for the Many Not for the Few. Bristol: Policy Press, 2000) who define the former as urbanism for the middle class and the latter as urbanism for the working class. While this opportunistic approach may ultimately succeed in producing development on the ground, it will not address the fundamental, and chronic, problem; the combination of push and pull that sees families relocating to suburban areas. Thus, if existing communities in East Manchester are to have their area buoyed up—or sustained—by incomers, and especially families, with greater levels of social capital and higher incomes urban policy in England will have to be challenged.     

A ‘Small Free Trade Oasis’?: agriculture,tariff policy,and the Danish example in Great Britain and Ireland,c. 1885–1911

During the late 19th and early 20th centuries, Denmark was an important overseas example in the United Kingdom's intertwined debates over free trade and agricultural modernization. Both countries remained open to foreign agricultural imports even as many other European states protected their farmers. But whilst British and Irish agriculture struggled, Denmark became a hugely successful exporter of dairy and pork. This achievement of rural prosperity under a liberal trade regime had obvious relevance to the future of agriculture in Britain, and particularly Ireland. Agricultural reformers in the two islands used the Danish example to show that technical education and co-operative production would allow farmers to profit even under free trade, whilst for British Liberals, ideologically committed to free trade, Denmark demonstrated that imported foodstuffs were actually a prerequisite for a flourishing rural economy. Several prominent Danish free traders personally intervened in the early 20th-century debate over tariff reform to affirm these very points. However, British and Irish protectionists contested the ‘free trade’ character of Denmark's fiscal policy. The article situates the Danish comparison within a broader Anglo-Scandinavian transnationalism, in which the themes of modernity and liberalism reside to the fore.