Urban and environmental historians are becoming increasingly interested in the social construction of expertise in the management and control of natural resources. Experts are often depicted as disinterested, neutral and objective professionals, sufficiently qualified to gauge an independent perspective on a given problem. Yet what happens when an expert's judgment is called into question by other professional experts? The micro-analysis of socio-technological disasters offers one way to interrogate the construction and challenge of professional expertise at both the empirical and conceptual levels. Taking a comparative approach towards the study of two major reservoir failures involving considerable death and destruction in the United Kingdom - Holmfirth in 1852 and Sheffield in 1864 - this paper draws on the under-utilised research of the sociologist Barry Turner and others on the social aetiology of disasters as a route into revealing and accounting for the contested nature of expertise within the Victorian engineering professions. It is based on extensive archival research, including the written records of local and central government, private waterworks' proprietors, the printed press and the records of public inquiry. The cases reveal remarkable continuities in administrative and professional knowledge regarding the explanation of socio-technological disasters, as well as the widespread use of outside experts to interrogate the supposed failings of interested parties
