Contention about who discovered the compound nature of water (the 'water controversy') occurred in two phases. During the first phase, in the 1780s, the claimants to the discovery (Antoine Lavoisier, Henry Cavendish, and James Watt) produced the work on which their claims were based. This phase of controversy was relatively short and did not generate much heat, although it was part of the larger debates surrounding the 'chemical revolution'. The second phase of controversy, in the 1830s and 1840s, saw heated (...) exchanges in Britain between advocates of Watt on the one hand and of Cavendish on the other. This paper concentrates on this second phase. The concern is not to arbitrate the contest but to delineate the pattern of advocacy and the arguments used to support the opposing cases. 'Discovery' is not treated as an event but as the outcome of an after-the-fact process of attribution of credit. Apart from identifying the opposing argumentative strategies employed in making different attributions, the paper also seeks to explain why there was so much concern about this priority dispute long after the deaths of the protagonists. It is shown that while Scottish-English rivalries were important they were not the only or most significant impetus. Ideological struggles over the nature of science provided a context in which the attribution of discovery to Cavendish or to Watt was of major import. These ideological struggles are shown to have roots in the politics of early Victorian science that ultimately lay behind the second phase of the water controversy and shaped the course that it took. (shrink)