This chapter examines the substance of William Vernon Harcourt's Address' and David Brewster's writings and conversion, placing them in the context of the British Association's early years and the 'boundary work' engaged in by its leaders. Brewster's struggles with the Cambridge elite in particular intersected substantially with the water controversy and profoundly shaped his, and their, stance within it. Brewster case is instructive not only because he changed sides in the water controversy but also because, unlike the 'foundation' members of the James Watt camp, he also fought explicitly, over the larger symbols of science. The British Association became a key forum in which the 'Gentlemen of Science' worked out their role within the burgeoning scientific enterprise in Britain. Harcourt argued that because of Henry Cavendish's 'training in the rules of demonstration' and his superior clarity of thought, to him 'hypothetical thoughts and expressions were no stumbling block'.