Eighteenth century river hydraulics used both theory and measurement to address problems of flood safety, navigation and defense related to the rivers. In the late eighteenth century the Dutch overseer of the rivers, Christiaan Brunings, integrated hydraulic theory and meteorological practices, which enabled him to design a unique instrument for measuring river flow. The question is whether the unprecedented detail of measurements fits the putative empirical stance in the eighteenth century. The interactions between theory, instrument, measurement, and other knowledge practices (...) are here assessed using experiences in similar measurement practices. I argue that Brunings had theoretical and embodied understanding of hydrodynamics, as he knew how to design an instrument for flow measurement of sufficient accuracy for his purpose in the sociopolitical context of river management. (shrink)