This paper takes a multimodal approach to analysing embodied interaction and discourses of scientific investigation using an interactive tangible tabletop. It argues that embodied forms of interaction are central to science inquiry. More specifically, the paper examines the role of hand actions in the development of descriptions and explanations of scientific phenomena in tangible digital learning environments. It reports an observational study of primary school students aged 10-11 years conducting scientific investigations via an interactive tangible tabletop. Through the systematic tracking and analysis of hand action in line with phases of scientific inquiry the paper maps, critiques and extends previous research, notably Roth's concept of a "developmental trajectory", to develop a "taxonomy" of hand actions for scientific inquiry in tangible digital learning environments. The paper concludes by presenting an alternative model through which to understand the semiotic role of the hands in scientific inquiry, one in which different hand actions do not follow a simple developmental sequence, but instead fulfil different functions across the inquiry process.