The project investigates which epistemological presuppositions are responsible for the different approach towards meteorological phenomena in the work of Descartes and Fromondus. The primary aim is to understand which different meanings could be ascribed to experimental and observational practices in the first half of the seventeenth century. In these analyses we will focus on the following two questions: what is the role of observation and experiment in the generation of new knowledge and how is the status of meteorological phenomena as natural phenomena understood.