The author, geologist, and professor of mineralogy Alexius Friedrich Pfaff (1825-1886), describes in this volume the water cycle, the sea, physical and chemical properties, water in the household of nature, humans and water, among other topics. Illustrated with 57 black and white images. Water is a fundamental prerequisite for life: without rain, there is no drinking water supply, no agriculture, no bodies of water with fish for consumption, no rivers for transporting goods, and no economy. Water significantly influences our climate and is the basis for nearly all weather phenomena, primarily due to its high mobility and heat capacity. In the oceans, incoming solar energy is stored. This regionally varying warming leads to different concentrations of dissolved substances due to evaporation, as these do not evaporate (especially salts).