J.J. Thomson discovered the electron in 1897 and received the Nobel Prize in 1906 for his research on the electrical conductivity of gases. In this work, which is based on lectures the author gave at the renowned Cavendish Laboratory in Cambridge when he was just 30 years old, he challenges the conventional practice of explaining relationships between physical phenomena using the main principles of thermodynamics. Thomson proposes an alternative model that utilizes the tools of dynamics and investigates what results can be achieved using purely dynamic principles. He addresses various topics and questions from physics and chemistry, including reciprocal relationships between physical forces, evaporation processes, and the general case of chemical equilibrium. This is a reprint of the German translation from 1890.