P. Drude's paper discusses the electron theory of metals, emphasizing that the electrical conductivity of metals is similar to that of electrolytes, where electrical current is carried by the transport of smaller charged particles. He introduces the concept of "elektronen" (electrons) or "elektrische kerne" (electric cores) to describe these particles, avoiding the terms "corpuskeln" or "ionen" to avoid the implication of ponderable mass. Drude argues that electrons do not necessarily have a significant ponderable mass, but they do have kinetic energy and inertia, which can be observed in phenomena like the deflection of cathode rays and the optical properties of metals. Drude's theory aims to explain the differences between metals and electrolytes, such as the lack of mass transport in metals and the absence of changes in metals when subjected to electric current. He proposes that electrons in metals lose their charge to adjacent mass particles after traveling a short distance, but this idea is not easily explained and leads to complications. Instead, he suggests that all metals contain free electrons of two types (positive and negative) with different charges but no ponderable mass. The theory is further developed to explain various physical properties of metals, including thermal and electrical conductivity, the Thomson effect, contact potential differences, and galvanomagnetic properties. Drude derives quantitative relationships, such as the Wiedemann-Franz law, which relates the thermal and electrical conductivities of metals. He also discusses the Thomson effect, where an electric current flowing through a metal in a temperature gradient generates a thermoelectric voltage. Drude's theory is compared with Riecke's earlier work, showing some agreements and differences. He emphasizes the importance of precise numerical calculations and the need to refine the theory to better explain the optical properties of metals. The paper concludes with a discussion on the contact potential difference between two metals and the conditions under which it occurs.P. Drude's paper discusses the electron theory of metals, emphasizing that the electrical conductivity of metals is similar to that of electrolytes, where electrical current is carried by the transport of smaller charged particles. He introduces the concept of "elektronen" (electrons) or "elektrische kerne" (electric cores) to describe these particles, avoiding the terms "corpuskeln" or "ionen" to avoid the implication of ponderable mass. Drude argues that electrons do not necessarily have a significant ponderable mass, but they do have kinetic energy and inertia, which can be observed in phenomena like the deflection of cathode rays and the optical properties of metals. Drude's theory aims to explain the differences between metals and electrolytes, such as the lack of mass transport in metals and the absence of changes in metals when subjected to electric current. He proposes that electrons in metals lose their charge to adjacent mass particles after traveling a short distance, but this idea is not easily explained and leads to complications. Instead, he suggests that all metals contain free electrons of two types (positive and negative) with different charges but no ponderable mass. The theory is further developed to explain various physical properties of metals, including thermal and electrical conductivity, the Thomson effect, contact potential differences, and galvanomagnetic properties. Drude derives quantitative relationships, such as the Wiedemann-Franz law, which relates the thermal and electrical conductivities of metals. He also discusses the Thomson effect, where an electric current flowing through a metal in a temperature gradient generates a thermoelectric voltage. Drude's theory is compared with Riecke's earlier work, showing some agreements and differences. He emphasizes the importance of precise numerical calculations and the need to refine the theory to better explain the optical properties of metals. The paper concludes with a discussion on the contact potential difference between two metals and the conditions under which it occurs.