By M. Pirani (Berlin) The significant advantages of electric heating were recognized early on, prompting inventors and designers from all nations to tirelessly work on the development of electrothermal methods. Consequently, the evolution of electrothermy has progressed at an astonishing pace. This is best illustrated by the following data: In 1849, Despret, during his experiments on the production of artificial diamonds, examined the behavior of a small retort made from sugar charcoal, measuring 15 mm in diameter, at the temperature of an electric arc, which he allowed to jump to a pointed carbon rod inside this retort. The retort itself served as the positive pole. The sugar charcoal had transformed into graphite at the areas most exposed to the arc. This graphite had taken on droplet-like shapes, leading Despret to...