gems, tourmaline, electricity, piezoelectricity, Ceylon, Sri Lanka

Account of the electrical properties of a gemstone from Ceylon, describing the ability of the stone to acquire electrical attraction when heated and to attract light objects such as ashes and small pieces of paper. The article discusses experiments made with specimens of the stone and compares its behavior with the electrical effects produced by rubbing glass and other substances. Particular attention is given to the unusual circumstance that heat, rather than friction, produces the effect, and to observations on how the electrical attraction varies as the stone is heated and allowed to cool. The paper places the Ceylon stone within the developing eighteenth-century study of electricity and considers contemporary attempts to explain such phenomena. The mineral described is the stone that became known in Europe as the tourmaline, whose pyroelectric behavior attracted considerable scientific attention during this period.