Lane electrometer on Leyden jar

Simple Lane discharging electrometer fitted to the lid of a Leyden jar to regulate its discharge. The spark gap between the electrode of the electrometer and that of the Leyden jar gives an indication of the quantity of electricity collected in the jar. The instrument was often used in electrical therapies. In such cases, it was also called "bottiglia medica" (medical bottle). Provenance: Lorraine collections.