Apparatus invented by Leopoldo Nobili. Consists of a black wooden base with a pillar from which project two brass arms, hinged at the middle. To each arm is secured a brass electrode that, by means of a toothed pinion and rack, can be raised or lowered in the vessel containing the lead acetate solution and the disk for metalochromes. Each electrode terminates in a clamp for the platinum point used to produce the metalochromes. Provenance: Lorraine collections.