Fireclay furnace with two openings resting on an iron tripod. This type of furnace, built in the second half of the eighteenth century, was used for many chemical operations. By placing a crucible over it, one could cast lead, tin, bismuth, and — generally speaking — all substances that did not require high temperatures to melt. Alternatively, by placing a basin or vase on top of it, one could calcinate metals. An identical furnace is described in the third section of Antoine-Laurent Lavoisier's Traité élémentaire de chimie (Paris, 1789).