A vessel employed in metallurgic operations. In figure it represents an oblong arch or vault, the hinder part of which is closed by a semicircular plane, and the lower part, or floor, is a rectangular plane. It is a little oven, that is placed horizontally in assay and enamelling furnaces, so that its open side corresponds with the door of the fire-place. Under this arched oven, small cupels or crucibles are placed; and the substances contained are thus exposed to intense heat, without contact of fuel, smoke or ashes.