A barograph's a recording aneroid barometer. It produces a paper or foil chart called a barogram that records the barometric pressure over time. Barographs use one or more aneroid cells acting through a gear or lever train to drive a recording arm that's at its extreme end either a scribe or a pen. A scribe records on smoked foil while a pen records on paper using ink, held in a knib. The recording material's mounted on a cylindrical drum which's rotated slowly by clockwork. Commonly, the drum… (More on Barograph)