Signedabel on base (ivory?): J.J. HICKS / LONDON ENG
Inscribedon paper graph: Stormograph
FunctionBarographs such as this use the partially evacuated metal capsule of aneroid barometers, which are very sensitive to pressure changes, and contract or expand in accordance with outside air pressure. Because the movement of a single aneroid capsule is extremely small, often there are many stacked in series to amplify the change. In this case, there are seven. These capsules are linked by a series of gears or levers to a metal arm with a scribe or pen tip so that the vertical position of the pen corresponds with the atmospheric pressure as read by the capsules. The pen then draws a continuous record of atmospheric pressure onto a chart of paper or smoked foil, mounted on to a drum which is rotated by internal clockwork. This instrument provides one week's wort of recordings per revolution of the drum.
Because atmospheric pressure also corresponds to changes in altitude, barographs can also be used to track elevation.
ProvenanceUsed by the A.T. Kinney Steamshop Co. Given to the Collection by a relative of Albert T. Kinney in 1982.