A barograph is a device for measuring atmospheric pressure, which enables mechanically recording the results obtained in the form of a chart called a barogram. The main pressure measurement component in the presented barograph is the so-called aneroid, i.e. a can with a needle attached to it. The lowered pressure inside the can allows it to deform under the influence of the surrounding atmospheric pressure, which results in movement of the needle. The rotating drum of the barograph with paper tape on it, on which a pen is moving, enables recording of data. Modern, miniature electronic barographs store measurements in the device memory instead of mechanically drawing a barogram. The presented instrument was made in the Specjalna Fabryka Instrumentów Geodezyjnych i Rysunkowych Gustawa Gerlacha in Warsaw in the 1930s. The establishment operated from 1816 until World War II and it specialised in the production of surveying instruments such as theodolites, levellers, range finders, steel squares and topographic tables. The company also produced other, small accessories for land surveyors. Instruments from the G. Gerlach factory were considered to be on par in terms of quality with products of the most renowned German manufacturers, such as Zeiss. The company’s strong position was evidenced by international awards and the presence of its branch offices and sales outlets in several cities.

References:
M. Kluza, Polscy wytwórcy instrumentów naukowych w XIX wieku [in:] Polscy twórcy aparatury naukowej, red. A. Strzałkowski, seria Monografie, vol. X, Kraków 2006, pp. 277–285.
G. Gerlach najstarsza polska wytwórnia sprzętu geodezyjnego, prepared by S. Walczak, exhibition catalogue of the Museum of Technology in Warsaw in accordance with the programme prepared by the Main Commission for Museums and Exhibitions of the Polish Surveyors’ Association, Warsaw, October 1973.