Signedpainted on case: J. RICHARD 2(?)5 R. MELINGUE PARIS
Inscribedpainted on case: STATOSCOPE;
beneath rectangular window on case, scratched and worn, end reads: TUBE NI LE LAISSER FERMÉ;
above rectangular window on case, scratch and worn, end reads: SPENDU;
in retangular window on instrument: Descente Montée / No. 41
FunctionStatoscopes are used to ascertain small changes in atmospheric pressure, or small changes in the altitude of an aircraft. This one was used for the latter purpose on a balloon.
Similar to a basic aneroid barometer, this instrument uses a relatively large partially evacuated metal chamber, which is sensitive to small changes in atmospheric pressure. The minute contractions and expansions of the chamber are amplified by internal clockwork, and reflected on the dial. Falling atmospheric pressure translates to an ascending condition, while increasing atmospheric pressure translates to a descending condition. This chamber is placed inside a closed box, and can be exposed to the atmosphere via the small metal tap that protrudes from the leather case.