This double barometer is mounted on a wooden and brass support. It consists of two connected tubes, one ending in a bulb, the other fitted with an ivory gudgeon pin. Both tubes are inserted into a single iron container. A tap allows communication between the tubes; the height of the mercury in the tubes is regulated by two screw knobs that compress leather membranes. The barometric scales, divided into Paris inches, are fitted with sliding verniers. The instrument was probably used for laboratory experiments. Its invention is attributed to Felice Fontana.