Large public barometer designed by Filippo Cecchi in collaboration with Giovanni Antonelli and made by the mechanician Niccolò Masini. In 1860, it was placed in the Loggia dei Lanzi in Piazza della Signoria (Florence) at the request of the Minister of Education, Cosimo Ridolfi. The instrument is of the balance type: it does not record the level of the mercury but its "weight." The barometric tube, fitted with a clutch, hangs from a balance mechanism fitted with a counterweight. The changes in pressure influence the mercury level in the tube; the subsequent variations in weight modify the position of the balance mechanism, which is connected to a pointer. The instrument, flanked by a large metal thermometer (now missing), ceased to operate as a public barometer c. 1930. The lodging for the mechanism was walled up and rediscovered by chance in 1993. The glass dial is a modern replacement. What remains of the original marble dials of the barometer and the thermometer is now displayed along the staircase leading to the second floor of the Istituto e Museo di Storia della Scienza.