Room X tells the story of the different types of instruments devised to measure and study the phenomena relating to atmospheric changes: barometers, hygrometers, thermometers, anemometers, and pluviometers. The barometer collection includes instruments for domestic use (such as the large gilt dial barometers) and research models. Noteworthy among the latter are (1) the barometer invented by Felice Fontana, one of the first instruments capable of periodically registering pressure variations, and (2) the mechanism of the Florence's first public meteorological instrument, made by Filippo Cecchi. Of special interest, too, are the hygrometers produced by Vincenzo Viviani and Francesco Folli, as well as some rare eighteenth-century thermometers of English manufacture, miraculously intact despite their fragile design.