Historical information
A barometer is an instrument used for measuring atmosphere pressure thus determining weather changes.The first apparatus generally accepted as a barometer was that set up in Florence in 1644 by Evangelista Torricelli (1608–1647), a mathematician and physicist. Torricelli filled a glass tube with mercury, sealed it at one end, and inverted it with its open end in a dish of mercury. The level always fell a short way down the tube, then settled at a height of about thirty inches. He concluded correctly that the mercury column was sustained by the weight of the air pressing on the open surface of mercury, and further experiments convinced him that the space above the mercury in the tube was a vacuum. He noted that the level rose and fell with changing temperature, but he was unable to use his apparatus to measure variations in the weight of the atmosphere because he had not foreseen that temperature would affect the level of the mercury.
News of this experiment circulated quickly among European scientists, who hastened to replicate the experiment. Torricelli's conclusions were not universally accepted because some disputed whether the air had weight, while both Aristotle and the Catholic Church denied the possibility of a vacuum. In France, the philosopher René Descartes (1596–1650) seems to have been the first person, probably in 1647, to attach a graduated scale to the tube so that he could record any changes attributable to the weather. At around this time Duke Ferdinand II of Tuscany organized the first short-lived meteorological network among scientists in other Italian cities, gathering observations of pressure, temperature, humidity, wind direction, and state of the sky.
Significance
Theis barometer is an example of a household item from the early 20th century, used to determine the day's weather. The barometer is significant as an aid to human social, material and scientific development.
Physical description
Barometer, round, brass housing inset into carved wooden casing (lacquer mostly worn off). Decorative lettering for weather conditions "Stormy, Rain, Change, Fair, Very Dry". Workings are visible through opening in centre of dial. Indicator needle and another adjustable needle . Hook screwed into back of case.
