Daniell Hygrometer
notes: label: Description
content: John Frederic Daniell, a young English natural philosopher, described this type of hygrometer in 1820. It consists of two glass balls, one partially filled with ether and the other covered with muslin, connected by a thin tube from which the air has been evacuated. There is a thermometer in the tube above the ball with the ether, and another on the supporting stand. When a few drops of ether are poured onto the muslin, their evaporation chills the covered ball; that in turn causes the ether vapor inside the instrument to condense, thereby cooling the other ball and causing dew to form on its surface.
label: Description
content: The stand of this example is wood. The interior thermometer has a paper inside the stem that is graduated every degree from +13 to +120. The exterior thermometer is mounted on a white porcelain plate that is marked "Fahrenheit" and graduated every degree from -20 to +122.
label: Description
content: This example came from the United States Military Academy, and may date from the middle years of the nineteenth century.
label: Description
content: Ref: J. F. Daniell, "On a new Hygrometer, which Measures the Force and Weight of Aqueous Vapour in the Atmosphere, and the Corresponding Degree of Evaporation,"<i> Quarterly Journal of Science </i>8 (1820): 298-336.
label: Location
content: Currently not on view
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Military
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content: Thermometers and Hygrometers
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content: Measuring & Mapping
creditLine: label: Credit Line
content: U.S. Military Academy
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.315734
label: catalog number
content: 315734
label: accession number
content: 217544
objectType: label: Object Name
content: Daniell hygrometer
physicalDescription: label: Measurements
content: overall: 9 11/32 in; 23.7236 cm
label: Measurements
content: overall: 10 1/4 in x 7 1/4 in x 5 in; 26.035 cm x 18.415 cm x 12.7 cm