- 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.
- 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.
- This example came from the United States Military Academy, and may date from the middle years of the nineteenth century.
- 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," Quarterly Journal of Science 8 (1820): 298-336.
- Currently not on view
- Object Name
- Daniell hygrometer
- overall: 9 11/32 in; 23.7236 cm
- overall: 10 1/4 in x 7 1/4 in x 5 in; 26.035 cm x 18.415 cm x 12.7 cm
- ID Number
- catalog number
- accession number
- Credit Line
- U.S. Military Academy
- See more items in
- Medicine and Science: Physical Sciences
- Measuring & Mapping
- Thermometers and Hygrometers
- Data Source
- National Museum of American History
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