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Psychrometer

Psychrometer

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Description
A psychrometer determines humidity by measuring the cooling effect of evaporation. This example has two mercury in glass thermometers, Each mounted a silvered brass plate, and the whole mounted on a wooden board. The plate holding the wet-bulb thermometer is marked "No. 1868 SIGNAL SERVICE U.S. ARMY" and the plate holding the dry-bulb theremometer is marked "H.J. GREEN, N.Y" and "No. 3070 SIGNAL SERVICE U.S. ARMY."
The Signal Service maintained a national weather service from 1870 until the establishment of the U.S. Weather Bureau in 1891. This instrument was made after 1885 when James Green retired and his nephew, Henry J. Green, went into business on his own; and it was probably made before 1890 when H.J. Green relocated to Brooklyn. The Weather Bureau transferred it to the Smithsonian in 1904.
Ref.: Henry J. Green, Meteorological and Scientific Instruments (Brooklyn, ca. 1890), p. 30.
Location
Currently not on view
Object Name
Psychrometer
date made
1885-1890
ca. 1890
maker
H. J. Green
place made
United States: New York, New York City
Measurements
overall: 2 1/2 in x 6 1/2 in x 12 5/8 in; 6.35 cm x 16.51 cm x 32.0675 cm
overall: 2 1/2 in x 7 in x 13 in; 6.35 cm x 17.78 cm x 33.02 cm
ID Number
PH.230007
catalog number
230007
accession number
42625
Credit Line
U.S. Weather Bureau
See more items in
Medicine and Science: Physical Sciences
Measuring & Mapping
Military
Data Source
National Museum of American History
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