Alluard Hygrometer
name: label: maker
content: W. M. Welch Scientific Company
notes: label: Description
content: Emile Alluard, professor of physics at the University of Clermont-Ferand and director of the meteorological observatory on the nearby Puy-de-Dôme, described this type of hygrometer in 1878. A modification of Regnault's instrument, it consists of a square vessel made of polished nickel-plated brass. At either side of the vessel, but not touching it, are strips of similar material. In use, the vessel would be filled with ether, and this ether would be cooled by evaporation by means of an aspirating bulb. When dew appears on the shiny surface of the vessel, a thermometer in the vessel indicates the temperature of the ether at that point. A second thermometer measures the ambient temperature.
label: Description
content: Robert A. Millikan described the Alluard hygrometer as being one of the "most perfect forms of the dew-point hygrometer" in his <i>Mechanics, Molecular Physics and Heat</i>, a popular college text that was first published in 1903 and that aimed "to present Physics as a science of exact measurement." This example is marked "A Sign of Quality WELCH A Mark of Service / W. M. Welch Scientific Company / ESTABLISHED 1880 / 1515 SEDGWICK ST. CHICAGO, U.S.A." It was made between 1921 (when the W. M. Welch Scientific Company began as such) and 1960 (when it became Welch Scientific). It is missing the aspirating bulb and both thermometers.
label: Description
content: Ref: M. Allouard, "Nouvel Hygromètre a Condensation,"<i> Journal de Physique et le Radium</i> 7 (1878): 328-330.
label: Description
content: W. M. Welch Scientific Co., <i>Catalog G</i> (Chicago, 1935), p. 157.
label: Location
content: Currently not on view
place: label: place made
content: United States: Illinois, Chicago
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Thermometers and Hygrometers
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content: Measuring & Mapping
creditLine: label: Credit Line
content: U.S. Weather Bureau
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.334152
label: catalog number
content: 334152
label: accession number
content: 308253
objectType: label: Object Name
content: Alluard hygrometer
label: Object Name
content: hygrometer
label: Object Name
content: alluard hygrometer
physicalDescription: label: Measurements
content: overall: 9 in x 4 1/2 in; 22.86 cm x 11.43 cm