Reflecting Circle
date: label: date made
content: ca 1845
name: label: maker
content: W. & S. Jones
notes: label: Description
content: This reflecting circle belonged to Georgetown University in Washington, D.C. and may have been purchased when Georgetown built an astronomical observatory in the early 1840s. It is of the "English" form designed by Edward Troughton in 1796. Here the telescope, mirror, and filters are on one side of the circle, while the silver scale is on the other side. This scale is graduated to 20 minutes, and read by three verniers (one has a micrometer screw) to 20 seconds. The circle is supported on a heavy brass stand with a counterweight. The inscription reads "W. & S. Jones, 30 Holborn, London."
label: Description
content: Ref: Abraham Rees, <i>The Cyclopaedia; or, Universal Dictionary of Arts, Sciences, and Literature</i> (London, 1819), vol. 8, art. "Circle," and Plate III of "Astronomical Instruments."
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, London
setName: label: See more items in
content: Medicine and Science: Physical Sciences
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content: Navigation
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content: Measuring & Mapping
creditLine: label: Credit Line
content: Georgetown University
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: PH.328403
label: catalog number
content: 328403
label: accession number
content: 272470
objectType: label: Object Name
content: reflecting circle
physicalDescription: label: Measurements
content: overall: 10 1/2 in; 26.67 cm
label: Measurements
content: overall; stand: 14 3/4 in x 9 1/2 in x 8 1/2 in; 37.465 cm x 24.13 cm x 21.59 cm
label: Measurements
content: overall; reflecting circle: 10 1/2 in x 11 3/4 in x 12 1/2 in; 26.67 cm x 29.845 cm x 31.75 cm