Astronomical Regulator
date: label: date made
content: ca 1790
notes: label: Description
content: This is a precision clock associated with Andrew Ellicott. Ellicott became Surveyor General of the United States in 1792 and completed critical national astronomical surveys—most notably the boundaries for the District of Columbia in 1791-92 and the border between the United States and Spanish Florida in 1800.
label: Description
content: The clock’s original case and seat board for the movement have not survived. The square iron dial is marked “Ellicott/Baltimore.” It was originally painted white, with added painted floral spandrels. It has Roman hour numerals, Arabic minute numerals and separate seconds in Arabic numerals under 12. Andrew Ellicott or his father Joseph Ellicott made the brass time-only, weight-driven movement sometime before about 1790. The younger Ellicott made and attached the gridiron temperature-compensating pendulum, which he described as the first ever made in the United States, in a letter to Thomas Jefferson on 6 March 1803.
label: Description
content: Astronomers and surveyors used precision clocks like this one to observe the time that specific "clock stars" passed overhead. With a transit, a special kind telescope for observing stars, they noted the instant the star passed the local line of longitude.
label: Description
content: Reference: Robert S. Edwards, “Andrew Ellicott’s Field Regulator,” NAWCC <i>Bulletin</i> (October 1990): 419-427.
label: Location
content: Currently not on view
place: label: place made
content: United States
setName: label: See more items in
content: Work and Industry: Mechanisms
label: See more items in
content: Measuring & Mapping
creditLine: label: Credit Line
content: Henry Ellicott Magill
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1986.0189.01
label: catalog number
content: 1986.0189.01
label: accession number
content: 1986.0189
objectType: label: Object Name
content: clock movement in wooden case
physicalDescription: label: Measurements
content: overall: clock: 158.1404 cm x 45.4152 cm x 27.305 cm; 62 1/4 in x 17 7/8 in x 10 3/4 in
label: Measurements
content: winding crank #1: 3 1/2 in x 2 1/2 in x 1/2 in; 8.89 cm x 6.35 cm x 1.27 cm
label: Measurements
content: winding crank #2: 3 1/2 in x 3 1/2 in x 1 1/4 in; 8.89 cm x 8.89 cm x 3.175 cm
label: Measurements
content: movement: 11 in x 13 1/2 in x 6 1/2 in; 27.94 cm x 34.29 cm x 16.51 cm
label: Measurements
content: pendulum bob: 2 in x 7 in; 5.08 cm x 17.78 cm
label: Measurements
content: pendulum rod: 45 1/2 in x 3 3/32 in x 1 in; 115.57 cm x 7.874 cm x 2.54 cm
label: Measurements
content: thumb screw #1: 1 1/2 in x 3/4 in x 1/4 in; 3.81 cm x 1.905 cm x .635 cm
label: Measurements
content: thumb screw #2: 1 19/32 in x 3/4 in x 1/4 in; 4.064 cm x 1.905 cm x .635 cm
label: Measurements
content: weight pulley: 3 in x 1 3/4 in x 1/2 in; 7.62 cm x 4.445 cm x 1.27 cm
label: Measurements
content: ring: 3/32 in x 1 in; .254 cm x 2.54 cm
label: Measurements
content: nail #1: 1 1/2 in x 1/16 in; 3.81 cm x .127 cm
label: Measurements
content: nail #2: 1 13/32 in x 1/16 in; 3.556 cm x .127 cm
label: Measurements
content: hood: 18 1/4 in x 18 in x 10 1/2 in; 46.355 cm x 45.72 cm x 26.67 cm
label: Measurements
content: case: 59 in x 15 in x 9 in; 149.86 cm x 38.1 cm x 22.86 cm