Bubble Sextant
date: label: date made
content: ca 1918
name: label: maker
content: Sewill
notes: label: Description
content: Marine sextant with a bubble level on the frame, and "Sewill. Maker to the Royal Navy. Liverpool" and "Hezzanith/___?__ Tangent Screw / Static Clamp / No. 17840" inscriptions.
label: Description
content: This was used by the Royal Air Force, probably during World War I, examined at the Hezzanith Observatory in London in 1919, purchased from a hock shop in San Francisco in 1923, and donated to the Smithsonian in 1994.
label: Description
content: Heath & Co. was an English firm that began making nautical instruments in 1835, adopted the Hezzanith trademark, and was still in business in the 1960s. The Sewill firm, established in Liverpool in 1835 and still in business in the 1990s, specialized in chronometers.
label: Description
content: This design resembles that of Heath's "Mark IV.E Patent 'Curve-Bar' Sextant." The frame is brass. The silvered scale is graduated every 10 minutes from -5° to +155° and read by vernier with tangent screw and swinging magnifier to 10 seconds of arc. A quick-release mechanism at the end of the arm engages with worm teeth cut on the underside of the limb. This mechanism, marked "‘HEZZANITH’ ENDLESS TANGENT SCREW AUTOMATIC CLAMP PATENT No. 17840," is designed to facilitate coarse adjustments. George Wilson Heath and Heath and Company, Ltd., both of Crayford, in Kent County, England, obtained a British patent for this feature in 1909. This sextant has two telescopes--one of high power and narrow field of view; the other of low power and wide field of view--as well as a pair of binoculars.
label: Description
content: Ref: G. W. Heath and Heath & Co., "Improvements in Devices for the Adjustments of Sextants and other like Instruments," British patent #17,840.
label: Description
content: Heath & Co., <i>Catalogue</i> (London, 1921-1922), p. 506.
label: Location
content: Currently not on view
place: label: place made
content: United Kingdom: England, Liverpool
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: Estate of Glynn James Petrie
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1994.0048.01
label: catalog number
content: 1994.0048.01
label: accession number
content: 1994.0048
objectType: label: Object Name
content: sextant
physicalDescription: label: Physical Description
content: mahogany (overall material)
label: Physical Description
content: brass (overall material)
label: Measurements
content: case: 27.3 cm x 27.7 cm x 13 cm; 10 3/4 in x 10 29/32 in x 5 1/8 in
label: Measurements
content: sextant radius: 6 1/2 in; 16.51 cm
label: Measurements
content: overall in box: 5 1/8 in x 10 3/4 in x 10 3/8 in; 13.0175 cm x 27.305 cm x 26.3525 cm