Octagonal Rule and Dividers Signed George Adams

This instrument is in the shape of a hollow octagonal prism. A pair of dividers (measuring 10.6 x 1.3 x 1.2 cm) screws into one end. One leg of the dividers may be removed and placed in a hole at the other end of the scale. A slide then moves the leg back and forth for use as a scriber.
A scale appears on each face of the instrument: inches (divided to 1/10" and numbered from 1 to 6); chords; sines; tangents; equal parts of 30, 25, and 20 to the inch; and "calibre." Many of these scales appeared on sectors; like those instruments, this object would have been used for surveying, architectural drawing, and artillery positioning.
The face with the calibre scale is marked: G. Adams LONDON. In 1734, George Adams Sr. (1709–1772) established a workshop on Fleet Street. From 1756 the firm fulfilled hundreds of commissions as instrument maker to His Majesty's Office of Ordnance. George Adams Jr. (1750–1795) took over the business after his father's death, with help from his mother, Ann, for the first couple of years. Although he retained the ordnance commissions, these became less profitable over time and the firm was in debt when he died. George Jr.'s wife, Hannah, sold the remaining stock and tools in 1796. Father and son both used the signature "G. Adams," so this instrument cannot be dated precisely.
References: Gloria Clifton, Directory of British Scientific Instrument Makers 1550–1851 (London: National Maritime Museum, 1995), 2–3; John R. Millburn, Adams of Fleet Street: Instrument Makers to King George III (Burlington, Vt.: Ashgate, 2000); Adler Planetarium, Webster Signature Database, http://historydb.adlerplanetarium.org/signatures/.
Currently not on view
Object Name
rule, sectorial
date made
ca 1750–1795
Adams, George
Physical Description
steel (overall material)
brass (overall material)
overall: 1.6 cm x 17 cm x 1.6 cm; 5/8 in x 6 11/16 in x 5/8 in
place made
United Kingdom: England, London
ID Number
accession number
catalog number
Scale Rules
Science & Mathematics
Dividers and Compasses
See more items in
Medicine and Science: Mathematics
Dividers and Compasses
Scale Rules
Data Source
National Museum of American History, Kenneth E. Behring Center
Additional Media

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