Scale RulesCalculating Rules
In addition to length measurements, scale rules could be marked with aids for calculation. Perhaps the most notable rule of this type was Gunter's scale, which was similar to a sector or a slide rule. Gunter's scales are named after Edmund Gunter, a 17th-century English mathematical practitioner who figured out how to put a table of logarithms on a rule so that logarithmic calculations could be made with the aid of dividers. These instruments were especially handy for mathematicians and navigators.
The mathematics collections contain several other objects, ranging from the 18th to the 20th centuries, that were used to simplify computations for tasks including designing sundials, keeping track of calendar dates, and plotting data for aeronautical engineering. A few of these rules were designed specifically for positioning artillery.
"Scale Rules - Calculating Rules" showing 1 items.
- 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
- date made
- ca 1750–1795
- Adams, George
- ID Number
- accession number
- catalog number
- Data Source
- National Museum of American History, Kenneth E. Behring Center