Mill Gear and Machine Wheel Scale Signed W. Wright

This brass measuring instrument resembles a sector, with a rounded apex and two rectangular legs. The front of the object is marked: MACHINE WHEELS. It bears a proportional scale with numbers 6, 8, 10, 16, and 20. One leg contains a proportional scale labeled "Pitch Line" (numbered 6, 8, 12, 16, 20) and a scale labeled "Depth of Tooth" that is uniformly divided into single units and numbered by tens from 20 to 160. The other leg is labeled "Gauge Point" and bears a scale uniformly divided into single units and numbered by tens from 20 to 160. Both scales are engraved with a small arrow at the 80 point. "Gauge Point" is separated from the scale by an ornate engraved arrow, so those words may refer to the proportional scale on the rounded part of the instrument. The legs bear a maker's mark: W. WRIGHT, (/) GLOSSOP. There are three posts, or mill feet, two on the legs and one at the center, on each side of the instrument, so that it stands about 3/4" away from the surface on which it rests.
The back of the object is marked: MILL GEER WHEELS. It bears a proportional scale with numbers and letters: 4, U, 12, 16, 20. ("Geer" and "gear" were both acceptable spellings in the 18th and 19th centuries.) Each leg contains a scale that is uniformly divided into single units and numbered by tens from 10 to 80. Small arrows are engraved on both legs at the 47 and 80 points. Another larger, ornate arrow on the left leg separates the words "Gauge Point" from the uniformly divided scale. The posts on the legs on this side are corroded. The instrument is stored in a mahogany case painted blue on the inside.
W. Wright manufactured instruments in the parish of Glossop in northwest Derbyshire, England, in the 18th century. Between ten and twenty cotton mills opened in Glossop in the 1790s. Wright apparently also worked at times in Manchester, 30 miles to the west. At least three other examples of this instrument were auctioned between 1996 and 2009, some marked "Glossop" and some marked "Manchester." The Smithsonian acquired this object in 1966.
Reference: Gloria Clifton, Directory of British Scientific Instrument Makers 1550-1851 (London: National Maritime Museum, 1995), 306–307.
Currently not on view
Object Name
scale rule
date made
18th century
Wright, W.
Physical Description
brass (overall material)
mahogany (box material)
overall: 4.5 cm x 7.6 cm x 40 cm; 1 25/32 in x 3 in x 15 3/4 in
box: 6.35 cm x 8.9 cm x 43.8 cm; 2 1/2 in x 3 1/2 in x 17 1/4 in
place made
United Kingdom: England, Glossop
ID Number
catalog number
accession number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Scale Rules
Data Source
National Museum of American History, Kenneth E. Behring Center


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