Proportional Dividers

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This instrument has brass slides with steel points. On one end, the points are 3/8" long; on the other, they are 1-3/4" in length. The longer points are corroded. Thumbscrews on both sides adjust the instrument along a gear and tooth mechanism (or "rack movement") on the back slide. The front slide is marked on both sides of the slot with what appears to be a single proportional scale for lines: 1/2, 1/3, 1/4, 1/5, 1/6, 7, 8, 9, 10. A wooden case fastened with brass hooks is lined with dark blue velvet. Red lines and numbers are on the bottom of the case. No legible maker's mark is present.
Currently not on view
date made
ca 1900
Physical Description
brass (overall material)
velvet (overall material)
wood (overall material)
steel (overall material)
overall: 2.5 cm x 23 cm x 4.5 cm; 31/32 in x 9 1/16 in x 1 25/32 in
ID Number
accession number
catalog number
Credit Line
Gift of Ursula N. Forbes
Drawing Instruments
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Dividers and Compasses
Data Source
National Museum of American History


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