Ramsden Dividing Engine

Making precisely divided scales was of great importance to eighteenth and nineteenth century navigation and science. In 1775 the English instrument-maker Jesse Ramsden completed this machine, designed to divide arcs of circles automatically. The instrument has a mahogany frame with three legs and three frictionless wheels. These wheels support a heavy bronze wheel which is covered on its outer rim with a brass ring, cut with 2160 gear teeth. These teeth engage a screw on one side of the machine. Turning this screw 6 times rotates the carriage for the stylus exactly one degree. An object to be divided was clamped to the arms of the bronze wheel, with the cutting mechanism was above it.
Ramsden's invention won him an award from the British Board of Longitude. By the mid-nineteenth century, even small American instrument-makers had begun to buy dividing engines. The Philadelphia firm of Knox and Shain, which made navigational instruments, purchased Ramsden's dividing engine from his successors for their use.
Object Name
dividing engine
date made
Jesse Ramsden
Physical Description
bronze (overall material)
brass (overall material)
mahogany (stand material)
overall: 109 cm x 123 cm x 114 cm; 42 29/32 in x 48 7/16 in x 44 7/8 in
place made
United Kingdom: England, London
ID Number
catalog number
accession number
Measuring & Mapping
Time and Navigation
See more items in
Medicine and Science: Mathematics
Time and Navigation
Time and Navigation, National Air and Space Museum
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Henry Morton
Additional Media

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