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The outer edge of this bronze wheel is covered with a brass ring, cut with 2,160 gear teeth. The teeth engage a screw on one side of the machine, which, when turned, rotates the carriage and guides the cutting of measurements into a circle's rim.
 

Ramsden's Dividing Engine
1775

Winner of the 1775 British Board of Longitude award
Invented by Jesse Ramsden of London, England, this was the first machine that could divide the rim of a circle automatically. It was of great importance in the manufacture of surveying and navigation instruments. By the mid-1800s, 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.

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