Circular instrument dividing engine made by Edward Troughton, London, England in 1793 and described by him in 1809. It was later modified by William Simms, his business partner after 1826, with the additional of a self-acting mechanism, the details of which Simms published in 1843. The engine has a 34-inch cast brass dividing plate with 2,160 teeth and a worm with 20 threads to the inch, all mounted on a wooden tripod base.