One of the first machines for performing semi-automated divisions of graduated scales of scientific instruments was developed in the 1760s by the Duc de Chaulnes. He used a circular platform, which held the circle to be divided. The platform was moved by means of a tangent endless screw. The divisions were inspected with micrometer microscopes. When the screw was rotated, the platform turned by the desired increment, and a mechanical system marked the divisions.
The method used by the Duc de Chaulnes was perfected by Jesse Ramsden, who, in the 1770s, built a more accurate dividing machine. Ramsden manufactured high-quality parts that made his machine exceptionally precise. Even an unskilled worker could accurately divide the limb of an octant or sextant in a relatively short time. Other machines, also incorporating micrometer screws, were used to divide linear measures and mark equidistant divisions on thermometers.
In the nineteenth century, other great instrument-makers such as Troughton, Gambey, Lerebours, Repsold, Porro, and Amici added many improvements to dividing machines.
Inv. 586, 3244
Maker unknown, Florence, 1762
Inv. 3457
Maker unknown, Florence, first half 19th cent.
Inv. 1023, 3244, 3368
Maker unknown, Florence, second half 18th cent.