Straight line dividing engine, Ramsden type

Straight line dividing engine, Ramsden type

Dividing engines partially mechanised the process of finely and accurately dividing scales for small instruments, helping to meet growing demand from navigators. A sextant or octant was fixed to the top of the engine, and angular divisions were marked on it using the engine’s precision screw and a ratchet to rotate the instrument by very small and precisely-measured amounts. Instrument-maker Jesse Ramsden constructed the first such engine in London in 1767, later reluctantly sharing its design with other makers at the request of the government’s Board of Longitude. This engine is for straight rather than angular scales. It is to the design originally developed by Ramsden, but has a cast-iron bed.