RAMSDEN Jesse (1735-1800), astronomical instrument maker, Avas born at Salterhebble near Halifax, Yorkshire, in 1735. He went to London in 1755, and AA r as shortly afterwards bound apprentice to a mathematical instrument maker. He afterwards started business on his own account and acquired great celebrity as an artist. He died on 5th November 1800.

Ramsden’s speciality was divided circles, which began to supersede the quadrants in observatories towards the end of the 18th century. His most celebrated work was a 5-feet vertical circle, which was finished in 1789 and was used by Piazzi at Palermo in constructing his well-known catalogue of stars. He was the first to carry out in practice a method of reading oif angles (first suggested in 1768 by the duke of Chaulnes) by measuring the distance of the index from the nearest division line by means of a micrometer screw which moves one or two fine threads placed in the focus of a microscope. Ramsden’s transit instruments were the first which were illuminated through the hollow axis; the idea was suggested to him by Professor Usslier in Dublin.