Jesse Ramsden

Who was Jesse Ramsden?

Jesse Ramsden FRS FRSE was an English mathematician, astronomical and scientific instrument maker.

Ramsden was born at Salterhebble, Halifax, West Riding of Yorkshire, England. He married Sarah Dollond, daughter of John Dollond. After serving his apprenticeship with a cloth-worker in Halifax, he went in 1755 to London, where in 1758 he was apprenticed to a mathematical instrument maker. About four years afterwards he started business on his own account and secured a great reputation with his products.

Ramsden created one of the first high-quality dividing engines. This led to his speciality in dividing 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 Giuseppe Piazzi at Palermo in constructing his catalogue of stars. He was the first to carry out in practice a method of reading off angles 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.