RAMSDEN, JESSÉ, a distinguished optician, was the son of an innkeeper, and was born near Halifax in Yorkshire in 1735. His love for mathematical studies began to appear while he was attending a school in his native county. A period of apprenticeship to a cloth-worker in Halifax did not extinguish it. At the age of twenty-four he was found in London, a mathematical and philosophical instrument-maker, skilful in hand and intelligent in head. His growing excellence soon enabled him to open a shop for himself, and to commence a successful business. A sextant invented shortly before 1766 was the first of a series of improved mathematical instruments which issued from his establishment. There followed at intervals a dividing-machine, a theodolite, an equatorial, a telescope, a mural quadrant, a micrometer, and several minor inventions. On account of these services to science, Ramsden was held in high estimation towards the close of his life. At his death in 1800 he was a member of the Royal Society, a fellow of the Imperial Academy of St Petersburg, and the wearer of a Copley medal.