RAMSDEN, JESSE, a celebrated English mathe matical and astronomical instrument maker. He was born in 1735, and was the son of an innkeeper at Sal terhebble, near Halifax, in Yorkshire. From the free school in Halifax, where he acquired, between the age of 9 and 12, the elements of a classical education, he went to his uncle at Craven, who sent him to the school of the Rev. Mr. Hall, who had gained some credit in teaching the mathematics. Here Ramsden studied ge ometry and algebra ; but his course was very short, As his father soon afterwards apprenticed him to a clothier of Halifax as a hot-presser. In 1775, he became a clerk in a wholesale cloth warehouse in London, a situation in which he continued for two years and a half; but his passion for the sciences could no longer be controlled, and he bound himself for four years to Mr. Barton in the Strand, who was skilful in the division of mathemati cal instruments, as well as in the other branches of his trade. When his period of servitude had expired, he wrought as a journeyman with Mr. Cole, with whom he afterwards connected himself as partner. He very soon, however, opened a shop for himself, and acquir ed the good opinion of the principal philosophical in strument makers in London. His marriage with Miss Rolland, brought him into still greater notice, and with her lie obtained a part of Dollond's patent right for achromatic telescopes. In the year 1766, Ramsden had opened a shop in the Haymarket; but he had before this invented his celebrated dividing engine, of which we have given an account in our article GRADUATION. ibis engine had many imperfections; but the ingenuity of its author produced a more perfect one, an account of which was published by the board of Longitude in 1775, who rewarded him with the sum of 6151.
In the year 1779, Mr. Ramsden, under the patron age of the board of Longitude, published an account of his engine for dividing straight lines, of which we have given drawings and a full description, in the article GRADUATION already quoted.
While Mr. Ramsden thus improved the art of gradua tion by these valuable engines, he made himself univer sally known by the splendid astronomical instruments which he constructed, and by the great accuracy with which his circles and nautical instruments were divided.
His nautical instruments, such as sextants and small circles, were all divided by the engine ; a method which he introduced, and which will never be superseded in the graduation of instruments of moderate size. Un fortunatety our author has not published any account of the method by which he divided his great circles, so that we arc left to form those conjectural opinions about it have been stated in the article GRADUATION.
In the manufacture of philosophical instruments, which Mc Ramsden carried on to a great extent, he collected in his workshops men of every branch of trade necessary for their construction. The same work men were always confined to the same kind of work; so that they were abte to execute it with wonderful perfection. In consequence of their cheapness, as well as their accuracy, the demand for his instruments was so great, that though he constantly employed sixty men, yet he was unable to execute the numerous orders which he received. Mr. Ramsdell was elected a Fellow of the Royal -Society of London in 1786, an honour which is always limited to two or three of the first rate artists in the metropolis. He was elected a Fellow of the Im perial Academy of St. Petersburg in 1794; and in 1795, the Royal Society adjudged to him the Copley medal for his various imentions. His health was greatly im paired by his devotion to his profession, and he died at Brighton, which had been recommended to him for the sea air, on the 5th November, 1800.
Mr. Ramsden was a man of acute judgment and fine taste, in all matters connected with his profession. As a relaxation from its severities, he perused the best au thors both in prose and verse, and he was particularly fond of Boileau and Moliere.
The following is a list of several of Mr. Ramsden'4 inventions and instruments, with references to the parts of this and other works where a description of them will be found.