RAMSDEN, JESSE (1735-1800), , was born at Salterhebble, near Halifax, Yorkshire, in 1735. He was the son of an innkeeper. When nine years old he was admitted into the free grammar-school of Halifax; and after attending there for about three years, he was placed under the protection of an uncle, who resided in the north of Yorkshire. By him he was sent to a school conducted by Mr. Hall, a clergyman, who ".vas in repute as a teacher of the mathemat cs, and under whom he attained to some proficiency in geometry and algebra. His studies were interrupted oy his father apprenticing him to a cloth-worker at Halifax. At the age of twenty we find him engaged as a clerk in a cloth warehouse in London, in which capacity he continued till 1757-8, when his predilection for other pursuits led him to bind himself for four years to a working mathematical and philosophical instrument maker, named Barton, in Denmark Cjurt, Strand. Upon the completion of his term, he engaged himself as assistant to a workman named Cole, at a salary of twelve shillings a week; but this connection was of short duration. He then commenced working on his own account, and his skill as an engraver and divider gradually recommended him to the employ of the leading instrument-makers, moro particularly Nairne, Sisson, Adams, and Dollond. Ramsden subsequently married Dolloud's daughter, and he received with her a part of Mr. Dollond's patent right in achromatic telescopes. His occupation afforded him frequent opportunities of observing the defec- tive construction of the sextants then in use, the indications of which, as had been pointed out by Lalande, could not be relied on within five minutes of a degree, and might therefure leave a doubt in the determination of the longitude amounting to fifty nautical leagues. The improvement* introduced by Ramsden are said by Piazzi to have reduced the limits of error to thirty seconds. This circumstance, added to the cheapness of his instruments, which were told for about two-thirds the price charged by other makers, soon produced a demand which, even with the assistance of nu- merous hands, he found difficulty in supplying. In hi* workshops the principle of the division of labour was carried out to a considerable extent, and a proportionate dextcnty was acquired by the workmen; but it is asserted that in none of these, even the most subordinate, and least of all in the higher departments, did the skill of the workmen surpass that of Ramsden himself. His attention was incessantly directed to new improvements and further simplification, the result of which was the invention of a dividing-machine, which has been already noticed under Graduation. The date of this invention is prior to the year 1766. At first it had many imperfections; but by repeated efforts of ingenuity throughout a period of ten years, they were successfully removed. In 1777 it was brought under the notice of the Commissioners of the Board of Longitude, by Dr. Shepherd, and by them a premium of 615/. was paid to the author. upon his engaging to divide ' sextants at six, and octants at three shillings, for other mathematical instrument makers. A description of the machine was immediately published, by order of the Board, under the su pcrvision of Dr. M as kely tie (London, 1777, 4to.), and was shortly after translated into French by Lalande. A duplicate of the machine itself it said to have been purchased by the president, Bocbard de Saron, and introduced into France concealed in the support of a table made for that purpose. (Weiss, Bing. Untrers.) As early as 1788 no less than 983 sextants and octants had issued from Ramsden's workshop. In 1779 the description of another machine constructed by Ramsden for dividing straight lines by means of a screw was also published by order of the Board; but this invention does not appear to have been of much practical use. It was however in the construction of many of the larger class of astronomical in struments that Ramsden acquired most reputation, though they were probably least productive of pecuniary gain. The theodolite employed by General Roy in the English Survey was made by Ramsden, and no instrument of the kind tbavt had been previously made would bear comparison with it. A similar remark is applicable to the equatorial constructed for Sir George Schuckburgh, which was also the largest that had then been attempted. Ramsden took out a patent for his new equatorial, and a description of it was published by the Hon. Stewart Mackenzie, brother to the earl of Bute; but his inventive genius seldom permitted him to construct two instruments alike. His telescopes, erected at the ob- servatories of Blenheim, Mannheim, Dublin, Paris, and Gotha, were remarkable for the superiority of their object- glasses; and in his mural quadrants, furnished to the ob- servatories of Padua and Vilna, Dr. Maskelyne was unable to detect an error amounting to two seconds and a half, a degree of accuracy which was then a matter of admiration among astronomers. Ramsden however always recom- mended that the mural quadrant should be superseded by the mural circle; and the circles erected in the observa- tories of Palermo and Dublin, the first of which was of ore and the latter of twelve feet diameter, were constructed by him in accordance with this recommendation.
Among Ramsden's minor inventions and improvements may be enumerated his catoptric and dioptric micrometers (described in the ' Phil. Trans.,' 1779), the former of which was an improvement upon that of Bougier; optigraph: dynamometer (for measuring the magnifying powers of telescopes); barometer; electrical machine; manometer; assay-balance; level; pyrometer; and the method introduced by him for correcting the aberrations of sphericity and refrangibility in compound eye-glasses. (Phil. 7V«fu_ 1783)
Ramsden was elected a fellow of the Roval Society ia 1786. In 1 794 a similar compliment was paid htm by the Imperial Academy of St. Petersburg; and the followicg year the Copley medal was awarded to him by the Rowi Society, in testimony of the importance of his various "m ventions. By this time his health had become much impaired by his ardent devotion to his profession. In Immi he was advised to visit Brighton, where he died, on the 5th of November of that year. From 1766 to 1774 his shop and residence was in the Haymarket; but in the latter year lie removed to Piccadilly, where his business continued to be conducted after his decease.
In his habits we are told that he was temperate to abstemiousness, and that for many years ho restricted himself to very few hours of repose. Most of the time that he could spare from the immediate duties of his profession was devoted to the perusal of works of science and literature. His memory was remarkably retentive, and at an advanced age he made himself sufficiently master of the French language to read Moliere and Boileau. The fortune of which he died possessed was not considerable, and a large portion of it was directed by his will to be distributed among his workmen. See Circle; Equatorial; Graduation; Transit-inStrument; Sextant; See.; and Pearson's Practical Astrortomy, Lond,, 1829, vol. li., pp. 12, IS, 47, 181-5, 194-6, 285-6, 413-28, 519, 533-46, 558-60, and 573.
(Piazzi's Account of the Life and Labours of Ramsden, in a letter addressed by him to Lalande, and published by the latter in the ' Journal des Scavans' for Nov., 17»8, p. 744. This interesting letter was written by Piazzi while urging the progress of his mural circle, the construction of which had been undertaken by Kamsden, but the advance of which towards completion does not appear to have kept pace with Piazzi's wishes; and though it doubtless contains no unmerited eulogium, it seems to have been intended by Piazzi to act as a stimulant. Pttilnsophical Magazine, vol. xvi.; European Magazine, February, 1769; Biog. Univers.; and the Communication of the Rev. L. Dutent to Dr. Aikin, in General Biography, art. ' Ramsden.')
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)