Chester Moor Hall

By Leslie T. Newman

Chester Moor Hall, of Leigh-on-Sea, has never received the recognition due to him for the invention of the achromatic lens. Today we expect that any optical instruments we buy, for example telescopes and binoculars, will give clear images free of coloured fringes. Such, however, would not be the case without Hall’s invention. Images formed by a combination of ordinary magnifying lenses are surrounded by coloured fringes that blur the outlines. The higher the magnification the more troublesome are the distortions. Even the great Isaac Newton attempted in vain to produce lenses free from these rainbow effects; and where Newton failed Hall succeeded. So highly regarded was he by the Royal Astronomical Society that a document bearing his signature was framed and hung in its council chamber at Burlington House. Chester Hall, born at Leigh-on-Sea and baptised at the parish church on 9th December 1703, was the only son of Jehu Hall and his wife, Martha, a co-heiress of Richard Bittridge, of New Hall, Sutton. The Halls were originally of Stepney, but through marriage with the Chester and the Moors of Leigh came by inheritance to settle in that place. Jehu, however, later moved to Brentwood, where he died in 1728. The recorded biographical details of Chester Moor Hall – such was how he always signed his name – are few. He was an only son with two sisters. From the records of the Inner Temple we learn that he was admitted as a student in 1724. In 1763 he was made a bencher of his inn – no mean honour – and was then described as “of Stillmans in the Barstaple hundred in Essex.” This property, sometimes spelt “Stilemans,” came to the Halls by inheritance from the Chesters. It was once a noble mansion near Runwell and was demolished early in the nineteenth century. Hall was a man independent of his profession, a considerable landowner in Essex and a county magistrate. His name is appended to many county records dealing not only with justice but with such varied matters as bridge and road maintenance and the militia. His invention of the achromatic lens leaves us in no doubt of his scientific and mathematical abilities. The details of the lens, then used exclusively for telescopes, are of interest and of such importance that they are worth recounting. Its use made possible the construction of instruments of increased magnifying power and thereby opened up further to astronomers the wonders of the heavens. We learn of his invention only through a law-suit heard before Lord Chief Justice Mansfield between two parties, each of whom claimed it for himself. In 1758 a John Dolland took out a patent for a new method of making telescope lenses by compounding them of different qualities of glass and thereby producing clear images free of spectral colours. When Dolland died in 1761 the patent was left to his son, who in 1766 brought an action against a Mr Champness, a mathematical instrument maker, for patent infringement. Champness said that Dollond was not the inventor and such telescopes had been made many years before by a Chester Moor Hall, who had shown his lens grinders how to make them. It appeared from an examination of Hall’s workmen that he had indeed made the achromatic telescope as early 1733. About 1729, so we learn from his private papers, Hall concluded from his studies of the human eye that if he could find the right glasses he could construct a lens capable of correcting the different refrangencies of light. After many experiments he found the properties he sought in “crown” and “flint” glasses. Lord Mansfield, however, upheld Dollond’s claim, remarking “It is not the person who has locked up his invention in his escritoire that ought to profit by a patent for such an invention, but he who brought it forth for the benefit of the public.” Damages of £250 were awarded to Dollond. It may seem strange that Hall, considering his legal training, did not contest the matter. The answer must surely be that being a gentleman, a county magistrate and a person of good private fortune he was above such unbecoming litigation between artisans. Certainly none of the instruments he made would have borne his name. In his later life he lived at New Hall, Sutton, inherited from his mother, and there he died on 17th March 1771. He was laid to rest in the attractive little parish church close by. Sutton church cannot boast of fine architectural features, but it does contain the monument to this seemingly modest man.