John Leigh, (8 June 1812 – 11 November 1888), was a British 19th-century chemist and surgeon in Manchester, becoming its first appointed Medical Officer of Health, having responsibility for Public Health. Early life John Leigh was born on 8 June 1812, probably at Foxdenton Hall in Chadderton but possibly in Liverpool. His father, Thomas, was a druggist and tea-dealer from Ashton-under-Lyne, whilst his mother, Hannah, came from Saddleworth. John said he was related to an ancient Cheshire family, the Leighs of West Hall, and thus also with the Earl of Bridgewater, but doubt has been cast on these claims. Leigh attended a school associated with Dukinfield Moravian Church and then pursued a career in medicine, being initially apprenticed to a doctor in Ashbourne, Derbyshire. From 1831, he studied at Thomas Turner's Pine Street medical school in Manchester and at Guy's Hospital, London, as well as working for a period as a clerk at the Manchester Infirmary. Possessed of much ability, Leigh was training other medical students and successfully proposing them for their professional qualifications before achieving his own qualification as a Member of the Royal College of Surgeons. After qualifying, he had an extensive private medical practice in Manchester until 1868 and worked as a resident medical officer at the Infirmary. He also held chairs in Chemistry and Forensic Medicine at the Pine Street School and also at one located on Marsden Street in the city, which eventually amalgamated to form the Manchester Royal School of Medicine. He was also a Registrar for births, marriages and deaths at this time. Chemist Manchester was one of the first towns to use coal gas extensively and Leigh, who became a Fellow of the Chemical Society, was employed as a chemical analyst by the municipally-owned Manchester Gas Works, perhaps beginning in 1837. Manufacture of coal gas was not a trivial undertaking, requiring analysis of the raw material and of methods of chemical purification and extraction. The purpose of Leigh's work was to enable production of a high-quality gas suitable for use in illumination and to prevent emission of noxious fumes and by-products. He developed a considerable expertise, presenting papers on the subject of gas analysis to learned societies such as the British Association and, in 1863, patenting a process for the extraction of benzole from coal gas. Interest in public health The professional interest in gas analysis, prior experiences at the Manchester Infirmary,