Public Health Act. Sir Robert Rawlinson, a noted sanitarian and engineer of the time, described how public policy in Manchester had affected the city's rivers by the 1840s: Leigh became recognised locally as an expert in matters relating to chemistry as applicable to civic administration. His ability to analyse manufacturing processes caused him to be consulted by the council when they were attempting to educate industrialists and enforce smoke abatement measures. In 1850, he co-authored A History of the Cholera in Manchester in 1849, the aims of which have been described by Robert Kargon, a historian of science, as "nothing less than the scientific assessment of disease and the public health measures taken against it." To that end, he not merely attempted to document the outbreak of cholera itself but also the environmental context in which it occurred. He attempted to map the progress of the disease from one area to another and he tested various theories of probable cause. After rejecting suggestions that the cause may have lain in, for example, a deficiency of "atmospheric electricity" or the amount of ozone in the air, the conclusions drawn were that the outbreak had been mostly restricted to areas where the standards of sanitation were particularly poor, although it was at pains to point out that those standards existed both before and after the outbreak and thus could not in themselves have caused it. While movement of infected people from one place to another seemed to explain how the disease was introduced from affected areas to previously unaffected locations, often at a relatively large distance, the study suggested that direct contact with a carrier was not necessary for propagation. Kargon quotes from the study: In 1859, Leigh was a member of a Nuisance Committee that examined air pollution caused by manufacturers in the Ardwick area and which was considered to have had success in improving the situation. All of these various efforts, and more, garnered Leigh a reputation for an investigative, analytical mind and an expertise in medicine and chemistry. They qualified him for appointment as Manchester's first Medical Officer of Health, responsible for matters relating to public health, but an initial proposal to that effect by the city council's General Purposes committee in 1867 was challenged by in general council discussion. A subsequent formal recruitment process led by another committee resulted in a recommendation in March 1868 to appoint a