In the 19th century, Britain was the center for rapid urbanization, and as a result, many health and sanitation problems manifested, for example cholera outbreaks and pandemics. This resulted in Britain playing a large role in the development for public health. Before discovering the link between contaminated drinking water and diseases, such as cholera and other waterborne diseases, the miasma theory was used to justify the outbreaks of these illnesses. Miasma theory is the theory that certain diseases and illnesses are the products of "bad airs". The investigations of the physician John Snow in the United Kingdom during the 1854 Broad Street cholera outbreak clarified the connections between waterborne diseases and polluted drinking water. Although the germ theory of disease had not yet been developed, Snow's observations led him to discount the prevailing miasma theory. His 1855 essay "On the Mode of Communication of Cholera" conclusively demonstrated the role of the water supply in spreading the cholera epidemic in Soho, with the use of a dot distribution map and statistical proof to illustrate the connection between the quality of the water source and cholera cases. During the 1854 epidemic, he collected and analyzed data establishing that people who drank water from contaminated sources such as the Broad Street pump died of cholera at much higher rates than those who got water elsewhere. His data convinced the local council to disable the water pump, which promptly ended the outbreak.