William Farr (1807-1883), British epidemiologist. In 1838, after having studied medicine, Farr joined the General Register Office where he was responsible for the collection of official medical statistics. He set up a system to record causes of death as a matter of routine, which lead to improved analyses of mortality rates. During the 1849, 1853 and 1866 cholera epidemics in London Farr gathered statistical evidence to determine the mode of transmission of the disease. At first he mistakenly believed it was carried in the air, but the overwhelming evidence for transmission by water had changed his mind by 1866 and he was able to show conclusively that cholera was water-borne.