William Farr (1807–1883). Report on the Mortality of Cholera in England, 1848-49. London: Clowes and Sons, 1852.
William Farr, a British doctor and government official, attempted to use statistics and data visualization to determine the cause of cholera, which had killed fifteen thousand people in 1849 London. He correlated temperature and mortality for each week of the 1840s and plotted them in this chart. But the chart has a flaw. It fails to take into account that people perceive differences in two dimensional diagrams by differences in area, not length. In this chart, for each unit increase in the death count, the area of the corresponding segment increases exponentially, greatly exaggerating the rates. However, Farr’s chart paved the way for Nightingale’s subsequent invention of the radial diagram. While his theory the cause of cholera was incorrect, he showed that the collection and examination of epidemiological data could serve public health.
Florence Nightingale (1820–1910). A Contribution to the Sanitary History of the British Army during the Late War with Russia. London: Harrison, 1859.
Trained as a nurse, Florence Nightingale was sent to the front of the Crimean War to improve care and reduce mortality in military hospitals. She was horrified at the conditions she found: the absence of systematic hygiene, poorly trained staff, and the lack of hospital records. She collected statistics showing that soldiers were approximately ten times more likely to die from disease in the hospitals than from their war-inflicted wounds. To convey this she created this chart, called a ‘rose’ or ‘Nightingale’ diagram, where a year is represented by a circle. Each segment of the circle represents a month. The size of the segments corresponds to the number of deaths in that month. The cause of death is coded by colour: blue for disease, red for death from wounds, and black for everything else. The pattern of mortality and the difference in causes is undeniable.
