Chapter 4

Vital Statistics: William Farr, John Snow and Cholera

Synopsis

A short time later, analogous widespread data collection was begun in the United Kingdom, but this was in the context of social welfare, poverty, public health and sanitation. From these efforts emerged two new heroes of data visualization, William Farr and John Snow, who worked independently trying to understand the causes of several epidemics of cholera and how the disease could be mitigated.

Chapter contents

• Cholera
  • Farr’s Diagrams
  • Farr’s Natural Law of Cholera
  • The Transcendent Effect of Water
• John Snow on Cholera
  • The Broad Street Pump
  • The Neighborhoods Map
• Re-visioning the Broad Street Pump
• Graphical Successes and Failures
  • The Answer: A Bug
  • Florence Nightingale’s Graphical Success

Selected Figures

Figure 4.1: Deaths from cholera and diarrhea Farr’s chart showing deaths from cholera and diarrhea in each day of the year 1849, together with charts of weather phenomena over this time period. The three line graphs at the top show, respectively barometric pressure, wind, rain, and temperature, recorded at Greenwich. The two at the bottom record the numbers of deaths from cholera (dark, with a large peak) and diarrhea (light). Source: General Register Office, Report on the Mortality of Cholera in England, 1848–49. London: Printed by W. Clowes, for HMSO, 1852, Plate 2.

Figure 4.2: Death and elevation Diagram of the inverse relation between number of deaths from cholera (width of horizontal lines) and elevation above the Thames (vertical position) for sixteen elevations, from 0 to 350 feet. Numbers on the lines give the predicted values; dotted lines, where present, show the actual number of deaths. Source: General Register Office, Report on the Mortality of Cholera in England, 1848–49. London: Printed by W. Clowes, for HMSO, 1852. p. lxv.

Figure 4.3: Scatterplot Farr’s elevation—mortality data as a scatterplot, showing mortality (y) as the outcome, in relation to elevation (x) as the explanatory variable. The values of cholera mortality calculated from Farr’s “law” are shown by the solid curve. A smoothed fit to the data points is shown by the dashed curve. Source: © The Authors. Rcode: 04_3-cholera-elevation-law.R

Figure 4.4: Inverse elevation plot Plot of Farr’s data, with elevation reexpressed as 1/(E+a). The predicted values from his theory are now shown to form a highly linear relation to cholera mortality in the solid curve. A few unusual districts are labeled. Source: © The Authors. Rcode: 04_4-cholera-mod.R

Figure 4.5: Schematic map Diagram of the registration districts of London, showing elevation (e), cholera deaths (c), deaths from all causes (m), population density (d), other variables and initials for the water company supplying each district. Source: General Register Office, Report on the Mortality of Cholera in England, 1848–49. London: Printed by W. Clowes, for HMSO, 1852, p. clxv.

Figure 4.6: Deaths by water supply region Reanalysis of Farr’s data by water supply region. Left: cholera mortality versus elevation; right: mortality versus poor rate. The lines show linear regression relations for each subset of districts. A few unusual districts are labeled in each plot. Source: © The Authors. Rcode: 04_6-cholera-water.R

Figure 4.7: Snow’s map John Snow’s dot map of Soho, showing the clusters of cases of cholera in the epidemic of 1854 from August 19 to September 30. Deaths from cholera are shown by stacked black bars at the address of residence. At right: a detail from the map, centered around the pump on Broad Street, highlighting the locations of the workhouse and the brewery. Source: John Snow, On the Mode of Communication of Cholera, 2nd ed. London: John Churchill, 1855 / Wikimedia Commons.

Figure 4.8: Boundary region Detail of a version of Snow’s second map of the cholera outbreak, showing the boundary of the region of addresses believed to draw their water from the Broad Street pump. Source: The John Snow Archive and Research Companion.

Figure 4.9: Presentation graphic Mark Monmonier’s re-vision of the Gilbert version of Snow’s map, as a presentation graphic. Source: Extracted from Mark Monmonier, How to Lie with Maps. Chicago: The University of Chicago Press, 1991, fig. 9.18.

Figure 4.10: Line graph of Nightingale’s data The data on causes of mortality plotted as a time-series line graph. Source: © The Authors. Rcode: 04_10-nightingale-line.R

Plate P.2: Radial diagram Farr’s radial diagram of temperature and mortality in London by week for the years 1840–1850. The yearly charts are arranged row-wise from 1840 at the top left. The chart at the bottom right corner shows the average over the years 1840–1849. In each chart, weeks of the year are arranged clockwise, starting from January 1 at 6:35. Source: General Register Office, Report on the mortality of cholera in England, 1848-49. London: Printed by W. Clowes, for H.M.S.O., 1852

Plate P.3: Snow’s map enhanced Re-drawn and enhanced versions of a central portion of Snow’s map of the cholera data using the most historically accurate known data digitized from the map. Deaths are shown by the jittered points, and the six pumps in this region by labeled triangles. Two guides for interpretation were added: Voronoi polygons showing the region of the map closest to each pump (top), and shaded contours of the intensity of deaths from cholera (bottom). Source: © The Authors. Rcode: 04_P3a-cholera-neighborhoods.R Rcode: 04_P3b-SnowMap-density.R

Plate P.4: Nightingale mortality diagram A radial diagram showing the number of deaths from preventible zymotic diseases (outer, blue wedges) compared with deaths from wounds (red) and from all other causes (gray). Right: data for April 1854 to March 1855; left: data for April 1855 to March 1865 after the arrival of the Sanitary Commission. Source: Wikimedia Commons.