The Ghost Map: The Story of London’s Most Terrifying Epidemic—and How It Changed Science, Cities, and the Modern World

Nonfiction | Book | Adult | Published in 2006

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Chapters 1-7

Chapters 8-9

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Chapters 8-9Chapter Summaries & Analyses

Chapter 8 Summary: “Conclusion: The Ghost Map”

As this chapter makes clear, the vestry investigative team’s findings were not vindicated right away. The miasma theory of cholera transmission continued to be a popular one for some years after the 1854 outbreak, and it lost influence by degrees rather than all at once. An elaborate sewer system (one that remains today) was constructed in London by the engineer Joseph Bazalgette; however, it was constructed in response to what was known as “the Great Stink” of 1858. This was a confluence of an unusually hot summer and the stink of the polluted Thames River.

There was then a second and final outbreak of cholera in London in 1866. While John Snow had already died—at age 45, and during the time of the Great Stink—he was posthumously vindicated by the investigation into this outbreak, which revealed its source to be a contaminated reservoir. The investigation was conducted by William Farr, and also by Henry Whitehead, who would live to see his friend’s waterborne theory of cholera transmission take hold.

This chapter discusses the long-reaching influence of Snow’s discovery and methodology on our lives today, suggesting that the latter was almost as important as the former. In particular, it highlights the innovation of a map that Snow made to support his team’s investigative findings: the “ghost map” of the book’s title. Johnson compares this map—with its tight focus and its mixture of aerial and on-the-ground perspectives—to the Google maps and other specialized internet maps of today. The map represented the dead from the 1854 epidemic, and also their migrations through the city; it had the aim of proving that their deaths were linked to their dependency on the Broad Street pump.

Johnson also celebrates Snow’s and Whitehead’s unlikely friendship as a “triumph of urbanism”(203)—two men from disparate backgrounds and with disparate temperaments coming together and pooling their skills and resources. He notes that while cholera has been eradicated in London and in other first world cities, it remains a problem in what he calls “squatter cities”(216)—poor, populous cities such as Mumbai and Delhi, where many improvised shantytowns exist. However, he sees cause for optimism in the innovation that exists even in these vulnerable communities.

Chapter 9 Summary: “Epilogue: Broad Street Revisited”

This epilogue examines metropolitan life today as compared to London in 1854. Johnson states that not only is the world becoming increasingly urbanized, but that being an urbanite has become a condition to aspire to. He points out that inhabitants of cities such as New York and today’s London have better access to healthcare and schools than do rural dwellers, and also that city dwellers have a smaller carbon footprint. He states that city dwellers tend statistically to be healthier and more long-lived than do their rural counterparts. Additionally, cities have large and varied populations that can lead to local, specialized cultures, such as to art house cinemas and multiplexes.

Johnson does acknowledge that cities are made vulnerable to chemical and nuclear attacks—as well as to the effects of global warming—by their density of population. He sees nuclear warfare as an ultimately bigger threat to cities than chemical attacks, as the former cannot be foreseen and prevented. In regard to chemical attacks, however, he notes that modern-day society has increasingly sophisticated means of anticipating lethal viruses. He discusses scientists’ recent long-sighted response to the Avian flu virus as an example. Scientists now have a better understanding of how viruses can mutate than they did in John Snow’s time; they therefore do not have to wait for the virus to do so but can attack it at its source.

At the same time, Johnson suggests that John Snow can remain a model for scientists today, in his innovative and open-minded attitude. He also uses the example of the 1854 London epidemic to remind the reader that city populations have faced down disasters before: “However profound the threats are that confront us today, they are solvable […] if we listen to science and not superstition, if we keep a channel open for dissenting voices that might actually have real answers” (256).

Chapters 8-9 Analysis

These concluding chapters of the book focus on the implications of the 1854 London cholera outbreak for urban life today. They are less novelistic in tone than the main part of the book and are closer to being a tract, or a manifesto. Rather than looking very closely at one particular neighborhood in one particular city—the Soho neighborhood in Victorian-era London—Johnson’s focuses widens to cities in general; likewise, his focus widens from the particular threat of cholera to the varied threats that face city dwellers today, from global warming to nuclear bombs to chemical warfare.

At the same time, Johnson draws parallels between Snow’s and Whitehead’s world and our own. He sees Snow’s “ghost map”—which he used to illustrate his thesis about cholera transmission—as anticipating today’s Google maps, and he sees Snow’s and Whitehead’s unlikely friendship as one that could only be forged in cities, where many different characters exist and mingle. He also sees their reliance on empirical observation—as opposed to abstract theories—as a model for scientists and other experts to follow today in confronting all manner of potential disasters.

Johnson is finally optimistic about the life of cities, seeing even Third World shantytowns as spaces for innovation and creativity. He is guardedly optimistic as well about city dwellers’ capacity to face down disasters. Even while taking on a broad, global focus in these final chapters, he urges the reader not to look at threats such as global warming in fatalistically broad or “apocalyptic” (256)terms. He suggests that we view our increasingly global world in light of Snow’s and Whitehead’s very local world, as a way to remember that “[w]e have confronted equally appalling crises before” (258).