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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Chapter Summaries & Analyses

Chapters 1-7

Chapters 8-9

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Themes

The Significance of Secret Histories

In ways both literal and metaphorical, much of the important action in this book takes place underground. Most obviously, there is the London sewage system that Joseph Bazalgette designed in 1858, and that Johnson compares to a more famous, public monument such as the Eiffel tower. However, this is not the only moment in the book when Johnson stresses the importance of buried or hidden events, as opposed to more traditionally celebrated ones. Writing of epidemic victims in Chapter 2, he observes that—unlike more traditional participants in history, such as army generals and presidents—epidemic victims are generally unaware of their public significance. They are simply going about their daily lives, with no knowledge of what is about to befall them. They are therefore unwittingly creating a “history from below”(32), one that will not be discovered until long afterwards.

John Snow’s “ghost map”—which also gives the book its title—is of course a record of this discovery. It is a map of the 1854 cholera victims—who are represented on the map by black bars—and Johnson draws a link between it and our internet maps of today, suggesting that Snow’s map anticipated Google maps in its intense locality and specialization. This is just one instance in the book when Johnson sees a tragedy or a failed idea as paving the way for a successful one. There is also the miasma theory that was widespread at the time of the 1854 epidemic: the theory that sickness is caused by bad smells. This theory was ultimately behind the decision to flood the Thames river with sewage, which ultimately caused cholera outbreaks. Yet this very act also served to make the source of cholera outbreaks clearer to a concentrated and independent thinker such as John Snow.

Johnson sees disasters as lamentable in themselves, but also as the black backdrops that serve to highlight—and even to usher in—progress and modernization. His is an ultimately optimistic long view of failure and tragedy, and his project is to unearth ghosts and buried old ideas of all kinds, and to celebrate their little-appreciated roles as catalysts for change.

Changing Ideas of Urban Life

Johnson describes London at the time of the 1854 cholera epidemic as a city that was half-village and half-metropolis, and half-modernized and half-backwards. While fully industrialized, it had a primitive sewage system; officials such as Edwin Chadwick were both forward-thinking in their actions (helping to create an elaborate government safety net) and blinkered and superstitious in their theories (holding on to a stubborn belief in the miasma theory of cholera transmission). In many ways, it seems to have been a city that had not yet caught up to itself, and Johnson states that the popular view of cities in general, at that time, was as corrupt, unsanitary, and overcrowded places. Even city-dwellers themselves shared this perspective.

Johnson contrasts this pessimistic view of cities with the view that many people in the modernized world have of cities today: as spaces for creativity, wealth, opportunity, even health and longevity. He points out that in the Victorian era, “[t]he metropolitan city, as a concept, was still unproven” (89). Large, densely populated spaces were relatively new, and people had not quite figured out how to live in them, or how to regard them either. A phrase that Johnson employs frequently in this book is “bird’s-eye view”—that is, a detached and aerial view of one’s surroundings—and he suggests that Londoners in 1854 did not yet have the means or the habit of regarding their surroundings in such a way. Although a large city, it was also a very local one, and people tended to have little knowledge of neighborhoods other than their own. This blinkeredness in turn made them susceptible to superstition and rumor.

John Snow is an important figure to Johnson because he was able, in his studies on cholera, to meld this “bird’s-eye view” with an on-the-ground one. On the one hand, he enlisted the help of statisticians like William Farr in his investigations into cholera transmission; on the other, he simply walked around his neighborhood, interviewing and observing. In this way, Johnson suggests, he helped to usher in a more modern view of cities, as places that we tend to see both aerially and at the level of our own neighborhoods. Johnson also sees Snow’s friendship with Henry Whitehead as a friendship that could only have flourished in a city: one between two very disparate characters who were able to find strength and purpose in their differences. He suggests that such unlikely friendships and collaborations are one commonly acknowledged wealth of cities today.

The Power of Prejudice and Received Opinions

While John Snow’s theory of cholera transmission seems sensible and obvious to a modern-day society, one of this book’s central points is just how long it took for the theory to take hold. Snow himself would die before his theory was commonly accepted as medical fact. During his lifetime he was regarded as a maverick—even while also an established figure in medicine—and most right-thinking and influential people believed that cholera was transmitted by smell, rather than by swallowing.

This was the case even after Snow and Henry had submitted their findings about cholera transmission to the Board of Health and to various medical journals. That officials such as Benjamin Hall—then the President of the Board of Health—continued to dismiss these carefully supported findings is an illustration of how stubborn received opinions can be, and how difficult it can be to change people’s minds. This is perhaps especially the case when the people and the ideas in question are very public and powerful, and changes in strategy can have great consequences. As Johnson points out in Chapter 7, men such as Benjamin Hall were not necessarily bad, corrupt, or stupid men: “They were not hacks, working surreptitiously for Victorian special-interest groups. They were not blinded by politics or personal ambition. They were blinded, instead, by an idea” (184).

Another received idea that Johnson wants to dispel in this book—an idea that is still popular today—is the idea of the eccentric solitary genius achieving a breakthrough all on his own. Johnson wishes to point out that Snow, while certainly brilliant and a loner, was also aided in his investigations by others: Henry Whitehead most obviously, and also William Farr. Much of Johnson’s book, indeed, is a celebration of collaborations of all kinds: not only collaborations such as Snow’s and Whitehead’s, but also the many types of collaborations—such as the sharing of survival strategies in shantytowns and the collective designing of internet maps—that are involved in city living.