The Ghost Map, by Steven Johnson, is a really excellent book. It chronicles the 1854 cholera outbreak in London, and the medical detective work by Dr. John Snow and Rev. Henry Whitehead which ultimately led to the discovery of the cause. (Here's a nifty TED talk by Johnson about the book.)
Johnson's book weaves several threads together. The most obvious is the story of the epidemic, which he details practically minute by minute. Johnson can do that because of the obsessive street-level research done by Snow and Whitehead during and after the outbreak. In a very real sense, they beat cholera by sheer dogged persistence and inquiry.
A second thread describes Snow's battle to overturn the prevailing theory of the day, that cholera was caused by a "miasma" of bad air. Johnson makes the startling point that well-intentioned Victorian efforts to combat cholera by draining away waste and combating foul smells did more harm than good -- the sewers emptied into the Thames, which was the source of drinking water for much of London.
The third thread in the weave is how we perceive information. Snow ultimately won his battle (posthumously, alas) by a remarkable stroke of graphic design: the "ghost map" of the title. By putting the number and location of deaths in a format which people could see, the connection between the cholera cases and the contaminated pump on Broad Street became obvious.
Finally, Johnson examines cities themselves -- as human constructions, but also as ecosystems. Victorian London was the world's first mega-city, and the Victorian engineers and city planners had to invent all the techniques and systems used in metropolitan centers everywhere: subways, pavement, water supplies, gas and electric light -- and, of course, sewage disposal. At the time, there was a very real concern that cities as big as London were unsustainable. The work of men like Snow, Whitehead, and other characters in the book made it possible to have even bigger cities, cities which weren't foul-smelling hives of misery and disease.
It's easy to look back at all the squalor of Victorian London and congratulate ourselves on how much more wise, clever, and humane we are. But that's entirely the wrong lesson to take away from this book. The Victorians were quite wise, incredibly clever, and humane people themselves. They were, however, only human and capable of mistakes, and some of those mistakes (like the miasma theory) were fatal ones for hundreds of people. The real lesson is to make sure that we don't stampede off to solve problems before we fully understand their real natures, and the potential costs.
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