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

by Steven Johnson

Densely packed populations of people without modern waste-management systems produced powerfully repellent odors. When Mayhew describes his repulsion at the smell of hydrogen sulfide on the streets of Bermondsey, you can see in the passage a clash between three distinct epochs somehow struggling to share the same space: an industrial-era city with an Elizabethan-era waste-removal system as perceived by a Pleistocene-era brain.

Our noses are far more adept than our eyes at perceiving the very small.

Microscopes had been in use for more than two centuries, and while a few isolated researchers had caught a glimpse of microbes in their labs, the existence of a bacterial microcosmos was still the stuff of fantasy and conjecture for the mid-Victorian mind.

The miasma theory drew on other sources for its power as well. It was as much a crisis of imagination as it was pure optics.

Miasma was so much less complicated. You didn’t need to build a consilient chain of argument to make the case for miasma. You just needed to point to the air and say: Do you smell that?

Neighborhoods with unsanitary water supplies generally suffered from poor air quality as well; many of them lay at the lower elevations that Farr relentlessly documented in his Weekly Returns.

Like the other great scientific embarrassment of the period—phrenology—the miasma theory was regularly invoked to justify all sorts of groundless class and ethnic biases. The air was poisoned, to be sure, but the matter of who fell ill, and what disease they suffered from, was determined by the constitution of each individual breathing in the air.

That constitutional failing was invariably linked to moral or social failing: poverty, alcohol abuse, unsanitary living. One alleged expert argued in 1850: “The probability of an outburst or increase during [calm, mild] weather, I believed to be heightened on holidays, Saturdays, Sundays, and any other occasions where opportunities were afforded the lower classes for dissipation and debauchery.”

The idea of one’s internal constitution shaping the manifestation of disease was not just useful for affirming social prejudices about the moral depravity of the lower classes. It also helped paper over a massive hole in the theory itself. If the miasma seemed unusually capricious in its choice of victims for poison allegedly circulating in the atmosphere—if it killed off two housemates but left the remaining two unscathed despite the fact that they were all breathing the same air—the miasmatists could simply point to the differences in constitution between the victims and the survivors to explain the disparity.

The scaffolding that kept miasma propped up for so long was largely made up of comparable half-truths, correlations mistaken for causes. Methane and hydrogen sulfide were in fact poisons, after all; they just weren’t concentrated enough in the city air to cause real damage.

Chadwick and Nightingale and Dickens were hardly bigots where the working classes were concerned. Miasma, for them, was not a public sign of the underclasses’ moral failing; it was a sign of the deplorable conditions in which the underclasses had been forced to live.

There may be no clearer example of miasma’s dark irony: on the very day that the outbreak in Golden Square was beginning, one of London’s most prestigious papers was urging the Board of Health to accelerate its work poisoning the water supply.

The weight of tradition, the evolutionary history of disgust, technological limitations in microscopy, social prejudice—all these factors colluded to make it almost impossible for the Victorians to see miasma for the red herring that it was, however much they prided themselves on their Gradgrindian rationality.