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

by Steven Johnson

But within the crowded parlors of Golden Square, the fear was inescapable. The outbreak hit a new peak a few hours before midnight on Thursday. Hundreds of residents had been seized by the disease within a few hours of one another, in many cases entire families, left to tend for themselves in dark, suffocating rooms.

Families continue to perish together in the developed world, of course, but such catastrophes usually unfold over the space of seconds or minutes, in car accidents and plane crashes or natural disasters.

Overnight, Henry Whitehead’s sociable rounds as assistant curate of St. Luke’s had become a death vigil. Within a few minutes of dawn, he had been called to a house where four people lay near death, their skin already taut and blue.

In one of the grandest of the homes, standing at the northwest corner of Green’s Court, all twelve residents would eventually perish. Yet the cholera had largely spared the cramped and grubby quarters on Green’s Court itself.

The contrast was striking, especially as the four houses on Peter Street had been commended by the parish authorities for their cleanliness during a 1849 survey of the neighborhood, while the survey had found nothing but squalor and soot in the surrounding houses. It occurred to Whitehead that, contrary to the prevailing wisdom, the sanitary conditions of the homes seemed to have no predictive power where the disease was concerned.

Rogers was starting to hear accounts of entire households falling ill overnight. And this strain of the disease seemed to do its damage with a terrifying velocity: sufferers were going from complete health to death in twelve hours.

Half the neighborhood, it seemed, had shuttered themselves inside, either to suffer in isolation or to ward off whatever foul effusion had brought the plague to the neighborhood. Outside, in the strangely incongruous glare of a summer afternoon, at the top of Berwick Street, a yellow flag was raised to alert the residents that the cholera had struck.

The usual chaos of the streetsellers had disappeared; most of the neighborhood’s residents had either evacuated or were suffering behind their doors. Seventy of them had perished over the preceding twenty-four hours, hundreds more were at the very edge of death.

Seventy deaths in a single parish was not an uncommon number to hear in an age of cholera epidemics. But it normally took months for the disease to chalk up so many victims. The Broad Street strain of cholera—whatever it was, wherever it had come from—had managed that terrible feat in a single day.

The young Snow observed that the sanitary conditions in the mine were dreadful, with workers granted no separate quarters to relieve themselves, thus forcing them to eat and defecate in the same dark, stifling caverns. The idea that the cholera outbreak was rooted in the social conditions of these impoverished workers—and not in any innate susceptibility to the disease—lodged in the back of Snow’s mind as the cholera ran its course.

Snow’s journey to London was typical of the earnest young doctor-in-training: he eschewed both horse and carriage and walked a meandering two-hundred-mile route alone.

The idea of microscopic germs spreading disease would have been about as plausible as the existence of fairies to most practicing doctors of the day. And as Surgeon-in-Chief G. B. Childs’ letter-writing campaign to the Times suggested, laudanum was regularly prescribed for almost any ailment.

WHERE SHEER PHYSICAL BRUTALITY WAS CONCERNED, THERE was little in Victorian society that rivaled the professional medical act of surgery. Lacking any form of anesthesia beyond opium or alcohol—both of which could only be applied in moderation, given their side effects—surgical procedures were functionally indistinguishable from the most grievous forms of torture.

Snow quickly hypothesized that the unreliability of ether was likely a problem of dosage, and embarked on a series of interlinked experiments to determine the best mechanism for delivering the miracle gas. From his earlier studies, Snow knew the concentration of any gas varied dramatically with temperature, and yet the early adopters of etherization had failed to take room temperature into account in their procedures.

Snow’s productivity during this period is truly astounding, when you think that the very concept of etherization simply hadn’t existed three months before. Not only had Snow detected one of the fundamental properties of the gas within two weeks of first seeing it applied, he had also engineered a state-of-the-art medical device to deliver it.

Snow managed to build his mastery of this embryonic field almost entirely through research conducted in his own home. He maintained a small menagerie in his Frith Street quarters—birds, frogs, mice, fish—where he spent countless hours watching the creatures’ response to various dosages of ether and chloroform.

SNOW’S MASTERY OF ETHER AND CHLOROFORM RAISED HIM to a new echelon in the London medical world. He became the most sought-after anesthesiologist in the city, assisting with hundreds of operations a year.

Snow’s work was constantly building bridges between different disciplines, some of which barely existed as functional sciences in his day, using data on one scale of investigation to make predictions about behavior on other scales. In studying ether and chloroform, he had moved from the molecular properties of the gas itself, to its interactions with the cells of the lungs and the bloodstream, to the circulation of those properties through the body’s overall system, to the psychological effects produced by these biological changes.

Snow was not interested in individual, isolated phenomena; he was interested in chains and networks, in the movement from scale to scale.

There were practically as many theories about cholera as there were cases of the disease. But in 1848, the dispute was largely divided between two camps: the contagionists and the miasmatists.

Folklore and superstition were also on the side of the miasmatists: the foul inner-city air was widely believed to be the source of most disease. While no clear orthodoxy existed regarding the question of cholera’s transmission, the miasma theory had far more adherents than any other explanatory model.

In September of that year, the German steamer Elbe docked in London, having left port at Hamburg a few days earlier. A crewman named John Harnold checked into a lodging house in Horsleydown. On September 22, he came down with cholera and died within a matter of hours. A few days later, a man named Blenkinsopp took over the room; he was seized by the disease on September 30. Within a week, the cholera began to spread through the surrounding neighborhood, and eventually through the entire nation. By the time the epidemic wound down, two years later, 50,000 people were dead.

In fact, the most puzzling element of the disease was that it seemed capable of traveling across city blocks, skipping entire houses in the process.

The layout of the Thomas Street flats provided Snow with an ingenious control study for his inquiry. The Surrey building backed onto a set of houses that faced another courtyard known as Truscott’s Court. These abodes were every bit as squalid as the Surrey building, with the exact same demographic makeup of poor working families living within them. For all intents and purposes, they shared the same environment, save one crucial difference: they got their water from different sources.

During his research, Snow had amassed an archive of information about the various companies that supplied water to the city, and that study had revealed a striking fact: that Londoners living south of the Thames were far more likely to drink water that had originated in the river as it passed through Central London.

But the South London Water Works drew its supply from the very stretch of the river where most of the city’s sewers emptied.

Snow next surveyed the tables of cholera death that had been compiled by William Farr, London’s registrar-general. What he found there followed the pattern that the water-supply routes predicted: of the 7,466 deaths in the metropolitan area during the 1848–1849 epidemic, 4,001 were located south of the Thames.

He had convincingly demonstrated that the South London neighborhoods were more at risk for cholera than the rest of the city, but it did not necessarily follow that the water in those neighborhoods was responsible for the disparity. Perhaps there was special toxicity to the air in those zones of the city that was absent in the slums to the north.

There was a correlation between water supply and cholera—that much Snow had convincingly proved. But he had not yet established a cause.

The Little Marlborough Street sample was worst of all. As he drew the water there, a handful of local residents on the street remarked that the pump water was notoriously poor—so poor, in fact, that many of them had taken to walking the extra blocks to Broad Street for their drinking water.

Snow didn’t realize it at the time, but as he walked home that Sunday night, the basic pattern of that experimentum crucis suggested five years before in the London Medical Gazette was finally taking shape, miles away from Broad Street, in the greenery of Hampstead. Susannah Eley had fallen ill earlier in the week after drinking her regular supply of Broad Street water, dutifully shipped to her by her children in Soho.

in Soho at the time, the bottom floors were more likely to be occupied by owners, with the upper floors rented out to the working poor. An increased death rate in the upper floors would suggest a fatal vulnerability in the constitution or sanitary habits of the poor.

Snow and Whitehead shared one other common experience that night. They both spent those last ruminating hours in the company of water drawn from the Broad Street pump. Snow was analyzing it in his home laboratory, his vision dimmed by the low light of candles. The young curate, however, had used the water in a different way, more recreational than empirical: he had mixed the water with a thimble of brandy and swallowed it.

At the Lion Brewery, a hundred feet down Broad Street from the pump, work continued with a strange semblance of normalcy. Not one of the eighty laborers there had perished yet. The cholera continued to spare the tenements of Green’s Court, despite their filthy, overcrowded quarters. Among the five hundred destitute residents at the St. James Workhouse on Poland Street, only a handful had come down with the disease, while the comparatively well-to-do houses that surrounded it had lost half their inhabitants in the space of three days.

The irony was that the terrified residents of Golden Square had it half right: those new sewers were in fact partly responsible for the outbreak that was devastating the city. But not because the sewers had disturbed a three-hundred-year-old graveyard. The sewers were killing people because of what they did to the water, not the air.

The postal service was famously efficient, closer to e-mail than the appropriately nicknamed “snail mail” of today; a letter posted at nine a.m. would reliably find its way to its recipient across town by noon. (The papers of the day were filled with aggrieved letters to the editor complaining about a mailing that took all of six hours to find its destination.) But if person-to-person communication was shockingly swift, mass communication was less reliable. Newspapers were the only source of daily information about the wider state of the city, but for some reason the Broad Street outbreak went unmentioned for nearly four days in the city’s main papers.

With the newspapers largely silent on the topic, word of the terrible plague in Soho trickled out through the amplifying networks of gossip. Rumors began circulating that the entire neighborhood had been wiped out, that some new strain of cholera was killing people within minutes, that the dead were lying uncollected in the streets.

One study of mortality rates from 1842 had found that the average “gentleman” died at forty-five, while the average tradesman died in his mid-twenties. The laboring classes fared even worse: in Bethnal Green, the average life expectancy for the working poor was sixteen years.

The 1842 study found that 62 percent of all recorded deaths were of children under five.

Imagine the terror and panic if a biological attack killed four thousand otherwise healthy New Yorkers over a twenty-day period.

Oof

The courage of those who stayed to fight the disease—or investigate its origins—is all the more impressive in this light, since simply breathing in the vicinity of an outbreak was assumed by almost everyone to be risking death. John Snow had at least the courage of his convictions to rely on: if the cholera was in the water, then venturing into the Golden Square neighborhood at the height of the epidemic posed no grave threat, as long as he refrained from drinking the pump water during his visits. The Reverend Whitehead had no such theory to allay his fears as he spent hour after hour sitting in the presence of the sick, and yet not once in his writing about the Broad Street outbreak is there mention of his own private dread.

We feel fear more strongly because our safety expectations have risen so dramatically over the past hundred years. Even with its higher crime rate, New York City in its debauched nadir of the 1970s was a vastly safer place to live than Victorian London.

In a very practical sense, no one had ever tried to pack nearly three million people inside a thirty-mile circumference before. The metropolitan city, as a concept, was still unproven. It seemed entirely likely to many reasonable citizens of Victorian England—as well as to countless visitors from overseas—that a hundred years from now the whole project of maintaining cities of this scale would have proved a passing fancy.

And so, in projecting back to the mind-set of a Londoner in 1854, we have to remember this crucial reality: that a sort of existential doubt lingered over the city, a suspicion not that London was flawed, but that the very idea of building cities on the scale of London was a mistake, one that was soon to be corrected.

The tremendous growth of London—like the parallel explosions of Manchester and Leeds—was a riddle that could not be explained by simply adding up decisions made by large numbers of individual humans. This was, ultimately, what perplexed and horrified so many onlookers at the time: the sense that the city had taken on a life of its own.

If you had somehow polled the population of Victorian England and asked them if stacking two million people inside a thirty-mile circumference was a good idea, the answer would have been a resounding no. But somehow, the two million showed up anyway.

Three related developments had triggered an unprecedented intensification of the energy flowing through the capital. First, the “improvements” of agrarian capitalism, where the dotted, irregular system of the feudal English countryside gave way to rationalistic agriculture; second, the energy unleashed by the coal and steam power of the Industrial Revolution; third, the dramatic increase in the portability of that energy thanks to the railway system.

Iberall observed that human societies appeared to cycle through comparable phase transitions, as the energy harnessed by the society increased: moving from the gaseous state of roaming hunter-gathers, to the more settled configuration of agrarian farming, to the crystalline density of the walled city.

Growing a city of three million from less than a million a century before required more than just increased energy inputs, however. It also required an immense population base that was willing to move from the country to the city. As it happened, the enclosure movement that dominated so much of British rural life during the 1700s and early 1800s created a huge surge in mobility by disrupting the open-field farming system that had been in place since medieval times.

In a sense, the Industrial Revolution would have never happened if two distinct forms of energy had not been separated from the earth: coal and commoners.