Modern history

Monday, September 4



THE BRIGHT LATE-SUMMER SUN THAT ROSE OVER LONDON that Monday revealed a ghost town in the streets around Golden Square. Most who hadn’t fallen ill, or who weren’t tending to the fallen, had fled. Many of the storefronts remained closed for the day. A terrible gloom hovered over the Eley Brothers factory: more than two dozen laborers had been seized with the cholera, and news had arrived of Susannah Eley’s death. (Little did the Eley brothers realize that their devotion to their mother had been instrumental in her demise.) The wife of Mr. G—the tailor who had been among the first to succumb—had herself collapsed the night before.

A few odd islands appeared in this sea of devastation. 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.

But every time the Reverend Whitehead thought he saw reason for hope, another tragedy would arrive to dampen his natural optimism. When he returned to the Waterstones on Monday, he found that the lively, intelligent daughter he had long admired—whose health had taken a turn for the better the day before—had suffered a sudden relapse and died during the night. The few remaining family members were attempting to conceal the death from the girl’s father, who continued his own struggle with the disease.

Whitehead began to hear talk spreading among his parishioners blaming the outbreak on the new sewers that had been constructed in recent years. The residents were whispering that the excavations had disturbed the corpses buried there during the Great Plague of 1665, releasing infectious miasma into the neighborhood’s air. It was a kind of haunting, couched in the language of pseudoscience: the dead of one era’s epidemic returning, centuries later, to destroy the settlers who had dared erect homes above their graves. 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.

Other distortions and half-truths circulated between the neighborhood and the wider city. The folklore spread in part because the communication system of London in the middle of the nineteenth century was a strange mix of speed and sluggishness. 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. One of the very first reports appeared in the weekly paper the Observer, though it greatly underestimated the magnitude of the attack: “It is said that Friday night will long be remembered by the inhabitants of Silver-street and Berwick-street. Seven persons were in good health on Friday night, and on Saturday morning they were all dead. Throughout the night people were running here and there for medical aid. It seemed as if the whole neighbourhood was completely poisoned.”

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. More than a few Golden Square residents who worked outside the area left because their employers demanded they abandon their homes immediately.

The information channels were unreliable in both directions. In the belly of the beast, the terrified citizens of Soho traded stories: that the epidemic had struck Greater London with equal ferocity; that hundreds of thousands were dying; that the hospitals were overloaded beyond imagination.

But not all the locals had succumbed to abject fear. As he made his rounds, Whitehead found himself musing on an old saying that invariably surfaced during plague times: “Whilst pestilence slays its thousands, fear slays its tens of thousands.” But if cowardice somehow made one more vulnerable to the ravages of the disease, Whitehead had seen no evidence of it. “The brave and the timid [were] indiscriminately dying and indiscriminately surviving,” he would later write. For every terrified soul who fell victim to the cholera, there was another equally frightened survivor.

Fear might not have been a contributing factor in the spread of disease, but it had long been a defining emotion of urban life. Cities often began as an attempt to ward off outside threats—fortified by walls, protected by guards—but as they grew in size, they developed their own, internal dangers: disease, crime, fire, along with the “soft” dangers of moral decline, as many believed. Death was omnipresent, particularly for the working class. 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. These numbers are so shockingly low because life was especially deadly for young children. The 1842 study found that 62 percent of all recorded deaths were of children under five. And yet despite this alarming mortality rate, the population was expanding at an extraordinary clip. Both the burial grounds andthe streets were filling up with children. That contradictory reality explains, in part, the centrality of children in the Victorian novel, particularly in Dickens. There was, for the Victorians, something singularly charged about the idea of innocent children being exposed to the diseased squalor of the city, a notion that is, interestingly, almost entirely absent from French novels of the same period. When Dickens introduces the vagabond child Jo in Bleak House, his language implicitly references the dismal child-mortality statistics of the day: “Jo lives—that is to say, Jo has not yet died—in a ruinous place known to the like of him by the name of Tom-all-Alone’s. It is a black, dilapidated street, avoided by all decent people, where the crazy houses were seized upon, when their decay was far advanced, by some bold vagrants who after establishing their own possession took to letting them out in lodgings.” The phrasing captures the dark reality of urban poverty: to live in such a world was to live with the shadow of death hovering over your shoulder at every moment. To live was to be not dead yet.

From our vantage point, more than a century later, it is hard to tell how heavily that fear weighed upon the minds of individual Victorians. As a matter of practical reality, the threat of sudden devastation—your entire extended family wiped out in a matter of days—was far more immediate than the terror threats of today. At the height of a nineteenth-century cholera outbreak, a thousand Londoners would often die of the disease in a matter of weeks—out of a population that was a quarter the size of modern New York. Imagine the terror and panic if a biological attack killed four thousand otherwise healthy New Yorkers over a twenty-day period. Living amid cholera in 1854 was like living in a world where urban tragedies on that scale happened week after week, year after year. A world where it was not at all out of the ordinary for an entire family to die in the space of forty-eight hours, children suffering alone in the arsenic-lit dark next to the corpses of their parents.

Outbreaks had an ominous preamble, too. Newspapers would track the disease’s progress through the harbors and trading towns of Europe, as it marched relentlessly across the Continent. When cholera first appeared in New York City in the summer of 1832, it attacked the city from the north: arriving first in Montreal via ships originating in France, the disease spent a month snaking along the trade routes of upstate New York toward the city, then floating straight down the Hudson. Every few days the papers would announce that the cholera had taken another step; when it eventually arrived, in early July, almost half the city had escaped to the countryside, creating traffic jams that resembled the Long Island Expressway on a modern-day Fourth of July weekend. The New York Evening Post reported:

The roads, in all directions, were lined with well-filled stage coaches, livery coaches, private vehicles and equestrians, all panic struck, fleeing from the city, as we may suppose the inhabitants of Pompeii or Reggio fled from those devoted places, when the red lava showered down upon their houses, or when the walls were shaken asunder by an earthquake.

The popular fear of cholera was amplified by the miasma theory of its transmission. The disease was both invisible and everywhere: seeping out of gulley holes, looming in the yellowed fog along the Thames. 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.

It is hard to peer behind that absence, to extract the real truth of Whitehead’s mental state: Was he terrified but still compelled into action by his faith and his sense of duty to the parish? And compelled, by pride, to avoid mention of his terror in his subsequent writing? Or did his religious convictions help him ward off his fear, as Snow’s scientific convictions helped him? Or had he simply acclimated to the constant presence of death?

Certainly some process of acclimation must have been at work. Otherwise, it is hard to imagine how Londoners survived such dangerous times without being paralyzed by terror. (Not all escaped the anxiety, however; witness the prevalence of hysterics in so much Victorian fiction. The corset may not have been the only culprit behind all those fainting spells.) The spike in cases of posttraumatic stress disorder experienced by big-city dwellers after 9/11 is conventionally attributed to a sudden rise in danger thanks to terrorist threat, particularly in iconic urban centers like New York, London, and Washington, D.C. But the long view suggests that this account has it exactly backward. 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. During the epidemics of the late 1840s and the 1850s, a thousand Londoners would typically die of cholera in a matter of weeks—in a city a quarter the size of present-day New York—and the deaths would barely warrant a headline. And so, as shocking as those numbers seem to us now, they may not have provoked the same mortal panic that they trigger today. The literature—both public and private—of the nineteenth century is filled with many dark emotions: misery, humiliation, drudgery, rage. But terror does not quite play the role that one might expect, given the body count.

Far more prevalent was another feeling: that things could not continue at this pace for long. The city was headed toward some kind of climactic breaking point that would likely undo the tremendous growth of the preceding century. This was a profoundly dialectical feeling, a thesis giving rise to an antithesis, the city’s success eventually breeding the very conditions of its destruction, like the “avenging ghost” in Dickens’ eulogy for the opium-addicted scrivener in Bleak House.

London, of course, had a long history of offending social critics, as in this cheery description from Scottish physician George Cheyne, written at the end of the eighteenth century:

The infinite number of Fires, Sulphurous and Bituminous, the vast expense of Tallow and foetid Oil in Candles and Lamps, under and above the Ground, the clouds of Stinking Breathes and Perspirations, not to mention the ordure of so many diseas’d, both intelligent and unintelligent animals, the crouded Churches, Church Yards and Bury Places, with the putrifying Bodies, the Sinks, Butchers Houses, Stables, Dunghills, etc. and the necessary Stagnation, Fermentation, and mixture of Variety of all Kinds of Atoms, and more than sufficient to putrefy, poison and infect the Air for Twenty Miles around it, and which in Time must alter, weaken, and destroy the healthiest of Constitutions.

Part of this disgust can be attributed to the fact that the classical distinction between the metropolis and the industrial towns to the north—one the center of commerce and services, the others of industry and manufacturing—was not nearly as clearly defined as it eventually became in the late 1800s. At the end of the eighteenth century, London had more steam engines than all of Lancashire, and it remained the manufacturing center of England until 1850. Factories like the Eley brothers’ would be dramatically out of place next to the shops and residences of today’s London, but they were an ordinary sight (not to mention smell) in 1854.

Accounts of London’s repulsive conditions inevitably imagined the city as a unified organism, a sprawling, cancerous body laid out along the Thames. In prose that sounds more like a medical diagnosis than an economic forecast, Sir Richard Phillips predicted in 1813 that

the houses will become too numerous for the inhabitants, and certain districts will be occupied by beggary and vice, or become depopulated. This disease will spread like an atrophy in the human body, and ruin will follow ruin, till the entire city is disgusting to the remnant of the inhabitants; at length the whole becomes a heap of ruins: Such have been the causes of decay of all overgrown cities. Nineveh, Babylon, Antioch, and Thebes are become heaps of ruins. Rome, Delphi, and Alexandria are partaking the same inevitable fate; and London must some time from similar causes succumb under the destiny of every thing human.

It is here that the modern urban mind confronts what may be the largest gap separating it from the Victorian worldview. 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. The monster would eat itself.

Most of us don’t harbor doubts of this scale today, at least where cities are concerned. We worry about other matters: the epic shanty-towns of Third World megacities; the terror threats; the environmental impact of a planet industrializing at such a dramatic rate. But most of us accept without debate the long-term viability of human settlements with populations in the millions, or tens of millions. We know it can be done. We just haven’t figured out how to ensure that it is done well.

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.

IF LONDON WAS SUCH A RANK, OVERCROWDED SEWER IN THE first half of the nineteenth century, then why did so many people decide to move there? No doubt there were those who savored the energy and stimulus of the city, its architecture and parks, its coffee-house sociability, its intellectual circles. (Wordsworth’s Prelude even included a paean to shopping: “the string of dazzling wares, / Shop after shop, with symbols, blazoned names, / And all the tradesman’s honours overhead.”) But for every intellectual or aristocrat moving to the city for its cosmopolitan flavor, there were a hundred mud-larks and costermongers and night-soil men who must have had a very different aesthetic response to the city.

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. It was the product of human choice, to be sure, but some new form of collective human choice where the collective decisions were at odds with the needs and desires of its individual members. 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.

That perplexity gave rise to an intuitive sense that the city itself was best understood as a creature with its own distinct form of volition, greater than the sum of its parts: a monster, a diseased body—or, most presciently, Wordsworth’s “anthill on the plain.” (The unplanned but complex engineering of ant colonies display a number of striking similarities to human cities.) The observers of the time were detecting a phenomenon that we now largely take for granted: that “mass” behavior can often diverge strikingly from the desires of the individuals that make up the mass. Even if you had the time to write it all down, you couldn’t tell the story of a city as an endless series of individual biographies. You had to think of collective behavior as something distinct from individual choice. To capture the city in its entirety, you had to move one level up the chain, to the bird’s-eye view. Henry Mayhew famously took to a hot-air balloon in any attempt to take in the entirety of the city from a single vantage point, but found, to his dismay, that the “monster city… stretched not only to the horizon on either side, but far away into the distance.”

The sense, then, of London as a monstrous, cancerous presence focused not merely on the smell or the overcrowding; it also included the uncanny feeling that, somehow, humans themselves were not in control of the urbanization process. In this the Victorians were grasping at an underlying reality that they were only partially able to understand. Cities tend to be imagined in terms of their streets, or markets, or buildings (or, to the twentieth-century mind, their skylines). But they are ultimately shaped by flows of energy. The hunter-gatherers or the early agriculturists couldn’t have formed a city of the size and density of 1850s London (much less today’s São Paulo) even if they had wanted to. To sustain a population of a million people—to keep them fed alone, much less power their SUVs or subways or refrigerators—you need a massive supply of stored energy to keep all those bodies alive. Small bands of hunter-gatherers collected enough energy, if they were lucky, to sustain small bands of hunter-gatherers. But when the Fertile Crescent’s proto-farmers began planting fields of cereal grains, they dramatically increased the energy available to their settlements, allowing populations to swell into the thousands, and, in the process, creating density levels that had never been seen before among the primates, much less the humans. Soon, positive feedback loops emerged: more people working the fields increased the food supply, which allowed more people to work the fields, and so on. Eventually, these first agricultural societies achieved what may still be the sine qua non of civilization: a large class of people liberated from the day-to-day problem of finding a new source of food. Cities were suddenly populated by a class of consumers, free to worry about other pressing matters: new technologies, new modes of commerce, politics, professional sports, celebrity gossip.

That same process drove the explosion of metropolitan London after 1750. 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. For millennia, most cities had been bound inexorably to the natural ecosystem that lay outside their walls: the energy flowing through the fields and forests around them established a population ceiling they couldn’t grow beyond. London in 1854 had shot through those ceilings, because the land itself was being farmed more efficiently, because new forms of energy had been discovered, and because shipping and railway networks had greatly expanded the distance that energy could travel. The Londoner enjoying a cup of tea with sugar in 1854 was drawing upon a vast global energy network with each sip: the human labor of the sugarcane plantations in the West Indies and the newly formed tea plantations in India; the solar energy in those tropical realms that allowed those plants to flourish; the oceanic energy of the trade currents, and the steam power of the railway engine; the fossil fuels powering the looms in Lancashire, making fabrics that helped fund the entire trade system.

The great city, then, could not be understood as an artifact of human choice. It was much closer to a natural, organic process—less like a building that has been deliberately constructed and more like a garden erupting into full bloom with the arrival of spring—a mix of human planning and the natural developmental patterns that emerge with increasing energy supplies. Several decades ago, the physicist Arthur Iberall proposed that patterns of human organization could be understood as the social equivalent of the patterns formed by molecules in response to changing energy states. A collection of water molecules follows a reliable pattern of transformations depending on how much energy is injected into the system: in low-energy situations, it takes on the crystal form of ice, while high-energy infusions transform liquid water into a gas. The dramatic shifts from one state to another are called phase transitions, or bifurcations. 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. When the supply of surplus energy spiked, thanks to the slave labor and transportation networks of the Roman Empire, the city of Rome itself surged to more than a million people, and dozens of towns connected to that network reached populations in the hundreds of thousands. But when the imperial system crumbled, the energy supply dried up, and the cities of Europe vaporized in a matter of centuries. By the year 1000—right around the time the next great energy revolution was stirring—Rome had been whittled down to a mere 35,000 people, one-thirtieth of its former glory.

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. Hundreds of thousands, if not millions, of tenant farmers who had resided in rural hamlets, living off common land, suddenly found their ancient lifestyle upended by a long wave of privatization. Those newly free-floating laborers became another, equally essential, energy source for the Industrial Revolution, filling its cities and coketowns with a nearly inexhaustible supply of cheap labor. 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.

The dramatic increase of people available to populate the new urban spaces of the Industrial Age may have had one other cause: tea. The population growth during the first half of the eighteenth century neatly coincided with the mass adoption of tea as the de facto national beverage. (Imports grew from six tons at the beginning of the century to eleven thousand at the end.) A luxury good at the start of the century, tea had become a staple even of working-class diets by the 1850s. One mechanic who provided an account of his weekly budget to the Penny Newsman spent almost fifteen percent of his earnings on tea and sugar. He may have been indulging in it for the taste and the salutary cognitive effects of caffeine, but it was also a healthy lifestyle choice, given the alternatives. Brewed tea possesses several crucial antibacterial properties that help ward off waterborne diseases: the tannic acid released in the steeping process kills off those bacteria that haven’t already perished during the boiling of the water. The explosion of tea drinking in the late 1700s was, from the bacteria’s point of view, a microbial holocaust. Physicians observed a dramatic drop in dysentery and child mortality during the period. (The antiseptic agents in tea could be passed on to infants through breast milk.) Largely freed from waterborne disease agents, the tea-drinking population began to swell in number, ultimately supplying a larger labor pool to the emerging factory towns, and to the great sprawling monster of London itself.

Do not mistake these multiple trends—the energy flows of metropolitan growth, the new taste for tea, the nascent, half-formed awareness of mass behavior—for mere historical background. The clash of microbe and man that played out on Broad Street for ten days in 1854 was itself partly a consequence of each of these trends, though the chains of cause and effect played out on different scales of experience, both temporal and spatial. You can tell the story of the Broad Street outbreak on the scale of a few hundred humanlives, people drinking water from a pump, getting sick and dying over a few weeks, but in telling the story that way, you limit its perspective, limit its ability to convey a fair account of what really happened, and, more important—why it happened. Once you get to why, the story has to widen and tighten at the same time: to the long durée of urban development, or the microscopic tight focus of bacterial life cycles. These are causes, too.

There is a lovely symmetry that comes from telling the story this way, because a city and a bacterium are each situated at the very extreme boundaries of the shapes that life takes on earth. Viewed from space, the only recurring evidence of man’s presence on this planet are the cities we build. And in the night view of the planet, cities are the only thing going at all, geologic or biologic. (Think of those pulsing clusters of streetlights, arranged in the chaotic, but still recognizable patterns of real human settlement patterns, and not the clean, imperial geometry of political borders.) With the exception of the earth’s atmosphere, the city is life’s largest footprint. And microbes are its smallest. As you zoom in past the scale of the bacterium and the virus, you travel from the regime of biology to the regime of chemistry: from organisms with a pattern of growth and development, life and death, to mere molecules. It is a great testimony to the connectedness of life on earth that the fates of the largest and the tiniest life should be so closely dependent on each other. In a city like Victorian London, unchallenged by military threats and bursting with new forms of capital and energy, microbes were the primary force reigning in the city’s otherwise runaway growth, precisely because London had offered Vibrio cholerae (not to mention countless other species of bacterium) precisely what it had offered stockbrokers and coffeehouse proprietors and sewer-hunters: a whole new way of making a living.

So the macro-growth of the urban superorganism and the microscopic subtleties of the bacterium are both essential to the events of September 1854. In some cases, the chains of cause and effect are obvious ones. Without the population densities and the global connectivity of industrialization, cholera might not have been as devastating in England, and thus might not have attracted Snow’s investigative skills in the first place. But in other places, the causal chains are more subtle, though no less important to the story. The bird’s-eye view of the city, the sense of the urban universe as a system, as a mass phenomenon—this imaginative breakthrough is as crucial to the eventual outcome of the Broad Street epidemic as any other factor. To solve the riddle of cholera you had to zoom out, look for broader patterns in the disease’s itinerary through the city. When health matters are at stake, we now call this wide view epidemiology, and we have entire university departments devoted to it. But for the Victorians, the perspective was an elusive one; it was a way of thinking about patterns of social behavior that they had trouble intuitively grasping. The London Epidemiological Society had been formed only four years before, with Snow as a founding member. The basic technique of population statistics—measuring the incidence of a given phenomenon (disease, crime, poverty) as a percentage of overall population size—had entered the mainstream of scientific and medical thought only in the previous two decades. Epidemiology as a science was still in its infancy, and many of its basic principles had yet to be established.

At the same time, the scientific method rarely intersected with the development and testing of new treatments and medicines. When you read through that endless stream of quack cholera cures published in the daily papers, what strikes you most is not that they are all, almost without exception, based on anecdotal evidence. What’s striking is that they never apologize for this shortcoming. They never pause to say, “Of course, this is all based on anecdotal evidence, but hear me out.” There’s no shame in these letters, no awareness of the imperfection of the method, precisely because it seemed eminently reasonable that local observation of a handful of cases might serve up the cure for cholera, if you looked hard enough.

But cholera couldn’t be studied in isolation. It was as much a product of the urban explosion as the newspapers and coffeehouses where it was so uselessly anatomized. To understand the beast, you needed to think on the scale of the city, from the bird’s-eye view. You needed to look at the problem from the perspective of Henry Mayhew’s balloon. And you needed a way to persuade others to join you there.

THAT WIDER PERSPECTIVE IS WHAT JOHN SNOW FOUND himself searching for by noon on Monday. He had reexamined his samples from the Soho wells in the light of day and found nothing suspicious in the Broad Street water. As he delivered chloroform to a patient of a nearby dentist who was performing a tooth extraction, he pondered the outbreak still raging a few blocks away. The more he thought about it, the more convinced he became that the water supply must have been contaminated somehow. But how to prove it? The water alone might not be sufficient, since he didn’t even know what he was looking for. He had a theory about cholera’s routes of transmission and its effects on the body. But he had no idea what the agent that caused cholera was exactly, much less how to identify it.

Ironically, just a few days before Snow had unsuccessfully attempted to see any telltale signs of cholera in the water, an Italian scientist at the University of Florence had discovered a small, comma-shaped organism in the intestinal mucosa of a cholera victim. It was the first recorded sighting of Vibrio cholerae, and Filippo Pacini published a paper that year describing his findings, under the title “Microscopical Observations and Pathological Deductions on Cholera.” But it was the wrong time for such a discovery: the germ theory of disease had not yet entered mainstream scientific thought, and cholera itself was largely assumed by the miasmatists to be some kind of atmospheric pollution, not a living creature. Pacini’s paper was ignored, and V. cholerae retreated back into the invisible kingdom of microbes for another thirty years. John Snow would go to his grave never learning that the cholera agent he had spent so many years pursuing had been identified during his lifetime.

The fact that Snow had no idea what cholera looked like under the microscope didn’t stop him from doing further tests on the water. After his appointment with the dentist, he returned to draw more samples from the Broad Street pump. This time he saw small white particles in the water. Back in his lab, he ran a quick chemistry experiment, which reported an unusually high presence of chlorides. Encouraged, he took the sample to a colleague, Dr. Arthur Hassall, whose skill with the microscope Snow had long admired. Hassall reported that the particles had no “organized structure,” which led him to believe they were the remnants of decomposed organic matter. He also saw a host of oval-shaped life-forms—Hassall called them “animalculae”—presumably feeding on the organic substances.

So the Broad Street water was not as pure as he had originally thought. But still, there was nothing in Hassall’s analysis that pointed definitively to the presence of cholera. If he was going to crack this case, the solution wouldn’t be found under the microscope, on the scale of particles and animalculae. He needed to approach the problem from the bird’s-eye view, on the scale of neighborhoods. He would try to find the killer through an indirect route: by looking at patterns of lives and deaths on the streets of Golden Square.

As it turned out, Snow had already spent much of the past year thinking about cholera from this perspective. After his first publications at end of the 1840s had failed to persuade the medical authorities of his waterborne theory, Snow had continued looking for evidence supporting this theory. He followed outbreaks in Exeter, Hull, and York from afar. He read William Farr’s Weekly Returns of Birth and Deaths the way the rest of the population devoured the installments of Bleak House and Hard Times. Each outbreak of the disease offered a new configuration of variables, a new pattern—and thus the possibility for a new kind of experiment, one that would unfold in the streets and cemeteries rather than in Snow’s crowded flat. In this, Snow developed a strangely symbiotic relationship with V. cholerae: he needed the disease to flourish to have a shot at conquering it. The quiet years between 1850 and 1853, during which the cholera was largely dormant in England, were good years for the health of the nation. But they were unproductive ones for Snow the investigator. When the cholera returned with a vengeance in 1853, he threw himself into Farr’s Weekly Returns with extra zeal, scanning the charts and tables for clues.

In Farr, Snow had the closest thing to an ally in the existing medical establishment. In many ways their lives had followed parallel paths. Born to poor Shropshire laborers five years before Snow, Farr had trained as a doctor in the 1830s but went on to revolutionize the use of statistics in public health in the following decade. He had joined the newly created Registrar-General’s Office in 1838, a few months after his first wife had died of that other nineteenth-century killer, tuberculosis. Farr had been hired to track the most elemental of demographic trends: the number of births, deaths, and marriages in England and Wales. Over time, though, he had refined the statistics to track more subtle patterns in the population. “Bills of Mortality” dated back to the plague years of the 1600s, when clerks first began recording the names and parishes of the dead. But Farr recognized that these surveys could be far more valuable to science if they included additional variables. He waged a long campaign to persuade physicians and surgeons to report a cause of death wherever possible, drawing upon a list of twenty-seven fatal diseases. By the mid-1840s, his reports tallied deaths not only by disease, but also by parish, age, and occupation. For the first time, doctors and scientists and health authorities had a reliable vantage point from which to survey the broad patterns of disease in British society. Without Farr’s Weekly Returns, Snow would have been stuck in the street-level view of anecdote, hearsay, and direct observation. He might still have been able to build a theory of cholera on his own, but it would have been almost impossible to persuade anyone else of its validity.

Farr was a man of science, and shared Snow’s belief in the power of statistics to shed light on medical riddles. But he also shared many assumptions with the miasma camp, and he used the number-crunching of the Weekly Returns to reinforce those beliefs. Farr thought that the single most reliable predictor of environmental contamination was elevation: the population living in the putrid fog that hung along the riverbanks were more likely to be seized by the cholera than those living in the rarefied air of, say, Hampstead. And so, after the 1849 outbreak, Farr began tabulating cholera deaths by elevation, and indeed the numbers seemed to show that higher ground was safer ground. This would prove to be a classic case of correlation being mistaken for causation: the communities at the higher elevations tended to be less densely settled than the crowded streets around the Thames, and their distance from the river made them less likely to drink its contaminated water. Higher elevations were safer, but not because they were free of miasma. They were safer because they tended to have cleaner water.

Farr was not entirely opposed to Snow’s theory. He seems to have entertained the idea that the cholera was somehow originating in the murky waters of the Thames, and then rising into the smoggy air above the river as some kind of poisonous vapor. He had clearly followed Snow’s publications and presentations closely over the years, and engaged the theory on occasion in the editorials that would sometimes accompany the Weekly Returns. But he remained unconvinced by the purely waterborne theory. He also suspected that Snow would have a difficult time proving his theory. “To measure the effects of good or bad water supply,” Farr editorialized in November of 1853, “it is requisite to find two classes of inhabitants living at the same level, moving in equal space, enjoying an equal share of the means of subsistence, engaged in the same pursuits, but differing in this respect,—that one drinks water from Battersea, the other from Kew.… But of such experimenta crucis the circumstances of London do not admit.”

Snow must have taken that last line as a slap in the face, having heard the exact same Latinate phrase used against him after the publication of his original cholera monograph four years before. Yet despite his skepticism, Farr had been intrigued enough by Snow’s waterborne theory to add a new category to his Weekly Returns. In addition to tracking the age and sex and elevation of the cholera victims, Farr would now track one additional variable: where they got their water.


THE SEARCH FOR UNPOLLUTED DRINKING WATER IS AS OLD as civilization itself. As soon as there were mass human settlements, waterborne diseases like dysentery became a crucial population bottleneck. For much of human history, the solution to this chronic public-health issue was not purifying the water supply. The solution was to drink alcohol. In a community lacking pure-water supplies, the closest thing to “pure” fluid was alcohol. Whatever health risks were posed by beer (and later wine) in the early days of agrarian settlements were more than offset by alcohol’s antibacterial properties. Dying of cirrhosis of the liver in your forties was better than dying of dysentery in your twenties. Many genetically minded historians believe that the confluence of urban living and the discovery of alcohol created a massive selection pressure on the genes of all humans who abandoned the hunter-gatherer lifestyle. Alcohol, after all, is a deadly poison and notoriously addictive. To digest large quantities of it, you need to be able to boost production of enzymes called alcohol dehydrogenases, a trait regulated by a set of genes on chromosome four in human DNA. Many early agrarians lacked that trait, and thus were genetically incapable of “holding their liquor.” Consequently, many of them died childless at an early age, either from alcohol abuse or from waterborne diseases. Over generations, the gene pool of the first farmers became increasingly dominated by individuals who could drink beer on a regular basis. Most of the world’s population today is made up of descendants of those early beer drinkers, and we have largely inherited their genetic tolerance for alcohol. (The same is true of lactose tolerance, which went from a rare genetic trait to the mainstream among the descendants of the herders, thanks to the domestication of livestock.) The descendants of hunter-gatherers—like many Native Americans or Australian Aborigines—were never forced through this genetic bottleneck, and so today they show disproportionate rates of alcoholism. The chronic drinking problem in Native American populations has been blamed on everything from the weak “Indian constitution” to the humiliating abuses of the U.S. reservation system. But their alcohol intolerance mostly likely has another explanation: their ancestors didn’t live in towns.

Ironically, the antibacterial properties of beer—and all fermented spirits—originate in the labor of other microbes, thanks to the ancient metabolic strategy of fermentation. Fermenting organisms, like the unicellular yeast fungus used in brewing beer, survive by converting sugars and carbohydrates into ATP, the energy currency of all life. But the process is not entirely clean. In breaking down the molecules, the yeast cells discharge two waste products—carbon dioxide and ethanol. One provides the fizz, the other the buzz. And so in battling the health crisis posed by faulty waste-recycling in human settlements, the proto-farmers unknowingly stumbled across the strategy of consuming the microscopic waste products generated by the fermenters. They drank the waste discharged by yeasts so that they could drink their own waste without dying in mass numbers. They weren’t aware of it, of course, but in effect they had domesticated one microbial life-form in order to counter the threat posed by other microbes. The strategy persisted for millennia, as the world’s civilizations discovered beer, then wine, then spirits—until tea and coffee arrived to offer comparable protection against disease without employing the services of fermenting microbes.

But by the middle of the nineteenth century, in England at least, water was finding a role for itself in the urban diet. Starting in the mid-1700s, a growing patchwork of privately owned water pipes began snaking their way through the city, supplying the wealthiest Londoners with running water in their homes (or, in some cases, depositing the water in a cistern near their house). It is difficult to overestimate the revolutionary impact of this advance. So many of the household conveniences of modern life—the dishwashers and washing machines and toilets and showers—depend on a reliable supply of water. Just being able to pour yourself a glass from a faucet in your home would have been miraculous to the Londoners who first experienced it.

By the mid-1800s, the loose assortment of small firms running the water pipes had consolidated into roughly ten major firms, each with its own protected turf in the city. The New River Water Company supplied the city proper, while the Chelsea Water Company piped to the West End. South of the Thames, two companies controlled the area: Southwark and Vauxhall (otherwise known as S&V), and Lambeth. Many of these companies—including S&V and Lambeth—had intake pipes within the tidal reach of the Thames. The water they supplied their customers was therefore contaminated by the raw waste of the city, thanks to the growing network of sewers that emptied into the increasingly foul river. Even the most ardent miasmatist could find something offensive in that arrangement, and so in the early 1850s, Parliament passed legislation ordering that all London’s water companies had to move their intake pipes above the tidewater mark by August 1855. S&V chose to delay its move to the very last minute, continuing to draw from Battersea, but Lambeth switched its waterworks to the far cleaner supply at Thames Ditton in 1852.

Snow had been following the water companies since his early investigation of 1849 and had already been tracking the results of Lambeth’s move. But the real breakthrough came in the form of a footnote in the November 26 edition of the Weekly Returns. Below the cholera deaths for South London, Farr had appended this seemingly innocuous line: “In three cases… the same districts are supplied by two companies.”

That minor bit of infrastructure trivia would have immediately struck Snow as a tremendous opportunity. A population all living in the same space, at the same elevation, divided between two water supplies, one rank with the sewage of the city, the other comparatively pure. Farr’s footnote had inadvertently supplied Snow with his experimenta crucis.

All Snow needed was a further breakdown: a record of deaths originating in houses that had been supplied with S&V water, and deaths in houses supplied by Lambeth. If Snow’s theory was right, there should be a disproportionate fatality rate in the S&V homes, despite the fact that they existed side by side with the Lambeth homes. Their elevation and air quality would all be the same—only the water would be different. Even economic status and upbringing would be taken out of the equation, since the rich and poor were just as likely to choose one water supply over the other. It would be the Thomas Street flats all over again: shared environment, different water. But this time the scale would be immense: thousands of lives, not dozens. As Snow would eventually describe it:

The experiment… was on the grandest scale. No fewer than three hundred thousand people of both sexes, of every age and occupation, and of every rank and station, from gentlefolks down to the very poor, were divided into two groups without their choice, and, in most cases, without their knowledge; one group being supplied with water containing the sewage of London, and, amongst it, whatever might have come from the cholera patients, the other group having water quite free from such impurity.

But the experimentum crucis would prove to be thornier than Snow anticipated. Farr’s original report had looked only at the level of entire districts, but Snow now divided the original data into subdistricts organized by water supplier. Twelve of them relied on water from S&V, while three drank Lambeth water exclusively. And indeed, the disparity between the two groups in terms of cholera deaths was pronounced: roughly 1 in 100 died in the S&V subdistricts, while not a single person had died of cholera among the 14,632 Lambeth drinkers. An unbiased observer might have been persuaded by those numbers, but Snow realized his audience required more, primarily because the subdistricts served by Lambeth alone were relatively well-to-do suburbs, in contrast to the smog-bound industrial zones that S&V serviced. Once the miasmatists had a look at the different neighborhoods, Snow knew his case would dissolve in a heartbeat.

And so the experiment would rise and fall on the sixteen remaining subdistricts that received both S&V and Lambeth water. If Snow could find a breakdown of cholera deaths within those districts along the lines of water supplier, he might well have conclusive proof of his theory, enough perhaps to turn the tide against the miasma model. But those numbers turned out to be elusive ones, because the pipes in those sixteen subdistricts were so promiscuously interlinked that it was impossible to tell from a given address which water company serviced it. If Snow wanted to disentangle the water supply of the sixteen, he would have to rely on old-fashioned shoe leather to do it. He would have to knock on every door mentioned in Farr’s account, and inquire where people procured their water.

It is worth pausing for a second to reflect on Snow’s willingness to pursue his investigation this far. Here we have a man who had reached the very pinnacle of Victorian medical practice—attending on the queen of England with a procedure that he himself had pioneered—who was nonetheless willing to spend every spare moment away from his practice knocking on hundreds of doors in some of London’s most dangerous neighborhoods, seeking out specifically those houses that had been attacked by the most dread disease of the age. But without that tenacity, without that fearlessness, without that readiness to leave behind the safety of professional success and royal patronage, and venture into the streets, his “grand experiment”—as Snow came to call it—would have gone nowhere. The miasma theory would have remained unchallenged.

Yet descending to the street-level scale of direct interviews ultimately proved unsatisfactory as well. Many residents had no idea where their water came from. Either the bills were paid by a distant landlord, or they had paid no notice to the company name when they last received an invoice and weren’t in the habit of keeping old paperwork around. The visible pipes were so jumbled that even direct inspection couldn’t reveal whether it was Lambeth or S&V water running into each house.

And so Snow’s inquiry had to venture down to an even smaller scale to track its quarry. The grand experiment that had begun with the bird’s-eye view of hundreds of thousands of lives would ultimately revolve around molecules invisible to the unaided human eye. In the course of his investigation, Snow had noticed that S&V water consistently contained about four times as much salt as Lambeth water. A simple test in his home lab could determine which company had supplied the water. From that point on, anytime Snow encountered a resident who had no idea who provided the water they were drinking, Snow would simply draw a small vial of water, mark it with the address, and analyze the contents when he returned home.

SO THIS IS WHERE JOHN SNOW FOUND HIMSELF PROFESSIONally when the cholera arrived at Golden Square: splitting his days between chloroform and shoe leather, leading a double life of celebrated anesthesiologist and South London investigator. By late August of 1854, the essential components of his grand experiment were in place, and the early returns were promising. All he needed was a few more weeks pounding the pavement of Kennington, Brixton, and Waterloo, and perhaps a few more weeks beyond that to tally up the numbers. When the cholera first struck a few blocks from his flat, the temptation to ignore the outbreak and continue with his grand experiment must have been tremendous. He had been chasing this thread for almost a year now, ever since Farr’s footnote had caught his eye. Another outbreak would be a distraction. But as word spread of the severity of the attack, Snow recognized that the Golden Square case might prove as revealing as his South London inquiry. By the end of Monday—with his water tests inconclusive, and the epidemic still raging around him—he was knocking on doors again, this time in his own neighborhood. All around him, the signs of devastation were inescapable. The Observer would later report: “In Broad-street, on Monday evening, when the hearses came round to remove the dead, the coffins were so numerous that they were put on top of the hearses as well as the inside. Such a spectacle has not been witnessed in London since the time of the plague.”



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