The Blue Death

by Dr. Robert D. Morris

  The letter, addressed to John Ayrton Paris, MD, DCL, FRS, President of the Royal College, consisted of a long list of excuses. First, Baly explained, reading through the survey responses required more time than expected. Then in 1850 as that task was completed, the reports from the General Board of Health (GBH) were released and, of course, the Royal College report could not be released until Baly had a chance to sift through the thoughts of the GBH. Shortly thereafter, he went on, he had learned that William Farr would be issuing a report on cholera mortality statistics and he wanted to incorporate that information in the Royal College’s report. However when Farr’s report came out in 1852, Dr. Baly concluded that he would need the raw data to draw his own conclusions. All these delays, he insisted, were unavoidable and the quality of the final report would demonstrate the necessity of the five years of preparation.

  One could give Dr. Baly the benefit of the doubt. Cholera had confounded the world’s best minds. Perhaps he had done his best to unravel the riddle. Perhaps each new piece of information was bringing him closer to the answer and the report could not have been completed any sooner. On the other hand, the reasons for the delay may well have lurked behind the thick stone walls of Millbank Prison.

  When cholera struck London, the prisons and mental hospitals often stood out like islands amidst the sea of their surrounding neighborhoods. Because many of these institutions had their own water supply, cholera incidence rates could rise or fall sharply as one entered their confines. Inmates of the Hospital of St. Mary of Bethlehem (an institution for the mentally ill memorialized by the word bedlam) died from cholera at a rate that was one third that of the unconfined residents around them in Lambeth. The inmates of Queen’s Prison also fared better than residents around them in the district of Southwark. Both the Hospital of St. Mary of Bethlehem and Queen’s Prison had their own wells. The districts that contained them, Southwark and Lambeth, relied on piped water from the Thames.

  The Millbank Prison had no well. Outside its gates a pipe jutted out into the murky waters of the Thames. Deep inside the prison, the inmates operated a pump that pulled water through this pipe into a large cistern. The cloudy water then passed through a filter, which gave it the appearance of clarity. When it came to removing Vibrio cholerae, however, appearances were deceiving. The inmates of Millbank Prison relied on this water to survive. In 1848 that reliance took a deadly toll. The epidemic of 1848–1849 had hardly begun before deaths from cholera filled the prison’s graveyard to capacity.

  It was John Snow who first made these observations. In October 1849 William Baly picked up a copy of the London Medical Gazette and discovered Snow’s description of conditions at the Hospital of St. Mary of Bethlehem and Queen’s Prison. Then came the shock of reading an indictment of the water supply at Millbank. Snow concluded not only that the water supply explained the prison’s high rates of cholera, but that it explained the incidence of outbreaks of dysentery in the intervening years as well. The report never mentioned Baly by name, but it implied that the prison physician had presided over a public health disaster.

  Snow had to be wrong. Baly had overseen the operation of the filter and assured himself that the filtered water was clear. Moreover the unique nature of Millbank Prison convinced him that cholera could not be spreading from prisoner to prisoner. Based on a system developed by Jeremy Bentham, the father of utilitarianism and the mentor of Edwin Chadwick, Millbank kept its inmates in almost complete isolation. The majority of prisoners spent most of the day working alone in their cells. Even on the occasions when they were together, they were forbidden to speak or even come close to one another. In Baly’s mind, only an airborne agent could spread cholera throughout the prison.

  For a thoughtful man like Baly, making Snow’s truths go away was no simple task. He devoted one in every ten pages of the report to counterarguments and examples intended to refute Snow’s theories. In 1853 however medical science often relied on anecdote, subjective observation, and “expert” opinion. Baly’s report was no exception. Its consideration of drinking water depended on the opinions of physicians throughout the country. Its assessment of the water at Hertford County Prison, for example, relied on the correspondence from a Dr. Davies who considered it to be “extremely sweet and pure.” The Wakefield Lunatic Asylum also had water that was “quite pure” according to Dr. Wright, a local physician. The water consumed by children at Dronet’s school was also “not contaminated” in the words of one Dr. Kite. All three institutions had suffered massive cholera outbreaks. Baly relied on the words of these three men as critical evidence of the errors in Snow’s theory.

  After twenty-three pages of similar examples, weak science, and flawed logic, Baly concluded that “It is not probable that in the case of Cholera the influence of water will ever be shown to consist in its serving as a vehicle for a poison generated in the bodies of those who had suffered from disease.” His next sentence began with the word but. He simply couldn’t bring himself to reject Snow completely. Perhaps “the poisonous matters which produce cholera…are capable of increasing in foul water as well as foul air.” “It is scarcely probable,” he continued, “that water containing putrid matters in a state of solution or of suspension can be habitually swallowed without at least the risk of injury to the health.” He then recapitulates the theory of William Farr that the poisonous matters might well be rising with the mists of evaporating water from the Thames. With his own Millbank prison perched on the banks of the Thames, Baly found a way to blame the river for its troubles. The miasma had emerged from the river and crept over the prison walls bringing cholera under its wing, an explanation that just happened to absolve him of responsibility.

  As Baly left Millbank Prison on that winter day in 1854, even the pending publication of his report brought him little solace. Cholera had returned to London a third time and the inmates of Millbank continued to suffer from serious disease at a rate far above anything experienced in London’s other prisons. Not only was this situation a public health disaster, but as Baly was recognized as one of the nation’s leading authorities on prison hygiene, it posed a direct threat to his professional reputation. Unfortunately for Dr. Baly and his charges, the coming year would unleash a catastrophe within the walls of his prison.

  John Snow read Baly’s report with a cool, objective eye. Unfazed by its critique of his ideas, he made careful notes of its weaknesses and its strengths. Even though it bore the imprimatur of the Royal College, Snow was not rattled. He would respond in his own way and in his own time. Meanwhile he was immersed in a far more important project.

  Epidemiology must count corpses to make a case. With the medical establishment continuing its efforts to explain away Snow’s findings, it was not clear how many more dead bodies would be required to overcome their resistance. It was clear however that cholera would provide them and, even before it returned in 1853, John Snow was counting.

  Ever since 1849 he had gathered whatever information he could on the London water companies and their relationship to cholera mortality during the first two epidemics. He had already demonstrated that districts using unfiltered water from the Thames tended to have higher rates of cholera mortality than districts with cleaner sources of water. His critics focused on inconsistencies in this pattern pointing toward high rates in districts with “clean” water or low rates in districts with dirty sources. Snow had explanations, but he would have preferred decisive evidence. By 1853 the water companies themselves would give it to him.

  In 1852 The Metropolitan Water Act had given the water companies three years to move their water supplies away from the most contaminated reaches of the Thames. When cholera struck in 1853, the quality of the Thames water was in a freefall and little had been done to improve the public water supply. John Snow had been working on additional analyses of the role of the water companies in earlier epidemics, but the results fell short of what he sought. He needed irrefutable evidence. In the winter of 1854, even as he read Baly’s report, he h
ad already begun to believe he might have found it.

  The decision by the owners of a single water company to move their intake before the deadline set the critical experiment in motion. Until 1853 the Lambeth waterworks had drawn their water from the Thames in the center of London, just opposite Hungerford Market. Then two years before the 1855 deadline, they finished work on a water pipeline that reached out to a new steam-powered water pump at Thames Ditton. The pump’s intake pulled water from the river at a point more than ten miles upstream from Hungerford Market and well out of reach of London’s sewage. In the moment that the old pump was shut down and the new pumps first sent water rushing into the Lambeth Company’s maze of pipes, one of London’s dirtiest water supplies became one of its cleanest.

  The move by Lambeth meant that the Southwark and Vauxhall Company (S&V) was now providing the dirtiest water in the city. S&V drew their water from Battersea, just half a mile upstream from the Millbank Prison. In no hurry to improve what they believed to be a clean water supply, its owners continued to send an unsavory cocktail of sewage-tainted water to their customers. Both Lambeth and S&V supplied the south bank of the Thames. If Snow could show sharply lower rates of cholera in the districts served by Lambeth, he would have a new and powerful piece of evidence. That analysis would be anything but simple.

  Snow’s challenge resulted from a war that had taken place twenty years earlier. The war was an economic war among the water companies of London that began in 1834, when Parliament eliminated a clause that had prevented competition among water companies south of the Thames. The Lambeth Company soon found itself locked in a vicious battle for territory with the two other companies supplying water to the districts south of the river, Southwark and Vauxhall, which were separate companies at that time.

  For three years corporate warfare raged through the streets of London. Lambeth invaded the district of Southwark at the same time workers from the Southwark and Vauxhall companies made incursions into Lambeth. In the fight for customers, the companies sent pipes coursing side by side beneath the same streets. They did not even hesitate to invade the same building. Above the street the battle was so intense that brawls erupted between work crews from the different companies.

  Soon the Lambeth Company found itself fighting for its life. In every district it served, it was locked in combat with Southwark or Vauxhall. On all sides the cost of the war soon became prohibitive. In 1837 the companies called a truce and agreed to halt the destructive competition, but the snarl of pipes remained.

  In 1853 this meant that John Snow could not find a single district served by Lambeth alone. Southwark and Vauxhall had merged in 1845 and every district served by Lambeth was also served by the newly formed S&V. This had mattered little in his analyses of earlier epidemics because S&V and Lambeth had water of similarly poor quality. Now it was critical.

  Snow was sure that cholera rates would be lower in homes served by the improved water supply of Lambeth. Through the course of the epidemic, William Farr and his staff at the Office of the General Registrar had tabulated cholera deaths in London and published them in the Weekly Returns, but these reports only listed results by district. If the Lambeth Company had no district as its exclusive province, how could Snow isolate the salutary effect of its improved water supply?

  The beginnings of an answer came late in November from Farr himself. Farr’s work on elevation and cholera was seen as the most important study of cholera of the time. Farr however was far more open-minded than many of his sanitarian colleagues and was intrigued by the idea that contaminated water might contribute to these low-lying miasmas. So he decided to assemble a table that grouped the districts according to water supply and published the cholera mortality for these groupings in the Weekly Returns. He gave separate figures for the districts served by S&V alone and those served by both S&V and Lambeth.

  Snow observed that districts served by both Lambeth and S&V had, on average, half the rate of death from cholera as compared with areas served by S&V alone. This suggested that cholera rates were lower for Lambeth customers, but was not conclusive. Snow needed a way to isolate the customers of the two companies. Once again he obtained key information from William Farr.

  Farr was nothing if not thorough. Early in 1854 the General Registrar published a list of the 796 deaths from cholera during 1853 in London. In the meantime Snow had broken down the water supply at the subdistrict level rather than the district level. Of the thirty-three subdistricts, twelve relied only on S&V and sixteen relied on both companies. Three small subdistricts, he found, were served by the Lambeth Company alone.

  Snow spread out a large map and worked his way through the 796 names on the list. He eliminated any deaths from outside the thirty-three subdistricts. As he sorted through the 374 deaths that remained, a startling picture emerged. Norwood, Streatham, and Dulwich, the three subdistricts served only by Lambeth, had 15,000 residents. None of them had died from cholera in 1853.

  But Snow needed more. Even if subdistricts that relied on contaminated water from the Thames had higher rates of cholera, those areas inevitably differed with respect to something other than the water supply. They might have lower income, poorer housing, inadequate drainage, or more miasma-generating industries. Norwood, Streatham, and Dulwich were more rural in character than most of the other subdistricts south of the Thames. He could not be certain that better water quality from Lambeth had been the true cause of lower cholera rates. Perhaps it was just the life-affirming air of the highlands. Today epidemiologists refer to this problem as confounding. Snow had no word for it, but knew he must address it.

  Snow began to believe that the evidence he wanted was not in those three subdistricts, but in the sixteen subdistricts served by both companies. There, he suspected, an experiment had occurred “on the grandest scale.” There the water companies had taken people living in the same neighborhoods, people of similar means, living in similar houses and breathing the same air, and divided them into two groups, “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.”

  If he could demonstrate that in those subdistricts served by both suppliers most deaths occurred among customers of S&V, his critics would lose their most powerful argument. He simply needed to go into the district as cholera cases occurred and identify the supplier of water. John Snow had only one problem. By the time he recognized what he had, winter had temporarily driven cholera from the streets of London. He would need to wait until warm weather returned.

  After battering London during the summer of 1853, cholera had pulled back in the winter of 1854. But the disease had merely retreated, not surrendered. It waited through the winter, holding on in isolated pockets, until the water warmed in the sun.

  When the waters of the English Channel yield to the tireless pull of the moon, the tide rushes into the mouth of the Thames, halting and then reversing the river’s flow. Climbing upstream, the ocean current runs past Southend and Gravesend, past Purfleet and Frith and on into London. In the summer of 1854, when the river was low, a salty tongue of seawater reached through London to Battersea and licked at the intake of the S&V waterworks.

  At the same time, the Port of London bustled with ships. Many had come from the ports of Europe where cholera had smoldered through the winter. The warmth of summer had breathed life into the embers of the epidemic and by the end of June, the coasts of the Continent were ablaze with cholera. When the sailors who took refuge in the sordid quarters that surrounded the docks of these unfortunate cities climbed aboard their ships to sail to England, cholera sailed with them. When they arrived in London, these ships dumped their wastewater into the Thames. Soon the river was alive with the bacteria brought by afflicted seamen. By July the pathogens had ridden the tides to Battersea and cholera exploded again.

  As cholera renewed its assault, John Snow went back to work. The heat of mid-August
found him walking the streets of Kennington with a satchel and a list of addresses provided by William Farr. Over the winter he had developed a plan that he would implement if cholera returned. Kennington comprised two subdistricts that both relied on the two water companies. Removed from the river and any purported miasma and inhabited by a broad mix of social classes, it seemed an ideal choice for his initial study.

  John Snow had spent the day knocking on doors to talk to the families and friends of cholera victims. At each home he had expressed his condolences and asked the name of the water supplier for the house. More often than not, the response was a puzzled face. He waited as homeowners disappeared to search for a receipt from the water company. Frequently they returned empty handed. Again and again renters confessed their ignorance with respect to their water supply. The intermingling of the water supplies, it seemed, was so complete that it might defy his efforts to record the progress of this natural experiment.

  John Snow had grown adept at navigating the ignorance of others. When he encountered uncertainty about the water supply, he opened his satchel, removed a vial and asked for a sample of tap water. He carefully labeled the vial and returned it to the satchel. If the building’s residents could not reveal the source, perhaps he could find a way to make the water talk.