By trying to determine if these people somehow have avoided consuming Broad Street pump water
In the 1850s, London's water supply is a mish-mash of various delivery systems. The poor go to the nearest free public pump, pump the water they need into a bucket, and carry it home. Other classes send their servants to fetch the household's water from a nearby pump, or from one that is considered to have exceptionally tasty or clean water. Some wealthier people pay to have larger amounts of water delivered by cart or by the newfangled method of a pipe run right to the house. Water delivery, whether by cart or pipe, is offered by private contractors; each householder hires a supplier from those that serve the neighbourhood. Businesses and factories that need large amounts of water often have their own private wells or buy piped water.
Dr. Snow begins interviewing people at addresses which have escaped the epidemic.
There is a Brewery in Broad Street, near to the pump, and on perceiving that no brewer's men were registered as having died of cholera, I called on Mr. Huggins, the proprietor. He informed me that there were above seventy workmen employed in the brewery, and that none of them had suffered from cholera, -- at least in a severe form, -- only two having been indisposed, and that not seriously, at the time the disease prevailed. The men are allowed a certain quantity of malt liquor, and Mr. Huggins believes they do not drink water at all; and he is quite certain that the workmen never obtained water from the pump in the street. There is a deep well in the brewery, in addition to the New River [Company] water.
The evidence Dr. Snow gathers supports the idea that, in households and businesses where water comes from sources other than the Broad Street pump, the rate of infection is much lower.
The situation at the local Workhouse, which houses the sick, starving, and elderly, provides further confirmation. Given the general state of health of its residents (and living conditions in the Workhouse), it is reasonable to expect that the Workhouse would have a higher death rate than the homes of the general public that surround it. However,
The Workhouse in Poland Street is more than three-fourths surrounded by houses in which deaths from cholera occurred, yet out of five hundred and thirty-five inmates only five died of cholera, the other deaths which took place being those of persons admitted after they were attacked. The workhouse has a pump-well on the premises, in addition to the supply from the Grand Junction Water Works, and the inmates never sent to Broad Street for water. If the mortality in the workhouse had been equal to that in the streets immediately surrounding it on three sides, upwards of one hundred persons would have died.
Dr. Snow has investigated the situation and gathered evidence that seems to prove that the cholera outbreak of 1854 was transmitted through the water of the Broad Street pump.
