By interviewing the victims or their families to see if victims might have consumed water from the Broad Street pump
Dr. Snow is able to document several cases in which cholera victims living outside the district had, in fact, ingested water from the Broad Street pump.
He recounts the case of
... an officer in the army, who lived at St. John's Wood, but came to dine in Wardour Street, where he drank the water from Broad Street pump at his dinner. He was attacked with cholera, and died in a few hours.
But the most convincing evidence comes from Dr. Snow's interview with a man whose mother had died during the outbreak. She had lived at West End, in the distant (at the time) suburb of Hampstead, but she had formerly lived in Soho, near the pump. Dr. Snow reports:
I was informed by this lady's son that she had not been in the neighborhood of Broad Street for many months. A cart went from Broad Street to West End every day, and it was the custom to take out a large bottle of the water from the pump in Broad Street, as she preferred it. The water was taken on Thursday, 31st August, and she drank of it in the evening, and also on Friday. She was seized with cholera on the evening of the latter day, and died on Saturday.... A niece, who was on a visit to this lady, also drank of the water; she returned to her residence, in a high and healthy part of Islington, was attacked with cholera, and died also. There was no cholera at the time, either at West End or in the neighborhood where the niece died.
While Dr. Snow cannot establish that every person who died in the outbreak had, at some point, consumed water from the Broad Street pump, he points out that
...there are various ways in which the deceased persons may have taken it without the knowledge of their friends. The water was used for mixing with spirits in all the public houses around. It was used likewise at dining-rooms and coffee-shops.... The pump-water was also sold in various little shops, with a teaspoonful of effervescing powder in it, under the name of sherbet; and it may have been distributed in various other ways with which I am unacquainted.
There is, however, another curious feature of the cholera outbreak that can still call into question the guilt of the Broad Street pump: cases of cholera have not been evenly distributed through the neighbourhood around the pump. Cholera has totally by-passed the occupants of some buildings and the workers at some businesses, even though these people were in the neighbourhood at the beginning of the outbreak. Why have they not fallen ill?
How does Dr. Snow investigate this issue?
