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A visit to John Snow's cholera-infected waterpump in London

On a walk early Saturday evening June 17 in London I visited the John Snow pub, which is mentioned in my account of the 1854 cholera epidemic in Visual Explanations, pp. 27-37. This is the site of the notorious wellhead pump that supplied the cholera-infected water that took the lives of 600 Londoners in September 1854. During that swift and terrible epidemic, Dr. John Snow did his brilliant streetcorner detective work (founding modern epidemiology), discovered the cause of the epidemic, and induced the Parish Council to remove the handle of the Broad Street pump, which ended the epidemic. It's more complicated than that, but the great contribution of John Snow was to identify the public health policy that ended cholera epidemics in England: keep the drinking water clean and free of sewage.

Here is a picture of the pub now and the sign with John Snow's portrait.

The friendly barman at the pub, Matthew, produced from a drawer under the bar what he described as the pump handle that John Snow had had removed to end the epidemic. My natural skepticism provoked the thought "Another relic of the true cross?" The handle is stamped and labeled by the UAB School of Public Health (University of Alabama in Birmingham?!) The UAB School of Public Health in Alabama has a publication called "The Handle," named after Snow's work.

Here are pictures of the putative pump handle, way too small to be a pump handle used by many people operating at the public well. And so, a reminder of the Stonehenge fiasco in Spinal Tap:

Spinal Tap's mini-Stonehenge debacle:

The above photograph of the souvenir handle in my hands was taken by my photographic assistants, engaged on the spot that Saturday evening at the JS pub. The photograph above was taken by my mate on the far right (holding the alleged pump handle); at far left, in this small world of endless coincidence, is a master's student in information design in London!

Below is a picture of a replica of the pump nearby and its accompanying rather battered plaque. Note the pivot pin on the pump, where the actual handle might have been, is quite large compared to the tiny pump handle in hand.

-- Edward Tufte

See the silhouette of the pump shown at the John Snow Society website along with the photograph of the pump above, which combine to indicate the pub's UAB souvenir handle is at about a one-quarter scale. The UAB should have put a scale of measurement on their tag; epidemiology is the not the place for dequantification.

-- ET

Dear ET,

I have been revising material on the Voronoi diagram (I have a 3D application in neuroscience that it fits quite nicely) and found a couple of mentions on the internet about John Snow using a Voroni map or diagram for his famous intervention in the London cholera outbreak, e.g. "A particularly notable use of a Voronoi diagram was the analysis of the 1854 cholera epidemic in London, in which physician John Snow determined a strong correlation of deaths with proximity to a particular (and infected) water pump on Broad Street." (

Do you know if this is true or just over enthusiastic revision of history?

Best wishes


-- Matt R (email)

Voronoi baloney

It's just a wrong guess.

-- Edward Tufte

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