Snow & the pump handle

The development of this history workshop unit is a trans-Atlantic partnership involving Peter Vinten-Johansen (US) and David Zuck (UK).

[This page is still in early stages of construction.]

On 23 September 1854, a London (UK) medical journal published a letter submitted earlier in the week by John Snow. It began as follows:

“To the Editor of the Medical Times and Gazette.

Sir,–As soon as I became acquainted with the situation and extent of the late outbreak of cholera in Broad-street, Golden Square, and the adjoining street[s], I suspected some contamination of the water of the much frequented street-pump in Broad-street, near the end of Cambridge-street: but on examining the water, on the evening of the 3rd inst., I found so little impurity in it of an organic nature, that I hesitated to come to a conclusion. Further inquiry, however, showed me that there was no other circumstance or thing common to the circumscribed locality in which this sudden increase of cholera occurred, and not extending beyond this locality, except the water of the above pump. I found, moreover, that the water varied, during the next two days, in the amount of organic impurity it contained; and I concluded that, at the commencement of the outbreak, it might have been still more impure. I requested permission, therefore, to take a list at the General Register Office of the deaths from [321/322] cholera registered during the week ending September 2, in the sub-districts of Golden-square, Berwick-street, and St. Ann’s, Soho. Eighty-nine deaths from cholera were registered during the week, in the three sub-districts. Of these, only six occurred in the four first days of the week, four occurred on Thursday, the 31st ult., and the remaining seventy-nine on Friday and Saturday. I considered, therefore, that the outbreak commenced on the Thursday; and I made an inquiry, in detail, respecting the eighty-three deaths registered as having taken place during the last three days of the week. On proceeding to the spot, I found that nearly all the deaths had taken place within a short distance of the pump. There were only ten deaths in houses situated decidedly nearer to another street pump. In five of these cases the families of the deceased persons informed me that they always sent to the pump in Broad-street, as they preferred the water to that of the pumps which were nearer. In three other cases the deceased were children who went to school near the pump in Broad-street. Two of them were known to drink the water, and the parents of the third think it probable that it did so. The other two deaths, beyond the district which this pump supplies, represent only the amount of mortality from cholera that was occurring before the eruption took place. With regard to the deaths occurring in the locality belonging to the pump, there were 61 instances in which I was informed that the deceased persons used to drink the pump water from Broad-street, either constantly or occasionally. In 6 instances I could get no information, owing to the death or departure of every one connected with the deceased individuals; and in 6 cases I was informed that the deceased persons did not drink the pump water before their illness.

The result of this inquiry, then, is, that there has been no particular outbreak or prevalence of cholera in this part of London except among the persons who were in the habit of drinking the water of the above-mentioned pump-well.

I had an interview with the Board of Guardians of St. James’s parish, on the evening of the 7th inst., and represented the above circumstances to them. In consequence of what I said, the handle of the pump was removed on the following day. The number of attacks of cholera had been diminished before this measure was adopted, but whether they had diminished in a greater proportion than might be accounted for by the flight of the great bulk of the population I am unable to say. In two or three days after the use of the water was discontinued the number of fresh attacks became very few.

. . . . . . .

The pump-well in Broad Street is from 28 to 30 feet in depth, and the sewer, which passes a few yards from it, is 22 feet below the surface. This sewer proceeds from Marshall-street, where some cases of cholera had occurred before the great outbreak.

I am of opinion that the contamination of the water of the pump-wells of large towns is a matter of vital importance. Most of the pumps in this neighbourhood yield water that is very impure and I believe that it is merely to the accident of the cholera evacuations not having passed along the sewers nearest to the wells that many localities in London near a favourite pump have escaped a catastrophe similar to that which has just occurred in this parish.”

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Possible History Workshop questions:

Excerpts from the above passage lend themselves to historical examination:

1. Why did Snow believe from the outset that the source of the cholera outbreak was a water pump, and the Broad Street pump in particular?

2. When did Snow begin taking water samples, and what did the samples reveal?

3. Why did Snow need to walk to the General Registry Office (GRO) to find out who had died from cholera? Why did he only copy the addresses of those registered as dying from cholera in three sub-districts for a single week ending 2 September?

4. Instead of plotting the addresses he had copied at the GRO on a map and be done with it, Snow conducted arduous house-to-house inquiries at 83 locations? He makes no mention of having used a map at all; how did he locate specific street addresses without one?

5. What were Snow’s findings and why did he consider them significant?

6. What might Snow have said when he met with parish authorities to make them recommend closure of the Broad Street pump?

7. Snow learned later in September that the local cholera epidemic was actually subsiding before the Broad Street pump was disabled, yet he retained his original belief that the pump was the proximal cause of this outbreak. Why?