The map below shows the areas served by the two companies. Snow honed in on the region where the two service areas overlap.

The only difference was in the water supply, “one group being supplied withwater containing the sewage of London, and amongst it, whatever might have comefrom the cholera patients, the other group having water quite free fromimpurity.”

The numbers pointed accusingly at S&V. The death rate from cholera in the S&Vhouses was almost ten times the rate in the houses supplied by Lambeth.