Snow began by plotting on a map the site of deaths from cholera as they occurred.  He found that in one particular location, at the corner of Cambridge and Broad Street, more than 500 deaths had occurred from cholera in just 10 days.  All the affected households, Snow realised, had one thing in common: they sourced their drinking water from the Broad Street pump.  Snow descended on the local Board of Guardians and recommended they immediately put the pump out of action by removing its handle.   The Board was incredulous, not a single one believing that Snow was correct.  However, they were panic-stricken and carried out Snow’s request.  The plague was stayed.   Some time later, further evidence appeared for Snow’s insight.  An infant girl living at 40 Broad Street had been struck down by cholera and died early in the epidemic.  During the diarrhoeal illness, her mother had soaked soiled napkins in a pail and emptied this into the cesspool at the front of the house.  An engineer’s examination demonstrated that the cesspool had decayed brickwork and that faecal matter was able to seep into the Broad Street pump water, which lay just three feet away.