高中英语必修五 Unit 1 Reading1 Summary
John Snow was a very expert doctor in London .He thought about ordinary people exposed to cholera. There were two theories he became interested in. One is that cholera multiplied in the air, the other is that people absorbed this disease into their bodies with their meals.
John Snow suspected that the second theory was correct, and he determined to find out why. First, he marked on a map which gave him a valuable clue that many of the deaths were near the water pump in Broad Street. It seemed that the water was to blame.
Next, john Snow looked into the source of the water and found that it came from the river pollute by the dirty water from London. After that, he found extra evidence from two deaths. Then he was able to announce with certainty that the water carried the virus.