There were many great works of spectacular engineering in the 19th century such as gigantic steamships, innovative bridges and fantastic buildings.
None of them, however, saved as many lives as this immense and complex infrastructure project under the streets of one of the largest cities of the world:
It was 1854 and John Snow, a physician with his practice in the Soho part of London, poured over his map of the city.
He’d been working on it since the first signs of a cholera outbreak that year. Carefully he had marked where each new case had appeared.
Photograph: Sewers of London Chief Construction Engineer: Joseph Bazalgette, an Italian Engineer.
Cholera was the scourge of big cities in the 19th century and an outbreak could kill hundreds or thousands of people.
The prevailing notion was that the infectious agent was carried through the air by smell, an idea called the “miasma theory.”
Snow suspected, however, that the disease was actually transmitted in some other way. In 1849 he’d written an essay, On the Mode of Communication of Cholera, suggesting that transmission was being made through unclean water.
His map seemed to bear out his idea. He found by looking at his records that all the recent cases clustered around a public water pump on Broad Street.
Of those few cases that occurred nearer to another pump he found that the residents were still using the Broad Street pump anyway because they preferred the taste of the water.
Especially telling was that of the 70 workers at a nearby brewery, none of them got sick. They only drank the beer provided to them for free.
His study of the pattern of infection was so thorough that he managed to convince the local council to remove the handle from the pump, bringing the outbreak to a close.