10 12 2007

As I’ve mentioned before, one of my favorite blogs is Indexed. I really enjoy the way Jessica Hagy illustrates the connections between things. Actually, I’ve been thinking about it quite a bit, and it moved me to pull out one of my favorite books, Edward Tufte’s Visual Explanations: Images and Quantities, Evidence and Narrative.

My brother gave me this book several years ago and I’ve never actually read the thing cover to cover, even though I’ve spent quite alot of time with it. I tend to pull it off the bookshelf a couple of times a year, either sit down with the intent to read the thing in its entirety, or simply dip in for some brain food. Anyway, Tufte’s very serious about the visual means of presenting quantitative information. One of his examples of success is the way in which John Snow identified the source of an unusually violent outbreak of cholera in London in 1854 because he mapped out deaths relative to the location of public water sources.

I’ve covered that chapter about twenty times already, but never while I was reading W. Hodding Carter’s Flushed: How the Plumber Saved Civilization. (By the way, this is not the same Hodding Carter, spokesman for the Carter administration who, I believe, was accused of cocaine use. But that’s irrelevant.) Anyway, one of the things that the Flushed author writes about is the creation of underground sewers in mid-19th century London, which were intended to deal with the increased quantity of sewage resulting from development of water closets that used water to carry waste out of the home. (Before the use of toilets, waste was deposited in backyard cesspits, undiluted by water. The use of water to carry waste out of the house dramatically increased the volume of sewage produced by London’s citizens.) A side effect of the underground sewers was their tendency to seep into wells used to supply drinking water. Since science was not yet aware of bacteria, Snow’s map was a major step in recognizing the link between cholera and tainted water. The bacteria that cause cholera were identified not so long after that.

So, now I’m thinking about how these three things link up: my interest in Jessica Hagy’s diagrams, Visual Explanations, and modern plumbing. I’m going to have to find some time to diagram it…




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