At the Dirt Exhibit in London I got to see John Snow’s “ghost map” graphing cholera cases during the 1854 outbreak:
This map helped prove that cholera spread not through “miasma” in the air but tainted water (the deaths marked on the map cluster around the Broad Street pump). It’s commonly credited with contributing to the birth of epidemiology.
Here’s another map, this time pertaining not to disease but to literature:
This version was drawn by Kathryn Kuitenbrouwer via Joseph Campbell’s The Hero With A Thousand Faces.
The hero’s journey (Campbell calls it the “monomyth”) may not have saved as many lives as Snow’s map. But it arguably led to the birth of literary criticism.