American Scientist

The first page of the Ohio State Geological Survey’s 1837 report bears an illustration of the rocks lying beneath the surface of the Earth in southern Ohio. Layers of rock lie one atop the next, in the order they were laid down in time. The smooth layers stretch horizontally across the page, disrupted only by two faint lines that cut vertically from the coal series at the top of the image to the sandstone layer in the middle. The labels next to these two lines read, in even fainter text, “salt well.” The wells were dug by early settlers eager to access the briny mineral deposits flowing beneath the surface of the state.