Lost in a dark library stack at the Geological Society London, another copy of the 1815 geological map by William Smith (1769-1839) has just been found. It was inside a leather pouch, where the exquisite water-colours were protected from the sun. Librarians at the society believe it is one of the first of the 70 copies that were printed.
Smith spent the better part of 15 years collecting the information needed to compile the map. It is said he covered about 10,000 miles a year on foot, on horse and in carriage, cataloguing the locations of all the formations that make up the geology of the three home nations.
The lower edge of a formation is saturated and then the paint is made to fade back to the high edge. It is this colouring technique, combined with the tendency of many of England’s rocks to dip to the south or southeast, that gives Smith’s map its iconic look.