Wednesday, November 4, 2015

William Smith’s seminal geologic map of Britain

During the Geological Society of America (GSA) 2015 annual meeting in Baltimore, Maryland, special sessions celebrated the 200th anniversary of William Smith’s geologic map of England, Wales, and southern Scotland. A synopsis on the map exhibition, sessions, and short biography of Smith, is on the GSA website.

In the Exhibit Hall, next to the GSA main booth, set up for viewing a few hours each on three days of the meeting, was a “1st edition facsimile print of the Smith map. Scaled at five miles to the inch, it encompasses nearly 50 sq. ft. (6 ft. × 8 ft.). The hand-colored hues are brilliant, in part because the linen original of this facsimile was only recently discovered 'hidden' in darkness in its folio box in the Burlington House, London, home of the Geological Society. The map is art and science combined.” (

The map laid out for viewing on November 2, with “William Smith” (lacy cuffs) answering questions.

I was interested to see what kind of detail was related to the Carboniferous coal beds, especially after I had been looking up maps and information on Welsh coalfields for my blog post last April on Titanic coal. (White Star Line used Welsh coal for ships sailing from the British Isles.) Coal played an important part in Smith’s work: mapping these fossil fuel resources was a driver for the compilation of the map (

This is a close-up of the legend. Carboniferous coal measures are gray-brown; the darker outlines enclosing this unit are clearly visible on large view of map above.  The “coalmeasures” unit here includes “Millstone”, a plant-fossil-bearing layer, and “Penant” (also spelled Pennant) Stone, a marine fossil unit. The contact between the two units is now known to be the Permo-Carboniferous boundary ( The Permian Pennant Stone is also an exterior/interior building stone.

Detail, above, of southeastern Wales, including city of Cardiff (lower left) and Monmouthshire/Breconshire coalfields, and adjacent England, with the Forest of Dean coalfield (north of Severn River) and Bristol coalfield (lower right corner near city of Bristol). The crosses are “the coals”, according to the legend, possibly identifying colliery locations.

Short summaries of Smith’s work and life on the web, besides Wikipedia, include NASA Earth Observatory (; cited above) and the United Kingdom Onshore Geophysical Library ( The book, The Map That Changed the World (2001), by Simon Winchester, is the story of William Smith, the making of his map, and the social and historical setting of this achievement.

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