Portrait by French painter Hugues Fourau (1803-1873) (https://en.wikipedia.org/wiki/William_Smith_%28geologist%29)

(http://earthobservatory.nasa.gov/IOTD/view.php?id=8733)

One of William Smith's drawings from his book. (https://en.wikipedia.org/wiki/William_Smith_%28geologist%29)

    William Smith,1769-1839
       The Father of English Geology

August 1, 2015 marked the 200th anniversary of the publication of William Smith's seminal map of the geology of Britain.

"One evening in southern England more than 200 years ago, three friends with a common interest in rocks and fossils met for dinner and discussed the fledgling field of geology. Two of the men, Joseph Townsend and Benjamin Richardson, were clergymen and fossil collectors who looked to the natural world for tangible evidence God’s handiwork. The third was a young surveyor and canal engineer named William Smith, who possessed an extensive understanding of England’s rock layers, or strata.
After dinner, the men made a  chart of the rock strata in the vicinity of Bath, identifying strata by color, hardness, and the fossils they held. In all, they named 23 layers, employing colorful names like Fuller’s Earth, Lias Blue, and Ditto White. Among these layers, the men noted something odd. Between strata they called Millstone and Pennant Stone was a dramatic change in the kinds of fossils found in the rocks. In the Millstone layer, plant fossils dominated. In the Pennant Stone layer, marine mollusk shells dominated.
Today, geologists recognize this fossil turnover as the boundary between the Carboniferous Period (360 to 300 million years ago), when abundant swamps laid the foundation for many of today’s coal beds, and the Permian Period (300 to 250 million years ago), when Earth’s landmasses coalesced into a single continent. In 1799, however, when Smith and his friends noted the fossil shift, they didn’t grasp the hundreds of millions of years of changing landscapes that geologists recognize today.

For Smith, the finding provided more evidence for his idea that rock layers across England occurred in a predictable pattern, and that wherever they occurred, they could be identified and connected to distant rock outcrops by the unique collections of fossils they held. He called this idea the principle of faunal succession, 0r  fossil succession."

Quoted from
http://earthobservatory.nasa.gov/Features/WilliamSmith/

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Get the book - "The Map That Changed the World" by Simon Winchester,
Published by Penguin Books among others.