Never saw a coccolith
But using macrofossil data
He ordered all the English strata" An anonymous clerihew dedicated to W. Smith
William Smith, born March 23, 1769, introduced in his "Strata - Identified by organized Fossils" (1816) the "principle of faunal succession" into stratigraphy. Geological maps before Smith mapped and catalogued rocks based only on the inorganic properties, like chemical composition or colour. This classification was very restricted and confusing. Smith discovered and applied a classification scheme that can identify sedimentary rocks of the same age with almost no doubt.
"Fossils have been long studied as great curiosities, collected with great pains, treasured with great care and at a great expense, and shown and admired with as much pleasure as a child's hobby-horse is shown and admired by himself and his playfellows, because it is pretty; and this has been done by thousands who have never paid the least regard to that wonderful order and regularity with which nature has disposed of these singular productions, and assigned to each class its peculiar stratum."
William Smith (1796)
Using this principle he compiled one of the first "true" geological maps in history, useful also to track the - at the time of the Industrial Revolution - much valuable coal seams.
Map.1. "A Delineation of the Strata of England and Wales...." by William Smith (image in public domain). The colours are based on the colours of the mapped rocks, coal appropriately shown in black. However Smith uses the characteristic assemblages of fossils to further subdivide similar looking rocks - providing a valuable tool to show the stratigraphic order of the underground.
WINCHESTER, W. (2001): The Map that Changed the World: William Smith and the Birth of Modern Geology. New York: Harper Collins: 352