HOW DID WILLIAM SMITH CARRY OUT HIS PIONEERING GEOLOGICAL MAPPING? (Invited Presentation)

Smith’s methods ALL depended on his two separate realizations.

A) that all stratified rocks were ordered. Based at Bath, he may have been helped by earlier work here, by John Player (1725-1808) land surveyor of Stoke Gifford, near Bristol, who collected Observations on the different strata (1766). These, never published, survive, with evidence that members of Smith’s circle had seen them, by October 1801. Smith’s own Tables of Bath Strata had evolved from the first version (1797), to his widely distributed one (1799).

After 1799, Smith had to depend on commissions (often as water finder/drainer, or mineral prospector) to take him round Britain. These took him further from Bath, so Smith could add new Units, as knowledge improved on his Bath-based Standard, adding units like Kellaways Rock (1800), or Coral Rag (1815) and shown on variants of his famous map from 1816. Above all Smith also realised that such Units were not universal (due to lateral variation).

B) His critical, separate, realization that fossils could enable such rocks to be identified elsewhereaway from this Standard. This had never depended on his first having traced scarped-outcrop features, as claimed. Fossils also allowed him to understand new problems caused a) by unconformity in the geological record, and b) by faulting, both shown in his work at Melbury, Dorset, 1801. Fossils also allowed him to search detritus thrown up in isolated borings, as demonstrated in 1805 at the abortive South Brewham trial for coal.

All these achievements entirely refute the claims made in September 1976 by Rachel Laudan in her Centaurus article “William Smith. Stratigraphy without Palaeontology”. This stated that Smith, by not using fossils, had mis-identified several outcrops because of his "supposed reliance on surface features”. This was claimed of rocks in the Weald (south east), North Yorkshire and Devon. But when each case is analysed, using Smith’s fossil collections (of whose survival she was completely unaware), Smith’s problems are explained. In such an embryonic science as stratigraphy, it was clear that some fossils (like Smith’s bones from the Wealden) could not yet have any correlative value, while others proved to have long ranges, and be less useful in the identification of rocks.