Following dismissal from the Somersetshire Coal Canal Company in 1799, William Smith (1769–1839) earned his living as a consultant, where much of his work involved water. At the time there were conflicting ideas on the origin of deep groundwaters and many considered rainfall alone inadequate to explain their presence. Smith's developing knowledge of stratigraphy enabled him to predict the position of water-bearing formations and provided a scientific basis for their discovery and exploitation. In 1807 his ideas were used by John Farey to explain the source of deep groundwaters beneath London. By 1815, when Smith's map was published, his ideas were known widely enough for the scientifically literate to be aware of their application to the search for groundwater supplies, however, there was still a lack of understanding amongst the general public, partly the result of reticence amongst Smith and his pupils. Examples of Smith's consultancy work show that he was able to accurately predict the depth at which water would be found. His estimates of yield were less successful, resulting from a lack of understanding of how water was stored and released from aquifers under confined conditions. His well-known geological reservoir, near Scarborough was an innovative idea but probably did little to alleviate local water problems.